WO1991018383A1

WO1991018383A1 - Computer aided design system utilizing large surface image

Info

Publication number: WO1991018383A1
Application number: PCT/US1991/003546
Authority: WO
Inventors: Brian M. Mann
Original assignee: Mann Brian M
Priority date: 1990-05-23
Filing date: 1991-05-20
Publication date: 1991-11-28
Also published as: AU8096391A

Abstract

A computer aided design (CAD) system (10, 10') projects or otherwise displays a drawing image onto a working surface (36). The displayed image and working surface are large enough to view the entire CAD-generated drawing with sufficient resolution, e.g., greater than four millon pixels, to permit working directly on the drawing surface, using familiar manual drafting or writing techniques, without having to magnify or enlarge the drawing image. The invention allows the desirable features of a CAD system, such as meory recall of commonly used drawn elements, scaling, rotation, indexing, etc., to be freely used, but without the annoyance, frustration, and inefficiencies of having to constantly change the magnification and location of the drawing, as is required using conventional CAD systems. Display of the drawing image is realized, in a preferred embodiment, through the use of multiple rear projection tubes (38) mounted behind the drawing surface in an X-Y grid. Data entry is realized, e.g., using a light pen (16, 46) on the drawing surface and/or a touch sensitive screen (44, 56) overlaying the drawing surface.

Description

COMPUTER AIDED DESIGN SYSTEM UTILIZING LARGE SURFACE IMAGE

BACKGROUND OF THE INVENTION The present invention relates to computer aided design (CAD) systems, and more particularly to a CAD system that displays a large drawing image on a working surface.

CAD systems are known in the art. A typical CAD system employs a computer, including sufficient memory for storage of large amounts of data; display means for displaying the particular design or drawing generated by the CAD system; means for making a hard copy of the design or drawing, such as an X-Y plotter; and means for entering design data and/or making revisions to the displayed design or drawing. The advantage of a CAD system, of course, is that the computer is used to accurately and rapidly perform many drawing or design tasks that previously had to be performed manually. Further, the memory capacity of the computer allows commonly drawn or designed elements to be saved, for subsequent retrieval and use; and further allows large complex designs, e.g. mechanical designs, to be viewed from varying angles or rotations, with various scaling factors, or allows different layers or levels of a design or object to be readily discerned by stripping away unwanted layers or levels. Indeed, the potential benefits provided by a CAD system are almost limitless. For purposes of this application, a CAD system includes any computer-based system that visually displays a desired item, such as a drawing, page(s) of text, or combinations of drawings and text, stored or held in the memory of the computer, and that allows modifications or changes to be made to such displayed item.

Unfortunately, the ergonomics of known CAD systems significantly limit the degree to which the potential benefits of the CAD system can be viably utilized. This is particularly true for design applications where large drawings must be prepared. A "large" drawing for purposes herein, is one having the approximate dimensions of engineering drawings prepared using conventional manual drafting techniques. The size of engineering drawings is typically referred to by a letter of the alphabet, e.g., a "B" size drawing being 11 x 17 inches, a "C" size drawing being 17 x 22 inches, a "D" size drawing being 22 x 34 inches, and an "E" size drawing being 34 x 44 inches. Such engineering drawings may thus range from 2-4 feet high and 3-5 feet wide when initially drawn, essentially filling the entire workspace of a conventional drafting table.

Large engineering drawings advantageously allow a draftsperson to draw whatever design is being drawn directly on the original drawing at any desired location on the drawing with sufficient resolution to portray details of the drawing. Such details cannot be drawn too small due to the limitations of the drafting implements. Since the draftsperson can view the entire drawing sheet, he or she can easily draw or write at any desired location. While reductions of such engineering drawings are frequently made, using conventional photocopy reduction techniques and equipment, such reductions do not generally show the details of the drawing with the same resolution as originally drawn.

Conventional CAD systems cannot display a large engineering drawing because the size and resolution of the screen of the display means, typically a conventional graphics monitor, or equivalent, provides a viewing area having a diagonal measurement on the order of only 12-19 inches. hile larger display screens are known in more sophisticated CAD systems, having diagonal measurements of up to 25-30 inches or larger, such display screens are still limited to a resolution of typically less than 2000 x 2000 pixels, or less than 4,000,000 pixels total, and still cannot display an entire engineering drawing on the screen at one time with sufficient resolution to allow many of the details of the drawing to be readily perceived. Hence, it is not possible to display a large drawing on a screen of the size commonly used in conventional CAD systems without significantly reducing, through conventional scaling techniques, the features of the drawing. When such reductions are made, the details of the drawing are not readily discernable, and in fact, are often totally lost. Hence, it is common in using a CAD system to first display the entire drawing at a reduced scale, e.g. at a reduction of 1/4 or 1/5, and to select, e.g., using a mouse or equivalent pointing device, an area or segment of the displayed reduced drawing where a change or addition is to be made to the drawing. Once this area or segment is selected, it is displayed on the screen using an enlarged scale, so that details in that area or segment of the drawing can be readily seen. However, as the operator is unable to see the field of view of the entire drawing while such enlarged segment or area of the drawing is displayed, some means must be employed to notify the operator where within the drawing the present enlarged segment or area is located. This is typically done by displaying, e.g., in a corner of the display screen, some numerical coordinates that define the location of the field of view displayed on the screen relative to the entire drawing. For some operators, particularly those more familiar with manual drafting techniques, such numerical coordinates are insufficient to fully appraise the operator of where within the overall drawing the currently displayed field of view is located. Thus, many operators find it necessary to regularly obtain visual confirmation as to the location of the current field of view relative to the entire drawing. To do so, they must regularly switch the magnification of that which is displayed from one scale to another. Further, if a particular element spans a distance in the drawing that exceeds the portion of the drawings that is displayed, placement of that element in the drawing can be very difficult and annoying. For example, to draw a line without being able to see the starting point and/or the ending point and all the space in between at the same time can be very time consuming and annoying. Moreover, when the operator desires to view a different area or segment of the drawing, he or she must either: (1) switch back to view the entire drawing (without being able to perceive any details of the drawing) , point to the area or segment of the drawing that is to be viewed, and then switch the magnification of the display so the selected area or segment of the drawing is displayed with sufficient resolution to allow the operator to discern if it is, in fact, the desired area of the drawing, or (2) pan to a new area. Such continual switching of magnification and location of the drawing is not only inefficient and annoying, but it can also be significantly frustrating to the operator. What is needed, therefore, is a CAD-based system that provides the advantages of conventional CAD systems, e.g., memory recall of commonly used drawn elements, scaling, rotation, indexing, etc., but without the annoyance, frustration, and inefficiencies of having to constantly change the magnification and location of the portion of the drawing being viewed.

A further problem and annoyance associated with conventional CAD systems relates to the "unnatural" manner in which changes or modifications must be made to the drawing or other item that is displayed. Typically, the display is presented on a screen positioned in front of the operator. The operator must then "point" to a desired location on the display where a change or addition is to be made. Such pointing is accomplished using a "mouse" or equivalent pointing device, which pointing device is physically remote from the display. It is as though the drawing (or other displayed item, such as a page of text) is not readily accessible to the operator, except indirectly through use of the pointing device. That is, unlike a hard copy of a drawing which a draftsman can place in front of him or her on a drafting table, and can physically touch with drawing implements (such as a pen, pencil, or eraser) , a displayed image on a screen is inaccessible except through a mouse or other pointing device. And while some pointing devices, such as a light pen, allow an operator to physically touch the display screen at a location where a desired operation is to be performed, the screen is usually disadvantageously positioned in a vertical orientation in front of the operator, like a chalkboard or whiteboard, not in a generally horizontal or slanted orientation in front of the operator, like a table top or drafting surface. Continually lifting a light pen, or equivalent device, to a vertically oriented screen is not only tiring, after many hours, but is also unnatural for those trained and conditioned to work with a hard copy of a drawing or sheet of paper on a table top or other working surface. Further, in order to efficiently use such conventional CAD systems, a great deal of time and training is required to teach the operator new "unnatural" ways of working. Hence, what is needed is a CAD system that is comfortable and natural for an operator to use, providing a generally horizontal or slanted working surface on which the drawing image is displayed and that is positioned in front of the operator, much as a table top or drafting surface holds a hard copy of a drawing and is positioned in front of a draftsperson.

The present invention advantageously addresses the above and other needs. SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, there is provided a computer aided design (CAD) system that projects, or otherwise displays, a CAD- generated drawing image onto a drafting or drawing surface (working surface) positioned in front of an operator of the system. Advantageously, the displayed image and drafting surface are sufficiently large to allow the entire drawing to be viewed in an orientation that permits working directly on the drawing surface, using familiar manual drafting techniques. Further, the displayed image is sufficiently large to allow the details of the drawing to be seen without the need to change the magnification of the displayed image. The invention thus allows the desirable features of a CAD system, such as memory recall of commonly used drawn elements, scaling, rotation, indexing, etc., to be freely used, but without the annoyance, frustration, and inefficiencies of having to constantly change the magnification and location of the drawing, as is typically required using conventional CAD systems. In accordance with another aspect of the invention, in a preferred embodiment the drawing image is projected onto the drafting or drawing surface using apparatus that includes multiple rear projection tubes mounted behind the drawing surface in an X-Y grid, or equivalent projection or display apparatus. Each projection tube projects just a segment or section of the overall drawing image. However, when viewed from the front of the drawing surface, all of the drawing segments are visible and are arranged appropriately so that the entire drawing image is visible. Appropriate control circuitry synchronizes the operation of the projection tubes. Data entry is realized using a light pen, or equivalent, on the drawing surface, with or without an electronic tablet. The number of pixels in each displayed segment of the drawing (which determines the resolution for such displayed segment) is the same as are available in a conventional graphics monitor, e.g. less than 2,000 x 2,000. Advantageously, however, the total pixels available to display the entire drawing is the sum of the pixels for each displayed segment, which sum far exceeds the number of pixels (and hence the resolution) that have heretofore been available in CAD systems to display a graphics image. For example, by using a segment display having only 600 x 600 pixels, and by using a 4 x 3 matrix of segments to display the entire drawing, it is thus possible to obtain a drawing image represented by over 4,000,000 pixels, thus providing a drawing resolution much better than has heretofore been available.

One embodiment of the invention may thus be characterized as a computer aided design (CAD) system that includes: (1) processing means for performing design computations related to defining and displaying a drawing; (2) input means for entering commands and instructions into the processing means; (3) a working surface; and (4) display means coupled to the processing means for graphically displaying the drawing on the working surface. The input means includes means for physically pointing to a location on the working surface where a change or addition is to be made to the drawing, and means for entering a command into the processing means that effectuates the change or addition in the drawing at the location pointed to by the pointing means. Advantageously, the working surface is sufficiently large to enable the simultaneous display of the drawing with sufficient resolution to enable a user of the CAD system to visually perceive the drawing details associated with the drawing as though the drawing had been drawn manually on a conventional drafting surface of approximately the same size as the working surface. A further embodiment of the invention is characterized by a computer aided design (CAD) system having a working surface on which the drawing image is displayed, and wherein the displayed image has a resolution of greater than four million pixels. Such CAD system further includes means for inputting data wherein the location of the drawing to be modified is determined by the location of the data input means.

Another embodiment of the invention may be characterized as a large-surface computer aided design (CAD) system that includes: (1) a working surface with which an operator may make desired manual contact, as though the operator were making a manual drawing on the working surface; (2) processing means for performing CAD operations; (3) display means coupled to the processing means for displaying an image of a CAD-generated drawing on the working surface; and (4) input means coupled to the processing means and working surface for converting appropriate manual contact with the working surface into a command that instructs the processing means to perform a desired operation on the CAD-generated drawing at a location within the drawing corresponding to the point of contact with the image of the drawing appearing on the working surface. As with the prior embodiment, the working surface is sufficiently large and the CAD- generated drawing image is displayed thereon with sufficient resolution to enable the operator to readily perceive details in the drawing image as though the drawing image were a manual drawing made by the operator on a conventional drafting surface of approximately the same size as the working surface.

A still further embodiment of the present invention may be characterized as an apparatus for displaying and altering a computer-generated image. Such apparatus comprises: (l) processing means for generating the computer-generated image, the image being sufficiently large so as to require its division into a plurality of sections, each section being displayed separately so that the image is displayed with sufficient resolution to enable details within the image to be readily seen; (2) display means for simultaneously displaying the said plurality of sections of the computer-generated image on a working surface; and (3) input means coupled to the processing means and the working surface for generating processing commands that alter (i.e., change, add to, or delete from) the computer-generated image at a desired location in a specified manner. While the input means of such embodiment may take many forms, it typically includes: (a) means for physically identifying the desired location within the computer-generated image where an alteration is to be made, e.g., by physically contacting the working surface at the location within a particular displayed section of the computer-generated image where the alteration is to occur, and (b) means for specifying a particular alteration that is to be made to the computer- generated image at the physically identified location. Thus, alterations may be made to a desired portion of the computer-generated image by simply manually contacting the working surface at the location in the computer- generated image where the alteration is to be made (which image is advantageously displayed on the working surface with sufficient resolution to enable details within the image to be readily seen) , thereby facilitating alterations of the image without having to change the magnification of the displayed image.

Yet another embodiment of the invention may be viewed as a method of operating a computer-aided design (CAD) system. Such method includes: (a) displaying an image generated by the CAD system on a working surface, this working surface being positionable in front of a user of the CAD system, much as a surface of a drafting table is positionable in front of a person using the drafting table, and this image being displayed on the working surface with sufficient resolution to allow details within the image to be readily seen, much as a drawing manually drawn on a drafting table shows details with sufficient resolution to allow such details to be readily seen without the aid of magnification devices; (b) modifying the displayed image, when desired, by (i) manually identifying a location on the working surface where a portion of the image to be modified is displayed, (ii) physically specifying the type of modification that is to be made to the image at the identified location, (iii) executing the specified modification at the specified location with the CAD system, and (iv) displaying the modified image on the working surface.

Use of this method advantageously allows modifications to the CAD-generated image to be initiated directly on the working surface on which the image is displayed at the same time that the image is visibly displayed on the working surface, similar to the manner in which manual modifications are made to a manual drawing.

It is thus a feature of the present invention to provide a CAD system that offers all of the advantages of a CAD system, but that is ergonomically designed to better suit conventional drafting techniques and methods. Such CAD system is therefore easier to use and requires less training than prior art CAD systems.

It is another feature of the invention to provide such a CAD system wherein a CAD-generated image is displayed on a working surface conveniently positioned in front of an operator of the system, much as a drawing on a drafting table is positioned in front of a draftsman.

It is a further feature of the invention to provide such a CAD system wherein the displayed image is sufficiently large so as to allow all relevant details within the image to be readily seen without having to change the magnification level of the displayed image. That is, it is a key feature of the invention to display the drawing image with sufficient resolution, e.g., 50 to 600 dpi (dots per inch) , to faithfully depict drawing details while still being able to view the entire drawing (A-E size) . Hence, the field of view of the displayed image is sufficiently large to show all relevant portions of the entire drawing, thereby visually orienting the operator as to a particular location within the overall drawing where a desired modification or addition is being made without requiring the operator to continually switch the displayed image from one magnification level to another. Moreover, another key feature of the invention provides a direct physical correlation of a pointing device, used to enter data into the CAD system, with the image displayed on a working surface. That is, the location of the drawing to be added or modified is determined directly by the location of the input device on the displayed image on the working surface.

Advantageously, the above-described features are similar to what is experienced using conventional manual drafting techniques. That is, a manual drawing always shows details only to the resolution provided by the manual drawing instruments, which resolution is sufficient to enable all relevant details to be readily seen. Similarly, a manual drawing always provides a field of view of the entire drawing, as the entire drawing must be manually placed on the drafting table, thereby leaving no doubt as to the location on the drawing where a particular change or addition is being made. Disadvantageously, these helpful features, long taken for granted using manual drafting techniques, have not heretofore been available in existing CAD systems. The present invention alleviates this deficiency. BRIEF DESCRIPTION OF THE DRAWINGS The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:

FIG. 1 is a basic block diagram of the present invention;

FIG. 2A is a partial cutaway side view of a rear-projection large-surface CAD system made in accordance with one embodiment of the present invention;

FIG. 2B is perspective view of the display table of the rear-projection large-surface CAD system of FIG. 2A; FIG. 3 shows a top plan view of the working surface of the display table shown in Fig 2B;

FIG. 4 depicts a working surface in accordance with an alternative embodiment of the invention utilizing an LCD display, or equivalent, as part of the working surface and a touch sensitive screen overlaying the LCD display; and

FIG. 5 is a more detailed block diagram illustrating the graphical display and data entry components of the invention shown in FIG. 2B.

DETAILED DESCRIPTION OF THE INVENTION The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.

Referring first to FIG. 1, a basic block diagram of a CAD system 10 in accordance with the present invention is shown. As seen there, the system 10 includes a central processing unit (CPU) 12, a display table 14, and a pointing/ ata entry pen 16. Other conventional data processing components, such as a keyboard 18 or a printer/plotter 20 may also form part of the system 10.

The CPU 12 includes means for performing computer aided design, means for carrying out and controlling a conventional CAD program, including a suitable computer operating system, and sufficient memory to store the data generated while operating the CAD program. The keyboard 18 and the printer/plotter 20 interface with the CPU 12 to enable data entry and printing or plotting of drawings generated by the CAD program. The CPU 12, keyboard 18 and printer/plotter 20 may be of conventional design and operation.

Also coupled to the CPU 12 is the display table 14. It is the function of the display table 14 to display an image of a drawing generated by the CAD system within the CPU 12. Advantageously, the display table 14 includes a display surface or screen 22 that is large relative to a conventional graphics monitor. Preferably, the display surface 22 has dimensions on the order of a conventional drafting table surface, e.g., 3-5 feet long and 2-4 feet wide. Further, the display table 14 includes means for orienting the display surface so that it is horizontal or slanted relative to an operator of the CAD system 10. Thus, the display surface 22 functions as a conventional drafting table top. Further coupled to the CPU 12 is a pointing/data entry pen 16. It is one function of this pen 16 to sense a particular location on the display surface 22 and signal the CPU of this location. As the CPU 12, or more particularly the CAD program within the CPU 12, keeps track of the image displayed on the display surface 22, including where each element of the drawing image appears on the display surface 22, the pen 16 thus signals the CPU 12 of a particular location within the drawing image. It is a further function of the pen 16 to instruct the CPU 12 to perform certain operations beginning or ending at the current location of the pen 16. That is, the pen 16 may mark a beginning or ending point for a line that is to be drawn or deleted (erased) , the center or perimeter of a circle or polygon, or the center or other point associated with a commonly drawn element. Thus, for example, by simply manually moving the pen 16 to a desired beginning point of, e.g., a line, in the drawing image displayed on the display screen 22, and by then moving the pen 16 to a desired ending point of the line in the displayed drawing image, the CAD program within the CPU 12 quickly and accurately generates a line between the two marked points as the pen is moved. In this or a similar manner, a drawing may be quickly and accurately drawn or revised using the CAD system 10 by simply moving the pen 16 about the display surface 22 to desired locations in the drawing image, and instructing the CPU 12 to perform desired operations at each identified location (such as drawing or deleting a drawing element) .

It is thus apparent that use of the CAD system 10 is advantageously similar to the well-known and ubiquitous technique of applying a pen or pencil to paper at a location on the paper where a drawing element is to be made, and taking whatever action is needed, e.g., moving the pencil as controlled by a desired template, in order to draw the desired element at the desired location. In the case of the present invention, however, the "paper" is the image of the drawing displayed on the display surface 22 of the display table 14; the "pen" is the pointing/data entry pen 16 that is moved to a desired location on the displayed image 16; and the "action" taken at the specified location is to instruct the CAD program in the CPU 12 to perform a desired operation in the CAD-generated drawing at the location specified by the pen 16.

Referring next to FIGS. 2A and 2B, the principal elements of a preferred embodiment of the present invention are shown. Such embodiment comprises a rear-projection large-surface CAD system 10'. FIG. 2A includes a partial cutaway side view of a display table 30 used in such a system 10'. Such display table includes a flat working surface 36 that may be adjusted to a desirable height and angle relative to support structure 40. A plurality of rear projection tubes 38 are mounted underneath the working surface 36..

The working surface 36 is made from a suitable transparent plate 42, e.g., glass or plastic. Each of the projection tubes 38 projects a segment of a drawing image to be displayed onto a respective portion of the back side of the transparent plate 42. Each displayed segment has a resolution determined by the individual projection tube 38, which resolution may be as high as 2000 x 2000 pixels. Such segments are thus visible from the front, or top, side of the plate 42. As explained below, the projection tubes 38 are mounted and controlled in an orderly fashion so that the resulting segments displayed on the working surface 36 combine to provide to the operator viewing the working surface an image of the entire CAD-generated drawing.

As explained more fully below, at least some portions of the plate 42 may be overlayed or combined with a transparent touch sensitive screen 44. Such touch sensitive screen 44, or equivalent devices, such as strategically placed infrared sensors, allow the CPU to resolve absolute position within the drawing.

Also shown in FIG. 2A is an optional auxiliary equipment table 32, on which a printer/plotter 20 and/or a keyboard 18 may be placed so as to be easily accessible to an operator of the system 10. Further, if desired, an electronic tablet may be made available to the operator on the equipment table 32 or an another surface adjacent to the working surface 36 of the display Table 30. (An electronic tablet is a device having a flat surface that allows any pointer on the surface of the tablet to be entered as data into a computer. Thus, for example, an electronic tablet may provide or display graphic menus to the operator so as not to require such menus to overlay, or otherwise occupy, space of the actual working surface. The DT-3500 Screenplay tablet, manufactured by Seiko Instruments, Inc., is an example of a commercially available electronic tablet.)

The operator, not shown in FIG. 2A, preferably sits in a chair 34 positioned in front of the display table 30 and next to the equipment table 32. The chair 34 illustrates the relative size of the display table 30. As desired, the keyboard 18 and/or electronic tablet (if used) may be moved from the equipment table 32 and placed in other convenient locations available to the operator, such as temporarily on the working surface 36, or on a . convenient surface adjacent, to the working surface 36.

As seen best in FIG. 2B, the working surface 36 is divided into a plurality of regions, identified as A, B, C, D, E, F, G, H, and I. Each region A-I is associated with a respective projection tube 38. That is, for the embodiment shown in FIGS. 2A and 2B, there are nine projection tubes 38, each of which projects a respective segment of the CAD-generated image, or other desired information, onto one of the respective regions, A-I, of the working surface 36. One or more of the regions A-I, such as the region C, may be used to display instructions or status information associated with operation of the CAD program loaded in the CPU 12, similar to the instructions or status displayed on a conventional CRT screen used with a conventional computer. (Alternatively, a separate CRT screen, or an electronic tablet, not part of the working surface 36, may be used for this purpose.) Further, such region C (or an adjunct CRT, electronic tablet, etc.) may display various commands that may be issued to the CAD program in the CPU, e.g., to draw a circle or polygon at the location specified by the pen 46. Such commands may be selected by way of the pen 46 or by the operator otherwise touching the screen at the location where the desired command option is displayed. Such selection process is similar to the common practice of using a mouse to move a cursor to a desired command option displayed on a CRT screen, and pressing a control button on the mouse to select such option.

It is to be emphasized that while the embodiment of the invention shown in FIGS. 2A and 2B utilizes nine rear projection tubes 38, arranged in three rows of three tubes in each row (3 x 3) , this number and arrangement of rear projection tubes is only exemplary, and not limiting. For example, it may be desirable for some embodiments of the invention to utilize three rows of four projection tubes each (3 x 4) , making a total of twelve projection tubes. Other possible configurations include two rows of four projection tubes each (2 x 4) , or two rows of three tubes each (2 x 3) , or two rows of two tubes each (2 x 2), or any other desired configuration.

As further shown in the embodiment of the invention shown in FIG. 2B, a pointing/data entry pen 46 may be used to allow an operator to specify a particular point on the working surface 36 where a desired operation is to be carried out. The pen 46 is coupled to the CPU by way of a wire 48, or equivalent, which wire may be held up off of the working surface 36 by way of an arm 50. The pen 46 is preferably a "light pen", of which numerous types and models are commercially available from several manufacturers. Typically, the projection tubes 38 will use the same video synchronization signals, as explained more fully below in connection with FIG. 5. In such instance, the operator "drags" the light pen 46 across the surface 36 in order to establish the current drawing position. The light pen software assumes all input to be within ± a projection tube width, W, for both x and y directions.

The concept of light pen positioning is illustrated in FIG. 3, where a top plan view of the working surface 36 is shown, including the various regions A-I associated with each projection tube (assuming a 3 x 3 projection tube arrangement) . The current drawing position is point P, located in the lower left quadrant of region E. This position is centered in a work area having dimensions W x W, approximately the same dimensions as the projection tube regions A-I. Thus, with the light pen 46 positioned at point P, the controlling light pen software assumes that all data input is within ± W/2 of point P in both the x and y directions. To move to another area of the drawings, the operator simply "drags" the light pen (moves it across the drawing surface without pressing a drawing button) to the desired drawing position, e.g., P¹, located in drawing region P* . Use of the light pen 46 represents just one embodiment for determining a drawing position on the work surface 36. Other embodiments, as already mentioned, may include the use of a "touch screen" that is positioned over all regions A-I of the working surface 36. Such touch screen allows an exact location on the working surface 36 to be determined relative to the drawing image displayed thereon. A touch screen may thus be used as either an adjunct to the light pen to resolve exact location, or in lieu of a light pen. Touch screens are known in the art, and typically utilize mechanical pressure, infrared sensing, or magnetic field sensing to ascertain a touched location on the screen. Of these, a mechanical pressure touch screen or an infrared sensing touch screen is preferred for use with the present invention as they can be used to sense a touched location regardless of whether the touching is performed with a finger of the operator, a pencil, or other implement.

It is noted that as used herein, the term "touched", "physical contact" or similar terms as used with reference to an input means, such as a touch screen overlaying a working surface, does not necessarily require actual direct physical contact between the input means and the touch screen or surface. Rather, depending upon the type of sensing mechanism used by the touch screen, it may be sufficient that the input means simply be in the proximity of the touch screen, in any of three dimensions. For purposes of the present invention, it is thus possible to "touch" the touch screen (or other input device) without actually physically contacting the touch screen. Another embodiment of the invention contemplates that the video sync signals of each projection tube be separated in time, thereby allowing a light pen's location to be deter inable without having to "drag" the pen across the entire surface 36. That is, in such embodiment, each region A-I has separate timing signals associated therewith. The light pen signals can thus be readily associated with a particular set of timing signals from a particular projection tube, thereby indicating the particular region A-I on which the light pen is used. The disadvantage of using separate video sync signals for each projection tube is that the control circuitry necessarily increases in quantity, complexity, and cost.

Referring next to FIG. 4, there is shown an alternative embodiment of a display table 14• that may be used with the present invention. Such embodiment utilizes a working surface that includes a flat liquid crystal display (LCD) display 52, or equivalent flat display, secured to a suitable table top 54. A transparent touch sensitive screen 56 overlays the LCD display 52. Back lighting is used, as required, in order to enhance the visibility of the LCD display. Apparatus for providing such back lighting is conveniently housed in a holding tray 58 located underneath the table top support structure 54. For the LCD embodiment of the invention shown in FIG. 4, the LCD display 52 may take several forms. At the present time, large LCD displays, i.e., of a size sufficient to overlay the entire table top 54 of the display table 14*, are not commercially available. However, such large LCD displays will likely be commercially available in the not too distant future. At such time, a single large LCD display 52 may be conveniently used for this embodiment of the invention. Until that time, a plurality of flat LCD displays, arranged side-by-side in an orderly fashion on the table top 54 may effectively function as a single LCD display to provide a large surface image of the CAD-generated drawing. The use of such a plurality of LCD displays is thus similar to the use of the plurality of projection tubes 38 (FIGS. 2A and 2B) to project different segments of the drawing image onto respective regions A-I of the working surface 36 to provide the equivalent of a large drawing image that covers most, if not all, of the working surface 36'. It is also noted that a light pen may be used with an LCD display in a manner similar to its use with other types of displays.

FIG. 5 shows a more detailed block diagram of the present invention. While FIG. 5 assumes an embodiment of the invention utilizing a plurality of projection tubes 38, and a light pen 46, such as is shown in FIGS. 2A and 2B, it is to be understood that the circuit configuration shown in FIG. 5, with only minor modifications, also has applicability to other embodiments of the invention, such as one utilizing multiple LCD displays and/or a touch screen.

As seen in FIG. 5, the CPU 12 interfaces through appropriate input/output (I/O) control circuitry 60 with light pen logic 62. Appropriate light pen detector circuitry 64 couples the light pen 46 to the light pen logic. Clock logic 66 generates the timing signals needed for operation of the projection tubes 38a, 38b, ... 38n. These timing signals include a vertical sync signal (VSYNC) , a horizontal sync signal (HSYNC) and a bit clock (BCLK) . The CPU also interfaces, through additional I/O control circuitry 68 with a video memory 70. The video memory 70 includes sufficient memory storage to define a bit map 72a, 72b, ... 72n, corresponding to each of the projection tubes 38a, 38b, ... 38n. Each bit map, in turn, provides appropriate image data to respective video driver circuits 74a, 74b, ... 74n. Each video driver circuit drives one of the graphics projection tubes 38a, 38b, ... 38n.

In operation, the CAD program in the CPU 12 defines the image to be displayed by each projection tube 38 by storing image data in the appropriate bit map of the video memory. Not shown, but considered as part of the CPU 12, is data storage memory, e.g., a RAM, a tape drive, and/or a disk drive, that enables the CPU to store the CAD program itself, including any operating data associated therewith, as well as images generated by the CAD program, which images, once stored, can be later retrieved. The video driver circuits 74 respond to the image data stored in the respective bit maps, in order to generate the appropriate signals that cause the respective projection tubes 38 to display the image on the working surface 36. These signals are all synchronized, as required by the VSYNC, HSYNC and BCLK signals generated by the clock logic 66.

The light pen 46, includes a light sensor that senses light generated by the projection tubes 38. Because the image displayed on the working surface is a scanned image, resulting from a beam of light that is scanned across each region of the working surface 36 as controlled by the VSYNC, HSYNC, and BCLK signals, there is only an instant of time within the overall scan cycle when the light beam is actually present at a given location of the displayed image for each segment. The light pen 46 senses the scanned light during this instant of time, and the light pen logic 62 determines when this time occurs relative to the scan cycle synchronization signals, e.g., the VYSNC, HSYNC, and BCLK signals. This determination, in turn, allows the light pen logic 62 to ascertain the relative location of the light pen within the displayed image, which information is sent back to the CPU 12. The detailed design of the circuitry shown in

FIG. 5 is not critical to operation of the present invention. Accordingly, those skilled in the design and operation of computer graphics systems, including video display systems, may readily fashion and design appropriate circuitry to perform the functions described. Additional information concerning the design and operation of representative computer graphics systems of the type that may be used to assist in such detailed design may be found in, e.g., Reghbati, et al. "Tutorial: COMPUTER GRAPHICS HARDWARE Image Generation and Display", published by the Computer Society Press of The Institute of Electrical and Electronics Engineers (IEEE) , Inc. (1988, 374 pages) . This reference may be obtained from the IEEE Service Center, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, as IEEE Catalog No. EH0273-3; ISBN 0-8186-0753-X. Numerous CAD programs are available commercially that may be utilized in the CPU 12 as part of the present invention. For example, AUTOCAD, made by AutoDesk. Such system can be used, e.g.. with an IBM (or IBM compatible) XT, AT or other personal computer, and only minor modification would be required to the CAD program in order for it to properly perform as part of the present invention. Further, as required, desirable features from several CAD programs may be combined in a "hybrid" CAD program for use with the present invention. Alternatively, a suitable CAD program may be written by those skilled in the programming arts.

The graphic projection tubes 38 may be of conventional design. Such tubes are available commercially from numerous vendors, such as Sony, Mitsubishi and Sharp.

Similarly, the light pen 46 (FIGS. 2B, 5), or equivalent pointing/Data Entry Pen 16 (FIG. 1) , may be obtained commercially from various sources. Appropriate light pen logic 62 (FIG. 5) , or information that readily permits one skilled in the art to design such logic, is typically included with the procurement of such a commercially-available light pen or pointing device.

Where an embodiment of the present invention utilizes a transparent or other type of "touch screen", it is noted that such touch screens may also be obtained commercially. Again, sufficient information is provided by the manufacturers of such touch screens to enable one skilled in the art to readily interface the use of such touch screen with the CPU 12 and the CAD program used therein.

Further, it is noted that there are numerous devices described in the literature, including the patent literature, that may optionally be used as an element of the CAD-system described herein. For example, U.S.

Patent No. 4,845,684 (Garwin et al.) discloses a computer input device that allows free-hand written data entry into a CAD system. U.S. Patent No. 4,561,183 (Shores) discloses a tracing tool employing a mouse coupled to a drafting arm. Such tool allows contours followed by a pointer to be copied exactly into the memory of a computer, thereby providing an easy and accurate method of graphical data entry. Numerous types of "mouse" input devices, and digitizers, are also commercially available as further aids to transferring graphical data into the computer of the CAD-system.

It is to be noted that the large surface CAD system of the present invention need not be limited in its application to the preparation of graphical drawings, e.g., engineering drawings, of the type commonly drawn by a CAD system. The large working surface provided by the invention, which may advantageously be divided into separate regions on which respective segments of the image are displayed by the respective projection means, or equivalent, also lends itself for use with word processing and/or data analysis (e.g., spread sheet) systems. Thus, for example, it is possible using a word processing system in the CPU 12 to simultaneously display separate pages of a multiple page document in an orderly array with sufficient resolution to allow the textual material on each displayed page to be read by the operator without magnification or enlargement. This is thus similar to spreading out pages of a multiple page document on a table top in front of a person reviewing the document. The light pen, or equivalent pointing device, may then be used in conjunction with the keyboard, to select words or paragraphs on one page that are to be revised, deleted or moved, either within the same page or to other pages, in conventional word processing manner. Desired graphics, such as figures or tables, may also be mixed with the displayed text. Hence, there is no need to constantly issue jump commands, or "GO TO" commands, as the operator wishes to view another page of the document under preparation and/or review.

Similarly, using the present invention, a large spread sheet may be viewed in its entirety at one time, without having to move around in the spread sheet to display an area of interest.

As thus described, it is seen that the present invention provides a CAD-based drawing system wherein regeneration delays are avoided because the entire drawing is viewed at one time. Hence, less training is required due to the greater similarity to conventional drawing methods and techniques.

As also described above, it is seen that the present invention provides a CAD system offering all of the advantages of a conventional CAD or word processing system, but ergonomically designed to better suit conventional drafting or writing techniques and methods. More particularly, it is seen that the present invention provides a CAD system wherein a CAD-generated image is displayed on a working surface conveniently positioned in front of an operator of the system, much as a drawing on a drafting table is positioned in front of a draftsman. Because the working surface is about the same size as the surface of a conventional drafting table, the displayed image is sufficiently large to allow all relevant details within the image to be readily seen without having to change the magnification of the displayed image. Further, the field of view of the displayed image is sufficiently large to show all relevant portions of the entire drawing with greater resolution than has heretofore been available using prior art CAD systems. Hence, continual visual orientation is always provided to the operator as to the present work position within the overall drawing, and the overall drawing is displayed with a resolution, e.g., greater than 4 million pixels, that allows all details of the drawing to be readily perceived.

While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.

Claims

CLAIMSWhat is claimed is:

1. A computer aided design (CAD) system comprising: processing means for performing design computations related to defining and displaying a drawing; input means coupled to said processing means for entering commands and instructions into said processing means; a working surface; display means coupled to said processing means for graphically displaying said drawing on said working surface; said input means including means for physically contacting a location on said working surface where a change or addition is to be made to said drawing, and means for entering a command into said processing means that effectuates said change or addition in said drawing at the location contacted by said physical contact means; said working surface being sufficiently large to enable the simultaneous display of said drawing with sufficient resolution to enable a user of said CAD system to visually perceive the drawing details associated with the drawing as though the drawing had been drawn manually on a conventional drafting surface of approximately the same size as said working surface.

2. The CAD system set forth in claim 1 wherein said display means comprises a plurality of separate display means, each separate display means including means for displaying a respective segment of said drawing on a different portion of said working surface.

3. The CAD system as set forth in Claim 2 wherein said plurality of display means are arranged in an x-y grid and positioned relative to said working surface so as to display each of said respective segments of said drawing in an orderly arrangement.

4. The CAD system as set forth in Claim 2 wherein said plurality of display means comprise a plurality of projection tubes positioned behind a front surface of said working surface, each of said projection tubes projecting a respective segment of said drawing on a portion of a backside of said working surface, said drawing segments being viewable from a front side of said working surface.

5. The CAD system as set forth in Claim 1 wherein said processing means includes means for overlaying selected portions of said working surface with information generated by said processing means to selectively display status information associated with the operation of said CAD system.

6. The CAD system as set forth in Claim 1 wherein said processing means includes means for overlaying selected portions of said working surface with menus that display command information associated with the operation of said CAD system, and wherein said input means includes means for selecting a desired command from said displayed command information.

7. The CAD system as set forth in Claims 1, 2, 3 or 4 wherein said input means includes a touch sensitive screen overlaying at least a portion of said working surface whereon said drawing is displayed, said touch sensitive screen being coupled to said processing means, said processing means including a means for physically correlating a location on said touch sensitive screen that is physically contacted by said user with a location within said drawing.

8. The CAD system as set forth in Claims 1,

2, 3 or 4 wherein said input means includes a light pen coupled to said processing means, said processing means including means for physically correlating a location on said working surface that is contacted by said light pen with a location within said drawing.

9. The CAD system as set forth in Claim 1 wherein said input means further includes an electronic tablet coupled to said processing means.

10. The CAD system as set forth in Claims 2, 3 or 4 wherein said drawing comprises a graphical drawing, and each of said segments of said drawing comprise a portion of an overall drawing made up of said respective segments.

11. The CAD system as set forth in Claims 2,

3, or 4 wherein said drawing comprises textual material, and each of said segments of said drawing comprise at least a portion of a page of said textual material.

12. A large-surface computer aided design

(CAD) system comprising: a working surface with which an operator may make desired manual contact, as though the operator were making a manual drawing on said working surface; processing means for performing CAD operations; display means coupled to said processing means for displaying an image of a CAD-generated drawing on said working surface; and input means coupled to said processing means and working surface for converting appropriate contact with said working surface into a command that instructs said processing means to perform a desired operation on said CAD-generated drawing at a location within said drawing corresponding to the point of contact with the image of said drawing appearing on said working surface; said working surface being sufficiently large and the CAD-generated drawing image being displayed thereon with sufficient resolution to enable said operator to readily perceive details in said drawing image as though said drawing image were a manual drawing made by said operator on a conventional drafting surface of approximately the same size as said working surface.

13. The large surface CAD system as set forth in Claim 12 wherein said display means includes means for projecting said CAD-generated drawing image on said working surface from a location behind said working surface.

14. The large surface CAD system as set forth in Claim 13 wherein said means for projecting includes a plurality of projection tubes, each projecting a respective segment of said drawing image onto a back side of said working surface, said working surface being sufficiently transparent to allow said drawing image to be visible from a front side of said working surface.

15. The large surface CAD system as set forth in Claim 12 wherein said display means includes at least one LCD display, said LCD display comprising part of said working surface.

16. The large surface CAD system as set forth in Claims 12, 13, 14 or 15 wherein said input means includes a touch sensitive screen overlaying at least a portion of said working surface and LCD display, said touch sensitive screen being coupled to said processing means, said touch sensitive screen providing a means for identifying a location on said working surface that is physically contacted by said operator.

17. The large surface CAD system as set forth in Claims 12, 13, 14 or 15 wherein said input means includes a light pen coupled to said processing means, said processing means including means for detecting a location on a front side of said working surface that is contacted by said light pen.

18. The large surface CAD system as set forth in Claim 17 wherein said input means further includes a touch sensitive screen overlaying at least a portion of said working surface, said touch sensitive screen being coupled to said processing means, said touch sensitive screen providing an additional means for identifying a location on said working surface that is physically contacted by said operator.

19. The large surface CAD system as set forth in Claim 17 wherein said input means further includes an electronic tablet coupled to said processing means.

20. The large surface CAD system as set forth in Claim 12 wherein said CAD-generated drawing comprises a graphical drawing, including graphical symbols, lines, and text.

21. The CAD system as set forth in Claim 12 wherein said CAD-generated drawing comprises multi-page textual material, and said display means includes means for simultaneously displaying a multiplicity of pages of said textual material on said working surface with sufficient resolution to allow the textual material on each displayed page to be read without magnification or enlargement.

22. Apparatus for displaying and altering a computer-generated image comprising processing means for generating said computer-generated image, said image being divided into a plurality of sections, each section being displayed separately and with sufficient resolution to enable details within said image to be readily seen without enlargement or magnification of said image sections; display means for simultaneously displaying said plurality of sections of said computer- generated image on a working surface; and input means coupled to said processing means and said working surface for generating processing commands that alter said computer-generated image at a desired location in a specified manner, said input means including means for physically identifying the desired location within said computer-generated image where an alteration is to be made by physically pointing to said working surface at the location within a particular displayed section of said computer-generated image where said alteration is to occur, and means for specifying a particular alteration that is to be made to the computer- generated image at said physically identified location; whereby alterations made to a desired portion of said computer-generated image may be made by physically contacting the working surface at the location in the computer-generated image where the alteration is to be made; and further whereby said computer-generated image is displayed on said working surface with sufficient resolution to enable details within said image to be readily seen, thereby facilitating alterations of said image without having to change the magnification of the image displayed on said working surface.

23. The apparatus as set forth in Claim 22 wherein said display means comprises a plurality of display means coupled to said processing means, each display means graphically displaying a respective section of said computer-generated image on said working surface, said plurality of display means being arranged to display their respective sections on respective portions of said working surface, the combined image presented by said . respective sections comprising said computer-generated image.

24. The apparatus as set forth in Claim 23 wherein said plurality of display means comprises a plurality of projection tubes that project the respective section of said computer-generated image on a back side of said working surface, said working surface being sufficiently transparent to allow said image sections to be visible from a front side of said working surface.

25. The apparatus as set forth in Claim 23 wherein said input means includes a touch sensitive screen overlaying at least a portion of said working surface whereon said computer-generated image is displayed, said touch sensitive screen being coupled to said processing means, said touch sensitive screen including a means for identifying a location on said working surface that is contacted by an operator of said apparatus.

26. The apparatus as set forth in Claim 23 wherein said input means includes a light pen coupled to said processing means, said processing means including means for detecting a location on said working surface that is contacted by said light pen.

27. The apparatus as set forth in Claim 26 wherein said input means further includes a touch sensitive screen, said touch sensitive screen being coupled to said processing means, said touch sensitive screen including a means for identifying a location on said working surface that is contacted by an operator of said apparatus.

28. A computer aided design (CAD) system comprising: processing means for performing computations related to defining and displaying a drawing; a working surface; display means coupled to said processing means for displaying a drawing image on said working surface, said drawing image having a resolution greater than four million pixels; and data input means coupled to said working surface for inputting drawing data into said processing means wherein the location where the drawing data is effective within said drawing is determined by the location of said data input means on said working surface.

29. The CAD system as set forth in Claim 28 wherein said data input means includes a light pen.

30. The CAD system as set forth in Claim 29 wherein said data input means further includes a touch sensitive screen overlaying at least a portion of said working surface.

31. The CAD system as set forth in Claim 28 wherein said display means includes a plurality of separate display means, each separate display means including means for displaying a respective segment of said drawing on a different portion of said working surface.

32. A computer aided design (CAD) system including: processing means for performing CAD functions; a working surface arranged to resemble a drafting table; display means coupled to said processing means for displaying a drawing image on said working surface, said drawing image having a resolution of greater than four million pixels; and data input means in contact with said working surface for inputting drawing data into said processing means wherein the location where the drawing data is effective within said drawing is determined by the location of said data input means on said working surface.

33. The CAD system as set forth in Claim 32 where said data input means includes a light pen.

34. The CAD system as set forth in Claim 33 wherein said data input means further includes a touch sensitive screen overlaying at least a portion of said working surface

35. A method of operating a computer-aided design (CAD) system comprising the steps of: displaying an image generated by said CAD system on a working surface with sufficient resolution to allow features within said image to be readily perceived, much as a drawing on a drafting table is drawn with sufficient resolution to allow features within said drawing to be drawn using conventional manual drawing tools and readily perceived; positioning said working surface in front of a user of such CAD system, much as a surface of a drafting table is positioned in front of a draftsperson; and correlating the location of a data input device on said working surface with a location within said drawing where an addition or modification is to be made to said drawing by said CAD system.

36. The method set forth in Claim 35 wherein said correlating step includes: physically identifying a location on said working surface with said data input device where a portion of said image is displayed, specifying the type of modification or addition that is to be made to said image at the physically identified location, executing said specified modification at the specified location with said CAD system, and displaying the modified image on said working surface.

37. The method set forth in Claim 35 wherein the step of displaying said CAD-generated image on said working surface comprises dividing said CAD-generated image into a plurality of sections, and displaying each of said sections on respective portions of said working surface.

38. The method set forth in Claim 37 wherein the step of displaying said CAD-generated image on said working surface comprises projecting said CAD-generated image onto a rear side of said working surface, said working surface being sufficiently transparent to allow said CAD-generated image thus projected to be visible from a front side of said working surface.

39. The method set forth in Claim 35 wherein the step of displaying said CAD-generated image comprises displaying said image with a resolution of at least four million pixels.