DISPLAY UNIT OF DIGITAL CAMERA
BACKGROUND OF THE INVENTION
1. Field of the Invention 5 The present invention relates to a display unit of a digital
camera, including a liquid crystal display (LCD) for displaying a photographed image.
2. Description of the Related Art 10 A digital camera is known that includes a LCD unit for
displaying a photographed image and related information, such as a date, an operation mode and so forth. Usually, the LCD is illuminated by a back-light such that the displayed image is sufficiently illuminated even outdoors. The back- 15 light has a high electric power consumption and exerts a negative influence upon a battery's duration of the digital camera. Symbolic information, such as a date, an operation mode and so forth, is generally displayed in an image display area of the LCD, and as such it is necessary to 20 illuminate the LCD unit with the back-light even when only the information is displayed. Occasionally, an additional display for displaying only the information is utilized. However, the digital camera including such an additional display is complex and a total number of components is 25 increased.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a display unit of a digital camera capable of displaying both 30 a photographed image and information with minimal electric power consumption.
A display unit of a digital camera according to the present invention comprises a liquid crystal display (LCD) panel, a 3J main back-light unit, a sub-back-light unit, and a driving circuit. The LCD panel displays a photographed image by the digital camera on an image display area of the LCD panel and displays a symbolic information on an information display area. The main back-light unit illuminates the image display area of the LCD panel. The sub-back-light unit illuminates the information display area of the LCD panel. The driving circuit independently drives the main back-light unit and the sub-back-light unit.
BRIEF DESCRIPTION OF THE DRAWINGS 45
The present invention will be better understood from the description of the preferred embodiments of the invention set forth below together with the accompanying drawings, in which: 50
FIG. 1 is a perspective view showing a digital camera that includes a first embodiment of a display unit according to the present invention;
FIG. 2 is a view showing an image exhibited by the display unit of the first embodiment; 55
FIG. 3 is a sectional side view showing the display unit of the first embodiment;
FIG. 4 is a block diagram of the digital camera in FIG. 1;
FIG. 5 is a sectional side view showing a display unit of a second embodiment;
FIG. 6 is a sectional side view showing a display unit of a third embodiment;
FIG. 7 is a sectional side view showing a display unit of a fourth embodiment; and 65
FIG. 8 is a graph showing a spectrum characteristic of a wavelength/luminance relationship of light generated by a
back-light unit, and a transmission factor of color filters used in the fourth embodiment.
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
Hereinafter, the preferred embodiments of the present invention are described with reference to the attached drawings.
FIG. 1 is a perspective view showing a first embodiment of a digital camera according to the present invention. The digital camera 10 includes a camera body 11 of a rectangular parallelepiped shape. A display unit 20, pivotable at a hinge lid on an upper surface 11a of the body 11, is swingable between an angle where the display unit 20 is disposed in a recess lie on the upper surface 11a and an angle X where the display unit 20 projects from the upper surface 11a. The display unit 20 includes a liquid crystal display (LCD) panel 21 for displaying an image and symbolic information (FIG. 2). An optical system 19, having a lens 18, is disposed on a front surface lib of the body 11 for photographing an image in a visual field thereof. A release button 51, a back-light selection button 52 and a mode selection button 53 are disposed on the upper surface 11a of the body 11, and a power switch 59 is disposed on a back surface 11c of the body 11.
FIG. 2 is a view showing an image exhibited by the LCD panel 21 of the display unit 20. The photographed image is displayed in a image display area El from a top A of the LCD panel 21 to a lower portion B adjacent to a bottom C of the LCD panel 21. The symbolic information, such as a date, an operation mode and so forth, are displayed on an information display area E2 between the portion B (a bottom) of the area El and the bottom C of the LCD panel 21. Therefore, the information display area E2 is separated from the image display area El.
As shown in FIG. 3, the LCD panel 21 is illuminated by a main, edge-light type back-light unit 22 and a sub-backlight unit 23 from a back side of the LCD panel 21. The main back-light unit 22 includes a fluorescent lamp light source 22b, a light transmitter 22a, and a reflector 22e. The light source 22b is a fluorescent tube, and the light transmitter 22a transmits light from the light source 22b toward image display area El of the LCD panel 21. The reflector 22e is a container-like concave mirror, which includes a semicircular cylindrical concave mirror 22c extending along a longitudinal axis of the light source 22b, and an inclined flat mirror 22d unitedly and uniformly connected to the semicircular cylindrical concave mirror 22c. Light from the light source 22b is reflected by the semicircular cylindrical concave mirror 22c substantially parallel to the LCD panel 21. The inclined flat mirror 22d extends along the LCD panel 21 and approaches the LCD panel 21 in a direction departing from the semicircular cylindrical concave mirror 22c. The light reflected by the semicircular cylindrical concave mirror 22c is then reflected by the inclined flat mirror 22d, and transmitted by the light transmitter 22a toward the image display area El of the LCD panel 21. A diffusion unit 24 is disposed along a total width of and parallel to a rear surface of the LCD panel 21, diffusing the light radiating from the main back-light unit 22.
The sub-back-light unit 23 includes a plurality of light emitting diodes (LEDs) 23a linearly aligned behind the information display area E2. One LED consumes less than 10% of an electric power consumed by the main back-light unit 22. Thus, the sub-back-light unit 23, consisting of two or three LEDs has significantly a lower electric power
consumption in comparison with that of the main back-light unit 22. While the power in the digital camera 10 is turned on, the information display area E2 is illuminated by the sub-back-light unit 23.
The main back-light unit 22 and the sub-back-light unit 23 5 are independently driven. When the photographed image is displayed on the LCD panel 21, both the main back-light unit 22 and the sub-back-light unit 23 are driven, thus the image is illuminated together with the symbolic information. When only the symbolic information is to be displayed, only 1Q the sub-back-light unit 23 is driven and the main back-light unit 22 is not driven, thus electric power consumption is minimized.
FIG. 4 is a block diagram of the digital camera 10. The optical system 19 focuses an optical image in the visual field on an image sensor (area sensor) 30. The optical image is converted into an analog electrical signal by the image sensor 30, amplified by an amplifier 31, and then converted by an A/D converter 32 into a digital image-pixel signal. The image sensor 30 is controlled by a sensor driving circuit 33. The sensor driving circuit 33 is controlled by a CPU 40.
An output of the digital image-pixel signal from the A/D converter 32 is input to a digital signal processor (DSP) 41 such that the output signal undergoes various image-signal processings, such as shading correction, interpolation and 2J noise reduction. The processed digital image-pixel signal in the DSP 41 is once stored in an image memory 43 according to a control of a memory controller 42. The processed digital image-pixel signal stored in the image memory 43 is read by the memory controller 42, controlled by a CPU 40, from the 3Q image memory 43, and encoded by an LCD signal processor 61 from R (red), G (green) and B (blue) digital signals to a video signal format consisting of a color differential signals (Cr, Cb) and a luminance signal (Y). Since images are continuously input to the image sensor 30 and transferred to 3J the image memory 43, the image in the visual field is displayed by the LCD panel 21 as a motion picture in real-time. The symbolic information, such as a date, an operation mode and so forth, are generated by the CPU 40. The date information is read from a clock circuit (not shown) 4Q in the CPU40, and the operation mode information is supplied from the mode selection switch 53 to the CPU 40. The CPU 40 reads character and symbolic data from a ROM 49, in accordance with the date information and the operation mode information. The CPU 40 transfers the character and symbolic data to a LCD signal processor 61, such that the information is displayed on the area E2.
The main back-light unit 22 and sub-back-light unit 23 are independently driven by driving circuits 62 and 63, respectively. 50
When the release button 51 is depressed halfway, images are continuously input to the image sensor 30 and transferred to the image memory 43a, such that the moving image is displayed in the area El. When the release button 51 is fully depressed, the still image is stored in a memory 44, 55 which stores photographed still images successively.
In the body 11, a battery 46 is disposed for supplying electric power to the components of the digital camera 10, such as the main back-light unit 22, sub-back-light unit 23 and sensor driving circuit 33. The electric power of the 60 battery 46 is supplied, through a DC/DC converter 45 for stabilizing the electric power, to the components. The power switch 59 is connected to an output of the DC/DC converter 45 for switching the electric power.
An interface 80 is connected to the CPU 40, for outputting 65 the image from the memory 44 to a personal computer (not shown) or other peripheral apparatus.
By pushing the mode selection switch 53, the operation mode of the digital camera 10 is successively changed in an order of: "monitor" mode, "photography" mode and "slide" mode.
In the "monitor" mode, an image focused on the image sensor 30 is displayed by the display unit 20 in real-time, as a moving image, and a photographing condition is selected and adjusted. An angle of view, an exposure value and other conditions are manually adjusted. In this mode, the main back-light unit 22 and the sub-back-light unit 23 are driven, thus both the image display area El and the information display area E2 are illuminated. However, the "monitor" mode is not so frequently selected.
In the "photography" mode, first, the display of the moving image is stopped and only the information is displayed. The main back-light unit 22 is turned off and only the sub-back-light unit 23 is turned on. When the release button 51 is depressed halfway, the moving image is displayed again in the area El. At this time, both the main back-light unit 22 and the sub-back-light unit 23 are turned on. If the halfway depression is released, the display of the moving image is stopped, and only the information is displayed. At this time, the main back-light unit 22 is turned off and only the sub-back-light unit 23 is turned on. When the release button 51 is fully depressed after the halfway depression of the release button 51, a still image from the image sensor 30 is displayed in the image display area El, and stored in the memory 44. The photographer can thus observe and confirm the image to be photographed. Then, after the still image is stored in the memory 44, the display of the still image in the area El is stopped, and only the information is displayed by using the sub-back-light unit 23. In the "photography" mode, the main back-light unit 22 is turned off unless the release button 51 is depressed, thus enabling a lower power consumption.
In the "slide" mode, the photographed still image, stored in the memory 44, is read out by the LCD signal processor 61, and is displayed on the area El. When a plurality of still images have been already photographed, these images are successively displayed, similarly to a slide projector. On starting the "slide" mode, the main back-light unit 22 is turned off, and is driven again when the still images are started to be displayed.
Since the main back-light unit 22 is driven only when the image is displayed in the image display area El, the electric power consumption is minimized. An LCD panel only for information display is unnecessary, so the digital camera 10 is simplified and a total number of components is decreased in comparison with a conventional digital camera.
The main back-light unit 22 and the sub-back-light unit 23 can be manually controlled by the back-light selection button 52, successively and scrolling through commands in rotation. For example, in a first selection, only the main back-light unit 22 is driven; in a second selection, additionally, the sub-back-light unit 23 is driven; in a third selection, the main back-light unit 22 is turned off; in a fourth selection, the sub-back-light unit 23 is also turned off.
FIG. 5 is a sectional side view showing a display unit 120 of a second embodiment. Like references indicate identical components to those of the first embodiments. In this embodiment, a main back-light unit 22' includes a flat fluorescent lamp 22b' as a light source and a reflector 22d for reflecting light of the flat fluorescent lamp 22b'. While a sub-back-light unit 23 includes a plurality of light emitting diodes 23a similar to those of the first embodiment. A half mirror 26 is positioned behind the information display area
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