EP2196725A1 - Lamp - Google Patents

Abstract

The lamp has an elongated lighting unit (12) extended in a longitudinal direction. An opaque covering element is provided below the lighting unit, where the covering element controls a direct light emission from the lighting unit. A counter-reflector is provided below the lighting unit, where the counter-reflector reflects a part of luminous flux emitted from the lighting unit on a main reflector (11) arranged above the lighting unit. Light is reflected by the main reflector downwardly emitted from the lamp through a prism plate (13).

Description

The present invention relates to a luminaire with a luminaire housing, and at least one longitudinally extending elongate luminous means, wherein at least a portion of the luminaire is covered at the bottom by a partially translucent prism plate and wherein below at least one luminous means is provided at least one opaque cover member which prevents direct light leakage from the bulb directly down.

Luminaires of the aforementioned type have a first portion of light, which is radiated downward and thereby exits through the prismatic plate and another portion of light, which is emitted from the lamp up towards the ceiling and reflected from the ceiling in the room and thus indirectly on a zone to be illuminated falls, for example, a workplace in a room. These lights are also referred to as direct / indirect-radiating.

At one of the DE 203 21 097 U1 known light is a ceiling pendant lamp of the aforementioned type, in which two fluorescent lamps are located in the outer edge regions of the lamp and are covered at the bottom over each closed areas of the lamp housing. In a central area between the two bulbs, the opening of the lamp is covered by a prismatic plate. There are also obliquely upwardly directed to the luminaire center inclined arranged Lichtleitbleche used to direct the proportion of light upwards and to let only light rays at shallower angles downwards through the prismatic plate. The aforementioned luminaire has a very flat luminaire housing and is particularly suitable for illuminating workplaces which have an increased requirement for reflected glare, and display workstations that have a highly tilted or flat screen. An advantage with luminaires of this type is that the light is decoupled so that below the 0 ° -30 ° level the luminance is <1000 cd / m ² . The 0 ° -30 ° plane is the plane at which reflected glare is created by the ray path of the light.

In the case of glare control, a distinction is made according to the standard DIN EN 12464-1 between the limitation of direct glare, in which a minimum screen angle must be observed for all radiation levels, in order to prevent the person from directly looking into the light source at work and avoiding reflected glare Reflexes on reflecting surfaces is caused. For the latter, luminance values above 1000 cd / m ^{2 should} be avoided at beam angles greater than 65 ° to the vertical. However, the standard is still based on conventional screens, which have a slope of only up to 15 ° to the vertical and does not consider more inclined or flat screens.

In the WO 00/50806 A1 a luminaire is described in which two fluorescent lamps are located in the central region of the luminaire and under these a conventional luminaire grid with longitudinal reflectors and cross blades is arranged. Hollow chambers are also provided on both sides of the fluorescent lamps, the underside of which is covered in each case by plate-shaped light distribution elements, through which light emerges downwards. These light distribution elements are intended to diffuse the light diffusely. This luminaire is also a direct / indirect light, as light is also emitted upwards towards the ceiling. The direct light emission from the light source directly downwards is not prevented here. This proportion of light is directed in the known lamp only by the lighting grid in a conventional manner.

Both prior art luminaires are those in which the indirect component of the radiated light results from the fact that the luminaire housing has a light-permeable cover at the top of the luminaire or the luminaire is partially open at the top. In the Normally, this concept can only be realized with luminaires suspended from the ceiling (pendant luminaires).

The object of the present invention is to provide a luminaire of the type mentioned above with a cover on the underside by a prismatic plate, which is based on an alternative lighting concept, has good Entblendungseigenschaften according to the standard and at the high luminance on the prism plate in Be avoided area below the bulb.

The solution to this problem provides a luminaire of the type mentioned above with the characterizing features of the main claim. According to the invention, it is provided that at least one light source is arranged approximately in the central region of the luminaire and below this luminous means is at least one counter reflector, which reflects a part of the luminous flux emitted by the luminous means to a main reflector arranged above the luminous means and light reflected by this main reflector through the prism plate down through the luminaire.

By using the counter-reflector according to the invention, it is possible to ensure that an excessively high luminance on the prism plate below the luminous means is prevented.

The counter-reflector is narrower than the main reflector, whereby a partial current of the light from the bulb falls on the main reflector, but a further partial current can also fall past the counter-reflector down on the prism plate. This can pass through the prism plate and thereby be deflected by refraction according to the specific configuration of the prismatic plate. Part of the light is also reflected by the total reflection at this prism plate and then strikes the main reflector. The width of the counter-reflector is preferably only a fraction of the width of the main reflector.

The shape of the counter-reflector depends inter alia on the arrangement of the lamps in the lamp, for example, their vertical distance from the main reflector and can also vary, for example, depending on the type of luminaire (surface-mounted, recessed, etc.), For example, forms with at least one laterally outer to horizontal downwardly angled or curved legs preferably, if the one or more bulbs are closer to the main reflector, that is further inside the lamp housing and it is then when the (vertical) distance of the bulbs from the main reflector is larger, shapes preferred in which the Counter reflector has at least one laterally outer to the horizontal upwardly angled or curved leg.

If in the present application of an elongated bulb or a longitudinally extending bulb is mentioned, this does not mean that it must be a single bulb. The term "elongated illuminant" is rather to be understood that this may also be an elongated arrangement of several bulbs. The technical nature of the illuminant used is not critical in the context of the present invention. This can be, for example, an arrangement of LEDs, for example in the form of an elongated LED strip, a single fluorescent lamp or even a plurality of fluorescent lamps. In principle, come within the scope of the invention as light bulbs gas discharge lamps, light-emitting diodes, induction lamps, light foils or incandescent lamps into consideration, provided that they have a suitable geometric shape and the desired photometric properties.

The light source, which includes, for example, one or more fluorescent lamps or an array of light emitting diodes, may also be located outside a ceiling (partially) recessed luminaire housing, in particular in recessed luminaires also the bottom of the lamp by a trough-shaped or in cross-section U-shaped prism cover may be covered, which includes the prism plate. In this variant of the luminaire, for example, a lateral region of the trough-shaped or U-shaped prism cover may have a different prism structure than that of the prism plate comprehensive remaining area of the prism cover. This lateral area can be used to deflect a light component that laterally escapes through the trough-like or U-shaped prismatic cover through the prismatic structure towards the ceiling. This proportion of light is then reflected by the ceiling and thus serves as an indirectly emitted light component. In order to create such a laterally exiting light component, it is also possible to form the prismatic cover in this lateral region with a different prismatic profile structure than in the lower region of the prismatic plate, which deflects the incidence of light coming from the luminaire downwards. For example, sawtooth prisms may be arranged in the lateral region.

In the area of the prism plate, for example, primers having a substantially triangular structure with an acute-angled or rectangular profile can be used. The invention is by no means limited to such a prism structure. Rather, it depends on which emission characteristic is desired in each case and the prism structure is adjusted accordingly. For example, a comparatively sharp-edged prism structure has proved to be advantageous for the prism plate since, in this case, directed light guidance through the prism plate is better achieved. The prism structure is preferably aligned either in the lamp longitudinal direction or in the longitudinal direction and in the transverse direction of the lamp axis direction. In the latter case, it may be, for example, a pyramidal prism structure.

Preferably, the main reflector of the luminaire is parabolic in cross section. The usually much narrower counter reflector is seen from the main reflector on the other side of the bulb arranged and can be designed, for example, single or multiple angled or curved.

Preferably, the luminaire according to the invention is a recessed ceiling or ceiling luminaire. If the main reflector is partially open at the top, the lighting principle can also be applied to pendant or floor lamps.

As illuminants are preferably used in lamps of this type elongate fluorescent lamps with smaller diameters or LED strips. The prism structure of the prism plate according to the invention preferably follows the lamp direction.

The prism plate used as a partial lower cover of the lamp could also possibly omit, in particular, if one replaced the prism plate by another cover with similar light scattering and / or light-directing properties, for example by a differently constructed translucent cover.

The features described in the dependent claims relate to preferred developments of the task solution according to the invention. Further advantages of the present invention will become apparent from the following detailed description.

• Figur 1 eine Querschnittansicht durch eine Leuchte gemäß einer ersten alternativen Ausführungsvariante der vorliegenden Erfindung ;
• Figur 1 a eine ähnliche Querschnittansicht durch eine Leuchte gemäß einer alternativen Ausführungsvariante der vorliegenden Erfindung, bei der ein anderes Leuchtmittel verwendet wird;
• Figur 2 eine Querschnittansicht einer dritten etwas abgewandelten Ausführungsvariante einer Leuchte gemäß der vorliegenden Erfindung;
• Figur 3 eine vergrößerte Detailansicht eines Ausschnitts III der in Figur 2 dargestellten Leuchte;
• Figur 4 eine Schnittansicht einer Leuchte des in Figur 1 gezeigten Typs, in der einige exemplarische Lichtstrahlen eingezeichnet sind, um den Strahlengang zu skizzieren;
• Figur 5 eine Schnittansicht einer Leuchte des in Figur 2 gezeigten Typs, in der einige exemplarische Lichtstrahlen eingezeichnet sind, um den Strahlengang zu skizzieren.

Hereinafter, the present invention will be explained in more detail by means of embodiments with reference to the accompanying drawings. Showing:

• FIG. 1 a cross-sectional view through a lamp according to a first alternative embodiment of the present invention;
• FIG. 1 a is a similar cross-sectional view through a luminaire according to an alternative embodiment of the present invention, wherein another illuminant is used;
• FIG. 2 a cross-sectional view of a third slightly modified embodiment of a lamp according to the present invention;
• FIG. 3 an enlarged detail view of a section III of in FIG. 2 illustrated light;
• FIG. 4 a sectional view of a lamp of in FIG. 1 of the type shown, in which some exemplary light beams are drawn in order to sketch the beam path;
• FIG. 5 a sectional view of a lamp of in FIG. 2 shown type in which some exemplary light rays are drawn to sketch the beam path.

First, on the FIG. 1 Reference is made, which shows a schematically simplified cross section through a lamp according to a first possible embodiment of the present invention. These are, for example, a ceiling-mounted luminaire or recessed ceiling luminaire with a rectangular, for example, rectangular elongate comparatively flat luminaire housing 10, in which the usual electrical installation devices such as ballasts, connection devices, etc. are accommodated, which will not be discussed in detail here. In the luminaire housing 10, a substantially parabolic reflector 11 is arranged in the cross-section for the light control, within which there is an elongate fluorescent lamp 12 as the illuminant, whose axis extends in the longitudinal direction of the housing. In this embodiment, the fluorescent lamp is arranged in the upper region of the reflector and is located approximately in the center of the reflector, seen in the transverse direction of the lamp. Towards the bottom, the housing of the luminaire is covered by a prism plate 13, which closes the cavity provided by the reflector and through which the light emerging down passes through. This prism plate 13 is one in which parallel in cross-section approximately triangular prisms extend in the longitudinal direction of the lamp. These triangular prisms can, for example, have a pointed or right angle on the underside.

According to the invention, a counter-reflector 14 is now located underneath the fluorescent lamp 12, by means of which a direct emission of the luminous flux coming from the fluorescent lamp vertically downwards onto the prism plate 13 is avoided, so that an excessively high luminance on the prism plate underneath the lamp is prevented. The latter would be the concern of achieving a directed exit of the light with the desired non-glare Lichtabstrahlcharakteristik run counter. A partial current of the light thus initially falls from the fluorescent lamp 12 to the counter-reflector 14 and is reflected upwards past the lamp onto the main reflector 11. From there, the light is then reflected in a corresponding angle according to the laws of optics, falls on the prism plate 13, there undergoes a deflection by refraction and exits down from the lamp in the desired beam angle.

A partial current of the light falls from the fluorescent lamp 12, starting laterally or upwards and impinges directly on the main reflector 11, where it is reflected in accordance with in the direction of the prism plate, through which it then exits after refraction. Another sub-stream of light falls from the fluorescent lamp 12 laterally down past the counter-reflector 14 and then passes at a shallower angle directly to the prism plate 13, where the light rays are deflected again and emerge down. At steep angles, however, because of the counter-reflector 14 arranged there, the light from the lamp 12 can not fall directly down onto the prism plate 13.

The partial flow which is radiated laterally downwards from the fluorescent lamp 12 at even flatter angles is also reflected at the top side of the prism plate due to the total reflection and thus does not pass directly therethrough. This portion of the light is thus thrown by the reflection on the main reflector 11, there again reflected and exits at a different angle downwards through the prism plate 13.

The shape of the counter-reflector 14 is as you look FIG. 1 can recognize so that a central in the installed state flat approximately horizontal portion 14 a below the fluorescent lamp 12 is provided, to which on both sides in each case laterally at an obtuse angle downwardly angled legs 14 b, 14 c connected. This results in a total for the back reflector 14, a flat tub shape or shape of a bottom open trapezium, which is virtually upside down, so that the broader side is down and open, while the narrower side is formed by the central portion 14 a and relatively close to the fluorescent lamp 12 adjacent. A similar one lighting effect can be achieved if the counter reflector is not bent twice but curved forms with a similar basic shape, but the middle section and the two lateral legs merge into one another in a radius.

FIG. 1 a shows an alternative embodiment of a luminaire with a similar constructive structure as in the variant according to FIG FIG. 1 , wherein here, however, an LED strip 12 a is used as the light source. It can be seen in the cross section only one LED, but there are usually a larger number of such LEDs arranged in a row one behind the other in the longitudinal direction of the lamp, which is preferably a so-called LED bar, which with the entirety of the LEDs also represents an elongated light source. Depending on the design and luminosity, the individual LEDs can have a smaller or larger distance between each other. The LEDs emit their light towards the top of the main reflector 11, from where it is then reflected downwards. The counter reflector prevents the insight into the light bulb through the translucent lower cover.

In this variant according to FIG. 1 a you could also use the counter reflector 14 to cool in the case of excessive heat in the area of the bulbs this. It is possible, for example, to form the counter-reflector with a somewhat greater material thickness or with ribs or the like on the underside in order to create a larger surface and thus dissipate the heat developed by the LEDs via the counter-reflector 14 on which they are mounted.

FIG. 2 , to which reference is made below, shows an alternative embodiment of the luminaire according to the invention, which is mainly used for recessed ceiling luminaires into consideration. Accordingly, the light is in FIG. 2 shown in a built-in a ceiling 15 state. The luminaire housing 10 is received in this variant mainly from the ceiling 15. Here, a cross-section of a trough-shaped or U-shaped prism cover 16 is used, which comprises a horizontal prism plate 13, which may have a similar structure as in the embodiment variant already described above FIG. 1 , The Prism cover 16 is located below (outside) the ceiling 15, in which the lamp is installed.

The main reflector 11 is also parabolic in cross section here. The fluorescent lamp also extends here in the longitudinal direction, wherein the housing is preferably again designed to be rectangular and in FIG. 2 is shown cut in the transverse direction. Unlike the variant described above, however, in the variant according to FIG. 2 arranged the fluorescent lamp 12 at a greater distance from the main reflector 11, so that the fluorescent lamp 12 compared with the variant of FIG. 1 located below, their axis runs here below the built-in ceiling of the lamp and thus slightly below the ceiling 15. This results in other lighting conditions. The counter reflector 14 is also in the variant FIG. 2 below the fluorescent lamp 12, but here has a different shape and the distance of the back reflector 14 from the main reflector 11 is substantially larger, since the distance of the fluorescent lamp 12 from the main reflector 11 is greater. For this reason, the shape of the counter-reflector has been changed. In this case, the counter-reflector in turn has a central horizontal portion, to which, however, laterally angled legs adjoin each other on both sides, which are angled upwards at an obtuse angle. As a result, rays emanating from the fluorescent lamp 12 can only reach the prism plate 13 when they are radiated at even shallower angles. A larger proportion of the light emitted by the lamp is therefore emitted by the counter-reflector 14 in the direction of the main reflector 11 and is then reflected by it in the direction of the prism plate 13.

As in the variant according to FIG. 2 the prism cover 16 has a trough shape or U-shape with lateral regions 17 which, as can be seen, are approximately at the level of the fluorescent lamp 12, a lateral light exit through the lateral regions 17 is possible here. In part, luminous flux components emitted by the fluorescent lamp 12, which impinge on the upper side of the prism plate 13 at shallow angles, are reflected by total reflection at the latter and, when passing through the lateral areas, which are likewise designed as a prism plate are, broken and distracted and then hit the ceiling 15 in the vicinity of the lamp. From the fluorescent lamp 12 directly upwards radiated light rays and those which are emitted by reflection on the counter-reflector upwards, reach the main reflector 11 and are reflected by this and discharged at steeper angles through the prism plate 13 from the lamp downwards ,

The enlarged detail view according to FIG. 3 shows that the side portions 17 are formed as a prism plate having a sawtooth prism profile structure on the outside, whereas the bottom of the horizontal prism plate 13 has a triangular prism profile structure with isosceles triangles. By choosing these different prism structures below the fluorescent lamp or laterally of this, the desired Lichtabstrahlcharakteristik can be supported. The light that passes through the lateral areas with the sawtooth prism profile structure is refracted towards the ceiling.

Due to the U-shape in cross section, the height of the luminaire is according to FIG. 2 slightly larger than in the variant according to FIG. 1 , Depending on the arrangement of the fluorescent lamp in the lamp and its distance from the main reflector, depending on the shape of the counter-reflector 14, cross-sectional shape of the prism cover 13, 16 and prism profile structure of the prism cover 16 and prism plate 13th you can vary the emission characteristics of the lamp according to the invention. In each of the two examples, luminaires with only one fluorescent lamp 12 were shown. As well, of course, you can use several fluorescent lamps, with two lamps can be arranged directly next to each other.

The following is with reference to FIG. 4 the beam path of the light emission of a lamp according to the invention of FIG. 1 illustrated type explained in more detail. There are only a few exemplary light beams shown to the principle of radiation with main reflector 11 and counter reflector to clarify. In fact, the beam path is more complex and not all radiated light components are considered here.

A first light beam 18 is shown, which first of all falls on the main reflector 11 from the lamp 12 at a shallower angle, is reflected there in accordance with the optical laws (angle of incidence = angle of reflection) and then falls on the prism plate 13, where it is refracted and in a deflected angle downwards out of the lamp 10 exits. Another light beam 19 is shown, which is incident from the lamp 12 at a steeper angle on the prism plate 13 and exits through the latter downwardly out of the lamp. On the right, a third light beam 20 is drawn, which first of the lamp 12 falls on the counter reflector 14, is reflected by this at the appropriate angle upwards and then hits the main reflector 11, is reflected at this turn down, then on the Prism plate 13 hits, there is broken and emerges down from the light.

Below will now be with reference to FIG. 5 the beam path of the light emission of a lamp according to the invention of FIG. 2 illustrated type explained in more detail. There are only a few exemplary light beams shown to illustrate the principle of radiation with main reflector 11 and counter reflector 14. In fact, the beam path is more complex and not all radiated light components are considered here. On the left side in the drawing, a light beam 21 is shown, which is initially emitted from the lamp 12 upwards and falls on the main reflector 11, where it is reflected downwards, so that it falls on the prism plate 13, where a refraction With change of direction occurs, so that the beam 21 in the direction shown downwards out of the lamp.

On the left side in the drawing, another light beam 22 is shown, which emerges from the lamp 12, starting at a very shallow angle, so that it exceeds the critical angle of total reflection when hitting the prism plate 13. Consequently, the light beam 22 does not pass through the prism plate 13, but is reflected at this, so that it then impinges on the side portion 17, where there is also a prism, which is designed so that a refraction of this light beam 22 upwards to the ceiling occurs. Such a proportion of the emitted light thus contributes to a brightening of the ceiling area surrounding the luminaire and forms an indirectly emitted light component.

The light beam 23 is directed by the lamp 12 starting downwards and first meets the counter-reflector 14 so that it is deflected towards the top of the main reflector 11. In this he meets at a relatively steep angle and is reflected there accordingly and deflected downwards, where he meets the prism plate 13 and is broken there, finally to exit to the right down out of the lamp.

The light beam 24 on the right side in the drawing emerges at a shallower angle from the lamp 12 to the right, so that it radiates past the counter-reflector 14 and at a relatively shallow angle to the prism plate 13 and reflected there due to the total reflection becomes. This light beam 24 then applies to the above FIG. 2 described lateral area 17 of the prism cover and is there broken and deflected upward to the ceiling.

The light beam 25, which is emitted virtually horizontally from the lamp 12 to the right, strikes the lateral area 17 of the priming cover directly, is broken there and also exits upward toward the ceiling. These embodiments show that the luminaire according to the invention by reflector 11 and counter reflector 14 achieves a light steering, which leads to a desired Lichtabstrahlcharakteristik, on the one hand a directional radiation is achieved with specific glare and on the other hand, a brightening of the ceiling surrounding the ceiling of the room ceiling.

The following is with reference to the FIGS. 4 and 5 another advantage of the lamp according to the invention explained. FIG. 4 shows a variant of the lamp, which is designed as a ceiling-mounted luminaire, in which the housing comprises a base body 26. Within this body 26 is located in the lower inner area an encircling in cross-section U-shaped angle frame 27, the lower horizontal leg 27 a can serve as a support for the prism plate 13.

It is advantageous that the same basic body 26 in principle for a variant of the lamp according to FIG. 5 can use, in which this is designed as a ceiling light. In this case, use is made of a Z-bracket 28 to be mounted on the outside of the vertical part of the main body 26, whose upper horizontal inwardly pointing leg 28 b rests on the base body 26 and whose lower horizontal outwardly pointing leg 28 a engages under the ceiling 15 the lamp is installed. In this way it is possible to use the housing base body 26 of a ceiling-mounted luminaire also for a recessed ceiling luminaire with comparatively simple means and slight changes.

LIST OF REFERENCE NUMBERS

10

luminaire housing

11

main reflector

12

Fluorescent Lamp

12 a

LED

13

prism plate

14

retroreflex

14 a

middle section

14b, c

lateral thighs

15

blanket

16

prism cover

17

lateral areas

18

beam of light

19

beam of light

20

beam of light

21

beam of light

22

beam of light

23

beam of light

24

beam of light

25

beam of light

26

body

27

Winkelrahmen

28

Z-angle

28 a

lower horizontal thigh

28 b

upper horizontal leg

Claims (13)

Luminaire with a luminaire housing, and at least one longitudinally extending elongate luminous means, wherein at least a portion of the luminaire is covered at the bottom by a partially translucent prismatic plate and below at least one illuminant at least one opaque cover is provided which direct light emission from the Prevents bulbs directly down,
characterized in that at least one lighting means (12, 12 a) is arranged approximately in the central region of the luminaire and below this luminous means is at least one counter-reflector (14) which transmits a portion of the luminous flux emitted by the luminous means to a main reflector arranged above the luminous means (11) reflected and that light reflected from this main reflector light through the prism plate (13) passes downwardly out of the lamp. Luminaire according to claim 1,
characterized in that the width of the counter-reflector (14) only a fraction of the width of the main reflector (11) and / or the prism plate (13). Luminaire according to claim 1 or 2,
characterized in that the lighting means (12) has a comparatively small distance from the main reflector (11) and the counter-reflector (14) has at least one laterally outer to the horizontal downwardly angled or curved legs. Luminaire according to one of claims 1 or 2,
characterized in that the lighting means (12) has a comparatively greater distance from the main reflector (11) and the counter reflector (14) has at least one laterally outer to the horizontal upwardly angled or curved legs. Luminaire according to one of claims 1 to 4,
characterized in that it is designed as a surface-mounted luminaire or recessed ceiling luminaire and the main reflector (11) is covered on the underside by a flat prism plate (13). Luminaire according to one of claims 1 to 4,
characterized in that it is designed as a ceiling luminaire and the underside of the lamp is covered by a trough-shaped or in cross-section U-shaped prism cover (16) which comprises the prism plate (13). Luminaire according to one of claims 1 to 6,
characterized in that the main reflector (11) is parabolic in cross-section. Luminaire according to claim 6,
characterized in that a lateral region (17) of the trough-shaped or U-shaped prism cover (16) has a different prismatic structure than the prismatic cover comprising the prismatic plate (13). Luminaire according to one of claims 1 to 8, characterized in that the prism plate (13) has a extending in the lamp longitudinal direction preferably rectangular or acute-angled triangular prism profile structure or extending in the lamp longitudinal direction and transverse direction preferably pyramidal prism profile structure. Luminaire according to claim 8,
characterized in that the lateral region (17) has a sawtooth prism profile structure. Luminaire according to one of claims 1 to 10,
characterized in that the prism plate (13) has a comparatively sharp-edged prism profile structure. Luminaire according to one of claims 6 to 11,
characterized in that the by the trough-like or U-shaped prism cover (16) laterally emerging light component is deflected by the prism structure to the ceiling. Luminaire according to one of claims 1 to 12,
characterized in that a portion of the luminous flux emerging from the fluorescent lamp (12) at the counter-reflector (14) exits the lamp at shallower angles through the prism plate (13), without first reaching the main reflector (11). to fall.

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