JP3130747B2 - Lighting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device which is used, for example, in an image projection display device using a liquid crystal display element and which increases the utilization of light emitted from a light source and makes the illuminance distribution uniform. Things.

[0002]

2. Description of the Related Art Conventionally, a display device has been developed as a device using a lighting device. As a display device,
For example, a liquid crystal projection display device has been developed which uses a liquid crystal display element and irradiates it with an illumination device to form and project an image. Although display elements used in such projection display devices have been miniaturized and miniaturized, further higher luminance is required. Therefore, high brightness of the display element is achieved by forming a micro lens on one surface of the liquid crystal display element.

On the other hand, as an illumination device used in the above-mentioned projection display device, a parabolic mirror is used as a reflecting mirror in order to efficiently collect light emitted from a light source on an illuminated portion such as a liquid crystal display element to obtain a bright image. There are lighting devices having a surface mirror or an elliptical mirror, and lighting devices combining a spherical mirror with a condenser lens. However, with the above-mentioned high performance of the display element, further downsizing and high performance of the lighting device are desired.

One of the conditions for downsizing and improving the performance of a lighting device is that light emitted from the lighting device is efficiently collected in a portion to be illuminated. That is, it is important to increase the light utilization rate.

In general, a method of brightening an illuminated portion having a certain size at a certain distance in an illuminating device includes not only increasing the light utilization rate but also increasing the height of the light source itself of the illuminating device. Output can be considered. In recent years, lamps of metal halide, xenon, halogen and the like have been used as light sources of lighting devices, and the performance such as brightness and the life of such lamps have been improved.

However, if the output of the light source is further increased, the life of the lamp due to heat generation and the like, and the life, size, and ease of use of the device using the lamp are affected. Outputting is becoming difficult. As a result, in order to make the illuminated part brighter, it is necessary to improve the light utilization factor as much as possible in the lighting device as described above. As this method, there is a method in which light reflected from a peripheral portion of a reflecting mirror which cannot be used for irradiation of a portion to be illuminated is condensed by a convex lens and returned to parallel light by a concave lens. Is disclosed.

Another condition for improving the performance of the lighting device is to reduce the uneven brightness of the illuminated portion. This brightness unevenness occurs even when a parabolic mirror is used as the reflector of the lighting device, the light source is an ideal point light source, and the light source is located at the focal point of the parabolic mirror and parallel light can be used. I do. For example, in a liquid crystal projection display device or the like, uneven brightness on an illuminated portion caused by an illumination device used in the above device becomes uneven brightness of an image as it is, and a high-performance projection display device cannot be obtained. That is, in the liquid crystal display element, variations in liquid crystal characteristics occur due to uneven temperature caused by uneven brightness, and an image becomes non-uniform. Alternatively, in a liquid crystal display element using polarized light, photoelastic distortion occurs, and the image becomes non-uniform. Therefore, in order to obtain a high-performance projection display device, an illuminating device with less luminance unevenness is required. As this method, a method of changing the shape of a pixel opening of a liquid crystal display element according to an illuminance distribution and a method of lowering the illuminance of a bright portion using a light attenuating means such as an ND filter are disclosed.

Further, another condition for the downsizing and high performance of the illuminating device is to optimize an angle at which light emitted from the illuminating device is incident on a portion to be illuminated (hereinafter referred to as parallelism). For example, when the illuminated portion is a liquid crystal display element, the liquid crystal characteristics are affected by the degree of parallelism of the light incident on the liquid crystal. Therefore, it is necessary to make light incident on each element as parallel as possible.

Also, when illuminating an optical component such as a dichroic mirror or the like that reflects or disperses light, or a microlens or fiber, the characteristics of each component are affected by the angle of light incident on the component. It is necessary to optimize the parallelism of light according to each component, and in many cases, it is better to enter the light at the same angle as much as possible.

A method including a parabolic mirror and a correction lens for improving the parallelism of light is disclosed in Japanese Patent Laid-Open No. Hei 6-3621. This method uses a correction lens to convert the illuminating light obtained by reflection from the reflector of the illuminating device to parallelism due to the shadow of the lamp electrode and the dropout due to the shape of the reflector. How to

Here, it is known that the above-mentioned method using a condenser lens and a spherical mirror has better parallelism of illumination light than a method using a reflecting mirror such as another parabolic mirror.
This method is described in Optical Symposium Proceedings 1993P7
3-76 "Optical system of compact liquid crystal rear projector"
As described above, the light utilization rate of the illumination system is at most 65%, but the light utilization rate of a parabolic mirror generally used for a projection display device or the like is 70%. But,
Parabolic mirrors have disadvantages. That is, since the light distribution of the illuminating device has a distribution as shown by the curve A in FIG. 4, in order to achieve uniform illumination without uneven brightness, only a narrow area where the illuminance distribution is somewhat uniform can be used. Low utilization.

[0012]

However, in the above-mentioned conventional illuminating device, it is necessary to eliminate the uneven brightness and to make the illuminance distribution uniform, to improve the parallelism and the light utilization of the illuminating light, and to reduce the size. Cannot be satisfied.

For example, in the method disclosed in Japanese Utility Model Application Laid-Open No. 63-124235, since the lenses are arranged so that the illumination area becomes smaller from the incident side to the emission side, the parallelism of light deteriorates. In addition, in a method of changing the shape of the pixel opening of the liquid crystal display element according to the illuminance distribution, or in a method of reducing the illuminance of a bright portion using a light attenuating means such as an ND filter, the light utilization rate is reduced. Further, JP-A-6-36
According to the method including the parabolic mirror and the correction lens disclosed in Japanese Patent Publication No. 21, the illuminance distribution cannot be made uniform,
Only a small area of the light emitted from the reflector is available.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the unevenness in brightness and the degree of parallelism of illumination light in a portion to be illuminated, which has a high light utilization rate from a light source. An object of the present invention is to provide an improved compact and high-performance lighting device.

[0015]

In order to solve the above-mentioned problems, an illuminating device according to a first aspect of the present invention comprises a light source and a reflecting mirror formed of a quadratic curved surface and reflecting light from the light source. For example, a parabolic mirror), and an afocal system that is disposed so that the optical axis coincides with the optical axis of the reflected light in the direction in which the reflected light from the reflecting mirror travels, and emits parallel light, and incident light distance y _i from the optical axis incident on the afocal system, the value of the ratio y _i / y _o and the distance y _o from the optical axis when emitted from the afocal system, from the optical axis Is the distance
It is configured to be smaller and change continuously as it gets closer
There is characterized in Rukoto.

The illumination device according to the second aspect is characterized in that the afocal system includes two Fresnel lenses.

[0017]

According to the structure of the first aspect, the reflecting mirror formed by the quadratic curved surface can obtain a parallel reflected light beam by selecting the position of the light source. However, in this case, the luminous flux density is large near the optical axis, and the luminous flux density becomes coarser as the distance from the optical axis increases. That is, the illuminance is large near the optical axis, and the illuminance is small at a portion far from the optical axis. On the other hand, in an afocal system arranged in the traveling direction of the reflected light from the reflecting mirror, an incident light beam at a distance y _i from the optical axis incident on the afocal system is a light beam emitted from the afocal system. when the distance y _o from the axis, the value of the ratio y _i / y _o is, take different values depending on the position from the optical axis. As a result, the light flux density that was not uniform on the incident side can be made uniform. In addition, light in a portion distant from the optical axis can be used as uniform illumination light, so that the light utilization rate increases.

Further, since the value of the ratio y _i / y _o is smaller as the portion is closer to the optical axis, that is, the afocal system is arranged in a direction in which the illumination area becomes wider near the optical axis.
The parallelism of the illumination light near the optical axis is good. Therefore, in the conventional lighting device, the parallelism near the optical axis is poor due to the shadow of the light source or the like, whereas in the present lighting device, the parallelism near the optical axis can be improved.

According to the second aspect of the present invention, two Fresnel lenses are used in the afocal system. As the Fresnel lens used, the incident side of the afocal system has the function of a concave lens, diffuses incident light with a high luminous flux density near the optical axis, and collimates the light with the Fresnel lens having the convex lens function on the exit side. Can be made uniform.

Alternatively, the Fresnel lens on the incident side of the afocal system has a concave lens function near the optical axis, diffuses incident light having a high luminous flux density near the optical axis, and has a convex lens function at the peripheral portion. Focuses incident light with a lower light flux density than near the axis. On the other hand, the Fresnel lens on the exit side has a convex lens function near the optical axis and a concave lens function near the optical axis, so that the light rays can be made parallel and the distribution state of the light rays can be made uniform.

Further, the Fresnel lenses on the entrance side and the exit side of the afocal system both have the function of a convex lens, once focus parallel incident light, make the distribution state of light rays uniform, and The focused light can be made parallel.

Therefore, the use of the above Fresnel lens corrects the undesirable characteristic that the luminous flux density is large near the optical axis and the luminous flux density decreases as the distance from the optical axis, due to the quadratic curved reflecting mirror. As a result, there is an effect of reducing unevenness in illuminance of the lighting device. In addition, light in a portion distant from the optical axis can be used as uniform illumination light, so that the light utilization rate increases. further,
Since the illumination area near the optical axis is wider on the output side than on the incident side, the parallelism of the illumination light near the optical axis can be improved. The use of the Fresnel lens is effective in reducing the weight of the apparatus and improving the productivity by using a synthetic resin even if the lens becomes large.

[0023]

【Example】

Embodiment 1 FIGS. 1 to 4 show an embodiment of the present invention.
This will be described below.

As shown in FIG. 1, the lighting apparatus according to the present invention comprises a light source 1, a parabolic mirror 2 as a quadratic curved reflecting mirror, and a Fresnel lens 3a and a Fresnel lens 3b as an afocal system 3. Have.

The light source 1 is arranged at a focal point on the optical axis 4 of the parabolic mirror 2. The parabolic mirror 2 is a rotator obtained by rotating a parabola around the optical axis 4 as a coordinate axis,
The inner surface is mirrored. The Fresnel lens 3a and the Fresnel lens 3b are perpendicular to the optical axis 4 and parallel to each other, and are arranged in this order on the side where light is reflected by the parabolic mirror 2 and travels. That is, the Fresnel lens 3a is on the incident side and the Fresnel lens 3b is on the outgoing side.

The Fresnel lens 3a has, for example, a function of a concave lens, and the Fresnel lens 3b has, for example, a function of a convex lens. Alternatively, the Fresnel lens 3a has a concave lens function near the optical axis, diffuses incident light with a high light flux density near the optical axis, has a convex lens function near the optical axis, and has a light flux density smaller than near the optical axis. The light is focused, and the Fresnel lens 3b has a convex lens function near the optical axis and a concave lens function near the optical axis, and makes the light rays parallel and makes the light distribution state uniform. .

The light source 1 is a point light source and has a light emission distribution of equal intensity in all directions. In FIG. 1, light rays emitted from the light source 1 at equal angles are drawn by solid lines. The illuminated part 6 is
For example, a liquid crystal display element is disposed on the opposite side of the light source 1 with the afocal system 3 interposed therebetween.

According to the above configuration, the light emitted from the light source 1 in all directions is reflected by the parabolic mirror 2 and becomes a light beam parallel to the optical axis 4. The parallel light is dense near the optical axis 4 and has a high luminous flux density, and has a low luminous flux density in a peripheral portion away from the optical axis 4. In other words, the area near the optical axis 4 where the light rays are dense is bright, and the peripheral area is dark. Therefore, the light beam incident on the Fresnel lens 3a has its optical axis 4
Light rays are concentrated in the vicinity, and the number is small in the peripheral area.

At this time, the Fresnel lens 3a of the afocal system 3 according to the present invention has a large diffusivity with respect to the light beam incident near the optical axis 4, and the diffusivity of the light increases toward the periphery. It has such a characteristic that it becomes smaller, and dispersed light beams are incident on the incident surface of the Fresnel lens 3b at substantially equal intervals. The light beam incident on the Fresnel lens 3b is emitted as parallel light with uniform illuminance, so that there is no luminance unevenness and the illuminance distribution in the illuminated portion 6 becomes uniform.

Here, among the parallel lights reflected by the parabolic mirror 2, focusing on a specific light ray 3 c whose distance from the optical axis 4 is y _i , the light ray 3 c is on the incident side of the afocal system 3. The light enters the Fresnel lens 3a and is refracted in a direction away from the optical axis 4. That is, the light is diffused with respect to the optical axis 4, enters the emission side Fresnel lens 3 b of the afocal system 3, is refracted, is emitted so as to be parallel to the optical axis 4, and irradiates the illuminated portion 6.

Assuming that the distance of the emitted light beam 3c from the optical axis 4 is a distance y _o , in this illumination device, the distance y _i from the optical axis 4 on the incident side is the distance from the optical axis 4 on the emission side. the ratio y _i / y _o for y _o is different for each portion by the distance from the optical axis 4. That is, it means that the light flux density distribution on the incident side changes on the output side. Also, the ratio y _i
/ _Yo is smaller for light rays closer to the optical axis 4. That is,
The incident-side Fresnel lens 3a of the afocal system 3 largely diffuses light rays in a portion near the optical axis 4, and the degree of diffusion decreases as the distance from the optical axis 4 increases. Part) has a function of converging light rays. On the other hand, the emission side Fresnel lens 3b emits light incident from the Fresnel lens 3a as parallel light. Thereby, the illuminated part 6 is illuminated with uniform illuminance.

Therefore, by using this illumination device for a projection display device, for example, a high-performance projection display device without image unevenness can be obtained. In addition, light in a portion distant from the optical axis 4 can be used as uniform illumination light, so that the light utilization rate is increased.

The above-mentioned afocal system is an optical system that emits parallel light when parallel light enters, and is typically used for a telescope or a viewfinder of a camera. The basic characteristic is indicated by a magnification γ, and the vertical magnification and the horizontal magnification of an object at a finite distance are always constant irrespective of the distance of the object. As shown in FIGS. 3A and 3C, the lenses on which the parallel light is incident are first lenses 13b and 15a,
The lenses that emit parallel light are referred to as second lenses 13a and 15b. Focal point of the first lens 13b · 15a distance f ₁ and the second
It is known that the following relationship holds between the distance d between the lenses and the magnification γ according to the focal length f ₂ of the lenses 13a and 15b.

D = f ₁ −f ₂ or d = f ₁ + f ₂ (1) γ = f ₁ / f ₂ (2) Here, if the sign of the magnification γ is negative, the type is an inverted type. If it becomes positive, it is upright. When this is used as an illumination device, the relationship between the illumination areas E and E ′ changes in proportion to γ ² which is the product of the vertical magnification and the horizontal magnification.

As shown in FIGS. 3B and 3D,
The following relationship exists between the incident angle U of the light beam entering the afocal system and the exit angle U 'of the emitted light beam. However,
Counterclockwise from the optical axis is defined as positive. Here, when γ> 1, the emission angle U ′ increases, and when γ <1, the emission angle U ′ decreases.

Tan U ′ = γ × tan U Therefore, when this is used as a lighting device, γ <
1 That is, if the afocal system is arranged in a direction in which the illumination area is widened from the illumination area E ′ to the illumination area E, the emission angle of the light beam is improved. That is, the parallelism is improved.

When the light source is an ideal point light source,
Light rays near the optical axis in the illuminated part are parallel, but are not parallel because the actual light source part has a finite value.
That is, the minimum value of the actual length of the light source unit is about 3 mm for a metal halide lamp, about 0.6 mm for a xenon lamp, and about 2 mm for a halogen lamp, and light having a certain inclination enters the illuminated part. In particular, for lamps arranged in parallel to the optical axis of a parabolic mirror, elliptical mirror, etc., the shadow of the lamp itself or the shadow of components for arranging the lamp due to the electrodes of the lamp deteriorates the parallelism near the optical axis. I have.

However, in this lighting device, the ratio y _i / y
_The closer the value of _o is to the optical axis 4, the smaller the value is, that is, since the afocal system 3 is arranged in a direction in which the illumination area becomes wider near the optical axis 4, the parallelism of the illumination light near the optical axis 4 is better. . Therefore, in the conventional lighting device, the parallelism near the optical axis is poor due to the shadow of the light source or the like, whereas in the present lighting device, the parallelism near the optical axis 4 can be improved.

On the other hand, at a position distant from the optical axis 4, as shown in FIG.
Is used. Here, since FIG. 1 shows an ideal case, the light rays of the parabolic mirror 2 are parallel. But,
Since they are not actually parallel, the degree of parallelism at a position distant from the optical axis 4 deteriorates.

Therefore, if all the light from the parabolic mirror 2 is made to widen the illumination area via the afocal system 3, that is, if the parabolic mirror 2 is made smaller with respect to the illuminated part 6, The degree of parallelism of light rays near the outermost part of the parabolic mirror 2 is also improved. As a result, the parallelism with respect to the illuminated portion 6 is improved not only in the vicinity of the optical axis 4 but also overall.

Also, the parabolic mirror 2 is
Since the size can be reduced, the size of the device can be reduced. Furthermore, the reflected light at the outermost part of the parabolic mirror 2 which could not be used conventionally can be used as light having uniform illuminance and good parallelism, which leads to an improvement in light utilization.

An example of a method of determining the curvature of the lens surface of the Fresnel lens of the afocal system 3 according to the present invention will be described below.

The illuminance distribution of the light beam reflected by the parabolic mirror 2 and incident on the Fresnel lens 3a of the afocal system 3 is, for example, a curve A as shown in FIG. The illuminance distribution emitted from the Fresnel lens 3b and required for the illuminated portion 6 is, for example, a curve B. Curves A and B shown in this figure are graphs of illuminance values on a plane orthogonal to the optical axis 4, and a three-dimensional curve having the optical axis 4 as a rotation axis is incident on the Fresnel lens 3a. Of the illuminance distribution.

In the curve A, a minute width Δy is set in the Y direction perpendicular to the optical axis 4, for example, a lens pitch of about 0.3 mm at which a Fresnel lens can be formed, and integration is performed in the X direction. Further, the volume of the rotating body having the optical axis 4 as the rotation axis is obtained for the integrated region. The minute width Δy ′, that is, the lens pitch, is determined so that this volume is equal to the volume obtained from the minute width Δy ′ of the curve B that is the desired illuminance distribution. The same calculation is performed for a minute width in the ± Y direction sequentially from a position adjacent to the optical axis 4.

Thus, the magnification γ at each position of the lens
Is obtained for each corresponding pitch. Therefore, assuming that the distance between the Fresnel lens 3a and the Fresnel lens 3b is d, the afocal system 3 is obtained from the above equations (1) and (2).
The shape of the lens blade surface at each location of the Fresnel lens is determined, and the lens surface shape of the Fresnel lens of the present invention can be determined. There is also a method of obtaining the shape of each lens blade surface from the law of refraction using the refractive index of the Fresnel lens material based on the distance d and the magnification γ.

The illuminance distribution shown by the curve A in FIG. 4 may be obtained by simulation such as ray tracing, or may be obtained by using a light source and a parabolic mirror which are actually used. . In an actual light source, illuminance unevenness such as a shadow of the light source itself, a shadow of an electrode part, and a shadow of a part where a parabolic mirror cannot be formed due to attachment of the light source may occur. It is possible to eliminate it.

[Embodiment 2] Next, as shown in FIG. 2, a case is considered in which all the afocal systems 5 used in the illumination device are Fresnel convex lenses. The incident side from the parabolic mirror 2 is a Fresnel convex lens 5a, and the exit side is a Fresnel convex lens 5b. The components other than the afocal system 5 are the same as those in the first embodiment, and the same member numbers are added, and the description thereof is omitted.

Also in this case, focusing on a specific incident light beam 5c at a distance y _i from the optical axis 4, the light beam 5c enters the Fresnel convex lens 5a on the incident side of the afocal system 5 and intersects the optical axis 4. And is incident on the Fresnel convex lens 5 b on the emission side of the afocal system 5, refracted, emitted parallel to the optical axis 4, and illuminates the illuminated part 6.

Assuming that the distance of the emitted light beam 5c from the optical axis 4 is y _o , in the apparatus of the present invention, the distance y _i from the optical axis 4 on the incident side is the distance from the optical axis 4 on the emission side. y _o for the ratio y _i / y _o is different for each portion by the distance from the optical axis 4, and small enough light portion close to the optical axis 4. In other words, the Fresnel convex lens 5a on the incident side of the afocal system 5 has such a characteristic that the focal length of the portion closer to the optical axis 4 is shortened, and the focal distance is longer for the portion of the light beam farther from the optical axis 4. On the other hand, the emission side Fresnel convex lens 5b emits the light incident from the Fresnel convex lens 5a as parallel light. In this case, the Fresnel convex lens 5b has such a characteristic that the focal length of the portion near the optical axis 4 is increased and the focal length of the portion far from the optical axis 4 is shortened.

Thus, similarly to the first embodiment, the illuminated portion 6 is illuminated with a uniform illuminance. Further, the degree of parallelism near the optical axis 4 is good. The determination of the lens surface shape of each of the Fresnel convex lenses 5a and 5b may be performed according to the first embodiment.

Since the illumination device has a high degree of parallelism of illumination light, it can be used in a projection display device including a dichroic mirror or the like for reflecting and dispersing light, or a projection display device including an optical component such as a microlens or a fiber. It can be used without reducing light utilization. Further, by separating a light source light having a white color or a mixture of two or more wavelengths into two or more light beams using a dichroic mirror or the like, and making this separated light incident on a single liquid crystal display element at different angles,
The micro-lens formed on the liquid crystal display element condenses the light rays at different places, and by forming picture elements of the liquid crystal display element to correspond to these different places, it can also be applied to the illumination system that performs color display it can.

The illumination device is not limited to a transmission type projection display device, but may be used in a reflection type projection display device. In this case, the same effect can be obtained.

The present illuminating device is not limited to the image display, but may be used as an illuminating device such as an exposure device. In an illumination system of an exposure apparatus, uneven brightness of a portion to be exposed affects variations in exposure time and uneven exposure.
In addition, if the parallelism of the illumination light on the exposed portion is good, accurate exposure can be performed without blurring the mask image in close contact exposure in which the mask is closely placed. Therefore, the present illumination device is also effective as an exposure illumination system.

[0054]

As described above, the lighting device according to the first aspect of the present invention has a light source, a reflecting mirror formed of a quadratic curved surface and reflecting light from the light source, and a reflecting mirror from the reflecting mirror. An afocal system that emits parallel light, with the optical axis aligned with the optical axis of the reflected light in the direction in which the light travels, and a distance y _i from the optical axis incident on the afocal system. The value of the ratio y _i / y _o between the incident ray and the distance y _o from the optical axis when emitted from the afocal system is the distance from the optical axis.
Is smaller, and changes continuously .

As a result, the value of the ratio y _i / y _o can take different values depending on the distance from the optical axis. That is, the luminous flux density that was not uniform on the incident side of the afocal system can be made uniform on the emission side of the afocal system. Therefore, it is possible to irradiate the illuminated portion with illumination light without uneven illumination. In addition, since light in a portion away from the optical axis can be used with uniform illuminance, the light utilization rate is increased. Furthermore, by arranging the afocal system in the direction in which the illumination area spreads near the optical axis, the parallelism near the optical axis is improved. In addition, even if the size of the reflecting mirror is reduced, illumination light with uniform illuminance and good parallelism can be obtained, so that there is an effect that the apparatus can be downsized.

The illumination device according to the second aspect of the present invention has a configuration in which the afocal system includes two Fresnel lenses.

Thus, the light beams are diffused at different diffusion degrees or focused at different convergence degrees depending on the distance from the optical axis by the incident-side Fresnel lens, and are uniformly formed on the emission-side Fresnel lens. Light can be incident at a light flux density, and illumination light with uniform illuminance can be obtained in the illuminated portion. As a result, in addition to the effect of the configuration of claim 1, if the lens is made of a synthetic resin, the weight can be reduced and the mass productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a lighting device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a lighting device according to another embodiment of the present invention.

FIGS. 3A to 3D are explanatory diagrams showing a basic afocal system.

FIG. 4 is an explanatory diagram showing an illuminance distribution of a light beam incident on an afocal system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Parabolic mirror (reflection mirror) 3 Afocal system 3a Fresnel lens 3b Fresnel lens 4 Optical axis 5 Afocal system 5a Fresnel convex lens 5b Fresnel convex lens

Continuation of the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 19/00 G02B 21/06 G02B 23/26 F21V 8/00

Claims (2)

(57) [Claims] 1. A light source, a reflecting mirror formed of a quadratic curved surface and reflecting light from the light source, and an optical axis extending in a direction in which the reflected light from the reflecting mirror travels, the optical axis being set to the optical axis of the reflected light An afocal system that emits parallel light, and an incident light ray at a distance _yi from the optical axis that enters the afocal system, and an afocal system that emits parallel light. distance y value of the ratio y _i / y _o with _o is, as the distance from the optical axis is close small and is configured to continuously vary
Which do illumination device according to claim Rukoto. 2. The lighting device according to claim 1, wherein said afocal system is constituted by two Fresnel lenses.