JPH0915044A - Illuminance sensor - Google Patents

Abstract

PURPOSE: To make it possible to reduce the influence of the difference of the reflectivity of the lower surface of an illuminance sensor by providing a photoreceiving sensitivity regulating means for increasing the decrease of the sensitivity of the sensor near the peak as compared with the decrease of the photoreceiving sensitivity of the other sensor, thereby making the photoreceiving sensitivity characteristics uniform up to the periphery. CONSTITUTION: As photoreceiving sensitivity regulating means, for example, a shielding plate S having smaller photoreceiving area than that of a photoreceiving surface is disposed at a distance (d) in front of a photodiode PD. When a light is incident from the direction deviated at an incident angle θ from the front surface on the photoreceiving surface of the photodiode PD, the more the area capable of photoreceiving, the greater the incident angle θ as shown by a shade J, and the change of the output of a photoreceiving sensor due to the angle θ can be reduced. The distance (d) between the photoreceiving surface and the plate S is altered by using the characteristics, thereby regulationg the photoreceiving sensitivity. Thus, the influence directly below the sensor is reduced, and it can be set so that the photoreceiving sensitivity becomes the same as each other up to about the incident angle θ=±30 degrees.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting reflected light from a surface to be illuminated and controlling illumination so that the illuminance of the surface to be illuminated is constant according to the detected value. The present invention relates to an illuminance sensor that detects

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 32, there is known an illuminating device in which a light receiving sensor S is arranged on the ceiling of an illuminating space and which detects reflected light from a surface to be illuminated to control the illumination. FIG.
3 is a block diagram of this type of illuminating device, in which the light receiving sensor S detects external light, and the lighting device T adjusts the dimming state of the lamp LA according to the increase or decrease in the detected external light.
Alternatively, the lamp LA may be used to correct the initial illuminance of the lamp LA.
The energy saving is achieved by correcting the output reduction due to the deterioration. As the structure of the light receiving sensor S, a light receiving element such as a photodiode is used as it is, a diffusion plate is provided on the front surface of the light receiving element, or a lens system for converging reflected light is provided on the front surface of the light receiving element. , The reflected light was detected.

FIG. 34 shows the characteristic of the ratio of the light receiving sensitivity of the reflected light from the illuminated surface viewed from the light receiving sensor S arranged on the ceiling depending on the angle θ. In the figure, the light receiving sensitivity immediately below the light receiving sensor S is set to 100%, and the light receiving sensitivity ratio according to the angle θ is shown. As for the light receiving sensitivity ratio of the single element, as shown in the characteristic A of FIG. 34, the sensitivity immediately below the element (0 degree) is the highest, and is a curve of cos ⁴ θ. Further, when the lens system is provided in front of the light receiving element, the light receiving sensitivity ratio is shown in FIG.
The characteristics B and C are obtained, and the light receiving sensitivity ratio in the vicinity immediately below the element becomes higher than that of the element alone. The shape of the lens system for obtaining the characteristics B and C is shown in FIGS. In the figure, PD is a light receiving element formed of a photodiode, and L is a lens. Even when the light receiving element is provided with the diffuser plate, the light receiving sensitivity ratio becomes a curve of cos ³ θ, and the sensitivity immediately below the element is high almost as in the case of the single element.

The light receiving sensor receives the reflected light from the surface to be illuminated, integrates the product of the light receiving sensitivity and the light receiving amount at each incident angle in the entire light receiving range, and outputs a light receiving signal. Then, the lamp output is controlled by the lighting device so that the received light signal becomes a predetermined level. That is, when the light receiving signal of the light receiving sensor is above a predetermined level or below a predetermined level, the lamp output is dimmed according to the level. Therefore, the lighting device is controlled according to the light reception signal of the light receiving sensor, and the lighting device maintains the predetermined illuminance within the predetermined range.

[0005]

In a conventional light-receiving sensor, when the amount of light reflected from the lower surface which is incident on the sensor is controlled to be constant, the light-receiving element has a high light-receiving sensitivity ratio and is located in the vicinity directly below. When an object having a different reflectance (for example, a white paper having a high reflectance or a black paper having a low reflectance) comes, a drastic change occurs such that the reflected light amount extremely increases or decreases. Therefore, if the lamp output is controlled so that the amount of reflected light is constant, the dimming state of the lamp varies. In addition, if the dimming ratio of the lamp changes depending on the state directly below the sensor, the surrounding visual environment changes, which causes an uncomfortable feeling.

The present invention has been made in view of the above points, and has a flat light receiving sensitivity characteristic of the light receiving sensor, which can detect not only directly below the sensor but also to the periphery.
The purpose is to reduce the influence of the difference in the reflectance of the lower surface of the sensor as much as possible. Further, by obtaining an average illuminated surface illuminance by the amount of light reflected on the illuminated surface of the lamp, it is an object to control the illuminated surface illuminance to be constant and to maintain the visual environment. It is a thing.

[0007]

According to the present invention, a reflected light from a surface to be illuminated is received, and a product of a light receiving sensitivity and a light receiving amount at each incident angle is integrated over the entire light receiving range to obtain a light receiving signal. The output illuminance sensor is characterized by comprising light-receiving sensitivity adjusting means for making a decrease in the vicinity of the peak of the light-receiving sensitivity larger than that of other light-receiving sensitivities.
Specifically, for example, a light shielding plate smaller than the light receiving area is arranged on the light receiving surface, or an optical multilayer film bandpass filter (for example, TiO ₂ and SiO ₂₎ for correcting the incident angle dependency of the light receiving sensitivity. A multilayer film) and a filter system using colored glass. Here, the center wavelength of the filter system is preferably about 600 nm.
In addition, in order to correct the incident angle dependence of the light receiving sensitivity, a filter having a plurality of transmittances, for example, a filter in which the thickness of the aluminum vapor deposition film is made thinner or thicker toward the central portion may be arranged on the light receiving surface. good. Further, a prism having a triangular cross section with the apex facing the sensor direction in the cross section including the central axis of the optical system may be arranged on the optical axis of the light receiving sensor.

[0008]

When the light receiving sensitivity itself of the light receiving sensor is input to the lighting device, when an object with high reflectance or a low reflectance (white, black paper, etc.) is detected in a part near the peak of the sensitivity, The detection amount of the light receiving sensor changes greatly. In this way, when the signal that greatly changes is sent to the lighting device, the lighting device is controlled to maintain the predetermined illuminance, and the illuminance of the entire control range controlled by the light receiving sensor increases or decreases. Therefore, the entire illuminance changes depending on a part of the object having a high reflectance, which adversely affects the visual environment including the surroundings. That is,
When the signals detected within the detection range are integrated and reach a predetermined level or more, dimming control is performed according to the level. If the detection sensitivity is high, the amount of integration of the detection signal will increase even if only a small white sheet having a high reflectance enters only that portion, and the overall illuminance will change. In view of this, the present invention has a light-receiving sensitivity adjusting means for making the decrease in the vicinity of the peak of the light-receiving sensitivity larger than that of other light-receiving sensitivities, and the irradiated surface within a predetermined range is substantially constant at the predetermined detection sensitivity. With this setting, even if an object with a high reflectance or an object with a low reflectance intrudes, it cannot be detected substantially, and the overall illuminance does not change, and the visual environment including the surroundings is not adversely affected. It is possible to prevent giving.

[0009]

FIG. 1 shows the configuration of a control system according to an embodiment of the present invention.
The operation is shown in FIG. In the control system of this embodiment, the photodiode PD used as the illuminance detecting element of the light receiving sensor
The photoelectric conversion signal by the operational amplifier OP and resistors R ₁ and R
It is amplified by the light receiving amplifier configured in ₂ , and the light receiving signal is obtained. FIG. 3 shows the relationship between the output voltage of the operational amplifier OP and the illuminance on the element surface of the photodiode PD. The output voltage of the operational amplifier OP is input to the terminal Pi of the microcomputer μC and converted into a digital value by the built-in A / D converter. In addition, microcomputer μC
Outputs the dimming signal with variable duty from the built-in PWM circuit via the output terminal Po. Based on the pulse width of the variable dimming signal, the ballast B can raise or lower the output of the lamp LA for dimming.
The photodiode PD looks at the amount of reflected light on the lower surface than the ceiling surface. The illuminance of the illuminated surface and the surface illuminance of the photodiode PD have a correlation as shown in FIG. 4 as long as there is no change in the reflectance of the lower surface. Therefore, the output voltage of the operational amplifier OP with respect to the surface illuminance of the photodiode PD when the desired illuminated surface illuminance is used as a reference.

As shown in the flow chart of FIG. 2, the microcomputer μC has a built-in A which holds the output voltage of the operational amplifier OP (that is, the detection signal of the amount of reflected light on the lower surface).
Read with the / D converter. Using the output voltage of the operational amplifier OP with respect to the preset illuminance of the illuminated surface as a reference voltage,
When the voltage is equal to the reference voltage, the output of the lamp LA is not changed, when it is high, the output of the lamp LA is lowered, and when it is low, feedback control is performed so that the output of the lamp LA is increased, and the illumination surface illuminance is kept constant. Control to be.

Here, the light receiving sensor of the present invention is provided with a light receiving sensitivity adjusting means for making the decrease in the vicinity of the peak of the light receiving sensitivity larger than that of other light receiving sensitivities, as shown in each of the following embodiments. There is. Using such a light receiving sensor, the illuminance of the illuminated surface is controlled to be kept constant, as shown in FIG.
The light receiving ranges Za and Z of the light receiving sensor suitable for each lighting such as the task lighting shown in FIG. 5 and the ambient lighting shown in FIG.
By determining b and making the sensitivity of the light receiving sensor flat within the light receiving range regardless of the incident angle, the change of the output of the light receiving sensor is suppressed against the partial change of the reflectance of the lower surface in the illumination range of the illumination. be able to. In such a control system, it is an object of the present invention to control the illumination surface illuminance to be constant regardless of the difference in reflectance of a part of the lower surface.

First, an embodiment in which a light shielding plate is used as the light receiving sensitivity adjusting means will be described. In this embodiment, as shown in FIG. 6, a light shielding plate S is installed in front of a portion of the light receiving sensor capable of detecting light (light receiving surface of the photodiode PD) with a distance d. As shown in FIG. 7, when the angle of the light incident on the light receiving sensor is 0 degree, the light receiving area (the light receiving surface of the photodiode) is the light shielding plate S as shown by the hatched portion J in FIG. The size of the unobstructed area. As shown in FIG.
When the light is incident from the deviated direction, the light-receivable area is expanded as shown by the hatched portion J in FIG. As the incident angle θ increases, the area where light can be received increases. Since the larger the light detecting area of the photodiode PD, the larger the generated current, the current also changes according to the change of the light receiving area due to the change of the incident angle, and the output of the light receiving sensor also changes. Generally, as the incident angle θ increases, the distance from the lower surface to the light receiving sensor increases and the light reaching distance increases, so the light becomes weak. However, in this embodiment,
Since the light receiving area of the photodiode PD becomes large, the change in the output of the light receiving sensor due to the incident angle θ can be reduced. By using this characteristic, the size of the light receiving surface, the size of the light shielding plate S, and the distance d between the light receiving surface and the light shielding plate S can be changed to adjust the light receiving range and the light receiving sensitivity with respect to the incident angle.

For example, the influence immediately below is reduced, and θ = ± 30
When it is desired to obtain a photosensitivity higher than the photosensitivity immediately below the light-sensing area, the light-receiving area is 9 × 9 mm and the light-shielding plate S has an area of 7.5.
If the distance d between the light shielding plate S and the light receiving surface is set to 10 mm, the light receiving sensitivity ratio with respect to the incident angle θ is as shown in the graph a of FIG. 11. Similarly, when the size of the light shielding plate S is changed, for example, the light receiving area is 9 × 9 mm, the area of the light shielding plate S is 6 × 6 mm, and the distance d between the light shielding plate S and the light receiving surface is 1.
The light receiving sensitivity ratio when 0 mm is shown in the graph b of FIG. In the figure, c is the light receiving sensitivity ratio of the light receiving element alone.

As described above, by installing the light shielding plate S, it is possible to reduce the influence directly below the sensor and to set the light receiving sensitivity to be almost the same until the incident angle θ = ± 30 degrees. Therefore, it is possible to obtain a substantially constant light-receiving sensor output regardless of the difference in reflectance at a part of the lower surface.
When the lamp output is controlled so that the amount of reflected light becomes constant by using the light receiving sensor having such a structure, it is possible to control the illuminance of the irradiated surface to be constant regardless of the difference in the reflectance of a part of the lower surface. .

Next, an embodiment using a filter system in which a colored glass and an optical multilayer film bandpass filter are used together will be described. In this embodiment, a colored glass filter (equivalent to Y50) that transmits visible light of 500 nm or more and 600 n
An optical multilayer film bandpass filter having a center wavelength of m is also used. The sensitivity of the silicon photodiode PD has a peak near 560 nm, and if it exceeds this wavelength, the sensitivity decreases. In addition, the multilayer bandpass filter has an incident angle dependency, and when the incident angle deviates from 0 degree,
Shift to the shorter wavelength side. Therefore, the angular dependence of sensitivity can be corrected by using a multilayer film bandpass filter having a center wavelength of more than 560 nm and a colored glass filter (equivalent to Y50) that transmits visible light of 500 nm or more. As a result, the sensitivity at 30 ° incidence can be improved by about 20% as compared with that at 0 ° incidence.

In order to manufacture a bandpass filter made of an optical multilayer film, as shown in FIG. 12, a multilayer film H, L, H, L, ... Is formed on a glass substrate G by a vacuum deposition method. . H is TiO ₂ (thickness t = 600), L is Si
O ₂ (thickness t = 600). Here, t means an optical film thickness. As a result, a bandpass filter having a center wavelength of 600 nm is constructed. As the size of the glass substrate G, for example, a 15 mm square glass substrate is used.

As shown in FIG. 13, the sensor system has a structure in which a silicon photodiode PD, a colored glass filter Cf, and a multilayer film bandpass filter M on a glass substrate G are stacked, as shown in FIG. Thus, the multilayer film bandpass filter M may be formed directly on the colored glass filter Cf. The characteristics of the filter thus manufactured are shown in FIGS. FIG. 15 shows a photosensitivity characteristic when only the multilayer film bandpass filter M is superposed on the light receiving surface of the photodiode PD (see FIG. 17), and FIG. 16 shows the multilayer film bandpass filter M and the colored glass filter Cf as a photo. It is the light receiving sensitivity characteristic when it is superposed on the light receiving surface of the diode PD (see FIG. 14).
In the figure, the broken line is the sensitivity of the photodiode PD, and the solid line is 0.
Degrees and chain lines show sensitivity to an incident angle of 30 degrees.

Here, the silicon photodiode PD has a maximum sensitivity in the vicinity of 560 nm, and if the wavelength exceeds this wavelength, the sensitivity decreases. Further, the multilayer bandpass filter (center wavelength 600 nm) exhibits an incident angle dependency, and when the incident angle deviates from 0 degree, it shifts to the short wavelength side, and when it becomes 30 degrees, it has a central wavelength at 560 nm. Therefore, the filter of the present method decreases the sensitivity as the incident angle approaches 0 degree, and can correct the incident angle dependency within the incident angle of 30 degrees of the sensor system.

FIG. 18 shows the dependency of the sensitivity of the entire sensor system of this embodiment on the light incident angle, where F is the case with a filter and N is the case without a filter. The sensitivity at 0 degree incidence was able to be suppressed by about 20% compared to at 30 degree incidence. As a result, the sensitivity distribution with respect to the incident angle could be made uniform within a range of ± about 8% in the incident angle range of ± 30 degrees.

Next, an embodiment using a transmittance distribution filter using an aluminum vapor deposition film will be described. In this embodiment, a transmittance adjusting filter made of a film thickness distribution type aluminum vapor deposition film is installed in front of the sensor so that the transmittance increases from the central portion to the peripheral portion. As shown in FIG. 19, by gradually reducing the aluminum deposition amount in a concentric manner from the center, the light transmittance increases from the center to the outside. FIG. 20 shows a sectional shape.
The aluminum vapor deposition film A has a maximum thickness of 400 nm, and a transparent protective film H is provided on the surface. In this way, an axially symmetric transmittance distribution can be created arbitrarily, and by installing such a transmittance distribution type filter on the front surface of the optical sensor, the loss amount of the light quantity incident in the oblique direction can be suppressed to a low level. You can

The film thickness (center maximum value) of the aluminum vapor deposition film A is 2
When the angular distribution of sensitivity was corrected using a filter of 00 nm, as shown in FIG. 21, it was possible to make the sensitivity uniform within a range of ± 60% in the region of an incident angle of ± 60 degrees. In the figure, F indicates the light receiving sensitivity with a filter and N shows the light receiving sensitivity without a filter.

Next, an embodiment for correcting the incident angle dependency using a prism will be described. When light is incident on a dielectric such as transparent plastic or glass, reflection and refraction occur at the interface with air. The reflectance and the refraction angle are determined by the ratio of the refraction indexes of the dielectric and air and the incident angle of light on the interface (Snell's law). In particular, when the light travels from the dielectric body to the air, the light is totally reflected when the incident angle β at the interface satisfies the following expression. At this time, the right side of the following formula is called a critical angle.

Β ≧ Arcsin (1 / n) where n is the refractive index of the dielectric. This property is used to provide a prism whose transmittance changes with incident angle. As described above, the basic object of the present invention is to provide a light-receiving sensitivity adjusting means in which the light transmittance decreases as the incident angle θ of light on the light-receiving element becomes smaller. Now, let the base angle α of the prism be the critical angle Arc of the prism material.
Consider the case where it is equal to sin (1 / n). At this time, the light incident at the incident angle θ = 0 is totally reflected as shown in FIG. On the other hand, when θ ≠ 0, as shown in FIG. 23, a part is totally reflected and the rest is transmitted, and the light receiving element PD
To reach. In the figure, the light incident on the left side a of the prism slope is totally reflected because β ₁ is larger than the critical angle,
It does not reach the light receiving element PD. On the other hand, the light incident on the right side b of the prism slope is not totally reflected because β ₂ is smaller than the critical angle and reaches the light receiving element PD. As is clear from the figure, as θ increases, the light incident on the left side a of the prism slope, that is, the light that does not reach the light receiving element PD, decreases. Therefore, in such a prism, θ = 0
Therefore, the transmittance is 0, and the transmittance increases as θ increases. In the case of implementing the present invention, a certain degree of transmittance is required even when θ = 0, so in practice, this basic configuration is modified as follows so that some light that is not totally reflected is generated. Need to The base angle α is slightly shifted from the critical angle β. When confirmed experimentally, it was favorable within β ± 10 degrees. The triangular vertex of the cross section is deformed into a flat or curved shape.

This embodiment is shown in FIGS. A cone or a polygonal pyramid (a quadrangular pyramid in the illustrated example) as shown in FIG. 24 is used as the triangular shape of the cross section. Prism P
As shown in FIG. 25, a flat portion 1 or a corner R portion 2 may be provided near the apex of the. However, FIG.
As shown in FIG. 5, the area of the flat portion 1 or the corner R portion 2 must be 70% or less of the entire area when viewed from the vertex direction. As the material of the prism P, for example,
Acrylic resin, glass, polycarbonate resin, etc. are used.

When the gap in the thickness direction of the prism is large, a reflecting plate R surrounding the prism P may be installed as shown in FIG. 27 or 28. An assembly drawing of the structure of FIG. 28 is shown in FIG. In this embodiment, the prism P is a truncated cone having a flat portion, and a cylindrical reflector R installed so as to surround the prism P is used.

As shown in FIGS. 30 and 31, a large number of prisms P may be arranged in an array. In this embodiment, a large number of small quadrangular pyramid prisms P are arranged.

[0027]

According to the first aspect of the present invention, it is possible to obtain an accurate amount of reflected light, that is, an average illuminance on the illuminated surface regardless of the partial reflectance of the illuminated surface. Therefore, by using the illuminance sensor of the present invention, the illuminance of the illuminated surface can be controlled to be constant, and there is an effect that the energy saving effect can be improved while maintaining the visual environment.

According to the second or third aspect of the invention, the incident angle dependency of the light receiving sensitivity can be corrected simply by providing the light shielding plate on the light receiving surface, so that there is an effect that it can be realized at an extremely low cost. According to the invention of claims 4 to 8,
The incident angle dependency is corrected by the combination of the optical multilayer film bandpass filter and the colored glass filter.
According to the invention of claims 9 to 12, the filter having a plurality of transmittances for correcting the incident angle dependency of the light receiving sensor sensitivity is provided on the light receiving surface by controlling the thickness of the aluminum vapor deposition film or dot printing. And further claims 13 to 15.
According to the invention, since the incident angle dependency of the light receiving sensor sensitivity is corrected by the prism, there is an effect that a desired illuminance detection range can be set by appropriately designing the optical system.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a lighting device using an illuminance sensor of the present invention.

FIG. 2 is a flowchart showing an operation of the above illumination device.

FIG. 3 is a characteristic diagram of a light receiving circuit of the illuminance sensor of the present invention.

FIG. 4 is a diagram showing a relationship between a light receiving surface illuminance and an illuminated surface illuminance of the illuminance sensor of the present invention.

FIG. 5 is an explanatory diagram of an illuminance detection range by the illuminance sensor of the present invention.

FIG. 6 is a side view showing the configuration of the invention of claim 2;

FIG. 7 is a side view showing the operation of the invention of claim 2;

FIG. 8 is a plan view showing a light-receivable area at the time of vertical incidence according to the second aspect of the invention.

FIG. 9 is a side view showing a light-receiving surface of the invention of claim 2 when obliquely incident.

FIG. 10 is a plan view showing a receivable area upon oblique incidence according to the invention of claim 2;

FIG. 11 is a characteristic diagram showing a light receiving sensitivity distribution of the illuminance sensor according to the invention of claim 2.

FIG. 12 is a cross-sectional view showing the structure of an optical multilayer film used in the invention of claim 4.

FIG. 13 is a sectional view showing a first embodiment of the illuminance sensor according to claim 4;

FIG. 14 is a cross-sectional view showing a second embodiment of the illuminance sensor according to claim 4;

FIG. 15 is a spectral sensitivity characteristic diagram of the illuminance sensor of claim 4 when there is no colored glass.

FIG. 16 is a spectral sensitivity characteristic diagram of the illuminance sensor according to claim 4 when there is colored glass.

FIG. 17 is a sectional view showing the structure of the illuminance sensor of claim 4 from which the colored glass is removed.

FIG. 18 is a diagram showing a sensitivity distribution of the illuminance sensor according to claim 4;

FIG. 19 is a plan view of the filter according to claim 11;

FIG. 20 is a sectional view of the filter of claim 11;

FIG. 21 is a characteristic diagram of the filter of claim 11;

FIG. 22 is an explanatory diagram of the operation at the time of vertical incidence in the invention of claim 13;

FIG. 23 is an explanatory diagram of the operation at the time of oblique incidence in the invention of claim 13;

FIG. 24 is a perspective view showing the outer appearance of the prism according to claim 13;

FIG. 25 is a perspective view showing another configuration example of the prism according to claim 13;

FIG. 26 is a plan view showing another configuration example of the prism according to claim 13;

FIG. 27 is a sectional view showing a combination of a prism and a reflecting plate according to claim 13;

FIG. 28 is a cross-sectional view showing a combination of the prism and the reflecting plate according to claim 13;

FIG. 29 is a perspective view showing a combination of a prism and a reflecting plate according to claim 13;

FIG. 30 is a cross-sectional view of an array-shaped prism according to claim 15.

FIG. 31 is a perspective view of an array-shaped prism according to claim 15;

FIG. 32 is an explanatory diagram showing an installation situation of a conventional illuminance sensor.

FIG. 33 is a block diagram of a conventional lighting device.

FIG. 34 is a characteristic diagram of a conventional illuminance sensor.

FIG. 35 is a side view showing a configuration example of a conventional illuminance sensor.

FIG. 36 is a side view showing another configuration example of a conventional illuminance sensor.

[Explanation of symbols]

 PD Photodiode LA Lamp S Light-shielding plate P Prism

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Murakami 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Ltd. (72) Fumiaki Ito, 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Ltd. (72) Inventor Miwako Iwai 1048, Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works, Ltd.

Claims (15)

[Claims] 1. A peak of light receiving sensitivity in an illuminance sensor that receives light reflected from a surface to be illuminated and outputs a light receiving signal obtained by integrating a product of light receiving sensitivity and light receiving amount at each incident angle in the entire light receiving range. An illuminance sensor comprising a light-receiving sensitivity adjusting means for making a decrease in the vicinity larger than that of other light-receiving sensitivities. 2. The illuminance sensor according to claim 1, wherein a light-shielding plate is provided on the light-receiving surface. 3. The illuminance sensor according to claim 2, wherein the area of the light shielding plate is smaller than the light receiving area. 4. The illuminance sensor according to claim 1, wherein a filter system using an optical multilayer film bandpass filter and colored glass for correcting the incident angle dependency of the light receiving sensitivity is provided on the light receiving surface. 5. The center wavelength of the filter system is about 600.
The illuminance sensor according to claim 4, wherein the illuminance sensor is set to nm. 6. The optical multilayer film bandpass filter
Is TiO_TwoAnd SiO _TwoBe composed of multiple layers of
The illuminance sensor according to claim 4, wherein. 7. The illuminance sensor according to claim 4, wherein the correction of the incident angle dependency reduces the sensitivity at an incident angle of 0 degree by about 20% or more with respect to the sensitivity at an incident angle of 30 degrees. . 8. The illuminance sensor according to claim 4, wherein the variation of the sensitivity within the incident angle range of 0 degree to 30 degrees is within about ± 8% based on the sensitivity at the incident angle of 0 degree. . 9. The illuminance sensor according to claim 1, wherein a filter having a plurality of transmittances is provided on the light receiving surface to correct the incident angle dependency of the light receiving sensitivity. 10. The illuminance sensor according to claim 9, wherein the filter has a thickness of an aluminum vapor deposition film that becomes thinner toward a central portion. 11. The illuminance sensor according to claim 9, wherein the filter has a thickness of an aluminum vapor deposition film that becomes thinner toward a peripheral portion. 12. The illuminance sensor according to claim 9, wherein the filter is formed by dot printing. 13. A material transparent to visible light,
The illuminance sensor according to claim 1, wherein a prism having a triangular cross section whose apex faces the sensor direction in a cross section including the central axis of the optical system is arranged on the optical axis of the light receiving sensor. 14. The base angle α of the triangle, which is the cross-sectional shape of the prism, is A, where n is the refractive index of the material of the prism.
14. The illuminance sensor according to claim 13, wherein the range is rcsin (1 / n) ± 10 degrees. 15. The illuminance sensor according to claim 13, wherein a large number of prisms are arranged in an array.