JP2011220770A - Photoreceiver for photometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoreceiver for a photometer, with its design flexibility improved and its size reduced, which can provide a desired oblique incident light property with high accuracy.SOLUTION: A oblique incident light property indicates a degree of change in the sensitivity of incident light falling on a light receiving spot, associated with a change in the incident angle of the incident light falling on a light receiving spot, to an optical axis; and a photoreceiver 10 for a photometer is designed so as to have a specific oblique incident light property. The photoreceiver 10 includes: a diffuser panel 12 which has a diffusion performance close to that of a perfectly diffusing surface; a light receiving member 17 which receives incident light diffused by the diffuser panel 12 and outputs an electric signal based on the amount of the received light; and an incident angle restriction member 14 which is disposed between the light receiving member 17 and the diffuser panel 12 and restricts the incident angle of the incident light falling on an incident surface 17a of the light receiving member 17.

Description

  The present invention relates to a light receiving device suitable for photometric devices such as an illuminance meter, a luminance meter, a color meter, an ultraviolet intensity meter, a photographic exposure meter, a photographic color meter, a spot meter, and an optical power meter.

  The light receiving device of the photometric device is designed to have a predetermined oblique incident light characteristic according to the measurement purpose of the photometric device. The oblique incident light characteristic indicates the degree of change in sensitivity with respect to a change in the incident angle, with the incident light traveling direction with respect to the optical axis direction to the incident end face as the light receiving portion of the light receiving device. Such a light receiving device of a photometric device is required to have an oblique incident light characteristic approximate to a so-called cosine law defined in JIS (Japanese Industrial Standard (JIS C 1609)) (for example, see Patent Document 1).

  As a means for realizing such a desired oblique incident light characteristic, it is known to form an incident surface using a hemispherical globe (light receiving sphere) made of a material having diffusion performance. In the light receiving device, by using a hemispherical glove having a diffusing performance, the reduction in the effective received light amount with respect to the change in the incident angle with the increase in the incident angle from 0 degree can be represented by the change in the incident angle with respect to the flat surface Therefore, the reduction in the amount of received light accompanying the increase in the incident angle can be made smaller than the cosine law. For this reason, by using a hemispherical globe with diffusion performance, the oblique incident light characteristics can be approximated to the cosine law simply by adjusting the received light amount in accordance with the incident angle. You can get the cosine law.

JP 2001-83008 A

  However, in the above-described configuration, since it is necessary to provide a hemispherical glove so as to protrude, the design is limited and the size (thickness) increases.

  The present invention has been made in view of the above circumstances, and an object thereof is to obtain desired oblique incident light characteristics with high accuracy while enabling improvement in design freedom and reduction in size. An object of the present invention is to provide a light receiving device for photometric equipment.

  According to the first aspect of the present invention, the light receiving device of the photometric device is designed so that the oblique incident light characteristic indicating the degree of change in sensitivity with respect to the change in the incident angle of the incident light with respect to the optical axis direction to the light receiving portion is predetermined A diffusion plate having a diffusion performance close to a perfect diffusion surface, a light receiving member that receives incident light diffused by the diffusion plate, and outputs an electrical signal corresponding to the amount of light received; the light receiving member; An incident angle limiting member disposed between the diffusion plate and limiting an incident angle of incident light on an incident surface of the light receiving member.

  The invention according to claim 2 is the light receiving device of the photometric device according to claim 1, wherein the incident angle limiting member effectively receives light by the light receiving member according to a change in incident angle of incident light. An incident angle to be limited is set so that a value obtained by multiplying the degree of change of the amount and the directivity characteristic of the light receiving member becomes a desired oblique incident light characteristic.

A third aspect of the present invention is the light receiving device of the photometric instrument according to the first or second aspect, wherein the diffusion plate is made of a resin material containing fluorine.
A fourth aspect of the present invention is the light receiving device of the photometric instrument according to the third aspect, wherein the resin material containing fluorine as the diffusion plate is a tetrafluoroethylene resin.

  The invention according to claim 5 is the light receiving device of the photometric device according to claim 1 or 2, wherein the diffusion plate is formed of ground glass.

  A sixth aspect of the present invention is the light receiving device of the photometric device according to the first or second aspect, wherein the diffusion plate is made of opal.

  A seventh aspect of the present invention is the light receiving device for a photometric device according to any one of the first to sixth aspects, wherein the incident angle limiting member is a through-hole formed in a plate member made of a non-transmissive material. The diameter of the opening on the entrance end side, the diameter of the opening on the exit end side, and the length dimension as viewed in the optical axis direction from the entrance end opening to the exit end opening; The size of the limiting angle is set by the ratio of.

  The invention according to claim 8 is the light receiving device of the photometric device according to any one of claims 1 to 6, wherein the incident angle limiting member has two diaphragms that make a pair on the optical axis. Of the aperture on the incident end side, the inner diameter size of the aperture on the output end side, and the distance dimension seen in the optical axis direction of both apertures. The size is set.

  The photometric device according to claim 9 is characterized in that the light receiving device of the photometric device according to any one of claims 1 to 8 is mounted.

  According to the light-receiving device of the photometric device of the present invention, desired oblique incident light characteristics can be easily obtained with high accuracy while enabling improvement in design freedom and reduction in size.

  In addition to the configuration described above, the incident angle limiting member multiplies the degree of change in the effective amount of light received by the light receiving member according to the change in the incident angle of incident light and the directivity characteristic of the light receiving member. If the incident angle to be limited is set so that the obtained value becomes the desired oblique incident light characteristic, the desired oblique incident light characteristic can be appropriately obtained using the light receiving member having an arbitrary directivity characteristic. Can do.

  In addition to the above-described configuration, if the diffusion plate is formed of a resin material containing fluorine, a diffusion plate having a diffusion performance close to a complete diffusion surface can be easily formed.

  In addition to the above-described configuration, when the resin material containing fluorine as the diffusion plate is a tetrafluoroethylene resin, a diffusion plate having diffusion performance close to a complete diffusion surface can be easily formed.

  In addition to the above-described configuration, if the diffusion plate is formed of ground glass, a diffusion plate having a diffusion performance close to a complete diffusion surface can be easily formed.

  In addition to the above-described configuration, if the diffusion plate is made of opal, a diffusion plate having diffusion performance close to a complete diffusion surface can be easily formed.

  In addition to the configuration described above, the incident angle limiting member is formed by providing a through-hole in a plate member made of a non-transmissive material, and the diameter of the opening on the incident end side and the diameter of the opening on the emission end side If the size of the angle to be limited is set by the ratio of the dimension and the length dimension seen in the optical axis direction from the incident end opening to the exit end opening, an incident angle limiting member is easily formed. can do.

  In addition to the configuration described above, the incident angle limiting member is formed of two diaphragms that make a pair on the optical axis, and the inner diameter dimension of the diaphragm on the incident end side and the inner diameter dimension of the diaphragm on the output end side. If the size of the angle to be limited is set by the ratio of the distance between the two apertures as viewed in the optical axis direction, the incident angle limiting member can be easily formed and the two apertures can be formed. The space between can be used.

It is explanatory drawing which shows typically the structure of the light-receiving device 10 in the illuminometer 50 as an example of the photometry apparatus which concerns on this invention. It is explanatory drawing which decomposes | disassembles and shows the light-receiving device 10 of FIG. 1 to an optical axis direction. It is a graph which shows the spectral transmittance of the infrared absorption filter 13, and the vertical axis | shaft has shown the spectral transmittance (%) and the horizontal axis has shown the wavelength (nm). It is a graph which shows standard spectral luminous efficiency V ((lambda)), the vertical axis | shaft has shown the ratio of the sensitivity on the basis of the maximum sensitivity, and the horizontal axis has shown the wavelength (nm). It is a graph which shows the spectral transmission factor of the long pass interference film and short pass interference film which were formed in interference filter 15, the vertical axis shows the transmittance (%), and the horizontal axis shows the wavelength (nm). It is a graph which shows spectral response degree PD ((lambda)) of the photoelectric conversion element 17, a vertical axis | shaft shows the ratio of the response degree on the basis of a maximum sensitivity, and the horizontal axis has shown the wavelength (nm). It is a graph which shows the spectral transmittance of the interference filter 15 with respect to the incident light from which an incident angle differs, A vertical axis | shaft shows the spectral transmittance (%) and the horizontal axis has shown the wavelength (nm). 4 is a graph showing an average angle combined spectral transmittance Fm ′ (λ), an average angle combined spectral transmittance ratio Fm (λ), and a spectral transmittance F ₀ (λ) in the interference filter 15, and the vertical axis indicates the spectral transmittance ( Spectral transmittance ratio) (%), and the horizontal axis represents wavelength (nm). It is a graph which shows the cosine law prescribed | regulated to JIS, the vertical axis | shaft shows the sensitivity ratio and the horizontal axis shows the incident angle (degree) with respect to the light-receiving device. It is a graph which shows the directional characteristic of the photoelectric conversion element 17, a vertical axis | shaft shows the ratio of the sensitivity on the basis of a sensitivity in case an incident angle is 0 degree | times, and a horizontal axis shows the incident angle (with respect to the light-receiving surface 17a of the photoelectric conversion element 17 ( Degree). It is explanatory drawing similar to FIG. 1 which shows the structure of the light-receiving device 101 typically. It is explanatory drawing of the light-receiving device 102, (a) shows a mode that it saw from the front (measurement location side), (b) has shown the structure typically similarly to FIG. 4 is a graph showing color matching functions x (λ), y (λ), and z (λ) defined by CIE, where the vertical axis indicates the spectral response ratio and the horizontal axis indicates the wavelength (nm). . FIG. 3 is an explanatory diagram schematically illustrating a configuration of a light receiving device 103 according to the first embodiment. It is explanatory drawing which shows typically the structure of the light-receiving device 203 as a comparative example. 5 is a graph showing an error from the cosine law in the oblique incident light characteristics of the light receiving device 103 and the light receiving device 203, where the vertical axis indicates an error rate (%) from the cosine law, and the horizontal axis indicates an incident angle (degree) with respect to the light receiving device. Is shown. It is explanatory drawing which shows typically the structure of the light-receiving device 104 of Example 2. FIG. It is explanatory drawing which shows typically the structure of the light-receiving device 204 as a comparative example.

  Embodiments of a light receiving device for a photometric device according to the present invention will be described below with reference to the drawings.

First, the concept of the light receiving device of the photometric device according to the present invention will be described. FIG. 1 is an explanatory view schematically showing a configuration of a light receiving device 10 in an illuminometer 50 as an example of a photometric device according to the present invention, and FIG. 2 is an exploded view of the light receiving device 10 in FIG. 1 in the optical axis direction. It is explanatory drawing shown. FIG. 3 is a graph showing the spectral transmittance of the infrared absorption filter 13, where the vertical axis indicates the spectral transmittance (%) and the horizontal axis indicates the wavelength (nm). FIG. 4 is a graph showing the standard spectral luminous efficiency V (λ), in which the vertical axis indicates the ratio of sensitivity based on the maximum sensitivity, and the horizontal axis indicates the wavelength (nm). FIG. 5 is a graph showing the spectral transmittance of the long-pass interference film and the short-pass interference film formed on the interference filter 15, where the vertical axis indicates the spectral transmittance (%) and the horizontal axis indicates the wavelength (nm). ing. In FIG. 5, the spectral transmittance of the short path interference film is indicated by a solid line, and the spectral transmittance of the long path interference film is indicated by a one-dot chain line. FIG. 6 is a graph showing the spectral response PD (λ) of the photoelectric conversion element 17, where the vertical axis shows the ratio of the response with the maximum sensitivity as a reference, and the horizontal axis shows the wavelength (nm). FIG. 7 is a graph showing the spectral transmittance of the interference filter 15 with respect to incident light having different incident angles. The vertical axis indicates the spectral transmittance (%), and the horizontal axis indicates the wavelength (nm). In FIG. 7, the spectral transmittance F ₀ (λ) with an incident angle of 0 degrees is indicated by a solid line, the incident angle is 15 degrees and the spectral transmittance F ₁₅ (λ) is indicated by a broken line, and the spectral transmittance with an incident angle of 30 degrees. The rate F ₃₀ (λ) is indicated by a one-dot chain line, and the spectral transmittance F ₄₅ (λ) at an incident angle of 45 degrees is indicated by a two-dot chain line. FIG. 8 is a graph showing the average angle combined spectral transmittance Fm ′ (λ), the average angle combined spectral transmittance ratio Fm (λ), and the spectral transmittance F ₀ (λ) in the interference filter 15. Spectral transmittance (spectral transmittance ratio) (%) is shown, and the horizontal axis shows wavelength (nm). In FIG. 8, the spectral transmittance F ₀ (λ) at an incident angle of 0 degrees is indicated by a solid line, and the average angle combined spectral transmittance ratio Fm (λ) not considering the spectral transmittance G (λ) is one point. An average angle combined spectral transmittance ratio Fm (λ) taking into consideration the spectral transmittance G (λ) is indicated by a two-dot chain line. FIG. 9 is a graph showing the cosine law defined in JIS, where the vertical axis indicates the sensitivity ratio and the horizontal axis indicates the incident angle (degrees) with respect to the light receiving device. FIG. 10 is a graph showing the directivity characteristics of the photoelectric conversion element 17, where the vertical axis indicates the ratio of sensitivity based on the sensitivity when the incident angle is 0 degrees, and the horizontal axis indicates the light receiving surface 17 a of the photoelectric conversion element 17. The incident angle (degree) with respect to is shown.

  The light receiving device 10 is configured as a light receiving device in an illuminometer that is an example of a photometric device according to the present invention. This light receiving device 10 is mounted on an illuminometer in order to measure the illuminance shown by converting the light incident on the measurement location into a light beam incident from every direction per unit area.

  The light-receiving device 10 of the photometric instrument according to the present invention is intended to obtain a desired oblique incident light characteristic with high accuracy while enabling improvement in design flexibility and reduction in size as a basic concept. On the optical axis, a diffusion plate having a diffusion performance close to a complete diffusion surface, and a light receiving member that outputs an electric signal corresponding to the amount of incident light diffused there, and on the incident surface of the light receiving member By placing and configuring an incident angle limiting member that limits the incident angle of incident light between the light receiving member and the diffusion plate, it is easy to achieve desired oblique incident light characteristics with high accuracy without using a hemispherical glove. It is possible to get to.

  As shown in FIGS. 1 and 2, the light receiving device 10 includes a cover plate 11, a diffusion plate 12, an infrared absorption filter 13, a spacer 14, an interference filter 15, and a diaphragm 16 in order from the measurement location side along the optical axis direction. And a photoelectric conversion element 17.

  The cover plate 11 basically protects the diffusion plate 12. The cover plate 11 covers the diffusion plate 12 to prevent contact with the diffusion plate 12 from the outside. In this example, the cover plate 11 is formed of a colorless and transparent acrylic resin material and has a plate shape. In the cover plate 11, the light (see the arrow shown in FIG. 1) that irradiates the measurement site with the outer surface (11 a) is directed toward the diffusion plate 12, that is, into the light receiving device 10. Hereinafter, the light taken into the light receiving device 10 from the outer surface (11a) of the cover plate 11 is referred to as incident light. For this reason, the outer surface of the cover plate 11 becomes the incident end surface 11 a of the light receiving device 10, and the incident end surface 11 a, that is, the cover plate 11 serves as a guide for the light receiving location in the light receiving device 10. Since the cover plate 11 only needs to protect the diffusion plate 12, for example, the cover plate 11 is formed of a milky white acrylic resin material (PMMA (polymethyl methacrylate resin)) to assist the diffusion action in the diffusion plate 12. It may be made hemispherical. Further, since the cover plate 11 basically protects the diffusion plate 12, it may not be provided from the viewpoint of optical action.

  The diffuser plate 12 diffuses incident light. The diffusion plate 12 is made of a material having a diffusion performance close to a complete diffusion surface, and has a plate shape. The diffusion performance close to the perfect diffusion surface here is a diffusion surface in which the luminance is uniform regardless of the difference in the incident angle of the incident light to the diffusion plate 12 at least within a predetermined angle range with respect to the optical axis direction. This means that the diffused light can have a uniform luminance regardless of the direction of the incident angle of the incident light on the diffusion plate 12 when viewed from any direction. The predetermined angle range referred to here is a predetermined size within 90 degrees to allow the incident light to travel, and is limited by an incident angle limiting member (in this example, the spacer 14 (which may include the diaphragm 16)) described later. It is desirable to be larger than the angle. Examples of such materials include fluorine-containing resin material-frosted glass, opal, and the like. In this example, the diffusion plate 12 is formed of white PTFE (tetrafluoroethylene resin) as an example of a resin material containing fluorine. Incident light that has passed through the diffusing plate 12 is diffused and reaches the infrared absorption filter 13.

  The infrared absorption filter 13 basically blocks transmission of components in a long wavelength band (long wavelength band longer than the visible region) that does not need to have sensitivity in a photometric device (illuminometer in this example). It blocks transmission in the infrared region. In this example, the infrared absorption filter 13 has a spectral transmittance characteristic as shown in FIG. 3, and completely absorbs a wavelength component in a wavelength band of approximately 900 nm or more in the transmitted incident light (transmits light). Hindering). Incident light that has passed through the infrared absorption filter 13 is transmitted light that does not have a wavelength component in a long wavelength band equal to or greater than a predetermined value and reaches the spacer 14.

  The spacer 14 constitutes an incident angle limiting member, and functions to limit the incident angle of incident light on the incident surface 15 b of the interference filter 15 and the incident angle of incident light on the light receiving surface 17 a of the photoelectric conversion element 17. have. In this example, the spacer 14 has a cylindrical shape formed by providing a through-hole 14a in a plate member made of a non-transmissive material having a predetermined thickness, and its inner peripheral wall surface prevents light reflection. It is supposed to be. In the spacer 14, the center position of the incident end opening 14 b on the measurement target side and the emission end opening 14 c on the interference filter 15 side (photoelectric conversion element 17 side) is located on the optical axis. In the spacer 14, of the incident light traveling from the incident end opening 14b into the through hole 14a, only the angular component traveling from the exit end opening 14c to the outside of the through hole 14a without reaching the inner peripheral wall surface of the through hole 14a. By passing the light, the incident angle of incident light on the incident surface 15 b of the interference filter 15 and the light receiving surface 17 a of the photoelectric conversion element 17 is limited. For this reason, in the spacer 14, the diameter dimension of the incident end opening 14b, the diameter dimension of the exit end opening 14c, and the length dimension in the optical axis direction from the entrance end opening 14b to the exit end opening 14c (the thickness of the spacer 14). The size of the angle to be limited can be set by the ratio of the height dimension). The size of the limiting angle will be described in detail later. The incident light that has passed through the spacer 14 reaches the interference filter 15 only with respect to the traveling direction (optical axis direction).

  The interference filter 15 has a spectral response PD (λ) (to be described later) of the photoelectric conversion element 17 in order to approximate a spectral response characteristic of the light receiving device 10 to a standard spectral luminous efficiency V (λ) (see FIG. 4) described later. The spectral transmittance characteristics are set in consideration of (see FIG. 6). The interference filter 15 is formed by laminating optical thin films made of dielectric materials having various refractive indexes on a plate-like glass substrate 15a. In this example, the interference filter 15 (glass substrate 15a) has a long-pass interference film (see the one-dot chain line in FIG. 5) formed on the incident surface 15b which is the surface to be measured (spacer 14 side), and the output on the opposite side. A short path interference film (see a solid line in FIG. 5) is formed on the surface 15c. The entrance surface 15b and the exit surface 15c are parallel to each other and orthogonal to the optical axis. In this example, the interference filter 15 is formed using the plate-shaped glass substrate 15a. However, as long as the substrate has optical transmission characteristics, for example, plastic or quartz may be used. It is not limited to this example.

  As shown by the solid line in FIG. 5, this short path interference film has a transmittance of about 100% in the wavelength band from 300 nm to about 570 nm, and the transmittance rapidly decreases in the wavelength band higher than this, and is about 700 nm. The transmissivity in the wavelength band exceeding 1 is assumed to be approximately 0%. Further, as shown by a one-dot chain line in FIG. 5, the long-pass interference film has a transmittance of about 0% in a wavelength band of about 400 nm or less, and the transmittance increases rapidly in a wavelength band of about 450 nm to about 570 nm. The transmittance is about 100% in the wavelength band higher than that, and the transmittance is not defined in the wavelength band of about 900 nm or more. For this reason, in the interference filter 15, the spectral transmittance F (λ) in which the short wavelength side characteristic is formed by the long path interference film and the long wavelength side characteristic is formed in the short path interference film (dots are added in FIG. 5). Area). A method for setting the spectral transmittance will be described later in detail. Incident light that has passed through the interference filter 15 is transmitted light having a predetermined spectral distribution characteristic and reaches the stop 16.

  The diaphragm 16 finely adjusts the incident angle of the incident light whose angle is limited by the spacer 14 on the light receiving surface 17 a of the photoelectric conversion element 17. This diaphragm 16 is a light beam that reaches the light receiving surface 17a of the photoelectric conversion element 17 in the incident light that has passed through the interference filter 15 in order to approximate the oblique incident light characteristic of the light receiving device 10 to a cosine law (see FIG. 9) described later. Limit the amount of light received. The oblique incident light characteristic indicates the degree of change in sensitivity with respect to a change in the incident angle in the light receiving device 10 with the incident light traveling direction relative to the optical axis direction to the incident end face 11a as the light receiving portion. It is. The diaphragm 16 is formed by providing a through-hole in a plate member made of a non-permeable material. Therefore, in this example, an incident angle limiting member that limits the incident angle on the light receiving surface 17 a of the photoelectric conversion element 17 is configured by the incident end opening 14 b of the spacer 14 and the through hole of the diaphragm 16. The diaphragm 16 is provided for fine adjustment of the incident angle of the incident light on the light receiving surface 17a of the photoelectric conversion element 17. Therefore, if the incident angle is sufficiently limited by the spacer 14, the diaphragm 16 is provided. It does not have to be. In this case, the spacer 14 (its incident end opening 14b and emission end opening 14c) constitutes an incident angle limiting member that limits the incident angle on the light receiving surface 17a of the photoelectric conversion element 17. Incident light that has passed through the diaphragm 16 reaches a photoelectric conversion element 17 with a predetermined incident angle or less (only an angle component equal to or less than a predetermined angle).

  The photoelectric conversion element 17 outputs a measurement result as the light receiving device 10. The photoelectric conversion element 17 has a light receiving surface 17a having a predetermined size, and is mounted with an electric signal (for example, a current value) corresponding to the intensity (light receiving amount) of light incident on the light receiving surface 17a. The light is output to a calculation control unit (not shown) of a photometric device (illuminometer 50 in this example). In this example, the photoelectric conversion element 17 is a photodiode having a spectral response PD (λ) shown in FIG. The photoelectric conversion element 17 outputs an electric signal (for example, a current value) obtained by multiplying the spectral distribution characteristic of incident light incident on the light receiving surface 17a by its own spectral response PD (λ) (see FIG. 6). For this reason, the photoelectric conversion element 17 functions as a light receiving member that outputs an electrical signal corresponding to the amount of received light.

  Thereby, the light receiving device 10 (illuminance meter 50) has a spectral response characteristic approximate to the standard spectral luminous efficiency V (λ) (see FIG. 4) and an oblique incidence approximated to the cosine law (see FIG. 9). It has optical characteristics. This will be described in detail below.

  The standard spectral luminous efficiency (standard relative luminous sensitivity) V (λ) shown in FIG. 4 represents human visual sensitivity (sensitivity) defined by CIE (International Commission on Illumination), that is, visible radiation (visible light). ) Is a scale indicating the degree of perception of brightness with respect to the wavelength felt when it enters the human eye. In the light receiving device 10, the spectral response is basically determined by the product of the spectral transmittance characteristic of the interference filter 15 (see FIG. 5) and the spectral response PD (λ) (see FIG. 6) of the photoelectric conversion element 17. . Here, since the spectral response PD (λ) of the photoelectric conversion element 17 is substantially determined by the type of the element to be used, the spectral response of the light receiving device 10 is adjusted by adjusting the spectral transmittance characteristic of the interference filter 15. The characteristic is set.

  As described above, the interference filter 15 is formed by laminating a plurality of optical thin films on the glass substrate 15a, thereby providing a long-pass interference film (see FIG. 5) on the incident surface 15b and shorting on the opposite exit surface 15c. A path interference film (see FIG. 5) is provided. In the interference filter 15, the long-pass interference film formed on the incident surface 15b forms a spectral transmittance characteristic corresponding to the short wavelength side in the standard spectral luminous efficiency V (λ), and is formed on the output surface 15c. The short-path interference film forms the spectral transmittance characteristic of the portion corresponding to the long wavelength side in the standard spectral luminous efficiency V (λ) (see FIG. 5).

Here, the interference filter 15 is known to have an incident angle dependency on the transmission wavelength due to its nature. The incident angle dependency is defined as an angle formed by the traveling direction of incident light with respect to the normal direction of the incident surface 15b and the emitting surface 15c that are parallel to each other. This means that the characteristic moves (shifts) to the short wavelength side. For example, as shown in FIG. 7, in the interference filter 15, when the spectral transmittance F ₀ (λ) in incident light with an incident angle of 0 degrees is a curve as indicated by a solid line, the incident angle in incident light is 15 degrees. Then, it moves to the short wavelength side as the spectral transmittance F ₁₅ (λ) indicated by the broken line. Similarly, when the incident angle of the incident light is 30 degrees, the incident light moves further to the short wavelength side with respect to the spectral transmittance F ₁₅ (λ) as indicated by a dashed line F ₃₀ (λ). When the incident angle at 45 is 45 degrees, it moves further to the short wavelength side with respect to the spectral transmittance F ₃₀ (λ) as the spectral transmittance F ₄₅ (λ) indicated by a two-dot chain line. In this incident angle dependence, the larger the incident angle, the larger the ratio of the amount of movement (the amount of shift of the characteristic line as seen in the direction of increasing or decreasing the wavelength) to the change of the incident angle, and the longer the wavelength region, the larger the amount of movement. There is a tendency that the ratio of (the shift amount of the characteristic line viewed in the direction of increase / decrease of the wavelength) increases. As a result, in the light receiving device 10, simply using the interference filter 15 constituted by the long path interference film on the incident surface 15b and the short path interference film on the output surface 15c, the incident angle dependence of the transmission wavelength in the interference filter 15 can be reduced. Due to the influence, the spectral response characteristic changes according to the incident angle of the incident light to the interference filter 15, and the spectral response characteristic stably approximated to the standard spectral luminous efficiency V (λ) (see FIG. 4). You will not be able to get.

  Further, it is known that the interference filter 15 has a polarization dependency in the transmission wavelength due to its property. This polarization dependence means that when obliquely incident light is incident, the spectral transmittance is different between P-polarized light oscillating in a direction parallel to the incident surface and S-polarized light oscillating in a direction perpendicular to the incident surface. As a result, in the light receiving device 10, the influence of the polarization dependence of the transmission wavelength in the interference filter 15 is simply obtained by simply using the interference filter 15 constituted by the long path interference film on the incident surface 15 b and the short path interference film on the output surface 15 c. As a result, the spectral response characteristic changes according to the difference in the magnitude of the polarization component in the incident light, and the spectral response characteristic that is stably approximated to the standard spectral luminous efficiency V (λ) (see FIG. 4) is obtained. I can't get it.

  For this reason, in the light receiving device 10 according to the present invention, the diffusion plate 12 having a diffusion performance close to a complete diffusion surface is provided at a position closer to the measurement location than the interference filter 15, and the diffusion plate 12 and the interference filter 15 A spacer 14 for limiting the incident angle of incident light on the incident surface 15b of the interference filter 15 is provided therebetween. In the light receiving device 10, incident light incident through the cover plate 11 (incident end surface 11 a) is diffused by being transmitted through the diffusion plate 12 having a diffusion performance close to a complete diffusion surface. Regardless of the difference in the incident angle, the light beams (angle components) in various traveling directions are present and travel toward the infrared absorption filter 13, the spacer 14, and the interference filter 15. That is, in the incident light directed to the infrared absorption filter 13, the spacer 14, and the interference filter 15, the distribution of the angle components is substantially equal regardless of the difference in the incident angle to the cover plate 11.

  The incident light passes through the infrared absorption filter 13, travels from the entrance end opening 14 b to the inside of the spacer 14 (in the through hole 14 a), and reaches the exit end opening 14 c without going to the inner peripheral wall surface. Only (angle component) passes through the spacer 14. For this reason, in the incident light that has passed through the spacer 14, the ratio of the diameter dimension of the incident end opening 14b, the diameter dimension of the exit end opening 14c, and the length dimension seen in the optical axis direction from the entrance end opening 14b to the exit end opening 14c. Therefore, it has only a light beam (angle component) in the traveling direction that is equal to or less than the angle corresponding to. The limit angle in the spacer 14 is preferably matched with the maximum value of the combined angle range in the interference filter 15 described later. In this example, the limit angle of the spacer 14 is set to 45 degrees, and the light flux (angle component) larger than 45 degrees is not allowed to pass through. Incident light that has passed through the spacer 14 enters the interference filter 15.

  In this way, the interference filter 15 (its incident surface 15b) has only an angle component (light beam) of the incident light diffused by the diffusion plate 12 that is equal to or less than the angle limited by the spacer 14 (45 degrees in this example). Reach. For this reason, in the light receiving device 10, the light beam (angle component) in the traveling direction from 0 degree to the limit angle (45 degrees) of the spacer 14 can be made to travel substantially uniformly as incident light to the interference filter 15. .

In addition to this, in the light receiving device 10 according to the present invention, spectral transmittance characteristics between 0 degrees and the limit angle (45 degrees) of the spacer 14 (reference numerals F ₀ (λ) to F ₄₅ (λ) in FIG. 7). Average angle composite spectral transmittance Fm ′ (λ) (see FIG. 8), which is an average value of the reference angle), and the spectral response in the photoelectric conversion element 17. The spectral transmittance F (λ) of the interference filter 15 is set so that the value obtained by multiplying PD (λ) (see FIG. 6) becomes the standard spectral luminous efficiency V (λ) (see FIG. 4). ing. This relational expression can be expressed by the following expressions (1), (2), and (3). In practice, the spectral transmittance in the cover plate 11, the diffuser plate 12, and the infrared absorption filter 13 is also a problem. Therefore, the following equation (1), ( The spectral transmittance F (λ) of the interference filter 15 is set by 2) and (4). Here, λ indicates a wavelength (nm). The average angle combined spectral transmittance ratio Fm (λ) indicates the ratio of spectral transmittance when the wavelength at which the transmittance is maximum is 100%.

For this reason, in the interference filter 15, the average angle combined spectral transmittance ratio Fm (λ) with respect to the angle obtained by combining from 0 degrees to the limit angle (45 degrees) of the spacer 14, and the spectral response PD (λ ), And the spectral transmittance F (λ) is set so that the product of the standard spectral luminous efficiency V (λ) is obtained, as shown in FIG. 8, when the incident angle is 0 degree. Characteristic line, that is, the characteristic line of the spectral transmittance F ₀ (λ) is shifted (shifted) to the longer wavelength side compared to the characteristic line of the average angle combined spectral transmittance ratio Fm (λ).

In the interference filter 15, the average angle combined spectral transmittance ratio Fm (λ) with respect to the angle obtained by combining from 0 degree to the limit angle (45 degrees) of the spacer 14, and the spectral response PD (λ) of the photoelectric conversion element 17. Since the spectral transmittance F (λ) is set so that the product of and the standard spectral luminous efficiency V (λ) is obtained, the spectral transmittance F (λ) with respect to a predetermined angle has a ripple characteristic. 8 (see the characteristic lines of spectral transmittance F ₃₀ (λ) and spectral transmittance F ₄₅ (λ) in FIG. 7), the average angle combined spectral transmittance ratio Fm (see FIG. 8). λ) can be a smooth characteristic line, and can be more appropriately approximated to the standard spectral luminous efficiency V (λ).

  The cosine law shown in FIG. 9 indicates a reference value of the degree of change in sensitivity with respect to a change in incident angle of incident light to a light receiving device defined in JIS (Japanese Industrial Standard (JIS C 1609)). It is equal to the cosine of the incident angle of light. This cosine law is also called a cosine characteristic. The light receiving device 10 is required to approximate the above-described oblique incident light characteristic to a cosine law, and a class classification is defined in JIS by an error from the cosine law.

  Here, in the light receiving device, even if a flat incident end surface is simply provided as a light receiving portion for measurement (corresponding to the incident end surface 11a in the light receiving device 10 of the present invention), the change in sensitivity with respect to the change in the incident angle of incident light. It is difficult to make the degree (oblique incident light characteristic) equal to the cosine (cosine law) of the incident angle of incident light. This is because the incident end face has a predetermined area and the incident light also has a predetermined area when viewed in a plane orthogonal to the traveling direction thereof. It is considered that the change in the amount of incident light is not equal to the cosine of the incident angle, and the reflectance and transmittance with respect to the incident angle in each optical component change. In addition, it is considered that the photoelectric conversion element has so-called directivity characteristics (see FIG. 10) in which the sensitivity changes according to the incident angle formed by the traveling direction of the incident light with respect to the light receiving surface.

  For this reason, in the light receiving device 10 according to the present invention, the diffusion near the complete diffusion surface in the optical path (position closer to the measured location than the photoelectric conversion element 17) in the incident light reaches the photoelectric conversion element 17 (light receiving surface 17a). A diffusion plate 12 having performance is provided, and an incident angle limiting member that limits the incident angle of incident light on the light receiving surface 17a between the diffusion plate 12 and the photoelectric conversion element 17 (in this example, the spacer 14 and the diaphragm 16). ). In the light receiving device 10, incident light that has entered through the cover plate 11 (incident end surface 11 a) is diffused by being transmitted through the diffuser plate 12, so that regardless of the difference in incident angle to the cover plate 11. It has a light beam (angle component) in every traveling direction, and travels toward the infrared absorption filter 13, the spacer 14, and the interference filter 15.

  The incident light passes through the infrared absorption filter 13, travels from the entrance end opening 14 b to the inside of the spacer 14 (in the through hole 14 a), and reaches the exit end opening 14 c without going to the inner peripheral wall surface. Only the (angle component) can pass through the spacer 14. For this reason, in the incident light that has passed through the spacer 14, the ratio of the diameter dimension of the incident end opening 14b, the diameter dimension of the exit end opening 14c, and the length dimension seen in the optical axis direction from the entrance end opening 14b to the exit end opening 14c. Therefore, it has only a light beam (angle component) in the traveling direction that is equal to or less than the angle corresponding to. The limiting angle in the spacer 14 is the degree of change in the luminous flux (light quantity) as incident light reaching the incident end opening 14b of the spacer 14 according to the change in the incident angle of incident light with respect to the incident end face 11a, and the photoelectric conversion element 17. The sensitivity characteristic (oblique incident light characteristic) with respect to the change in the incident angle of the incident light with respect to the incident end face 11a is set so as to coincide with the cosine law (see FIG. 9) in consideration of the directivity characteristic (see FIG. 10). Has been. That is, the limiting angle in the spacer 14 is the degree of change in luminous flux (light quantity) as effective incident light reaching the light receiving surface 17a of the photoelectric conversion element 17 in accordance with the change in incident angle of incident light with respect to the incident end face 11a. The value obtained by multiplying the directivity characteristic of the photoelectric conversion element 17 (see FIG. 10) is set to be a cosine law (see FIG. 9). In this example, the limit angle of the spacer 14 is set to 45 degrees, and the light flux (angle component) in the traveling direction larger than 45 degrees is not allowed to pass through. Incident light that has passed through the spacer 14 enters the light receiving surface 17 a of the photoelectric conversion element 17 through the interference filter 15.

  As described above, only the angle component (light beam) of the incident light diffused by the diffusion plate 12 below the angle limited by the spacer 14 (45 degrees in this example) is received on the light receiving surface 17a of the photoelectric conversion element 17. To reach. For this reason, in the light receiving device 10, as incident light to the light receiving surface 17 a of the photoelectric conversion element 17, a light flux (angle component) in the traveling direction from 0 degree to the limit angle (45 degrees) of the spacer 14 is substantially even. Can be advanced. In addition, the incident light incident on the light receiving surface 17a of the photoelectric conversion element 17 after being diffused by the diffusion plate 12 and passing through the interference filter 15 becomes natural light whose vibration direction is uniform with respect to the incident surface. The influence of can be eliminated. In this example, a diaphragm 16 is provided between the interference filter 15 and the photoelectric conversion element 17, and reaches the light receiving surface 17 a of the photoelectric conversion element 17 out of incident light that has passed through the interference filter 15 by the diaphragm 16. Since the incident angle of incident light is finely adjusted, the diameter of the incident end opening 14b of the spacer 14, the inner diameter of the diaphragm 16, and the incident end of the photoelectric conversion element 17 (its light receiving surface 17a) are adjusted. Only the angle component (light beam) equal to or smaller than the angle limited by the length dimension in the optical axis direction from the opening 14b to the stop 16 reaches the light receiving surface 17a. Therefore, in this example, the spacer 14 and the diaphragm 16 constitute an incident angle limiting member that limits the incident angle of incident light on the photoelectric conversion element 17 (the light receiving surface 17a). Since the fine adjustment of the incident angle by 16 assists the effect of the angle limitation by the spacer 14, the fine adjustment by the diaphragm 16 is not considered in the following description.

  For this reason, in the photoelectric conversion element 17, only the light beam in the traveling direction (angle component) whose angle is limited by the spacer 14 (incident angle limiting member) is incident on the light receiving surface 17a, and the incident angle of the incident light on the light receiving surface 17a is relative to the incident angle. An electrical signal (for example, a current value) is output according to sensitivity (directivity characteristics (see FIG. 10)). At this time, in the output electric signal, the limit angle in the spacer 14 is an effective incident light that reaches the light receiving surface 17a of the photoelectric conversion element 17 according to the change in the incident angle of the incident light with respect to the incident end surface 11a. Since the product of the degree of change of the luminous flux (light quantity) and the directivity characteristic (see FIG. 10) of the photoelectric conversion element 17 is set to the cosine law (see FIG. 9), the oblique incident light The characteristic approximates the cosine law (see FIG. 9).

  Therefore, in the light receiving device 10 according to the present invention, the degree of change in the luminous flux (light quantity) as the incident light reaching the incident end opening 14b of the spacer 14 according to the change in the incident angle of the incident light with respect to the incident end face 11a, and the diffusion The oblique incident light characteristic is approximated to the cosine law (see FIG. 9) by the diffusion of the incident light by the plate 12, the limiting angle by the spacer 14, and the directivity characteristic of the photoelectric conversion element 17 (see FIG. 10). In this example, as described above, the limit angle in the spacer 14 is set to coincide with the maximum value of the combined angle range in the interference filter 15, so that the change in the incident angle of the incident light with respect to the incident end face 11a is changed. In order to approximate the sensitivity characteristic to the cosine law (see FIG. 9), a diaphragm 16 is provided between the interference filter 15 and the photoelectric conversion element 17, and the incident angle of the incident light reaching the light receiving surface 17a, that is, the light receiving surface 17a. In this configuration, fine adjustment of the degree of change in the effective amount of received light is performed.

  As described above, in the light receiving device 10 according to the present invention, the incident light is diffused by the diffusion plate 12, the angle component in the diffused incident light is limited by the spacer 14, and the wavelength in the incident light in which the angle component is limited. Since the component is limited by the interference filter 15, it is possible to reduce the influence of the incident angle dependency and the polarization dependency of the transmission wavelength in the interference filter 15, and to obtain a desired spectral response characteristic (this) with high accuracy. In the example, a characteristic approximating the standard spectral luminous efficiency V (λ) can be obtained.

  Further, in the light receiving device 10, the interference filter 15 has an average angle combined spectral transmittance ratio Fm (based on an average value of spectral transmittance characteristics between 0 degrees and a predetermined magnitude when viewed at an incident angle to the incident surface 15b. Since the product of λ) and the spectral response PD (λ) of the photoelectric conversion element 17 is set to the standard spectral luminous efficiency V (λ), it is diffused by the diffusion plate 12 Since it has spectral transmittance characteristics suitable for incident light having various angle components substantially evenly, a desired spectral response characteristic (in this example, standard spectral luminous efficiency V (λ)) (Approximate characteristics) can be appropriately obtained.

  Further, in the light receiving device 10, the interference filter 15 has an average angle combined spectral transmittance ratio Fm (based on an average value of spectral transmittance characteristics between 0 degrees and a predetermined magnitude when viewed at an incident angle to the incident surface 15 b. λ), the spectral response PD (λ) of the photoelectric conversion element 17, and the spectral transmittance G (λ) of the cover plate 11, the diffuser plate 12, and the infrared absorption filter 13 are standard spectral luminous efficiency. Since it is set to be V (λ), it has a spectral transmittance characteristic that is more suitable for incident light that has various angular components approximately evenly by being diffused by the diffusion plate 12. Therefore, desired spectral response characteristics (characteristics approximating the standard spectral luminous efficiency V (λ) in this example) can be appropriately obtained.

  In the light receiving device 10, the average angle combined spectral transmittance ratio Fm (λ) as a reference for setting the interference filter 15 is from 0 degree to the limiting angle of the spacer 14 (incident angle limiting member) (45 degrees in the above example). Is calculated based on the average angle combined spectral transmittance Fm ′ (λ) (see FIG. 8), which is an average value between the angle components, and the setting of the interference filter 15 and the angle component of the incident light that has passed through the spacer 14 Since the target angle component is equal, the wavelength component of the incident light whose angle component is limited by the spacer 14 can be more appropriately limited (transmitted at a predetermined spectral transmittance) by the interference filter 15. Desired spectral response characteristics (characteristics approximating the standard spectral luminous efficiency V (λ) in this example) can be obtained more appropriately.

  In the light receiving device 10, since the limit angle of the spacer 14 is set in conformity with the spectral transmittance characteristic of the interference filter 15, the wavelength component of incident light whose angle component is limited by the spacer 14 is converted by the interference filter 15. Since it can limit more appropriately, a desired spectral response characteristic (characteristic that approximates the standard spectral luminous efficiency V (λ) in this example) can be obtained more appropriately.

  In the light receiving device 10, in the interference filter 15, a long-pass interference film is formed on the incident surface 15 b and a short-path interference film is formed on the output surface 15 c, so that the transmission wavelength of the interference filter 15 depends on the incident angle. The influence can be further reduced. This is due to the following. With respect to the diameter dimension of the incident end opening 14b of the spacer 14, the effective diameter dimension on the light receiving surface 17a of the photoelectric conversion element 17 (mainly determined by the diameter dimension of the exit end opening 14c or the inner diameter dimension of the diaphragm 16). By setting the effective light receiving area) to be small, the area on the emission surface 15c as viewed in the optical path incident on the light receiving surface 17a of the photoelectric conversion element 17 through the interference filter 15 is the area on the incident surface 15b. Therefore, the light emitted from the spacer 14 (including the diaphragm 16 in some cases) is larger than the limit value of the incident angle of the incident light on the incident surface 15b by the spacer 14 (including the diaphragm 16 in some cases). It is conceivable that the limit value of the incident angle of the light incident on the surface 15c is substantially larger (allowing only a narrower angle component to pass). Here, in the optical thin film (interference film (interference filter 15)), as described above, the ratio of the movement amount of the spectral transmittance characteristic line is increased in the longer wavelength region due to the influence of the incident angle dependence of the transmission wavelength. For these reasons, in the spectral transmittance set as the interference filter 15, a long-pass interference film that forms the spectral transmittance characteristic on the short wavelength side is provided on the incident surface 15 b, and the short that forms the spectral transmittance characteristic on the long wavelength side. By providing the path interference film on the exit surface 15c, the limit value of the incident angle in the long wavelength band where the influence of the incident angle dependency is large can be substantially increased, in other words, in the incident light reaching the exit surface 15c. Since the angle component can be further restricted, the influence of the incident angle dependence of the transmission wavelength can be reduced.

  In the light receiving device 10, since the wavelength component of the wavelength band of approximately 900 nm or more in the incident light is completely absorbed by the infrared absorption filter 13, it is desirable to reduce the number of optical thin films (the number of layers) in the interference filter 15. The spectral responsivity characteristics (characteristics approximated to the standard spectral luminous efficiency V (λ) in this example) can be obtained more appropriately. This is due to the following. As described above, the interference filter 15 has a spectral transmittance characteristic set by laminating optical thin films made of dielectric materials having various refractive indexes on the glass substrate 15a. This spectral transmittance characteristic can expand the non-transmission band (wavelength band having reflection performance) by increasing the number of layers (stacking number) of the optical thin film. In the interference filter 15, the spectral transmittance characteristic is set so as to approximate the spectral response characteristic in the light receiving device 10 to the standard spectral luminous efficiency V (λ). Since the wavelength component of the wavelength band can be completely absorbed, if the infrared absorption filter 13 is provided, it is not necessary to have reflection performance for a wavelength band of approximately 900 nm or more. For this reason, it is not necessary for the short path interference film that forms the portion corresponding to the long wavelength side of the spectral transmittance F (λ) of the interference filter 15 to have the reflection performance in the long wavelength band. As shown by a two-dot chain line in FIG. For this reason, the number of optical thin films (the number of stacked layers) in the short path interference film can be reduced, and the number of optical thin films (the number of stacked layers) in the interference filter 15 can be reduced.

  In the light receiving device 10, the wavelength component of the wavelength band of approximately 900 nm or more in the incident light is completely absorbed by the infrared absorption filter 13, and the influence of the incident wavelength dependence of the transmission wavelength in the interference filter 15 is reduced. Thus, it is possible to more appropriately obtain a desired spectral response characteristic (a characteristic approximate to the standard spectral luminous efficiency V (λ) in this example) while further reducing the number of optical thin film layers (the number of layers) in the interference filter 15. Can do. This is due to the following. As described above, since the wavelength component of the wavelength band of approximately 900 nm or more in the incident light is completely absorbed by the infrared absorption filter 13, the interference filter 15 does not require reflection performance for the wavelength band of approximately 900 nm or more. However, in the interference filter 15, there is a scene where the spectral transmittance characteristic moves to the short wavelength side due to the influence of the incident angle dependence of the transmission wavelength. It is necessary to set the reflection performance. In the configuration of the present invention, since the influence of the incident wavelength dependence of the transmission wavelength in the interference filter 15 can be reduced, the movement of the spectral transmittance characteristic to the short wavelength side due to the influence of the incident angle dependence of the transmission wavelength is reduced. Since the amount to be considered can be reduced, the upper limit wavelength of the reflection performance for the long wavelength band in the interference filter 15 can be set closer to 900 nm (in the long wavelength band as shown by a two-dot chain line in FIG. 5). (See the arrow between the characteristic lines that allow transmission). For this reason, the non-transmission band in the short path interference film can be expanded, the number of optical thin films (the number of layers) in the short path interference film can be reduced, and the number of the optical thin films in the interference filter 15 (lamination). Number) can be reduced.

  In the light receiving device 10, the incident light is diffused by the diffusion plate 12, the angle component in the diffused incident light is limited by the spacer 14, and the incident light whose angle component is limited is received by the light receiving surface 17 a of the photoelectric conversion element 17. Since the light is received, the oblique incident light characteristic in the light receiving device 10, that is, the degree of change in sensitivity with respect to the change in the incident angle of the incident light on the incident end surface 11a of the light receiving device 10 is approximated to the cosine law (see FIG. 9). It can be made easy. This is due to the following. In the light receiving device 10, since the diffusion plate 12 has a diffusion performance close to a complete diffusion surface, the incident light incident angle tends to increase as viewed from the optical axis direction (in this example, the normal direction of the incident end surface 11a). The degree of decrease in the amount of light received at the light receiving surface 17a in consideration of the directivity characteristics (see FIG. 10) of the photoelectric conversion element 17 with respect to the change in the light receiving area, the degree of decrease in the light receiving area due to the change in the increasing tendency of the incident angle with respect to the flat surface. Therefore, the effective reduction in the amount of received light at the light receiving surface 17a of the photoelectric conversion element 17 accompanying the increase in the incident angle can be made smaller than the cosine law. For this reason, the light receiving device 10 can be adapted to the cosine law simply by adjusting the received light amount in accordance with the incident angle in the direction of decreasing. Here, in the light receiving device 10, a spacer 14 is provided between the diffusion plate 12 and the photoelectric conversion element 17 (light receiving surface 17 a) to limit the angle component in the incident light diffused by the diffusion plate 12. By adjusting the limit angle in the spacer 14, it is possible to adjust the amount of received light according to the incident angle so as to reduce the amount of received light, so that it can be easily adapted to the cosine law with high accuracy. Here, the effective decrease in the amount of received light on the light receiving surface 17a in consideration of the directivity characteristics (see FIG. 10) of the photoelectric conversion element 17 is the intensity of light incident on the light receiving surface 17a (light reception). The amount of decrease in the output value (electrical signal) from the photoelectric conversion element 17 is output from an electrical signal (for example, a current value) indicating the magnitude obtained by multiplying the amount of the directivity and the directivity characteristic. Say.

  In the light receiving device 10, the limit angle of the spacer 14 is such that the effective light reception amount (the output value from the photoelectric conversion element 17) on the light receiving surface 17 a of the photoelectric conversion element 17 according to the change in the incident angle of incident light with respect to the incident end surface 11 a. Since the value obtained by multiplying the degree of change in (electrical signal)) and the directivity characteristic of the photoelectric conversion element 17 (see FIG. 10) is set as the cosine law (see FIG. 9), The oblique incident light characteristic in the light receiving device 10 can be approximated to the cosine law (see FIG. 9) with high accuracy by using a photoelectric conversion element having an arbitrary directivity characteristic (see FIG. 10).

  In the light receiving device 10, incident light whose angle component is limited by the spacer 14 is received by the light receiving surface 17 a of the photoelectric conversion element 17, so that the oblique incident light characteristic in the light receiving device 10 is approximated to the cosine law (see FIG. 9). Therefore, the diffusion plate 12 that diffuses incident light is formed of a material having a diffusion performance close to a complete diffusion surface (in Example 1, white PTFE (tetrafluoroethylene resin) as an example of a resin material containing fluorine). Therefore, it can be approximated to the cosine law with high accuracy without using a hemispherical glove as in the prior art.

In the light receiving device 10, in the interference filter 15 formed by laminating optical thin films made of dielectric materials having various refractive indexes on the glass substrate 15a, the angle from 0 degree to the limit angle (45 degrees) of the spacer 14 is combined. The product of the average angle composite spectral transmittance ratio Fm (λ) based on the average angle composite spectral transmittance Fm ′ (λ) and the spectral response PD (λ) of the photoelectric conversion element 17 is the standard spectral luminous efficiency V ( Since the spectral transmittance F (λ) is set so as to be λ), the spectral transmittance F (λ) with respect to a predetermined angle has a ripple characteristic line (spectral transmittance F ₃₀ (λ in FIG. 7). ) And spectral transmittance F ₄₅ (λ) characteristic line), as shown in FIG. 8, the average angle combined spectral transmittance ratio Fm (λ) may be a smooth characteristic line. And the standard spectral luminous efficiency V ( It can be approximated to).

  In the light receiving device 10, since the incident light is diffused by the diffusion plate 12, even if the incident light is polarized light, it can be converted into a state of natural light without polarization. Therefore, the interference filter 15 is used. Therefore, it is possible to obtain a desired spectral transmittance characteristic with high accuracy, that is, to approximate the standard spectral luminous efficiency V (λ) more appropriately.

  In the light receiving device 10, spectral response characteristics are obtained using an interference filter 15 formed by laminating optical thin films made of dielectric materials having various refractive indexes on a glass substrate 15a (a base material having optical transmission characteristics). Therefore, without using a material with high environmental impact as in the case of using a colored glass filter, the thickness dimension is increased compared to the case of using a colored glass filter. The desired spectral transmittance characteristic can be obtained with high accuracy without incurring the above.

  In the light receiving device 10, the spacer 14 can limit the angle component in the incident light reaching the interference filter 15 to be equal to or less than a predetermined angle, and thus it is not assumed in the light (incident light) transmitted through the interference filter 15. It is possible to prevent the wavelength component from being included. This is because in an interference filter using an interference film, when light exceeding a predetermined incident angle is incident, transmission of light of a wavelength component that is not assumed at all may be allowed.

  In the light receiving device 10, spectral response characteristics are obtained using an interference filter 15 formed by laminating optical thin films made of dielectric materials having various refractive indexes on a glass substrate 15a (a base material having optical transmission characteristics). Since the degree of freedom in setting the spectral transmittance in the interference filter 15 is higher than in the case of using a color glass filter or a dye film filter, the desired spectral response characteristics ( In this example, the characteristic that approximates the standard spectral luminous efficiency V (λ)) can be obtained more appropriately.

  In the light receiving device 10, spectral response characteristics are obtained using an interference filter 15 formed by laminating optical thin films made of dielectric materials having various refractive indexes on a glass substrate 15a (a base material having optical transmission characteristics). Therefore, the spectral transmittance characteristics do not change due to the absorption of heat and ultraviolet rays unlike colored glass filters and dye film filters, so the spectral response characteristics are affected by the influence of heat and ultraviolet rays. The change can be prevented, and a stable spectral response characteristic can be obtained. Here, although the infrared absorption filter 13 is used in the light receiving device 10, the infrared absorption filter 13 prevents transmission of a component in a long wavelength band that does not need to have sensitivity in a photometric device (illuminance meter in this example). In addition, since the configuration does not directly affect the adjustment of the spectral response characteristic, the influence of heat and ultraviolet rays on the infrared absorption filter 13 does not reach the spectral response characteristic.

  In the light receiving device 10, since the diaphragm 16 is provided in addition to the spacer 14, the limit angle of the spacer 14 is set in accordance with the spectral transmittance characteristic of the interference filter 15, that is, as a reference for setting the interference filter 15. Is calculated based on the average angle combined spectral transmittance Fm ′ (λ) (see FIG. 8), which is an average value between 0 degree and the limit angle of the spacer 14. Thus, a desired spectral responsivity characteristic (in this example, a characteristic approximating the standard spectral luminous efficiency V (λ)) can be obtained, and the limiting angle of the spacer 14 is corrected by the diaphragm 16 to Incident light characteristics can be approximated to cosine law (see FIG. 9) with high accuracy.

  In the light receiving device 10, from the viewpoint of limiting the incident angle of incident light to the photoelectric conversion element 17, the diffusion plate 12, the spacer 14, and the photoelectric conversion are sequentially arranged from the measurement target side on the premise that the above-described setting is possible. By arranging the element 17 and setting each of the above settings, the oblique incident light characteristic can be approximated to the cosine law (see FIG. 9) with high accuracy. Sphere) is not required, so it is not necessary to use a relatively large cover member that can accommodate the glove protruding in a hemispherical shape when not in use, etc. Can do.

  Therefore, in the light receiving device 10 according to the present invention, the desired oblique incident light characteristic, which in this example approximates the cosine law, can be obtained with high accuracy while improving the degree of freedom of design and reducing the size. Obtainable.

  In the above example, as shown in FIGS. 1 and 2, the light receiving device 10 includes the cover plate 11, the diffusion plate 12, the infrared absorption filter 13, and the spacer 14 in order from the measurement location side along the optical axis direction. And the interference filter 15, the diaphragm 16, and the photoelectric conversion element 17. However, if the angle component in the incident light reaching the interference filter 15 or the photoelectric conversion element 17 is limited, for example, the spacer 14 Instead, a pair of diaphragms 18 (see FIG. 11) (when individually shown, 18a and 18b from the measurement site side) may be provided, and the invention is not limited to the above example. An example of the light receiving device 101 provided with the two stops 18 is shown in FIG. Since the basic configuration of the light receiving device 101 is the same as that of the light receiving device 10, the same reference numerals are given to portions having the same configuration, and detailed description thereof is omitted. In the light receiving device 101, a pair of diaphragms 18 (18 a, 18 b) is provided behind the diffusion plate 12 as viewed from the measurement site, and an infrared absorption filter 131 is provided between the diaphragms 18. . In this pair of diaphragms 18, the diaphragm 18 a located on the measurement target side corresponds to the incident end opening 14 b (see FIG. 2) in the spacer 14, and the diaphragm 18 b located on the interference filter 15 side emits from the spacer 14. This corresponds to the end opening 14c (see FIG. 2), and is limited by the ratio of the inner diameter of the diaphragm 18a, the inner diameter of the diaphragm 18b, and the distance between the two diaphragms 18a and 18b as viewed in the optical axis direction. Sets the size of the angle. For this reason, in the light receiving device 101, the infrared absorption filter 131 can be arranged by using the interval between the diaphragm 18a and the diaphragm 18b provided for limiting the angle component. Therefore, the light receiving device 101 can obtain the same effect as the light receiving device 10 and can reduce the size in the optical axis direction.

  In the above example, the light receiving device 10 is configured as a light receiving device in the illuminometer 50 that is an example of the photometric device according to the present invention, but may be another photometric device, and is limited to the above example. Is not to be done. FIG. 12 shows a light receiving device 102 in a color illuminometer 60 as an example of another photometric device. The light receiving device 102 is configured to obtain spectral response characteristics approximate to the color matching functions x (λ), y (λ), and z (λ) defined by the CIE shown in FIG. Although symbols with bars are generally used as symbols representing color matching functions, the bars are omitted for convenience. Since the basic configuration of the light receiving device 102 is the same as that of the light receiving device 10, the same reference numerals are given to portions having the same configuration, and detailed description thereof is omitted. The light receiving device 102 includes a single cover plate 11, a diffusion plate 12, an infrared absorption filter 13, three spacers 142, an interference filter 152, a diaphragm 162, and a photoelectric conversion element 172 (when individually shown, a, and b and c). In FIG. 12, the boundary lines of the three spacers 142a, 142b, 142c are not clearly described. The spacer 142a, the interference filter 152a, the diaphragm 162a, and the photoelectric conversion element 172a are coordinated with the common cover plate 11, the diffusion plate 12, and the infrared absorption filter 13, and the color matching function x (λ) (see the solid line in FIG. 13). The spacer 142b, the interference filter 152b, the diaphragm 162b, and the photoelectric conversion element 172b are configured in cooperation with the common cover plate 11, the diffusion plate 12, and the infrared absorption filter 13. The spectral response characteristics approximate to the color matching function y (λ) (see the one-dot chain line in FIG. 13) are obtained. , The color matching function z (λ) (two-dot chain in FIG. 13) by cooperation with the diffusion plate 12 and the infrared absorption filter 13. It is configured to obtain a spectral responsivity characteristic which approximates to the reference). In these, it goes without saying that the oblique incident light characteristics are approximated by the cosine law (see FIG. 9). Therefore, the light receiving device 102 can obtain the same effect as the light receiving device 10, and approximates the color matching functions x (λ), y (λ), and z (λ) with high accuracy using the interference filter 152. Spectral response characteristics can be obtained. In the light receiving device 102, the color illuminance meter 60 includes three spacers 142 and interference to obtain spectral response characteristics approximate to the color matching functions x (λ), y (λ), and z (λ) (see FIG. 13). Although the filter 152, the diaphragm 162, and the photoelectric conversion element 172 are used, the configuration does not require the use of a hemispherical glove having a diffusing performance. Therefore, the oblique incident light characteristic is approximated to the cosine law with high accuracy. Can be made. This is because, when a hemispherical globe is used, the positional relationship from the optical axis viewed on the surface orthogonal to the optical axis in each photoelectric conversion element 172 is not equal regardless of the angular position viewed around the optical axis. This is because the oblique incident light characteristics change according to the change of the angular position. Furthermore, since the light receiving device 102 uses the diffusing plate 12 having a diffusing performance close to a perfect diffusing surface, the color illuminance meter 60 has color matching functions x (λ), y (λ), z (λ ) (See FIG. 13), the color can be appropriately evaluated even when the three spacers 142, the interference filter 152, the stop 162, and the photoelectric conversion element 172 are used in order to obtain a spectral response characteristic approximate to that shown in FIG. This is because the positional relationship from the optical axis viewed from the plane orthogonal to the optical axis in each spacer 142, each interference filter 152, each aperture 162, and each photoelectric conversion element 172 is irrespective of the angular position viewed around the optical axis. If it is not uniform, when the incident light is tilted with respect to the optical axis direction, the balance of the incident amounts with respect to the respective elements cannot be made uniform. The configuration of the light receiving device 102 can be a color luminance meter by appropriately providing an imaging lens as an optical member.

  Next, the light receiving device 103 of Example 1 which is an example of a specific configuration of the light receiving device of the photometric device according to the present invention will be described. Note that the light receiving device 103 of the photometric instrument of the first embodiment has the same basic configuration as the light receiving device 10 of the above-described example. Omitted. FIG. 14 is an explanatory diagram schematically showing the configuration of the light receiving device 103. FIG. 15 is an explanatory diagram schematically showing a configuration of a light receiving device 203 as a comparative example. FIG. 16 is a graph showing an error from the cosine law in the oblique incident light characteristics of the light receiving device 103 and the light receiving device 203, where the vertical axis represents the error rate (%) from the cosine law, and the horizontal axis represents the incidence on the light receiving device. The angle (degree) is shown. In FIG. 16, the error of the light receiving device 103 is indicated by a solid line, and the error of the light receiving device 203 is indicated by a one-dot chain line. In addition, in FIG. 16, the standard of the maximum allowable error of AA class defined by JIS when the incident angle is 10, 30, 50, 60 and 80 degrees is indicated by a short horizontal line, and similarly determined by JIS. A rough horizontal line indicates the maximum allowable error of the precision class.

  The light receiving device 103 according to the first embodiment is configured as a light receiving device in an illuminance meter 503 that is an example of a photometric device according to the present invention, and exposes a cover plate 113 (its incident end surface 113a), which will be described later, to the outside. Thus, the illuminometer 503 is provided on the main body 503a. As shown in FIG. 14, the light receiving device 103 includes a cover plate 113, a diffusion plate 12, an infrared absorption filter 13, a spacer 14, an interference filter 15, and a photoelectric conversion element 17 in this order from the measurement location side along the optical axis direction. With.

  The cover plate 113 covers the diffusion plate 12 so as to prevent contact with the diffusion plate 12 from the outside, and is formed of a milky white acrylic resin material (PMMA (polymethyl methacrylate resin)), and is hemispherical. It has a shape. In the cover plate 113, the light that irradiates the measurement site on the outer surface (incident end surface 113 a) is directed toward the diffusion plate 12, that is, into the light receiving device 103. The cover plate 113 can assist the diffusion action in the diffusion plate 12 because the acrylic resin material has a low diffusion performance. Further, since the cover plate 113 has a hemispherical shape, the cover plate 113 has a light receiving surface 17a of the photoelectric conversion element 17 with respect to a change in incident angle of incident light with respect to the optical axis direction as compared with a case where the cover plate 113 is formed with a flat surface. The effective reduction in the amount of received light can be made small. Since the basic configuration of the light receiving device 103 is the same, the same effect as that of the light receiving device 10 can be obtained.

  Here, a light receiving device 203 as a comparative example will be described with reference to FIG. The light receiving device 203 is configured using a colored glass filter as an optical filter. As shown in FIG. 15, the light receiving device 203 includes a globe (light receiving sphere) 41, a first glass filter 42, a second glass filter 43, and a photoelectric conversion element 44 in order from the measurement location side along the optical axis direction. The first glass filter 42 and the second glass filter 43 constitute an optical filter. The globe 41 is made of a milky white acrylic resin material (PMMA (polymethyl methacrylate resin)) and has a hemispherical shape. In the light receiving device 203, the spectral response characteristic of the photoelectric conversion element 44 is determined by the product of the spectral transmittance characteristic of the optical filter (42, 43) and the spectral response characteristic of the photoelectric conversion element 44. Therefore, the spectral response characteristic as the light receiving device is obtained by adjusting the spectral transmittance characteristic in the optical filter (42, 43).

  Since it is difficult to obtain an arbitrary spectral transmittance characteristic in the color glass filter as the optical filter, the light receiving device 203 uses the two first glass filters 42 and the second glass filter 43 to obtain a desired characteristic. The spectral transmittance characteristic is obtained. For this reason, the thickness dimension of the optical filter is increased. In addition, since it is difficult to obtain an arbitrary spectral transmittance characteristic in a color glass filter, the types of color glass filters to be combined are limited, that is, used as the first glass filter 42 and the second glass filter 43. However, it is difficult to obtain desired spectral transmittance characteristics with high accuracy even if they are combined. This is the same even when a dye film filter is used. Further, the spectral response characteristic as the light receiving device is approximated to the standard spectral luminous efficiency V (λ) (even in the case of the color matching functions x (λ), y (λ), and z (λ)). In many cases, the color glass filter suitable for the above contains a substance having a high environmental load (for example, cadmium), which makes the production itself difficult.

  Further, in the light receiving device 203 as a comparative example, by using the hemispherical globe 41 having the diffusion performance, the incident angle is increased from 0 degree with the angle formed by the traveling direction of the incident light with respect to the optical axis direction as the incident angle. The effective decrease in the amount of received light with respect to the incident angle change is less than the decrease in the light reception area with the change in the incident angle with respect to the flat surface. It is supposed to be smaller than the rule. For this reason, in the light receiving device 203, by using the hemispherical globe 41 having the diffusing performance, the light receiving device 203 can be adapted to the cosine law simply by adjusting the received light amount in accordance with the incident angle. In the light receiving device 203, an annular inclined wall 45 is provided so as to surround the hemispherical globe 41 in order to adjust the received light amount in accordance with the incident angle in a direction to reduce the received light amount. In the annular inclined wall 45, the height dimension with respect to the globe 41 is adjusted so as to adjust the received light amount according to the incident angle in order to adapt the effective reduction amount of the received light amount with respect to the change in the incident angle of the incident light to the cosine law. A (size size seen in the optical axis direction) and an inclination angle are set.

  However, in the configuration of the light receiving device 203, since it is necessary to provide the hemispherical globe 41 so as to protrude, the design is restricted and the size (thickness) increases. Further, in the light receiving device 203, since the globe 41 is formed from a milky white acrylic resin material (PMMA (polymethyl methacrylate resin)), it is difficult to obtain sufficient diffusion performance for obtaining the above-described action. For this reason, it is necessary to ensure sufficient diffusion performance for obtaining the above-described effect by increasing the distance from the globe 41 to the photoelectric conversion element 44 (its light receiving surface), and therefore the size (thickness) increases. Will be invited.

  On the other hand, since the light receiving device 103 according to the present invention uses the interference filter 15, the thickness dimension of the optical filter can be greatly reduced as compared with the light receiving device 203.

  In addition, since the light receiving device 103 according to the present invention uses the interference filter 15, it is possible to obtain a desired spectral transmittance characteristic with higher accuracy than the light receiving device 203.

  Furthermore, since the light receiving device 103 according to the present invention uses the interference filter 15, the spectral response characteristic as the light receiving device can be obtained with high accuracy without using a substance having a higher environmental load than the light receiving device 203. It can be approximated to the standard spectral luminous efficiency V (λ) (the same applies to the case of the color matching functions x (λ), y (λ), and z (λ)).

  In the light receiving device 103 according to the present invention, since the diffusion plate 12 (formed from white PTFE (tetrafluoroethylene resin) in Example 1) having a diffusion performance close to a complete diffusion surface is used. The light flux in the incident light reaching the light receiving surface 17a in consideration of the directivity (see FIG. 10) of the photoelectric conversion element 17 with respect to the change in the incident angle of the incident light with respect to the axis (in this example, the normal direction of the incident end face 11a). Since the degree of reduction in (light quantity) can be reduced more than the degree of reduction in the light receiving area associated with the change in the incident angle with respect to the flat surface, the degree of freedom in design is greatly improved compared to the light receiving device 203 and the magnitude is large. The size can be greatly reduced. In addition, in the light receiving device 103 of the first embodiment, a hemispherical cover plate 113 made of white PTFE is provided, but this has a large side in order not to give a sense of incongruity to a user of a conventional illuminometer, As described above, since the diffusion plate 12 is substantially protected and may not be provided from the viewpoint of optical action, the cover plate 113 may not be provided.

  In the light receiving device 103 according to the present invention, a diffusion plate 12 (formed from white PTFE (tetrafluoroethylene resin) in Example 1) having a diffusion performance close to a complete diffusion surface is used. Compared to the distance from the globe 41 to the photoelectric conversion element 44 (its light receiving surface) in the apparatus 203, the distance from the diffusion plate 12 to the photoelectric conversion element 17 (its light receiving surface 17a) can be greatly reduced.

  In the light receiving device 103 according to the present invention, a diffusion plate 12 (formed from white PTFE (tetrafluoroethylene resin) in Example 1) having a diffusion performance close to a complete diffusion surface is used. A spacer 14 for limiting the angle component in the incident light diffused at 12 is provided, and the limit angle of the spacer 14 reaches the light receiving surface 17a according to the change in the incident angle of the incident light with respect to the incident end surface 11a. The value obtained by multiplying the degree of change in the luminous flux (the amount of light) as light and the directivity characteristic (see FIG. 10) of the photoelectric conversion element 17 is set to be a cosine law (see FIG. 9). Therefore, unlike the light receiving device 203, it is not necessary to provide a hemispherical glove for adjusting the amount of received light according to the incident angle and the annular inclined wall 45. It is possible to, it is possible to greatly improve the degree of freedom in design. In the light receiving device 103 according to the first embodiment, a cover plate 113 similar to a hemispherical glove and an annular inclined wall 45 ′ corresponding to the annular inclined wall 45 of the light receiving device 203 are provided so as to surround the cover plate 113. However, this has a large aspect that it does not give a sense of incongruity to the user of the conventional illuminometer, and the oblique incident light characteristic can be adapted to the cosine law by the limit angle of the spacer 14, so that the annular inclined wall 45 ' Is not necessary.

  Here, the oblique incident light characteristics (see FIG. 16) obtained by actually manufacturing the light receiving device 103 and the light receiving device 203 are compared. As described above, the light receiving device 103 diffuses the incident light with the diffusion plate 12, restricts the angle component in the diffused incident light with the spacer 14, and converts the incident light with the angle component restricted into the photoelectric conversion element 17. The light receiving surface 17a of the photoelectric conversion element 17 has a limit angle of the spacer 14 in accordance with a change in the incident angle of the incident light with respect to the incident end surface 11a. A value obtained by multiplying the degree of change in the output value (electric signal) from the conversion element 17 and the directivity characteristic (see FIG. 10) of the photoelectric conversion element 17 is set to be a cosine law (see FIG. 9). Has been configured. For this reason, the light receiving device 103 substantially satisfies the maximum allowable error of the precision class defined by JIS, though it is a simple configuration that merely adjusts the limit angle in the spacer 14. Therefore, it was possible to obtain oblique incident light characteristics that approximated the cosine law with extremely high accuracy. On the other hand, as described above, the light receiving device 203 surrounds the hemispherical globe 41 having the diffusion performance with the annular inclined wall 45, and the height dimension and the inclination angle of the annular inclined wall 45 with respect to the globe 41 are incident light. In order to adapt the effective decrease in the amount of received light with respect to the change in the incident angle to the cosine law, the amount of received light is adjusted according to the incident angle. For this reason, the light receiving device 203 satisfies the AA class maximum allowable error defined by JIS, although it is necessary to relatively set the design values of the dimensions of the annular inclined wall 45 and the globe 41. However, as compared with the light receiving device 103, the approximation to the cosine law has an oblique incident light characteristic with low accuracy.

  In the light receiving device 103 according to the first embodiment, the diaphragm 16 (see FIGS. 1 and 2) is not provided, but the photoelectric conversion element 17 (the spacer 14) is interposed between the interference filter 15 and the photoelectric conversion element 17. A stop 16 (see FIGS. 1 and 2) may be provided for fine adjustment of the limit of the incident angle on the light receiving surface 17a).

  Next, the light receiving device 104 according to the second embodiment which is another example of the specific configuration of the light receiving device of the photometric device according to the present invention will be described. The basic structure of the light receiving device 104 of the photometric device of the second embodiment is the same as that of the light receiving device 10 of the above-described example. Omitted. FIG. 17 is an explanatory diagram schematically showing the configuration of the light receiving device 104. FIG. 18 is an explanatory diagram schematically showing the configuration of a light receiving device 204 as a comparative example.

  The light receiving device 104 according to the second embodiment is configured as a light receiving device in an illuminometer 504 that is an example of a photometric device according to the present invention, and exposes a cover plate 11 (its incident end surface 11a), which will be described later, to the outside. Thus, the illuminometer 504 is provided on the main body 504a. As shown in FIG. 17, the light receiving device 104 includes a cover plate 11, a diffusion plate 12, an infrared absorption filter 13, a spacer 14, an interference filter 15, and a photoelectric conversion element 17 in this order from the measurement location side along the optical axis direction. With.

  The cover plate 11 covers the diffusion plate 12 in order to prevent contact with the diffusion plate 12 from the outside, and is formed from a milky white acrylic resin material (PMMA (polymethyl methacrylate resin)). It has a shape. In the cover plate 11, the light that irradiates the measurement site on the outer surface (incident end surface 11 a) is directed toward the diffusion plate 12, that is, into the light receiving device 104. The cover plate 11 can assist the diffusion action in the diffusion plate 12 because the acrylic resin material has low diffusion performance. Since the basic configuration of the light receiving device 104 is the same, the same effect as that of the light receiving device 10 can be obtained.

  Here, a light receiving device 204 as a comparative example will be described with reference to FIG. The light receiving device 204 is configured using a colored glass filter as an optical filter. Since the basic structure of the light receiving device 204 is the same as that of the light receiving device 203 as a comparative example in the first embodiment, the same reference numerals are given to portions having the same configuration, and detailed description thereof is omitted.

  As shown in FIG. 18, the light receiving device 204 includes a diffusion cover 414, a first glass filter 42, a second glass filter 43, and a photoelectric conversion element 44 in order from the measurement location side along the optical axis direction. The first glass filter 42 and the second glass filter 43 constitute an optical filter. The diffusion cover 414 is formed of a milky white acrylic resin material (PMMA (polymethyl methacrylate resin)) and has a plate shape. In the light receiving device 204, spectral response characteristics as a light receiving device are obtained by adjusting the spectral transmittance characteristics in the optical filters (42, 43).

  Further, in the light receiving device 204 as a comparative example, by using the diffusion cover 414 having diffusion performance, the incident angle is increased from 0 degree with the angle formed by the traveling direction of the incident light with respect to the optical axis direction as the incident angle. The effective reduction of the received light amount with respect to the change in incident angle is adapted to the cosine law, and the effective decrease of the received light amount with respect to the change in the incident angle of incident light is adapted to the cosine law. For this reason, in the light receiving device 204, compared with the light receiving device 203, the diffusion cover 414 (the globe 41) is not hemispherical, and the annular inclined wall 45 is not provided.

  In the configuration of the light receiving device 204, since the diffusion cover 414 is formed from a milky white acrylic resin material (PMMA (polymethyl methacrylate resin)), it is possible to obtain sufficient diffusion performance to obtain the above-described action. Since it is difficult, it is necessary to ensure sufficient diffusion performance for obtaining the above-described effect by increasing the distance from the diffusion cover 414 to the photoelectric conversion element 44 (its light receiving surface). Increase in thickness).

  On the other hand, since the light receiving device 104 according to the present invention uses the interference filter 15, the thickness dimension of the optical filter can be significantly reduced as compared with the light receiving device 204.

  In addition, since the light receiving device 104 according to the present invention uses the interference filter 15, it is possible to obtain a desired spectral transmittance characteristic with higher accuracy than the light receiving device 204.

  Furthermore, since the light receiving device 104 according to the present invention uses the interference filter 15, the spectral response characteristic as the light receiving device can be obtained with high accuracy without using a substance having a higher environmental load than the light receiving device 204. It can be approximated to the standard spectral luminous efficiency V (λ) (the same applies to the case of the color matching functions x (λ), y (λ), and z (λ)).

  In the light receiving device 104 according to the present invention, a diffusion plate 12 (formed from white PTFE (tetrafluoroethylene resin) in Example 2) having a diffusion performance close to a complete diffusion surface is used. A spacer 14 for limiting the angle component in the incident light diffused at 12 is provided, and the limit angle of the spacer 14 reaches the light receiving surface 17a according to the change in the incident angle of the incident light with respect to the incident end surface 11a. Since the value obtained by multiplying the degree of change of the luminous flux (light quantity) as light and the directivity characteristic of the photoelectric conversion element 17 (see FIG. 10) is set as the cosine law (see FIG. 9). Compared with the light receiving device 204, it is possible to obtain oblique incident light characteristics that approximate the cosine law with high accuracy. That is, in the light receiving device 204, the diffusion rate of the low performance (formed from milky white acrylic resin material (PMMA)) in the diffusion cover 414 and the distance between the diffusion cover 414 and the photoelectric conversion element 44 (its light receiving surface). And the ratio of the effective incident aperture in the diffusion cover 414 to the effective light receiving area in the photoelectric conversion element 44 (its light receiving surface) approximates the oblique incident light characteristic to a cosine law. Is difficult, and the approximation to the cosine law is an oblique incident light characteristic with low accuracy. When the light-receiving device 104 and the light-receiving device 204 were actually manufactured, the light-receiving device 104 was able to obtain oblique incident light characteristics satisfying the maximum allowable error of the precision class defined by JIS, whereas the light-receiving device 204 was JIS. It was not possible to obtain oblique incident light characteristics that satisfy the maximum allowable error of class AA defined in.

  In the light receiving device 104 according to the second embodiment, the diaphragm 16 (see FIGS. 1 and 2) is not provided. However, the photoelectric conversion element 17 (the spacer 14) is interposed between the interference filter 15 and the photoelectric conversion element 17 (see FIG. 1). A stop 16 (see FIGS. 1 and 2) may be provided for fine adjustment of the limit of the incident angle on the light receiving surface 17a).

  In each example and each example described above, an illuminometer (color illuminometer) is shown as a photometric device equipped with the light receiving device according to the present invention. However, a luminance meter, a color meter, an ultraviolet intensity meter, and a photographic exposure meter It may be a photographic color meter, a spot meter, an optical power meter, etc., and is not limited to the above examples and examples, and the same effect can be obtained with any photometric device. it can. For example, in the light receiving device according to the present invention, since the influence of the incident angle dependency and the polarization dependency of the transmission wavelength in the interference filter is reduced, it is a case where the interference filter is mounted on a luminance meter that switches the measurement angle. However, since it is possible to prevent the spectral response from changing when the measurement angle is switched, an arbitrary spectral response characteristic can be obtained with high accuracy regardless of the measurement angle. When mounted on a luminance meter in this manner, although not shown, an imaging lens is provided as an optical member in the light receiving device, and the above-described spectral transmittance G (λ) includes the spectral transmittance of the imaging lens. It will be.

  In the light receiving device of each example and each embodiment described above (excluding the light receiving device 101 shown in FIG. 11), the cover plate 11 (113) and the diffusion plate 12 are sequentially arranged from the measurement location side along the optical axis direction. And an infrared absorption filter 13, a spacer 14 (142), an interference filter 15 (152), a diaphragm 16 (162) (this diaphragm may not be provided), and a photoelectric conversion element 17 (172). However, from the viewpoint of limiting the incident angle of the incident light to the interference filter 15 (152), the diffusion plate 12 and the spacer 14 (142) are provided from the measurement target side on the premise that the above-described setting is possible. As long as they are arranged in the order of the interference filter 15 (152), the arrangement of the other members may be changed as appropriate, and is not limited to the above examples and examples.

  Further, in the light receiving device of each of the above examples and each embodiment (excluding the light receiving device 101 shown in FIG. 11), the cover plate 11 (113) and the diffusing plate 12 are sequentially arranged from the measurement location side along the optical axis direction. And an infrared absorption filter 13, a spacer 14 (142), an interference filter 15 (152), a diaphragm 16 (162) (this diaphragm may not be provided), and a photoelectric conversion element 17 (172). However, from the viewpoint of limiting the incident angle of the incident light to the photoelectric conversion element 17, the diffusion plate 12, the spacer 14 (142), and the photoelectric element are measured from the measurement site side on the assumption that the above-described setting is possible. As long as the conversion elements 17 (172) are arranged in this order, the arrangement of the other members may be appropriately changed, and is not limited to the above examples and examples.

  Furthermore, in the light receiving device of each of the above examples and each embodiment (excluding the light receiving device 101 shown in FIG. 11), a cylinder formed by providing a through hole in a plate member made of a non-transmissive material as an incident angle limiting member. Although the spacer 14 (142) having a shape is provided, the incident angle limiting member is configured such that the incident angle of the incident light on the incident surface 15b of the interference filter 15 (152) and the incident light on the light receiving surface 17a of the photoelectric conversion element 17 are provided. May be formed by a pair of apertures (reference numeral 18 in FIG. 11) as in the light receiving device 101 (see FIG. 11). The present invention is not limited to the examples. At this time, the entrance-side opening (incident end opening 14b or stop 18a) and the exit-side opening (exit end opening 14c, stop 16 or stop 18b) are preferably provided on the same optical axis. .

  In the light receiving device of each example and each example described above, in the interference filter 15, the long path interference film is formed on the incident surface 15b and the short path interference film is formed on the output surface 15c. For example, a short path interference film may be formed on the incident surface 15b and a long path interference film may be formed on the output surface 15c as long as it has the spectral transmittance set as described above to obtain the characteristics. The present invention is not limited to the above examples and examples. However, since the influence of the incident angle dependence of the transmission wavelength in the interference filter 15 can be further reduced, it is desirable to configure as in each of the above examples and examples.

  In the light receiving device of each example and each example described above, the interference filter 15 is formed by providing the long path interference film and the short path interference film on both surfaces of the single glass substrate 15a. For example, an interference film may be formed on two or more substrates having optical transmission characteristics, as long as it has a spectral transmittance set as described above to obtain An interference film may be formed on the infrared absorption filter, and the present invention is not limited to the above examples and examples.

  As mentioned above, although the light-receiving device of the photometric device of the present invention has been described based on each example and each example, the specific configuration is not limited to each example and each example, and the gist of the present invention As long as they do not deviate, design changes and additions are permitted.

10, 101, 102, 103, 104 Light-receiving device of photometric device 12 Diffusion plate 13, 131 Infrared absorption filter 14, 142 Spacer 14b (as incident angle limiting member) Spacer 14b (As opening on incident end side of incident angle limiting member) Incident end opening 14c Emission end opening 15, 152 (as an opening on the outgoing end side of the incident angle limiting member) Interference filter 15b Incident surface 15c Emission surface 17, 172 Photoelectric conversion element 18 (as light receiving member) (incident angle limiting member) Aperture 50, 503, 504 Illuminometer (as photometric device) 60 Color illuminometer (as photometric device)

Claims (9)

A light receiving device of a photometric device designed to have a predetermined oblique incident light characteristic indicating a degree of change in sensitivity with respect to a change in incident angle of incident light with respect to an optical axis direction to a light receiving portion,
A diffusion plate having a diffusion performance close to a perfect diffusion surface;
A light receiving member that receives incident light diffused by the diffusion plate and outputs an electrical signal corresponding to the amount of light received;
An incident angle limiting member that is disposed between the light receiving member and the diffusion plate and limits an incident angle of incident light on an incident surface of the light receiving member;
A light receiving device for a photometric device, comprising:   In the incident angle limiting member, a value obtained by multiplying the degree of change in the effective amount of light received by the light receiving member in accordance with the change in the incident angle of incident light and the directivity characteristic of the light receiving member is a desired oblique angle. 2. The light receiving device for a photometric device according to claim 1, wherein an incident angle to be limited is set so as to obtain an incident light characteristic.   3. The light receiving device for photometric equipment according to claim 1, wherein the diffusion plate is made of a resin material containing fluorine.   The light receiving device for a photometric device according to claim 3, wherein the resin material containing fluorine as the diffusion plate is a tetrafluoroethylene resin.   3. The light receiving device for a photometric device according to claim 1, wherein the diffusion plate is formed of ground glass.   3. The light receiving device for a photometric device according to claim 1, wherein the diffusion plate is made of opal.   The incident angle limiting member is formed by providing a through-hole in a plate member made of a non-transmissive material, and has a diameter dimension of an opening on the incident end side, a diameter dimension of an opening on the exit end side, and the incident end opening. The size of the angle to restrict | limit is set by ratio with the length dimension seen in the optical axis direction from the said to the said output end opening. Light receiving device for photometric equipment.   The incident angle limiting member is formed of two diaphragms that make a pair on the optical axis. The inner diameter dimension of the diaphragm on the incident end side, the inner diameter dimension of the diaphragm on the emission end side, and the light of the both diaphragms. The light receiving device for a photometric device according to any one of claims 1 to 6, wherein the size of the angle to be limited is set according to a ratio with a distance dimension seen in the axial direction. A photometric device comprising the light receiving device of the photometric device according to any one of claims 1 to 8.

Images