JP7136136B2 - Light-receiving characteristic evaluation device and light-receiving characteristic evaluation method for optical sensor - Google Patents

Description

The present invention relates to a light-receiving characteristic evaluation apparatus and a light-receiving characteristic evaluation method for an optical sensor.

Various optical sensors are used in manufacturing sites for process control, quality control, and the like. Such an optical sensor may be affected by environmental factors such as dust, dirt, and temperature changes, and its light-receiving characteristics may change compared to when it was first introduced due to aged deterioration or the like. The optical sensor described here has a specific wavelength range such as various light, such as visible light, infrared light, and ultraviolet light, depending on the application, and receives light in an unpolarized state or a specific polarized state. A device that converts a signal into an electrical signal. Such a change in light receiving characteristics degrades the quality of the measured electrical signal and hinders stable operation of the process. Especially in the field of radiation temperature measurement, a slight change in the amount of light greatly affects the measurement accuracy. Therefore, it is very important to evaluate the light-receiving characteristics of the optical sensors installed at the manufacturing site.

Against this background, Patent Document 1 proposes a method for evaluating spectral sensitivity characteristics of an image sensor. Specifically, in the method described in Patent Document 1, the light generated from the light source through the spectroscope is received by the imaging device, converted into light of an arbitrary single wavelength by the spectroscope, and the spectral sensitivity characteristics of each wavelength It is to evaluate whether there is any change from the original design. In the field of radiation temperature measurement, a device called a black body furnace that can emit light under the condition of an emissivity of 1.0 is used to evaluate the soundness of the radiation thermometer offline and adjust the parameters for calculating the temperature. are being implemented.

JP 2007-17344 A JP-A-9-178669

"Fundamental Theory of Polarization and Its Applications" Transactions of Information Processing Society of Japan Transactions of Transactions 2008(1), 64-72, 2008-11

However, when the method described in Patent Document 1 is applied to an optical sensor installed at a manufacturing site, the apparatus becomes large-scale, and the optical sensor installed at the manufacturing site is once removed for evaluation, then re-installed for imaging. It is necessary to adjust the angle, focus, aperture, etc., which is very time-consuming. Furthermore, it is often necessary to stop the production line when removing or adjusting the optical sensor, which is a factor in lowering production efficiency. In addition, when considering the confirmation method using a black body furnace, since the black body furnace is generally heavy and difficult to bring to the site, there is no method of directly evaluating the soundness of the radiation thermometer at the manufacturing site or readjusting the parameters. not exist. Furthermore, there is a surface inspection apparatus using polarization characteristics as described in Patent Document 2, and the polarization characteristics of optical sensors are also important, but there is no method capable of evaluating such characteristics.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a light receiving characteristic evaluation apparatus and a light receiving characteristic evaluation method for an optical sensor that can easily evaluate the light receiving characteristic of an optical sensor at a manufacturing site. It is in.

A light-receiving characteristic evaluation apparatus for an optical sensor according to the present invention is a light-receiving characteristic evaluation apparatus for an optical sensor that evaluates the light-receiving characteristic of an optical sensor, and includes a light source installed at a position capable of irradiating a light-receiving surface of the optical sensor. a diffusion plate installed between the optical sensor and the light source; and calculating the brightness of the light received by the optical sensor via the diffusion plate; and calculating the brightness of the optical sensor based on the calculated brightness and an evaluation unit for evaluating light receiving characteristics.

The light receiving characteristic evaluation apparatus for an optical sensor according to the present invention is characterized in that, in the above invention, the light is light of a single wavelength.

According to another aspect of the present invention, there is provided a light-receiving characteristic evaluation apparatus for an optical sensor according to the above-described invention, including at least one of a wavelength transmission filter and a polarizing plate between the diffusion plate and the optical sensor.

The apparatus for evaluating light receiving characteristics of an optical sensor according to the present invention is, in the above-described invention, a reflector provided between the diffuser plate and the optical sensor so that the light diffused by the diffuser plate is incident at Brewster's angle. and a light shielding wall that transmits only the light in the specular direction from the reflector to the optical sensor side.

According to another aspect of the present invention, there is provided a light-receiving characteristic evaluation apparatus for an optical sensor according to the above invention, further comprising a wavelength transmission filter between the light shielding wall and the optical sensor.

A method for evaluating light receiving characteristics of an optical sensor according to the present invention is a method for evaluating light receiving characteristics of an optical sensor for evaluating light receiving characteristics of an optical sensor, comprising: an irradiation step of irradiating the optical sensor with light through a diffusion plate; and an evaluation step of calculating the luminance of the light received by the optical sensor and evaluating the light receiving characteristics of the optical sensor based on the calculated luminance.

The method for evaluating light receiving characteristics of an optical sensor according to the present invention is characterized in that, in the above invention, the irradiating step comprises the diffuser plate, a reflector installed so that the light diffused by the diffuser plate is incident at Brewster's angle, and The method is characterized by including a step of irradiating the optical sensor with light through a light shielding wall that transmits only the light in the specular direction from the reflector to the optical sensor side.

In the method for evaluating light receiving characteristics of an optical sensor according to the present invention, in the above invention, the evaluation step includes changing a direction of linearly polarized light irradiated to the optical sensor about the optical axis of the optical sensor, and determining whether the brightness is the minimum or the maximum. and calculating an angle range including the direction of the linearly polarized light, and evaluating the light receiving characteristics of the optical sensor.

According to the light-receiving characteristic evaluation apparatus and light-receiving characteristic evaluation method of an optical sensor according to the present invention, the light-receiving characteristic of an optical sensor can be easily evaluated at the manufacturing site.

FIG. 1 is a schematic diagram showing the configuration of a light-receiving characteristic evaluation system for an optical sensor, which is one embodiment of the present invention. FIG. 2 is a diagram for explaining changes in the amount of light received by the optical sensor that accompany changes in position and tilt. FIG. 3 is a diagram for explaining the effect of the diffusion plate. FIG. 4 is a diagram for explaining diffusion characteristics of a diffusion plate. FIG. 5 is a schematic diagram showing the configuration of a modification of the light receiving characteristic evaluation system for the optical sensor shown in FIG. FIG. 6 is a schematic diagram showing the configuration of a modified example of the light receiving characteristic evaluation system for the optical sensor shown in FIG. FIG. 7 is a schematic diagram showing the configuration of a modified example of the light receiving characteristic evaluation system for the optical sensor shown in FIG. FIG. 8 is a diagram showing the relationship between the polarization direction of linearly polarized light and the luminance value. FIG. 9 is a schematic diagram showing the configuration of a modified example of the light receiving characteristic evaluation system for the optical sensor shown in FIG. FIG. 10 is a schematic diagram showing the configuration of a modification of the light receiving characteristic evaluation system for the optical sensor shown in FIG. FIG. 11 is a diagram showing changes in reflectance for S-polarized light and P-polarized light with respect to changes in incident angle.

Hereinafter, the configuration of a light receiving characteristic evaluation system for an optical sensor, which is an embodiment of the present invention, will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of a light-receiving characteristic evaluation system for an optical sensor, which is one embodiment of the present invention. As shown in FIG. 1, an optical sensor light receiving characteristic evaluation system (hereinafter abbreviated as a light receiving characteristic evaluation system) 1 according to an embodiment of the present invention evaluates the light receiving characteristic of an optical sensor 2 to It is a system for evaluating soundness, and includes an irradiation device 3, an evaluation device 4, and a display device 5 as main components.

The irradiation device 3 includes a light source 31 , a diffusion plate 32 , a DC power supply 33 and a CRD (Current Regulative Diode) 34 .

The light source 31 is arranged in front of the optical sensor 2 so that the light L is emitted substantially perpendicularly to the light receiving surface of the optical sensor 2 through the lens system 2a of the optical sensor 2, and irradiates the optical sensor 2 with the light L. do. The light source 31 may be a thermal radiation light source such as an incandescent light bulb or a halogen light bulb, a discharge light source such as a metal halide light source or a xenon light source, an electroluminescence light source such as an LED (Light Emitting Diode) or an EL (Electro Luminescence) light source, or a laser light source. can be used. Of these, the thermal emission light source has a problem of stability due to deterioration, while the discharge light source has a problem of large-scale equipment and time responsiveness. In addition, LED and laser light sources are compact, have high responsiveness, and often stabilize the amount of light in a short period of time, but often have high directivity. The optical characteristics of the light L are known by being measured in advance.

In order to stabilize the light intensity of the light source 31, a temperature compensation circuit is incorporated in consideration of changes in the light intensity of the light source 31 due to temperature changes, or the temperature of the usage environment is measured with a thermocouple or the like, and the measured value of the light intensity is taken as a reference temperature. You may correct|amend to the light quantity in. Also, the light quantity of the light source 31 may be evaluated by a calibrated power meter or the like with traceability before use, and the light quantity of the light source 31 itself may be used after confirming that it satisfies the standard.

The diffusion plate 32 weakens the directivity of the light source 31 by diffusing the light L emitted from the light source 31 and supplies the light to the optical sensor 2 side. As shown in FIGS. 2A and 2B, when a highly directional light source 31 is installed in front of the optical sensor 2, the optical sensor 2 may be affected by a slight change in position or inclination of the optical sensor 2 or the light source 31. The amount of received light greatly changes (light L1 changes to light L2 in this example). In general, it is difficult to accurately install the optical sensor 2 at the manufacturing site. Therefore, it is difficult to use the light source 31 with high directivity while the optical sensor 2 is installed at the manufacturing site. On the other hand, as shown in FIGS. 3(a) and 3(b), by weakening the directivity of the light from the light source 31 with the diffusion plate 32, a constant amount of light L3 can be emitted even if the installation accuracy is slightly lowered. The optical sensor 2 can be illuminated. A plurality of diffuser plates 32 may be installed as necessary.

The diffusion characteristics of the diffusion plate 32 are determined by the achievable installation accuracy, the directivity of the light from the light source 31, and the target accuracy when measuring the amount of light. In other words, based on the directivity of the light emitted from the light source and passing through the diffusion plate, the amount of change in light when the mechanical alignment deviates from the design position is determined, and the light is diffused so that this amount of change is within the allowable range. Determine the diffusion properties of the plate. Here, FIG. 4 shows the concept of the diffusion characteristics of the diffusion plate 32. As shown in FIG. For example, let α be the spread angle of light at which the amount of light from the light source 31 to be used is regarded as uniform, β be the alignment angle error of the optical sensor 2 assumed at the time of installation, and γ be the diffusion angle of the diffusion plate 32. If the diffusion angle of the diffuser plate 32 is set so as to satisfy the formula (1) shown, the light source 31 can always irradiate a constant amount of light L stably. If the angular characteristic α is unknown, the following formula (2) should be satisfied.

Return to FIG. The DC power supply 33 is composed of a battery or the like, and supplies power to the light source 31 via the CRD 34 . The CRD 34 supplies a constant current to the light source 31 so that the current supplied to the light source 31 does not change due to aged deterioration of the power supply source.

The evaluation device 4 is composed of a well-known information processing device such as a computer, and functions as a brightness calculation unit 41 and a light reception characteristic evaluation unit 42 by executing a computer program by an arithmetic processing device inside the information processing device.

The optical sensor 2 detects the light L with a predetermined exposure time and gain, and converts it into an electric signal and an image. The converted electric signal or image is sent to the brightness calculator 41 to calculate the representative value of brightness. It is preferable to calculate the representative value of luminance after a sufficient period of time has passed since the light source 31 was turned on and the output of the optical element has stabilized. In addition, as a method for calculating the representative value of luminance, various calculation methods such as maximum luminance, average luminance, and average luminance in a certain range obtained by rearranging the luminance of all pixels in ascending order are conceivable. Anything is fine.

The light-receiving characteristic evaluation unit 42 evaluates the light-receiving characteristic of the optical sensor 2 by comparing the representative value of the luminance calculated by the luminance calculating unit 41 with the reference luminance. The light receiving characteristics evaluated by the optical sensor 2 are different. For example, in a radiation thermometer, the light reception characteristics of light in a specific wavelength range are important. In this case, a light source 31 suitable for that wavelength band may be used, or, as shown in FIG. A long-pass filter, a short-pass filter, a band-pass filter, or the like can be used as the wavelength transmission filter 35, and a plurality of wavelength transmission filters may be combined as necessary.

For optical sensors that are sensitive only to specific polarized light, it is also important to evaluate the light-receiving characteristics of that polarized state. For example, when it is desired to evaluate the light receiving characteristics of an optical sensor that is sensitive only to linearly polarized light of θ°, as shown in FIG. Light receiving characteristics can be evaluated by attaching the sensor at a constant angle. In addition, by similarly installing a polarizing plate with a transmission axis angle of (θ + 90)° and evaluating whether or not the luminance is below the reference value, it is possible to confirm whether the direction of the received linearly polarized light has changed. . If the brightness is not below the reference value, the orientation of the linearly polarized light to which this optical sensor has the highest sensitivity can be evaluated by gradually changing the mounting position around the optical axis and finding the angle at which the brightness is the minimum. can.

Also, for an optical sensor having a light-receiving characteristic in which a polarizing plate and a wavelength plate are combined, a similar evaluation can be made by appropriately placing the polarizing plate and the wavelength plate behind the diffusion plate. Specifically, assuming that the transmission axis angle of the polarizing plate is θ° and the fast axis angle of the wave plate (here, a 1/4λ wave plate) is φ°, as shown in FIG. By installing a polarizing plate 37 with a transmission axis angle of (θ+90)° and a 1/4λ wavelength plate 38 with a fast axis angle of (φ+90)° and evaluating whether the brightness obtained is below a reference value, light is received. It can be checked whether the polarization state of the light has changed.

Return to FIG. The display device 5 is composed of a well-known display device such as a liquid crystal display device, and displays the evaluation result of the light receiving characteristics of the optical sensor 2 by the evaluation device 4 . Refer to the evaluation result of the light receiving characteristics, and if a luminance difference exceeding the allowable light amount error occurs, take measures such as removing the optical sensor 2 to investigate the cause, readjusting the optical sensor 2, etc. . Further, the luminance value and the amount of irradiation light obtained in this measurement may be regarded as positive, and the temperature calibration curve itself may be corrected.

One of the factors that require a large-scale apparatus when evaluating the light receiving characteristics of an optical sensor is the need to make a reference light beam incident on the target optical sensor with a certain mechanical alignment. In many cases, the light from the light source is directional, and small changes in mechanical alignment with respect to the optical sensor will change the received brightness of the optical sensor. Therefore, as described above, in this embodiment, the diffuser plate that weakens the directivity of the light from the light source and provides uniform angular characteristics is used to overcome the problem of mechanical alignment, thereby providing a portable and stable light source at the manufacturing site. By applying it directly to the optical sensor being installed, it is possible to easily evaluate the light-receiving characteristics of the optical sensor without removing it.

[Example 1]
In this example, before introducing the light receiving characteristics of an optical sensor for radiation temperature measurement into a production line and after operation for a certain period of time, it was evaluated whether or not the wavelength related to a specific wavelength changed. Specifically, first, when the optical sensor is introduced, the amount of light is measured with a power meter in advance for the light source for the light receiving characteristic evaluation system described above, and the light receiving sensor is measured using the light receiving characteristic evaluation system that you want to evaluate this light source. was measured. The light receiving wavelength of the optical sensor is 900 nm, the number of pixels is 640 × 480, the target is imaged under the conditions of aperture 2.8 and exposure time 1.0 ms, and the brightness value is calculated by converting it into an 8-bit 256-gradation digital signal. evaluated. An example of an area sensor camera is shown here, but the same applies to line sensor cameras and spot sensors. Under these conditions, the light source was installed in front of the optical sensor, and the reference luminance was calculated based on the image obtained by the optical sensor receiving light. When the luminance of all pixels was sorted in ascending order and the average value of the luminance of the 1st to 50th pixels was calculated, the luminance before introducing the optical sensor into the production line was 150 (8 bits, minimum value 0, maximum value 256). there were. At this time, an LED was used as the light source for the light receiving characteristics evaluation system, and the diffusion plate was experimentally determined for the mechanical alignment error when the light source was installed on the optical sensor. element was adopted. Next, we installed the optical sensor at the manufacturing site, evaluated its optical characteristics after using it for a certain period of time, and compared it with the value measured with a power meter in advance of the light source, confirming that the amount of light had not changed from before it was introduced. The representative value of the luminance was 147 as a result of installation, imaging, and processing under the same conditions and the same method as when the light amount of the light source was introduced. Assuming that the allowable light amount error is within ±5%, 5% of the luminance 150 at the time of introduction is 7.5, so the luminance difference 3 is within the reference range. Therefore, it was determined that the light receiving characteristics of the optical sensor were within the allowable range.

[Example 2]
In this example, the light-receiving characteristics of an optical sensor having polarization characteristics were evaluated. For an optical sensor that transmits only 0° linearly polarized light, such as by installing a linear polarizing plate in front of the light receiving element, the light receiving characteristics may be evaluated before introducing the production line and during operation in the same manner as in Example 1 above. Attention should be paid to the following points.

・When installing the light source on the optical sensor, always install it at the same position around the optical axis.
・As shown in FIG. 6, the light L from the light source 31 is transmitted through the diffusion plate 32, and then transmitted through a polarizing plate having a transmission axis angle of 0° or a transmission axis angle of 90°, and then received by the optical sensor 2. .

An optical sensor adjusted to have sensitivity in the direction of polarization of γ before being introduced into the production line was evaluated by comparing the brightness after use for a certain period of time with the brightness before being introduced into the production line. When a polarizing plate is attached in front of the light source so that the transmission axis angle perpendicular to the polarization direction of the optical sensor is γ + 90°, the light source is placed in the optical sensor and the light is irradiated. If the orientation had changed, the brightness should have increased. When the luminance was actually measured and the representative value was evaluated, it was 150% of the luminance before introduction. For example, if the allowable range is 120% or less, it exceeds the allowable range. Therefore, the luminance value was evaluated by gradually changing the polarizing plate placed in front of the light source around the optical axis. As a result, it was found that the direction of the linearly polarized light received by the optical sensor was deviated by 2°. adjusted to be in the state of In this standard, the luminance value under the condition that the polarizing plate is attached to the light source so that the transmission axis angle is γ + 90° in the initial adjusted state is used. The representative value Ib of luminance is measured in advance under the condition that the polarizing plate is attached to the light source so that the angle is γ, and the polarizing plate is attached to the light source so that the transmission axis angle is γ + 90° when managing during operation. A ratio r (for example, 3% or less) to the representative value Ib of the luminance when

In this example, the transmission axis of the polarizing plate placed in front of the light source was set perpendicular to the direction of the polarized light to which the optical sensor is sensitive. can be checked. At that time, for example, a criterion such as that the luminance does not decrease by 5% or more may be set. Further, when the polarizing plate mounted in front of the light source is changed around the optical axis so as to minimize the luminance, the light source and the polarizing plate may be integrated and the light source itself may be rotated around the optical axis.

When the light source is installed in the optical sensor, the polarizing plate installed in the light source is changed around the optical axis to search for the direction of the polarized light received by the optical sensor from the minimum position, as shown in FIG. Thus, the controller 7 may be used to automatically adjust the transmission axis angle of the polarizing plate 6 based on the obtained representative value of luminance. Specifically, the representative luminance value I is measured by the optical sensor 2 while changing the transmission axis angle θ by Δθ from the luminance representative value I ₀ and the transmission axis angle θ ₀ obtained by the optical sensor 2 in the initial state. Based on the obtained change in the representative value I of luminance and the change in the transmission axis angle θ, the controller 7 further changes the transmission axis angle θ so that the representative value I of luminance becomes smaller. is the minimum transmission axis angle θ. As a method of searching for the minimum value, a full search method, a steepest descent method, or the like can be used, but any method may be used as long as the direction of polarization that finally becomes the minimum can be calculated.

Here, in adjusting the orientation of the polarizing plate of the optical sensor, the orientation (angle) that achieves the minimum luminance or the maximum luminance is examined, the polarization orientation of the optical sensor is confirmed, and the entire surface of the light receiving element of the optical sensor is checked. The direction of the polarizing plate is adjusted. In this case, the concepts of minimum luminance and maximum luminance do not need to completely match the minimum luminance value and maximum luminance value. After searching the angular range of the polarization direction of the optical sensor that includes the minimum luminance value or the maximum luminance value, based on the angle sufficiently close to the minimum luminance value or maximum luminance value that satisfies the luminance tolerance range, the optical sensor The orientation of the polarizing plate over the entire surface of the light receiving element may be adjusted.

In addition, although this example uses only linearly polarized light, the phases of circularly polarized light and elliptically polarized light can also be evaluated in the same way by installing a wave plate and a polarizing plate in front of the optical sensor. It is possible. Also, when evaluating a plurality of wavelengths such as the light receiving characteristics of a color camera, one light source having broad wavelength characteristics may be used, or a light source may be prepared for each wavelength. In addition, when evaluating multiple polarization characteristics such as the light receiving characteristics of a 4-channel polarization camera, one light source having polarization characteristics is installed at multiple positions around the optical axis, or four light sources are used. may

[Example 3]
In Example 2, the linearly polarized light transmission characteristics of the optical sensor were evaluated by changing the orientation of a polarizing plate with a known transmission axis angle around the optical axis and evaluating the luminance value. However, there is a possibility that the direction of the transmission axis of the polarizing plate may change due to the position of the polarizing plate being displaced due to deterioration over time or vibration during use. Cannot be evaluated. Therefore, in this embodiment, linearly polarized light is realized by utilizing the physical property that when light is incident on a reflecting surface at Brewster's angle, the P-polarized light of the reflected light in the direction of regular reflection becomes 0. FIG. 10 shows the configuration of a specific light-receiving characteristic evaluation system for an optical sensor, where the Brewster's angle is θb.

As shown in FIG. 10, in this embodiment, a reflector 51 is installed behind the diffusion plate 32, and the light from the light source 31 diffused by the diffusion plate 32 enters the reflector 51 at the Brewster angle θb. The orientation of the reflector 51 is adjusted as shown in FIG. Here, when a glass substrate having a refractive index of 1.5 is used as the reflector 51, the Brewster angle θb is 56°. However, the reflector 51 is not limited to a glass substrate, and an aluminum mirror or the like may be used. Moreover, it is preferable that the reflector 51 has high specularity. Moreover, since the refractive index of light on the surface of the reflector 51 changes slightly depending on the wavelength, the light source 31 is preferably a single-wavelength light source.

According to such a configuration, the light beam reflected by the reflector 51 and incident on the optical sensor 2 becomes only the S-polarized component perpendicular to the plane formed by the incident light and the reflected light. It is possible to obtain light beams with linearly polarized light that is practically accurate. Note that light rays in directions other than the specular reflection direction contain P-polarized light components and thus cause noise. Therefore, as shown in FIG. 10, a light shielding wall 52 is used between the reflector 51 and the optical sensor 2 so that only light rays in the specular direction are transmitted to the optical sensor 2 side. As a result, when the optical sensor 2 has a linearly polarized light transmission characteristic, by rotating the irradiation device 3 around the optical axis and searching for the position where the light receiving luminance of the optical sensor 2 is the minimum, the transmission polarization direction of the optical sensor 2 is determined. can be evaluated accurately.

A wavelength transmission filter 35 that transmits only light in a specific wavelength band may be installed behind the light shielding wall 52 . Moreover, it is desirable that the incident light to the reflector 51 is in a non-polarized state. If the incident angle is the same as Brewster's angle θb, the P-polarized component is 0 regardless of the polarization state. However, if the incident angle is slightly different from the Brewster angle θb, the phase may change and the maximum vibration direction may differ from the S-polarized direction unless it is in a non-polarized state such as circularly polarized light. It becomes an error factor when evaluating Therefore, if the incident light to the reflector 51 is in a non-polarized state, the maximum vibration direction will be the same as the S-polarization direction even if the incident angle is slightly different from the Brewster angle θb. As a result, when evaluating the transmission polarization direction of the optical sensor 2, even if some P-polarized components are present, the irradiation device 3 is rotated around the optical axis to search for the position where the light-receiving luminance of the optical sensor 2 is the minimum. Thus, the linearly polarized light transmission characteristic of the optical sensor 2 can be evaluated without deviation from the Brewster angle .theta.b becoming an error factor.

FIG. 11 shows changes in the reflectance of S-polarized light and P-polarized light with respect to changes in the incident angle when the relative refractive index n is 1.5. In FIG. 11, a solid line L1 indicates the reflectance for S-polarized light, and a dashed line L2 indicates the reflectance for P-polarized light (see Non-Patent Document 1). As shown in FIG. 11, within an angle range of at least ±10° with respect to the incident angle (Brewster angle) at which the reflectance of P-polarized light is 0, the reflectance of S-polarized light is higher than that of P-polarized light. It turns out to be strong enough. Therefore, by adjusting the orientation of the reflector 51 so that the light from the light source 31 diffused by the diffusion plate 32 is incident on the reflector 51 within an angle range of at least ±10° with respect to Brewster's angle θb, It can be seen that the transmission polarization direction of the optical sensor 2 can be accurately determined.

Although the embodiments to which the inventions made by the present inventors are applied have been described above, the present invention is not limited by the descriptions and drawings forming part of the disclosure of the present invention according to the embodiments. That is, other embodiments, examples, operation techniques, etc. made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

REFERENCE SIGNS LIST 1 optical sensor light receiving characteristic evaluation system 2 optical sensor 2a lens system 3 irradiation device 4 evaluation device 5 display device 6 polarizing plate 7 controller 31 light source 32 diffusion plate 33 DC power supply 34 CRD
35 wavelength transmission filter 36 polarizing plate 37 polarizing plate 38 1/4λ wavelength plate 41 luminance calculator 42 light receiving characteristic evaluation unit 51 reflector 52 light shielding wall L, L1, L2, L3 Light

Claims (8)

A light-receiving characteristic evaluation device for an optical sensor for evaluating light-receiving characteristics of an optical sensor,
a light source installed at a position capable of irradiating the light receiving surface of the optical sensor;
a diffusion plate installed between the optical sensor and the light source;
an evaluation unit that calculates the luminance of the light received by the optical sensor through the diffusion plate and evaluates the light receiving characteristics of the optical sensor based on the calculated luminance;
Let α be the light spread angle at which the light intensity of the light source is considered uniform, β be the alignment angle error of the optical sensor assumed at the time of installation, and γ be the diffusion angle of the diffuser plate. A light-receiving characteristic evaluation apparatus for an optical sensor, wherein the angle γ satisfies the condition shown in the following formula (1).

2. The apparatus for evaluating light receiving characteristics of an optical sensor according to claim 1, wherein said light is light of a single wavelength. 3. The apparatus for evaluating light receiving characteristics of an optical sensor according to claim 1, wherein at least one of a wavelength transmission filter and a polarizing plate is provided between said diffusion plate and said optical sensor. a reflector installed between the diffuser plate and the optical sensor so that the light diffused by the diffuser plate is incident at Brewster's angle; 3. The apparatus for evaluating light receiving characteristics of an optical sensor according to claim 1, further comprising a light shielding wall for transmitting light to the sensor side. 5. The apparatus for evaluating light receiving characteristics of an optical sensor according to claim 4, further comprising a wavelength transmission filter between said light shielding wall and said optical sensor. A light-receiving characteristic evaluation method for an optical sensor for evaluating light-receiving characteristics of an optical sensor, comprising:
an irradiation step of irradiating the optical sensor with light from a light source through a diffusion plate;
an evaluation step of calculating the luminance of the light received by the optical sensor and evaluating the light receiving characteristics of the optical sensor based on the calculated luminance;
Let α be the light spread angle at which the light intensity of the light source is considered uniform, β be the alignment angle error of the optical sensor assumed at the time of installation, and γ be the diffusion angle of the diffuser plate. A method for evaluating light receiving characteristics of an optical sensor, wherein the angle γ satisfies the condition shown in the following formula (1).

The irradiation step includes the diffusion plate, a reflector installed so that the light diffused by the diffusion plate is incident at Brewster's angle, and only the light in the specular direction from the reflector to the optical sensor side. 7. The method for evaluating light receiving characteristics of an optical sensor according to claim 6, further comprising the step of irradiating the optical sensor with light through a light shielding wall that allows the light to pass through. In the evaluation step, the direction of linearly polarized light irradiated to the optical sensor is changed around the optical axis of the optical sensor, the angle range including the direction of the linearly polarized light that minimizes or maximizes the brightness is calculated, and the optical 8. The method for evaluating light receiving characteristics of an optical sensor according to claim 6, further comprising a step of evaluating light receiving characteristics of the sensor.

Images