Light measuring device and method for measuring light

Abstract

To provide a light measuring device and a method for measuring light which can suppress increase of measurement errors and enlarge a dynamic range by inserting an optical attenuation member into an optical path for measurement target light or removing the optical attenuation member from the optical path for measurement target light.SOLUTION: The light measuring device includes: a division optical system for dividing a measurement target light from a measurement target object into plural measurement target lights; a wavelength selection filter which the measurement target lights formed by division by the division optical system enter; and a color measurement optical system having a light reception sensor for receiving the measurement target light having passed through the wavelength selection filter. The light measuring device further includes a light attenuation member which can be inserted into an optical path for measurement target light or can be removed from the optical path for measurement target light, and the light attenuation member is arranged ahead of the division optical system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photometric device and a photometric method capable of measuring the luminance, chromaticity, etc. of light emitted from an object to be measured, such as a display or liquid crystal monitor of a smartphone. [Background technology]

[0002] As such a photometric device, as shown in FIG. 24, a photometric device 100 is known that includes a branching optical system 120 that branches a light 201 to be measured from an object 200 to a plurality of beams (see, for example, Patent Document 1).

[0003] This photometric device 100 includes an objective optical system 110 consisting of a convex lens or the like, a branching optical system 120, and color measurement optical systems 130 to 150. As an example, a fiber bundle is used for the branching optical system 120. A fiber bundle is formed by bundling a plurality of small-diameter bare fibers, randomly branching the bundle into a plurality of fibers (for example, three corresponding to the tristimulus values ​​of color matching functions X, Y, and Z defined by the CIE (International Commission on Illumination)) at the output end (exit) side, and bundling the fibers together. In some cases, a diffusion plate is used as the branching optical system 120.

[0004] As the color measurement optical systems 130 to 150, for example, wavelength selection filters and light receiving sensors are combined in the same number as the number of branches of the branching optical system 120 and used.

[0005] The light received by each light receiving sensor is converted into an electric signal, and then subjected to processing such as I / V conversion and amplification in the corresponding electrical processing units 161a to 161c, and input as light receiving data to the control unit 162. The control unit 162 performs calculations based on the input light receiving data to calculate a measurement value.

[0006] Recently, displays with a wide dynamic range of luminance are used in smartphones, etc. For this reason, photometric devices are required to have the ability to measure a wide range of luminance from dark to bright when performing gamma inspection and adjustment. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5454675 Summary of the Invention [Problem to be solved by the invention]

[0008] In order to widen the dynamic range of the photometric device 100, it is necessary to control the amount of received light due to the photoelectric conversion capability of the light receiving sensor (saturation of the light receiving sensor) and the constraints of the design conditions of the electrical processing units 161a to 161c. For this purpose, it is conceivable to insert and remove a light attenuation member in the optical path of the measured light 201 from the measured object 200 until it is incident on the light receiving sensor, depending on the brightness of the measured object 200.

[0009] However, the inventors' research has revealed that, depending on the position at which the light attenuation member is inserted or removed in the optical path, multiple reflections can occur between the light attenuation member and other components of the photometric device 100, such as the wavelength selection filters and light receiving sensors of the colorimetric optical systems 130-150, which can cause changes in the light receiving spectral sensitivity of the colorimetric optical systems 130-150 and increase measurement errors.

[0010] This invention has been made based on the above technical background, and aims to provide a photometric device and a photometric method that can expand the dynamic range by inserting and removing a light attenuation member in the optical path of the light to be measured, while suppressing an increase in measurement error. [Means for solving the problem]

[0011] The above object can be achieved by the following means. (1) a branching optical system that branches the light to be measured from the object to be measured into a plurality of beams; a color measuring optical system having a wavelength selection filter into which the light to be measured branched by the branching optical system is incident, and a light receiving sensor that receives the light to be measured that has passed through the wavelength selection filter; In a photometric device comprising: a light attenuating member that can be inserted into and removed from an optical path of the light to be measured, A photometric device, wherein the light attenuation member is disposed in front of the branching optical system. (2) A photometric device as described in the preceding paragraph 1, wherein the light attenuation member is inserted or removed depending on the brightness of the object to be measured. (3) A photometric device according to the preceding paragraph 1 or 2, wherein the light attenuation member is a thin film filter. (4) The photometric device according to the preceding paragraph 1 or 2, wherein the light receiving sensor is a silicon sensor. (5) A photometric device according to the preceding paragraph 1 or 2, wherein the wavelength-selective filter is a thin-film filter. (6) The photometric device according to the preceding paragraph 1 or 2, wherein the branching optical system is a diffusion plate. (7) A photometric device according to the preceding paragraph 1 or 2, wherein the branching optical system is a bundle fiber. (8) The photometric device according to the preceding paragraph 7, wherein the length of the bundle fiber is 50 times or more the diameter of the core of the fiber. (9) A mirror is provided in front of the branching optical system to guide the light to be measured to an observation optical system, 3. The photometric device according to claim 1 or 2, wherein the light attenuation member is disposed between the mirror and the branching optical system. (10) The photometric device according to item 1 or 2, wherein the wavelength selection filter is a color matching function filter. (11) The photometric device according to item 1 or 2, wherein the wavelength-selecting filter is a spectral filter, and the light-receiving sensor is a line sensor. (12) a branching optical system that branches the light to be measured from the object to be measured into a plurality of beams; a color measuring optical system having a wavelength selection filter into which the light to be measured branched by the branching optical system is incident, and a light receiving sensor that receives the light to be measured that has passed through the wavelength selection filter; In a photometric device having the above-mentioned, a position in front of the branching optical system is provided, A photometric method comprising inserting and removing a light attenuating member into and from the optical path of the light to be measured. Effect of the Invention

[0012] According to the photometric device and photometric method of the present invention, the light attenuating member is disposed ahead of the branching optical system and is inserted into and removed from the optical path of the light to be measured. When the light attenuating member is inserted into the optical path, the light to be measured that passes through the light attenuating member and is branched by the branching optical system is transmitted through the wavelength selection filter and received by the light receiving sensor, but a part of the light to be measured is reflected by the surfaces of the wavelength selection filter and the light receiving sensor.

[0013] The light to be measured reflected by the colorimetric optical system passes through the branching optical system and returns to the light attenuation member, but as a result of passing through the branching optical system and being diffused and emitted from the branching optical system, the intensity of the light traveling straight to the light attenuation member is reduced. This straight-traveling light is reflected by the light attenuation member and passes through the branching optical system again to reach the colorimetric optical system, but the intensity of this reflected light is also reduced. The reflected light that returns to the colorimetric optical system is received by the light receiving sensor, but a portion of it is reflected again by the colorimetric optical system and returns to the light attenuation member, and this process is repeated, causing multiple reflections between the light attenuation member and the colorimetric optical system. However, as a result of the reflected light being scattered each time it returns to the branching optical system, the influence of the total reflected light received by the light receiving sensor is significantly reduced.

[0014] In other words, by inserting and removing the light attenuation member into the optical path of the light to be measured before the branching optical system, the effects of multiple reflections that occur between the light attenuation member and the colorimetric optical system can be reduced, thereby suppressing changes in the spectral sensitivity of the received light and thereby suppressing increases in measurement errors. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing an internal configuration of a photometric device according to a first embodiment of the present invention. [Diagram 2] FIG. 13 is an explanatory diagram of a light attenuation member using a thin film filter. [Diagram 3] 1 is a graph showing an example of the actual transmittance for each wavelength of a glass absorption filter and a thin film filter, both of which have a transmittance T≈5%. [Figure 4] 1 is a graph showing the transmittance for each wavelength when a glass absorption filter and a thin film filter are combined with a Y filter, which is a wavelength-selective filter, in comparison with the color matching function Y. [Diagram 5] 1 is a graph showing an example of the reflection characteristics of a silicon sensor used as a light receiving sensor. [Figure 6] FIG. 1A is a schematic diagram for explaining how incident light is reflected by an interference filter used as a wavelength-selective filter, and FIG. 1B is a graph showing the transmittance and reflectance of the interference filter. [Figure 7] Graphs (A) and (B) respectively show an example of the transmittance and reflectance in the visible light region (wavelengths of 380 to 780 nm) of a light-attenuating member made of a thin-film filter in which the thin film is a metal oxide film of niobium oxide. [Figure 8] 13 is a configuration diagram of a photometric device when the insertion / removal position of the light attenuation member is between a wavelength selection filter and a light receiving sensor. FIG. [Figure 9] 9 is a schematic explanatory diagram showing the occurrence of multiple reflections between the light attenuation member and the wavelength selection filter and light receiving sensor in the configuration of FIG. 8. FIG. [Figure 10] FIG. 1A shows the transmission and reflection of the light to be measured at a wavelength of about 500 nm when using a Y filter as an example, and FIG. 1B shows the transmission and reflection of the light to be measured when a light attenuation member is inserted behind the Y filter. [Figure 11] 11 is a graph showing the effect of multiple reflection between a light attenuation member and a wavelength selective filter in a state where the light attenuation member is inserted behind the wavelength selective filter. [Figure 12] 11A and 11B are diagrams illustrating transmission, reflection, and reception of light to be measured in a state in which a light attenuating member is inserted in front of a light receiving sensor. [Figure 13] 13 is a graph showing the effect of multiple reflections between a light attenuating member, the wavelength selective filter, and the light receiving sensor in a state where the light attenuating member is inserted behind the wavelength selective filter. [Figure 14] 13 is a configuration diagram of a photometric device when the insertion / removal position of the light attenuation member is in front of the wavelength selection filter. FIG. [Figure 15] 15 is a schematic explanatory diagram showing the occurrence of multiple reflections between the light attenuation member and the wavelength selection filter and light receiving sensor in the configuration of FIG. 14. FIG. [Figure 16]FIG. 2 is a schematic explanatory diagram for explaining the reason why the influence of multiple reflections is reduced in the configuration of the first embodiment. [Figure 17] FIG. 11 is a block diagram showing the internal configuration of a photometric device according to a second embodiment of the present invention. [Figure 18] 1A and 1B are diagrams illustrating the optical mixing effect of an optical fiber. [Figure 19] 13(A) and 13(B) are diagrams for explaining the optical mixing effect in an optical fiber. [Figure 20] FIG. 11 is a block diagram showing the internal configuration of a photometric device according to a third embodiment of the present invention. [Figure 21] FIG. 11 is a block diagram showing the internal configuration of a photometric device according to a fourth embodiment of the present invention. [Figure 22] FIG. 11 is a block diagram showing the internal configuration of a photometric device according to a fifth embodiment of the present invention. [Figure 23] 5 is a flowchart for explaining a control method for inserting and removing a light attenuation member, which is performed in each photometric device according to the present embodiment. [Figure 24] FIG. 1 is a block diagram showing a general configuration of a photometric device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Embodiment 1] <Overall composition> FIG. 1 is a block diagram showing the configuration of a tristimulus value type photometric device according to an embodiment of the present invention.

[0017] In FIG. 1, a photometric device 10 is used, for example, in an inspection process on a manufacturing line for smartphone displays, and measures the brightness, chromaticity, and the like of a display surface of an object 1 to be measured, that is, a display.

[0018] The photometric device 10 includes an objective optical system 11, a branching optical system 12, colorimetric optical systems 13-15, and a light attenuation member 40. A convex lens 11a having a positive power is used in the objective optical system 11. A diffusion plate 20 having the functions of branching and diffusing light is used in the branching optical system 12.

[0019] An aperture stop 11b is disposed at the rear focal position of the convex lens 11a, and a front telecentric optical arrangement is adopted in order to capture components within a predetermined angle (e.g., ±2.5 degrees) with respect to the normal to the measurement surface, which is the display surface of the object 1. A diffuser 20 is disposed behind the aperture stop 11b.

[0020] An optical attenuation member 40 is disposed between the convex lens 11a and the diffusion plate 20, in front of the aperture stop 11b surface. The optical attenuation member 40 is driven by an insertion / removal device 50, which is a driving device, so as to be inserted into or removed from the optical path of the measured light 2. The insertion / removal device 50 is formed, for example, of a linear actuator. When the optical attenuation member 40 is inserted into the optical path of the measured light 2, the amount of the measured light 2 incident on the diffusion plate 20 is reduced by the optical attenuation member 40. When the optical attenuation member 40 is removed from the optical path of the measured light 2, the measured light 2 is incident on the diffusion plate 20 without a reduction in the amount of light.

[0021] The light attenuating member 40 is inserted or removed depending on the brightness of the object 1 to be measured. Specifically, when the object 1 to be measured is dark, it is in a retracted state, and when the object 1 to be measured is bright, it is inserted into the optical path to reduce the amount of light and prevent saturation of the light receiving sensors 13b, 14b, and 15b. This allows the intensity of the light to be measured 2 to be within the dynamic range of the light receiving sensors 13b, 14b, and 15b, and as a result, the dynamic range of the photometric device 10 is expanded. In the following description, the light attenuating member is also referred to as an ND filter.

[0022] It is desirable to place the light attenuating member 40 near the focusing position of the objective optical system 11 (position of the aperture stop 11b). In the light receiving path of the measured light 2, the effective light path at the position of the aperture stop is small. The smaller the effective light path, the smaller the size of the light attenuating section 40 material can be, the smaller the insertion / removal device 50 can be, and the lower the driving torque can be. This makes the product size more compact, lighter, and less expensive. It is not necessary to provide the aperture stop 11b.

[0023] The type of light attenuating member 40 is not limited, and various types such as a thin film filter, a glass absorption filter, and a porous plate can be used. However, it is important that the light attenuating member 40 has spectral flatness (uniformity). This is because the flatness affects the spectral response when the light attenuating member 40 is inserted or removed (when the light attenuating member 40 is present or removed). If the light attenuating member 40 is not flat, the received light spectral sensitivity when the light attenuating member 40 is not present (retracted from the optical path) will differ from the received light spectral sensitivity when the light attenuating member 40 is present (inserted into the optical path). If the received light spectral sensitivity deviates from the color matching function, it will result in an error in luminance and chromaticity. It is also important that there is no change due to the environmental temperature, etc.

[0024] Glass absorption filters have poor spectral flatness and large changes in transmittance due to environmental temperature. Perforated plates have spectral flatness, but measurement unevenness occurs in the acceptance angle. Strict position repeatability is also required. Thin film filters have good spectral flatness and are highly reliable regardless of environmental temperature. For this reason, it is preferable to use a thin film filter as the light attenuation member 40.

[0025] An example of a light attenuating member 40 using a thin film filter is shown in FIG.

[0026] 2, the light attenuating member 40 includes thin films 42 and 43, and a transparent substrate 41 that supports the thin films 42 and 43. The transparent substrate 41 is formed of an optical material that is transparent to the light to be measured 2, such as glass, plastic, quartz, or sapphire. The transparent optical material that forms the transparent substrate 41 can be appropriately selected depending on the wavelength range of the light to be measured 2.

[0027] Each of the thin films 42 and 43 is formed on at least one of the incident surface 41a or the exit surface 41b of the corresponding transparent substrate 41. Specifically, the light attenuation member 40 includes at least one of the thin films 42 and 43. The thin film 42 is formed on the incident surface 41a of the transparent substrate 41. The thin film 43 is formed on the exit surface 41b of the transparent substrate 41. Specifically, the thin films 42 and 43 are formed on both the 41a and the exit surface 41b of the corresponding transparent substrate 41.

[0028] Specifically, the light attenuation member 40 includes a thin film 42 formed on the incident surface 41a of the transparent substrate 41 and a thin film 43 formed on the exit surface 41b of the transparent substrate 41. The thin films 42 and 43 may have the same film configuration or different film configurations. The thin films 42 and 43 may be formed of the same material or different materials. The thin films 42 and 43 may be interference films using a dielectric material such as SiO2 or MgF2 as their material, or may be metal oxide films using a metal oxide material such as Al2O3, TiO2, Nb2O5, or NbO. Alternatively, a metal material such as Cr or Nb may be used.

[0029] As the light attenuating member 40, an absorptive light attenuating member that absorbs light inside a substrate (e.g., a glass substrate) is known. The degree of freedom in designing the transmission spectrum of the absorptive light attenuating member is relatively low. Furthermore, the stability of the absorptive light attenuating member against environmental temperature and environmental humidity is relatively low. In contrast, the degree of freedom in designing the transmission spectrum of an interference type light attenuating member (e.g., a light attenuating member 40 including thin films 42, 43 made of interference films) is relatively high. Furthermore, the stability of the interference type light attenuating member against environmental temperature and environmental humidity is relatively high.

[0030] For reference, Fig. 3 shows the actual transmittance for each wavelength of the glass absorption filter and thin film filter in the visible light region (wavelengths 380 to 780 nm). In both cases, the average transmittance is T ≈ 5%. Fig. 4 shows the transmittance for each wavelength when the glass absorption filter and thin film filter are each combined with Y filter 14a, one of color filters 13a, 14a, and 15a, in comparison with the color matching function Y. The thin film filters shown in Figs. 3 and 4 use niobium oxide and chromium oxide films as the thin films.

[0031] As shown in Figure 3, the thin film filter has better spectral flatness than the glass absorption filter. Also, as shown in Figure 4, there is a deviation from the color matching function in the case of the glass absorption filter, but there is almost no deviation in the case of the thin film filter.

[0032] The colorimetric optical systems 13, 14, and 15 include wavelength selection filters (also referred to as color filters in the following description) 13a, 14a, and 15a, which are color matching function filters corresponding to the tristimulus values ​​of X, Y, and Z, respectively, and light receiving sensors 13b, 14b, and 15b used in combination with these.

[0033] The color filters 13a, 14a, and 15a may be configured by laminating a plurality of light-absorbing filters so that the incident light has a transmittance corresponding to a desired spectral characteristic such as the tristimulus values ​​of X, Y, and Z. However, such a configuration has a problem that it is not possible to design a filter having transmittance peaks in two wavelength ranges, that is, there is a problem that the degree of freedom in filter design is small. There is also a problem that light-absorbing filters have a low transmittance and a large loss of light. Furthermore, there is a problem that film-shaped color filters, in particular, are subject to rapid aging (poor stability) in response to heat, light (ultraviolet rays), humidity, and the like.

[0034] Therefore, it is desirable to use interference type filters (hereinafter referred to as interference film filters) instead of light absorption type filters for the color filters 13a, 14a, and 15a. This interference film filter is a filter in which several tens of layers of dielectrics or oxides are laminated on a glass substrate by methods such as vacuum deposition or sputtering, and which selects wavelengths to transmit or reflect by the interference of light.

[0035] Therefore, compared to the above-mentioned light absorption type filters, this interference film filter makes it easier to obtain the desired transmittance (i.e., it is easy to design and has a high degree of design freedom), and it is also possible to create a filter with two peaks (mountains) like the color matching function X. In addition, because the interference film filter has high transmittance, for example, the peak transmittance is close to 100%, whereas the absorption type has a transmittance of 50% or less. Furthermore, interference film filters have the advantage of being highly reliable (there is little change in transmittance over time due to exposure to temperature, humidity, and light).

[0036] In this embodiment, silicon sensors are used as the light receiving sensors 13b, 14b, and 15b.

[0037] The light received by each of the light receiving sensors 13b, 14b, and 15b is converted into an electric signal, and then subjected to processing such as I / V conversion and amplification in the corresponding electrical processing units 16a, 16b, and 16b, and then input as light receiving data to the control unit 17. The control unit 17 performs calculations based on the input light receiving data to calculate a measurement value.

[0038] When the light to be measured 2 reaches the color filters 13a, 14a, and 15a of the colorimetric optical system 13, the light to be measured 2 passes through the color filters 13a, 14a, and 15a, but a part of the light to be measured 2 is reflected by the surfaces of the color filters 13a, 14a, and 15a. A part of the reflected light returns to the light attenuation member 40 and is reflected again by the surface of the light attenuation member 40, and this reflected light is repeatedly passed through and reflected by the color filters 13a, 14a, and 15a. In this way, multiple reflections are repeated between the color filters 13a, 14a, and 15a and the light attenuation member 40.

[0039] On the other hand, the light to be measured 2 that passes through the color filters 13a, 14a, 15a and reaches the light receiving sensors 13b, 14b, 15b is received by the light receiving sensors 13b, 14b, 15b, but a part of the light to be measured 2 is reflected by the surfaces of the light receiving sensors 13b, 14b, 15b. A part of the reflected light passes through the color filters 13a, 14a, 15a and returns to the light attenuating member 40, and is reflected again by the surface of the light attenuating member 40, and this reflected light is repeatedly received and reflected by the light receiving sensors 13b, 14b, 15b. In this way, multiple reflections are repeated between the light receiving sensors 13b, 14b, 15b and the light attenuating member 40.

[0040] The inventors have found that the behavior of multiple reflections occurring between such light attenuating member 40 and the color filters 13a, 14a, 15a or the light receiving sensors 13b, 14b, 15b varies greatly depending on the position at which the light attenuating member 40 is inserted or removed, and that by inserting or removing the light attenuating member at a position in front of the branching optical system 12, the effect of multiple reflections on the measurement values ​​can be reduced.

[0041] FIG. 5 shows an example of the reflection characteristics of silicon sensors used as the light receiving sensors 13b, 14b, and 15b.

[0042] Generally, in a silicon sensor, about 1 / 3 of the input light energy is converted into electricity and sent to the electrical processing units 16a, 16b, 16c and the control unit 17. About 1 / 3 is converted into heat and escapes into the atmosphere. About 1 / 3 is reflected. As shown in FIG. 5, the reflectance of a silicon sensor is 30 to 40%, depending on the wavelength range of the light to be measured.

[0043] The interference filters used as the color filters 13a, 14a, and 15a have almost no absorption by the film material (dielectric). As shown in Figure 6(A), the incident light (measured light) other than the transmitted light is reflected by each layer and becomes a reflected light.

[0044] Figure 6(B) shows a graph of the transmittance and reflectance of an interference filter used as an X filter. In the figure, the inner black part of the characteristic curve of transmittance versus wavelength corresponds to transmitted light, and the outer white part corresponds to reflected light, with transmittance + reflectance ≒ 100%.

[0045] 7(A) and (B) show an example of the transmittance and reflectance in the visible light region (wavelength 380 to 780 nm) of a light attenuation member (called an ND filter in the figure) made of a thin film filter whose thin film is a metal oxide film of niobium oxide. The average transmittance is ≒ 5%, and the average reflectance is ≒ 10%.

[0046] Next, the reason why the effect of multiple reflections on the measurement value can be reduced by inserting and removing the light attenuating member 40 at a position in front of the branching optical system 12 will be explained by comparing the case where the insertion and removal position of the light attenuating member 40 is between the color filters 13a, 14a, 15a and the light receiving sensors 13b, 14b, 15b (see Figure 8) and the case where it is between the color filters 13a, 14a, 15a and the diffusion plate 20 (see Figure 14). <When the insertion / removal position of the light attenuating member 40 is between the color filters 13a, 14a, 15a and the light receiving sensors 13b, 14b, 15b> In this case, as shown in Fig. 9, multiple reflections occur between the light attenuating member 40 and the color filters 13a, 14a, and 15a. Multiple reflections also occur between the light attenuating member 40 and the light receiving sensors 13b, 14b, and 15b. Note that, although Fig. 9 shows the color filter 14a and the light receiving sensor 14b as representatives, the same applies to the other color filters 13a and 15a and the light receiving sensors 13b and 15b. (1) Multiple reflections between the light attenuating member 40 and the color filters 13a, 14a, and 15a 10(A) shows the transmission and reflection of the light 2 to be measured at a wavelength of about 500 nm using the color filter 14a, which is a Y filter, as an example. The transmittance T and reflectance R of the Y filter 14a are T≒30% and R≒70%, respectively. When the intensity of the incident light is 1, the intensity of the transmitted light is 0.30 and the intensity of the reflected light is 0.70.

[0047] 10B, consider a state in which the light attenuating member 40 is inserted behind the Y filter 14a. The transmittance T and reflectance R of the light attenuating member 40 are T=5% and R=10%, respectively.

[0048] When the transmitted light with an intensity of 0.3 that has been transmitted through the Y filter 14a passes through the light attenuation member 40, the intensity of the transmitted light becomes 0.015 (=0.30×0.05). On the other hand, the intensity of the reflected light reflected by the light attenuation member 40 becomes 0.03 (=0.30×0.1).

[0049] The reflected light with an intensity of 0.03 reflected by the light attenuating member 40 returns to the Y filter 14a, but is reflected again by the Y filter 14a and travels to the light attenuating member 40 as reflected light with an intensity of 0.021 (=0.03×0.7).

[0050] The reflected light with an intensity of 0.021 is transmitted through the light attenuation member 40. The intensity of this transmitted light is 0.00105 (=0.021×0.05). Note that a portion of the reflected light with an intensity of 0.021 is reflected by the light attenuation member 40, but subsequent multiple reflections are ignored.

[0051] Due to the above-described behavior of the measured light 2, the total intensity of the measured light 2 transmitted through the light attenuation member 40 is 0.01605 (=0.015+0.00105).

[0052] Next, similar calculations were performed for the wavelength range of 380 to 780 nm for each of X-filter 13a, Y-filter 14a, and Z-filter 15a, with light-attenuating member 40 inserted and retracted. The results are shown in Figures 11(A1) to (A3).

[0053] The curve "without ND" represents the received light intensity when the light attenuating member 40 is retracted, and represents the intensity of the light transmitted through the color filters 13a-15a after the measured light 2 of intensity 1 is input to each of the color filters 13a-15a. The curve "with ND" represents the received light intensity when the light attenuating member 40 is inserted, and represents the intensity of the light transmitted through the light attenuating member 40 (including the light transmitted again by reflection) after the measured light 2 of intensity 1 is input to each of the color filters 13a-15a.

[0054] 11(B1) to (B3) are graphs in which the characteristics of (A1) to (A3) in the same figure are normalized by area in order to use the same evaluation criteria. In each graph, there is a slight difference in the received light intensity between "with ND" and "without ND" depending on the presence or absence of the light-attenuating member 40.

[0055] In order to clarify the difference in light receiving intensity depending on whether or not the light attenuating member 40 is present, the results of calculating the light receiving intensity "with ND" / light receiving intensity "without ND" are shown by dashed lines in Figures 11 (B1) to (B3). The dashed vertical axis is shown on the right. When there is no difference, the vertical axis is "1", and the larger the value, the larger the difference. (2) Multiple reflections between the light attenuating member 40 and the light receiving sensors 13b, 14b, and 15b 12 shows the transmission, reflection, and reception of the measured light 2 for the light attenuating member 40 and each of the light-receiving sensors 13b, 14b, and 15b. The transmittance T and reflectance R of the light attenuating member 40 are T=5% and R=10%, respectively, and the photoelectric conversion rate and reflectance R of the light-receiving sensors (silicon sensors) 13b, 14b, and 15b are photoelectric conversion rate≈30% and R≈30%, respectively.

[0056] When the intensity of the incident light is taken as 1, the intensity of the transmitted light that passes through the light attenuation member 40 is 0.05, and the intensity of the reflected light is 0.10.

[0057] The transmitted light with an intensity of 0.05 that has passed through the light attenuation member 40 reaches each of the light receiving sensors 13b, 14b, and 15b, where it is received and photoelectrically converted. The intensity of the photoelectrically converted light is 0.015 (=0.05×0.3). A portion of the light that reaches the light receiving sensors 13b, 14b, and 15b is reflected by the light receiving sensors 13b, 14b, and 15b. The intensity of the reflected light is 0.015 (=0.05×0.3).

[0058] The reflected light with an intensity of 0.015 reflected by the light-receiving sensors 13b, 14b, and 15b returns to the light-attenuating member 40, but part of it is reflected again by the light-attenuating member 40 and travels toward the light-receiving sensors 13b, 14b, and 15b, and part of it passes through the light-attenuating member 40 and returns toward the branching optical system 12. The intensity of the light reflected again and traveling toward the light-receiving sensors 13b, 14b, and 15b is 0.0015 (=0.015×0.1), and the intensity of the light that passes through the light-attenuating member 40 and returns toward the branching optical system 12 is 0.00075 (=0.015×0.05).

[0059] The reflected light with an intensity of 0.0015 that travels again to the light receiving sensors 13b, 14b, and 15b is partially received by the light receiving sensors 13b, 14b, and 15b and photoelectrically converted. The intensity of the photoelectrically converted light is 0.00045 (=0.0015 x 0.3). Note that although a portion of the reflected light with an intensity of 0.0015 is reflected by the light receiving sensors 13b, 14b, and 15b, subsequent multiple reflections are ignored.

[0060] Due to the behavior of the light to be measured described above, the total intensity of the light to be measured photoelectrically converted by the light receiving sensors 13b, 14b, and 15b is 0.01545 (=0.015+0.00045). (3) Effects of multiple reflections occurring between the light attenuating member 40, the color filters 13a, 14a, 15a, and the light receiving sensors 13b, 14b, 15b Next, for the wavelength range of 380 to 780 nm for each of the X filter 13a, the Y filter 14a, and the Z filter 15a, the total intensity of the photoelectrically converted light was calculated when the light to be measured 2 with intensity 1 was incident on each of the color filters 13a, 14a, and 15a and photoelectrically converted by each of the light receiving sensors 13b, 14b, and 15b with the light attenuating member 40 inserted and retracted. The results are shown in Figures 13(A1) to (A3).

[0061] The curve "without ND" represents the intensity of photoelectrically converted light (received light intensity) when the light attenuating member 40 is retracted, and is the intensity of light when the measured light 2 of intensity 1 is input to each color filter 13a, 14a, 15a, passes through the color filters, is received by the light-receiving sensors 13b, 14b, 15b, and is photoelectrically converted. The curve "with ND" represents the received light intensity when the light attenuating member 40 is inserted, and is the intensity of light when the measured light 2 of intensity 1 is input to each color filter 13a, 14a, 15a, passes through the light attenuating member 40, is received by the light-receiving sensors 13b, 14b, 15b, and is photoelectrically converted (including light received again by reflection).

[0062] 13(B1) to (B3) are graphs in which the characteristics of (A1) to (A3) in the same figure are normalized by area in order to use the same evaluation standard. In each graph, there is a slight difference in the received light intensity depending on whether or not the light attenuating member 40 is used.

[0063] In order to clarify the difference in light receiving intensity depending on whether or not the light attenuating member 40 is present, the results of calculating the light receiving intensity "with ND" / light receiving intensity "without ND" are shown by dashed lines in Figures 13(B1) to (B3). The dashed vertical axis is shown on the right side. When there is no difference, the vertical axis is "1", and the larger the value, the larger the difference.

[0064] Such a difference in the received light intensity is considered to represent the influence of multiple reflections between the color filters 13a, 14a, and 15a, the light attenuating member 40, and the light receiving sensors 13b, 14b, and 15b.

[0065] Specifically, if the optical member 40 is designed (e.g., the transmittance of the objective optical system 11, the transmittance of the color filters 13a, 14a, 15a, the sensitivity of the light-receiving sensors 13b, 14b, 15b, etc.) to match the color matching functions when the light-attenuating member 40 is not present, the received light spectral sensitivity changes due to multiple reflections between the color filters 13a, 14a, 15a, the light-attenuating member 40, and the light-receiving sensors 13b, 14b, 15b that occur when the light-attenuating member 40 is inserted. In other words, since the received light spectral sensitivity deviates from the color matching functions, it is thought that the measurement error in luminance and chromaticity will increase. <When the insertion / removal position of the light attenuation member 40 is between the color filters 13a, 14a, 15a and the diffusion plate 20> This is the case shown in Fig. 14. In this case, as shown in Fig. 15, multiple reflections occur between the light attenuating member 40 and each of the light receiving sensors 13b, 14b, and 15b, and between the light attenuating member 40 and each of the color filters 13a, 14a, and 15a. For this reason, as explained in the above-mentioned <When the insertion / removal position of the light attenuating member 40 is between the color filters 13a, 14a, and 15a and the light receiving sensors 13b, 14b, and 15b>, differences occur in the light receiving intensity of the light receiving sensors 13b, 14b, and 15b depending on the presence or absence of the light attenuating member 40, and it is presumed that this affects the increase in measurement error. <When the insertion / removal position of the light attenuation member 40 is in front of the branching optical system 12> Next, the reason why measurement errors are suppressed when the insertion / removal position of the light attenuation member 40 is in front of the diffusion plate 20, which is the branching optical system 12, as in the first embodiment shown in FIG. 1, will be described.

[0066] In this case, when the light attenuating member 40 is inserted, the reflected light from the color filters 13a, 14a, and 15a and the reflected light from the light receiving sensors 13b, 14b, and 15b return to the diffuser plate 20, pass through the diffuser plate 20, and return to the light attenuating member 40.

[0067] 16, however, the light returning to the diffusion plate 20 is diffused and transmitted by the diffusion plate 20 (the angle increases), so the intensity of the light returning in a straight line (angle of 0 degrees) to the light attenuating member 40 becomes smaller. Therefore, the intensity of the light reflected again by the light attenuating member 40 and traveling again to the color filters 13a, 14a, and 15a and the light receiving sensors 13b, 14b, and 15b becomes smaller.

[0068] That is, the influence of multiple reflections on the light receiving intensity of the light receiving sensors 13b, 14b, and 15b is reduced, so that the degree to which the light receiving spectral sensitivity deviates from the color matching function is reduced, thereby suppressing measurement errors in luminance and chromaticity.

[0069] In the photometric device 10 shown in FIG. 1, when the brightness of the object 1 to be measured is equal to or lower than a predetermined value, the light attenuating member 40 is retracted from the optical path of the light 2 to be measured, and measurement is performed without the light attenuating member 40 being present.

[0070] On the other hand, when the brightness of the object 1 to be measured exceeds a predetermined value, the light attenuating member 40 is inserted into the optical path of the light 2 to be measured, and measurement is performed with the light attenuating member 40 present. The presence of the light attenuating member 40 expands the dynamic range of the photometric device 10. Furthermore, by inserting the light attenuating member 40 in front of the diffusion plate 20, measurement errors can be suppressed. As a result, the photometric device 10 becomes a highly functional device capable of performing highly accurate measurements over a wide dynamic range. [Embodiment 2] In this embodiment, as shown in Fig. 17, a bundle fiber 30 is used instead of the diffusion plate 20 as the branching optical system 12 in the first embodiment, and an aperture stop 11b is not provided. Note that an aperture stop 11b may be provided. In addition, condenser lenses 19a, 19b, and 19c are disposed between the exit end of the bundle fiber 30 and each color filter.

[0071] The light attenuation member 40, the insertion / removal device 50, the color filters 13a, 14a, 15a, the light receiving sensors 13b, 14b, 15b, the electrical processing units 16a to 16c, the control unit 17, and other components are the same as those in the first embodiment shown in Fig. 1, and therefore the same reference numerals are used and the description thereof is omitted. However, in Fig. 17, the electrical processing units 16a, 16b, 16c, and the control unit 17 are omitted.

[0072] The bundle fiber 30 is made by bundling a plurality of n (n = hundreds to thousands) of small-diameter (φ = about 0.03 to 0.3 mm) bare fibers at the inlet side, randomly branching them into a plurality (three corresponding to the tristimulus values ​​of X, Y, and Z in this embodiment) at the outlet side, and bundling a plurality of m fibers each. Reference numerals 31, 32, and 33 denote branching sections. The shapes of the input end 30a and the output ends 31a, 32a, and 33a of the branching sections 31, 32, and 33 are arbitrary (circular, rectangular, etc.).

[0073] In the photometric device 10 of FIG. 17, the light to be measured 2 from the object to be measured 1 passes through the objective optical system 11, passes through the light attenuation member 40 or directly, enters the entrance end 30a of the bundle fiber 30, and is then transmitted through the bundle fiber 30 to be output from each of the exit ends 31a, 32a, 33a of the three branching sections 31, 32, 33.

[0074] The emitted light to be measured is incident on condenser lenses 19a, 19b, and 19c, and then travels to color filters 13a, 14a, and 15a and further to light-receiving sensors 13b, 14b, and 15b, where it is received.

[0075] In this embodiment 2, similarly to the embodiment 1, when the light attenuation member 40 is inserted, the measured light 2 passes through the bundle fiber 30 and travels from the focusing lenses 19a, 19b, 19c to the color filters 13a, 14a, 15a and further to the light receiving sensors 13b, 14b, 15b. A part of the measured light 2 is reflected by the color filters 13a, 14a, 15a and the light receiving sensors 13b, 14b, 15b. Then, this reflected light returns to the bundle fiber 30 , passes through the bundle fiber 30 , and returns to the light attenuation member 40 .

[0076] However, if the bundle fiber 40 has a certain length or more, the reflection angle is randomized (mixed). Therefore, similar to the diffuser plate 20, the light emitted from the incident end 30a of the bundle fiber 30 to the light attenuating member 40 is diffused, and the intensity of the light returning in a straight line (angle 0 degrees) to the light attenuating member 40 becomes small. Therefore, the intensity of the light reflected again by the light attenuating member 40 and traveling again to the color filters 13a, 14a, 15a and the light receiving sensors 13b, 14b, 15b becomes small.

[0077] In other words, the same effect as that of the diffuser 20 can be obtained with the bundle fiber 30, and the effect of multiple reflections on the light receiving intensity of the light receiving sensors 13b, 14b, and 15b is reduced, so that the deviation of the light receiving spectral sensitivity from the color matching function is reduced, and measurement errors in luminance and chromaticity can be suppressed.

[0078] Here, the mixing effect of the bundle fiber 30 will be described.

[0079] Optical fibers utilize the difference in refractive index between the core and cladding to ideally guide incident light by total reflection as shown in Figures 18(A) and (B). However, in reality, local differences in refractive index (striae), local differences in fiber diameter (thick, thin), or curvature of the reflecting surface due to bending of the fiber or distortion of the material (refractive index) make the exit position and exit angle random, so the incident light is not transmitted in such an ideal way, and the exit light is uniform (exit position and exit angle are random).

[0080] That is, in the case of a relatively long optical fiber, the emitted light is uniform and always emitted under stable emission angle conditions, regardless of the characteristics of the light incident on the optical fiber (having the same effect as the diffuser plate 20; a greater amount of light can be obtained than with the diffuser plate 20). The photometric device 10 of the second embodiment utilizes such characteristics of optical fibers.

[0081] The experimental results are shown in Figure 19. Figure 19(B) is a graph showing the measured data of the output angle of the optical fiber. In this experiment, as shown in Figure 19(A), roughly parallel light (a light beam of ±2 degrees or less) was incident on the optical fiber, and measurements were performed using a not shown luminance meter placed at the output end. The fiber was bent 90° at one point. The fiber was a plastic fiber (NA=0.5, φ=1mm), and its length was changed to 30mm (×), 50mm (▲), 100mm (■), and 300mm (◆).

[0082] 19B, when the parallel light is incident, the effective aperture angle (width of 5% of the peak intensity) is about ±35° when the fiber length is 50 mm, and the aperture angle hardly changes even when it is longer than 50 mm, remaining stable. On the other hand, when the fiber length is 30 mm, the intensity distribution of the emitted light becomes narrow, and the degree of mixing (homogenization) is low.

[0083] If the single fiber has a length of 50 mm or more, it can mix sufficiently evenly. The relationship between the incident light, the outgoing light, and the fiber length depends on the number of reflections between the core and cladding when the light is guided through the fiber. Therefore, in this experimental data, the necessary fiber length for φ=1 mm is 50 mm, so the fiber length should be 50 times or more the fiber diameter. By using an optical fiber of this length, the outgoing angle is made uniform (no information specific to the outgoing angle) and stable outgoing angle conditions are always obtained.

[0084] As mentioned above, by making the fiber length of the single fiber sufficiently long, the light with different incident angles is randomly mixed while passing through the inside of the fiber, and the information contained in the light must be converted into uniform information with a spread defined by the numerical aperture (NA). The sufficient length that can cancel the information contained in the incident angle to such a fiber is 50 times or more the core diameter, as mentioned above.

[0085] For example, when the diameter of the strands of the bundle fiber 30 is φ0.03 mm, the length is preferably 1.5 mm or more, and when the diameter of the strands of the bundle fiber 30 is φ0.3 mm, the length is preferably 15 mm or more. [Embodiment 3] This third embodiment is provided with a finder optical system that allows the measurer to visually recognize the periphery of the area to be measured.

[0086] That is, as shown in Fig. 20, a mirror M that bends a part of the optical path of the light 2 to be measured is disposed between the objective optical system 11 and the incident end of the branching optical system 12 (bundle fiber 30). The light beam that is not reflected by the mirror M is guided to the branching optical system 12 and the light receiving sensors 13b, 14b, and 15b to measure the luminance, chromaticity, etc. On the other hand, the light beam reflected by the mirror M is guided to the finder optical system 60 so that the person taking the measurement can visually confirm the periphery of the area to be measured. In the figure, symbols S1 and S2 denote slits.

[0087] If the light attenuating member 40 is disposed in front of the mirror M, the light attenuating member 40 is inserted and removed depending on the brightness of the object to be measured 1, making it difficult to visually recognize. For this reason, it is preferable that the light attenuating member 40 is disposed behind the mirror M.

[0088] The configuration other than the finder optical system 60, the mirrors M, S1, and S2 is the same as that of the second embodiment, and therefore the description will be omitted. Also, in Fig. 20, the condenser lenses 19a, 19b, and 19c behind the bundle fiber 30 are omitted. Also, the diffuser plate 20 may be used instead of the bundle fiber 30. [Embodiment 4] In this embodiment 4, as shown in Fig. 21, the convex lens 11a and the aperture stop 11b, which are the objective optical system 11, are omitted in the photometric device 10 of the embodiment 1 shown in Fig. 1. Therefore, the light to be measured 2 from the object to be measured 1 is directly incident on the light attenuation member 40.

[0089] The configuration other than the objective optical system 11 is the same as that of the photometric device 10 shown in Fig. 1, and therefore a description thereof will be omitted. Note that a fiber bundle 30 may be used in place of the diffusion plate 20. [Embodiment 5] In this embodiment 5, the configuration of the colorimetric optical system 13 in the photometric device 10 of the embodiment 1 shown in FIG. 1 is changed.

[0090] That is, as shown in Fig. 22, a linear variable filter (LVF) 70 that is a spectral filter and can continuously change the wavelength is used instead of the three color filters 13a, 14a, and 15a. Also, a line sensor 80 is used as the light receiving sensor. However, instead of the line sensor 80, multiple light receiving sensors may be arranged and used. The configuration other than the colorimetric optical systems 13, 14, and 15 is the same as that of the photometric device 10 shown in FIG. 1, and therefore a description thereof will be omitted.

[0091] The photometric device 10 of this embodiment 5 also generates multiple reflections between the light attenuation member 40 and the linear variable filter 70 and the line sensor 80, but similar to the photometric device 10 of embodiment 1, the effects of multiple reflections can be suppressed by the diffusing effect of the diffuser 20 on the returning light.

[0092] Instead of the diffusion plate 20, a fiber bundle 30 may be used. [Insertion and removal control of light attenuation components] 23 is a flowchart for explaining a control method for inserting and removing the light attenuating member 40, which is performed in each photometric device 10 according to this embodiment.

[0093] After the measurement starts, in step S01, the received light data V X , V Y , V Z Next, in step S02, it is determined whether the light attenuation member 40 is inserted into the light path (on) or retracted (off).

[0094] If it has been saved (Off in step S02), in step S03, it is checked whether the received light data is smaller than the threshold value A. If it is smaller (YES in step S03), the calibration coefficient knon is referenced in step S04, and then the stimulus values ​​X, Y, Z, luminance LV, and chromaticity x and y are calculated in step S05 and output in step S07.

[0095] If the light reception data is not smaller than threshold value A in step S03 (NO in step S03), the light attenuation member 40 is inserted into the optical path in step S06, and then the process returns to step S01 to obtain the light reception data again.

[0096] If the light attenuation member 40 is inserted into the optical path in step S02 (on in step S02), then in step S08 it is checked whether the received light data is greater than the threshold value B. If it is greater (YES in step S08), then in step S09 the calibration coefficient knd is referenced, and then in step S10 the stimulus values ​​X, Y, Z, luminance LV, and chromaticity x and y are calculated and output in step S07.

[0097] If the light reception data is not greater than threshold value B in step S08 (NO in step S08), the light attenuation member 40 is retracted from the light path in step S11, and then the process returns to step S01 to obtain the light reception data again. [Industrial Applicability]

[0098] The present invention can be used as a photometric device capable of measuring the luminance, chromaticity, etc. of light emitted from a measurement object such as a smartphone display or liquid crystal monitor. [Explanation of symbols]

[0099] 1 Object to be measured 2 Light to be measured 10 Photometering device 11 Objective optical system 11a Convex lens 11b Aperture diaphragm 12 Branching optical system 13~15 Colorimetric optical system 13a, 14a, 15a Wavelength selection filters 13b, 14b, 15b Light receiving sensor 16, 16a to 16c Electrical processing section 20 Diffuser 30 Fiber bundles 30a entrance end 31~33 Branch 31a~33a Output end 40 Light attenuating material 41 Transparent plate 41a Incidence plane 41b Output surface 42, 43 Thin Film 50 Insertion / extraction device 60 Viewfinder optical system

Claims

1. a branching optical system that branches the light to be measured from the object to be measured into a plurality of beams; a color measuring optical system having a wavelength selection filter into which the light to be measured branched by the branching optical system is incident, and a light receiving sensor that receives the light to be measured that has passed through the wavelength selection filter; In a photometric device comprising: a light attenuating member that can be inserted into and removed from an optical path of the light to be measured, A photometric device, wherein the light attenuation member is disposed in front of the branching optical system.

2. 2. The photometric device according to claim 1, wherein the light attenuating member is inserted or removed depending on the brightness of the object to be measured.

3. 3. A photometric device according to claim 1, wherein said light attenuating member is a thin film filter.

4. 3. The photometric device according to claim 1, wherein the light receiving sensor is a silicon sensor.

5. 3. A photometric device according to claim 1, wherein said wavelength-selective filter is a thin-film filter.

6. 3. A photometric device according to claim 1, wherein the branching optical system is a diffusion plate.

7. 3. A photometric device according to claim 1, wherein the branching optical system is a bundle fiber.

8. 8. The photometric device according to claim 7, wherein the length of the bundle fiber is 50 times or more the diameter of the core of the fiber.

9. a mirror for guiding the light to be measured to an observation optical system in front of the branching optical system; 3. A photometric device according to claim 1, wherein the light attenuating member is disposed between the mirror and the branching optical system.

10. 3. The photometric device according to claim 1, wherein the wavelength selection filter is a color matching function filter.

11. 3. The photometric device according to claim 1, wherein the wavelength-selective filter is a spectral filter, and the light-receiving sensor is a line sensor.

12. a branching optical system that branches the light to be measured from the object to be measured into a plurality of beams; a color measuring optical system having a wavelength selection filter into which the light to be measured branched by the branching optical system is incident, and a light receiving sensor that receives the light to be measured that has passed through the wavelength selection filter; In a photometric device having the above-mentioned, a position in front of the branching optical system is provided. A photometric method comprising inserting and removing a light attenuating member into and from the optical path of the light to be measured.

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