Light measuring device, method for measuring light, and calibration system

Abstract

To provide a light measuring device, a method for measuring light, and a calibration system which can eliminate the issue that measured values cannot provide a linear continuity in a case where an optical attenuation member is inserted in an optical path of measurement target light and in a case where an optical attenuation member is not inserted in the optical path.SOLUTION: The present invention includes: a light reception unit having at least one light reception sensor 13b, 14b, and 15b for receiving light from measurement target light 2 from a measurement target object 1; control means 17 for calculating a measured value on the basis of output from the at least one light reception sensor; an optical attenuation member 40 removably provided in the optical path of the light measurement target light 2, the optical attenuation member attenuating light which enters the light reception unit; and correction means for correcting the difference between the measured value calculated by the control menas 17 when the attenuation member 40 is inserted in the optical path, the measured value being changed according to characteristics of the measurement target object 1, and a measured value calculated by the control means 17 when the optical attenuation member 40 is not inserted in the optical path.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] As a photometric device as described above, as shown in FIG. 25, a photometric device 100 including a branching optical system 120 that branches a light 201 to be measured from an object 200 to a plurality of beams is known (see, for example, Patent Document 1).

[0003] This photometric device 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 them at the output end (exit) side into a plurality (for example, three corresponding to the tristimulus values ​​of color matching functions X, Y, and Z defined by CIE (Commission Internationale de Illumination)) and bundling the plurality together. Also, a diffusion plate may be 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 which are light receiving elements 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 unit 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, when a light attenuating member is inserted or removed to expand the dynamic range, if a light attenuating member whose surface reflectance on the side of the object to be measured differs from the internal reflectance of the photometric device (reflection of the XYZ wavelength selection filter or the light receiving sensor) is used, an error occurs due to the insertion or removal of the light attenuating member.

[0010] Therefore, when calibrating the photometric device at a manufacturing factory (factory calibration), it is conceivable to store in the photometric device not only the correction coefficients when the light attenuation member is not inserted in the optical path, but also the correction coefficients when the light attenuation member is inserted in the optical path.

[0011] However, as a result of experiments conducted by the inventors, it was found that in some cases, linear continuity was not obtained in the measurement values ​​between when the light attenuation member was inserted and when it was not inserted into the optical path, and a step occurred in the measurement values ​​when switching between inserting and removing the light attenuation member.

[0012] As a result of investigating the cause, the inventors discovered that this is due to differences in the characteristics of the object to be measured, such as the surface reflectance.

[0013] This invention has been made in consideration of the above technical background, and has as its object to provide a photometric device, a photometric method, and a calibration system that can solve the problem of no linear continuity being obtained in the measured values ​​when a light attenuation member is inserted into the optical path of the light to be measured and when it is not, regardless of differences in the characteristics of the object to be measured. [Means for solving the problem]

[0014] The above object can be achieved by the following means. (1) a light receiving unit having one or more light receiving sensors for receiving light to be measured from an object to be measured; A control means for calculating a measurement value based on an output from the light receiving sensor; a light attenuating member that is removably provided in an optical path of the light to be measured and that attenuates light incident on the light receiving unit; a correction means for correcting a difference between a measurement value calculated by the control means in a state where the light attenuation member is inserted in the optical path and a measurement value calculated by the control means in a state where the light attenuation member is not inserted in the optical path, the difference varying depending on the characteristics of the object to be measured; A photometric device comprising: (2) The photometric device described in the preceding paragraph 1, wherein the correction means is a reflective member that is inserted into the optical path when the light attenuation member is inserted into the optical path and that retracts from the optical path when the light attenuation member is retracted from the optical path. (3) The photometric device according to item 2, wherein the reflecting member is integrally formed with the light attenuation member. (4) A photometric device as described in the preceding paragraph 2, wherein the reflective member is made of one or more members and is a member separate from the light attenuation member. (5) The photometric device according to any one of the above items 1 to 4, wherein the reflectance of the reflective member is an optimum reflectance ±4%. (6) The photometric device according to claim 1, wherein the correction means is constituted by a control means for calculating the measurement value using a correction coefficient corresponding to the physical property of the object to be measured. (7) The photometric device according to item 6 above, further comprising a memory unit for storing the correction coefficients. (8) A photometric device as described in paragraph 6 or 7 above, wherein the control means determines, based on an instruction from a user, an output value output from the light receiving unit when the light attenuation member is inserted in the optical path and an output value output from the light receiving unit when the light attenuation member is not inserted in the optical path, and determines the correction coefficient based on these. (9) A photometric device as described in paragraph 8 above, in which an exposure time required to obtain an output value output from the light receiving unit when the light attenuation member is inserted is longer than an exposure time required to obtain an output value output from the light receiving unit when the light attenuation member is not inserted. (10) A photometric device as described in paragraph 8 above, which calculates the correction coefficient when an output value output from the light receiving unit when the light attenuation member is inserted in the optical path and an output value output from the light receiving unit when the light attenuation member is not inserted in the optical path are within a predetermined range. (11) The photometric device according to the preceding paragraph 7, wherein the memory unit stores a plurality of correction coefficients respectively corresponding to the plurality of objects to be measured. (12) A photometric device as described in the preceding paragraph 6 or 7, wherein the characteristic of the object to be measured is the reflectance of the object to be measured. (13) A calibration system for calibrating the photometric device according to the preceding paragraph 8, comprising an information processing device, the information processing device requesting the control means to obtain the first correction coefficient based on an instruction from a user when the correction coefficient according to the preceding paragraph 8 is a first correction coefficient, and a calibration system characterized by further requiring a second correction coefficient to be determined based on a reference value of the object to be measured and an output value when the light receiving unit receives light from the object to be measured with the light attenuation member not inserted in the optical path. (14) The calibration system according to item 13 above, further comprising a request to determine the second correction coefficient after requesting to determine the first correction coefficient. (15) A calibration system for calibrating the photometric device according to the preceding paragraph 8, comprising an information processing device, wherein when the correction coefficient according to the preceding paragraph 8 is a first correction coefficient, the information processing device performs the following processing in addition to a process of requesting the control means to obtain the first correction coefficient based on an instruction from a user: A calibration system characterized by having a mode that only requires processing to determine a second correction coefficient based on a reference value of the object to be measured and an output value when the light receiving unit receives light from the object to be measured with the light attenuation member not inserted in the optical path. (16) A calibration system for calibrating the photometric device according to paragraph 8, comprising an information processing device, wherein when the correction coefficient according to paragraph 8 is a first correction coefficient, the information processing device performs the following steps in addition to a process of requesting the control means to obtain a second correction coefficient based on a reference value of the object to be measured and an output value when the light receiving unit receives light from the object to be measured in a state in which the light attenuation member is not inserted in the optical path, based on a user's instruction: A calibration system having a mode that requires only a process for determining the first correction coefficient. (17) A photometric device as described in any one of items 1, 2, 6, or 7 above, wherein the light attenuation member is inserted or removed depending on the brightness of the object to be measured. (18) A photometric device according to any one of the preceding paragraphs 1, 2, 6, or 7, wherein the light receiving sensor is a silicon sensor. (19) A photometric device according to any one of items 1, 2, 6 and 7, further comprising a wavelength-selecting filter provided in front of the light receiving sensor. (20) A photometric device according to any one of items 1, 2, 6, or 7, wherein the wavelength-selective filter is a thin-film filter. (21) A photometric device as described in any one of items 1, 2, 6, or 7 above, wherein the light attenuation member is a thin film filter. (22) A photometric device according to any one of the preceding paragraphs 1, 2, 6, or 7, further comprising a branching optical system for branching the light to be measured into a plurality of beams. (23) A photometric device according to any one of items 1, 2, 6, or 7, wherein the measurement wavelength range of the light to be measured is the visible light range. (24) A photometric device according to any one of items 1, 2, 6 and 7, wherein the wavelength selection filter is a color matching function filter. (25) A photometric device according to any one of items 1, 2, 6, or 7, wherein the wavelength-selecting filter is a spectral filter, and the light-receiving sensor is a line sensor. (26) A light receiving unit having one or more light receiving sensors for receiving light to be measured from the object to be measured; A control means for calculating a measurement value based on an output from the light receiving sensor; and correcting a difference between a measurement value calculated by the control means when the light attenuation member is inserted in the optical path and a measurement value calculated by the control means when the light attenuation member is not inserted in the optical path, the difference varying depending on a characteristic of the object to be measured. (27) A calibration system for calibrating the photometric device described in paragraph 8 for each reference display color, the calibration system being characterized in that the correction coefficient is obtained by switching between inserting and removing a light attenuation member while the reference display color is fixed. (28) A calibration system for calibrating the photometric device described in paragraph 8 above, characterized in that, when saturation of a light receiving sensor in the photometric device is detected in the process of calculating a correction coefficient, the brightness of the object to be measured is reduced. Effect of the Invention

[0015] According to the photometric device and photometric method of the present invention, a light attenuating member is provided which is removably inserted into the optical path of the light to be measured and attenuates the light incident on the light receiving unit, and the difference between the measurement value calculated by the control means when the light attenuating member is inserted into the optical path and the measurement value calculated by the control means when the light attenuating member is not inserted into the optical path, which varies depending on the characteristics of the object to be measured, is corrected. Therefore, regardless of the difference in the characteristics of the object to be measured, linear continuity of the measurement value can be ensured between the state where the light attenuating member is not inserted into the optical path of the light to be measured and the state where it is inserted. As a result, it is possible to perform measurements with a wide dynamic range and little error.

[0016] According to the calibration system of the present invention, calibration can be performed that ensures linear continuity in the measurement values ​​when the light attenuation member is inserted and when it is not inserted in the optical path of the light to be measured, regardless of differences in the surface characteristics of the object to be measured. [Brief description of the drawings]

[0017] [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] 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 4] FIG. 1A is a schematic diagram for considering the state when the light to be measured from a glare-type object to be measured is incident on the measurement optical unit of a photometric device when the light attenuation member is not inserted in the optical path of the light to be measured, and FIG. 1B is a schematic diagram for considering the state when the light attenuation member is inserted in the optical path of the light to be measured. [Diagram 5] 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 chromium oxide film. [Figure 6] FIG. 1A is a schematic diagram for considering the state when the light to be measured from a non-glare type object to be measured is incident on the measurement optical unit of a photometric device when the light attenuation member is not inserted in the optical path of the light to be measured, and FIG. 1B is a schematic diagram for considering the state when the light attenuation member is inserted in the optical path of the light to be measured. [Figure 7] 13 is a graph for explaining a measurement error. [Figure 8]FIG. 1A is a schematic diagram for considering the state when the light to be measured from a glare-type object to be measured is incident on the measurement optical unit of a photometric device using a light attenuation member with high surface reflectance when the light attenuation member is not inserted in the optical path of the light to be measured, and FIG. 1B is a schematic diagram for considering the state when the light attenuation member is inserted in the optical path of the light to be measured. [Figure 9] FIG. 1A is a schematic diagram for considering the state when light to be measured from a non-glare type object to be measured is incident on a measurement optical unit of a photometric device using a light attenuation member with high surface reflectance when the light is not inserted into the optical path of the light to be measured, and FIG. 1B is a schematic diagram for considering the state when the light attenuation member is inserted into the optical path of the light to be measured. [Figure 10] 1A and 1B are diagrams for explaining an example of a method for measuring a passing rate and a returning rate. [Figure 11] Graph (A) shows the transmittance in the visible light range of a light-attenuating member made of a thin film filter in which the thin film is a niobium oxide film, and graph (B) shows the reflectance in the visible light range of a light-attenuating member made of a thin film filter in which the thin film is three types of niobium oxide film 1, niobium oxide film 2, and niobium oxide film 3. [Figure 12] Graphs (A), (B), and (C) show the transmittance in the visible light region of a light-attenuating member made of a glass absorption filter, the reflectance when a single-layer antireflection coating is formed, and the reflectance when there is only a protective coating without an antireflection coating, respectively. [Figure 13] FIG. 11 is a configuration diagram of a photometric device according to a first modified example. [Figure 14] FIG. 13 is an explanatory diagram of a case where the objective optical system is front telecentric. [Figure 15] FIG. 11 is a configuration diagram of a photometry device according to Modification 2. [Figure 16] FIG. 11 is a configuration diagram of a photometry device according to a third modified example. [Figure 17] FIG. 13 is a configuration diagram of a photometry device according to a fourth modified example. [Figure 18] FIG. 13 is a configuration diagram of a photometry device according to Modification 5. [Figure 19]Graphs (A), (B), and (C) show the transmittance of transparent glass in the visible light range, the reflectance when a single layer of anti-reflection coating is formed, and the reflectance when there is only a protective coating without an anti-reflection coating, respectively. [Figure 20] FIG. 13 is a configuration diagram of a photometry device according to Modification 6. [Figure 21] 10 is a flowchart for explaining a control method for inserting and removing a light attenuating member performed in the photometric device. [Figure 22] FIG. 11 is an overall configuration diagram of a calibration system according to a second embodiment of the present invention. [Diagram 23] FIG. 4 is a block diagram showing details of a control unit. [Figure 24] 13A and 13B are flowcharts showing the calculation process performed by the control unit when calculating tristimulus values ​​(X, Y, Z). [Diagram 25] 13 is a flowchart showing a calculation process when tristimulus values ​​are calculated using an ND conversion user calibration coefficient Un. [Figure 26] 13 is a screen for selecting a correction coefficient calculation mode. [Figure 27] FIG. 11 is a diagram for explaining a state in which a plurality of types of ND conversion user calibration coefficients Un are stored. [Figure 28] FIG. 1 is a block diagram showing a general configuration of a photometric device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] A light attenuating member 40 is disposed between the convex lens 11a and the diffusion plate 20, in front of the aperture stop 11b surface. The light attenuating member 40 is driven by an inserting / removing device 50, which is a driving device, so as to be inserted into or removed from the optical path of the light 2 to be measured. The inserting / removing device 50 is, for example, a linear actuator. When the light attenuating member 40 is inserted into the optical path of the light 2 to be measured, the amount of the light 2 to be measured incident on the diffusion plate 20 is reduced by the light attenuating member 40. When the light attenuating member 40 is removed from the optical path of the light 2 to be measured, the light 2 to be measured is incident on the diffusion plate 20 without being reduced in amount. In the following description, the "light attenuating member" is also referred to as a "light reducing member" or an "ND filter".

[0023] The light-reducing member 40 is inserted and removed depending on the brightness of the object 1. Specifically, when the object 1 is dark, the light-reducing member 40 is retracted, and when the object 1 is bright, the light-reducing member 40 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 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.

[0024] 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 aperture stop position is small. The smaller the effective light path, the smaller the size of the light attenuating member 40 can be, the smaller the insertion / removal device 50 can be, and the lower the driving torque can be. This makes the product size compact, lightweight, and inexpensive. It is not necessary to provide the aperture stop 11b.

[0025] In this embodiment, the light reducing member 40 must have a transparent reflective material on its surface. This will be described later. As long as it has a reflective material, various types of filters, such as a thin film filter, a glass absorption filter, a porous plate, etc., can be used.

[0026] 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 not). 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 in the optical path). If the received light spectral sensitivity deviates from the color matching function, this will result in an error in luminance and chromaticity. It is also important that there is no change due to factors such as the environmental temperature.

[0027] 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.

[0028] An example of a light attenuating member 40 using a thin film filter is shown in FIG.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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, which are light receiving elements used in combination with these.

[0034] 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.

[0035] 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.

[0036] 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).

[0037] The interference film filters used as the color filters 13a, 14a, and 15a have almost no absorption by the film material (dielectric). As shown in Figure 3(A), the incident light (measured light) other than the transmitted light is reflected by each layer and becomes a reflected light.

[0038] Figure 3(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%.

[0039] In this embodiment, silicon sensors are used as the light receiving sensors 13b, 14b, and 15b.

[0040] The light received by each of the light receiving sensors 13b, 14b, 15b is converted into an electric signal, and after being subjected to processing such as I / V conversion and amplification in the corresponding electrical processing units 16a, 16b, 16b, the signal is input as received light data to the control unit 17. The control unit 17 performs calculations based on the input received light data to calculate a measurement value.

[0041] As described in the section on the problem to be solved by the invention, the inventors have found that when the light-reducing member 40 is inserted into or removed from the optical path of the measured light 2, linear continuity of the measured values ​​cannot be obtained due to differences in the surface reflectance of the object 1 to be measured. First, this problem will be described. <Problems that occur when inserting and removing the light reducing member 40> As shown in the schematic diagram of FIG. 4A, a state will be considered when the light to be measured 2 from the object to be measured (denoted as "DUT" in FIG. 4A) 1 is incident on the measurement optical unit of the photometric device 10 in a state where the light-reducing member 40 is not inserted in the optical path of the light to be measured 2 (is retracted from the optical path). The measurement optical unit includes a branching optical system 12 and color measurement optical systems 13 to 15, which are collectively denoted as "optical members" in FIG. 4. A part of the light incident on the optical member 90 passes through the branching optical system 12 and color filters 13a, 14a, and 15a in the optical member 90 and is received by the light-receiving sensors 13b, 14b, and 15b. A part of the light is reflected on the surfaces of the color filters 13a, 14a, and 15a and the light-receiving sensors 13b, 14b, and 15b, passes through the optical member 90 in the opposite direction, and returns to the object to be measured 1 side.

[0042] Here, the proportion of the light 2 to be measured that is incident on the optical member 90 and passes through the optical member 90 and is ultimately received by the light receiving sensors 13b, 14b, and 15b is called the transmittance rate, the proportion of the light that is reflected, passes through the optical member, and returns to the object to be measured 1 is called the return rate, and the light that returns to the object to be measured 1 and the light that is re-reflected by the object to be measured 1 and returns to the optical member are called return light.

[0043] Furthermore, among the objects under test 1, displays with high surface reflectance are called glare-type objects under test, or simply glare. Generally, most have a specular reflectance of around 5%. On the other hand, among the objects under test 1, displays with low surface reflectance are called non-glare-type objects under test, or simply non-glare. Generally, most have a specular reflectance of around 1%. Furthermore, most smartphones are of the glare type, while most personal computer displays are of the non-glare type.

[0044] In the schematic diagram of Fig. 4(A), a glare with a reflectance of 5% is used as the object 1 to be measured, and the intensity of the incident light emitted from the object 1 and incident on the photometric device 10 is set to 100. The transmission rate of the optical member 90 of the photometric device 10 is set to 90%, and the return rate is set to 10%.

[0045] Under these conditions, when incident light=100 enters the optical member 90, the optical member 90 has a transmittance=90%, so the amount of light received by the light-receiving sensors 13b, 14b, and 15b is 1=90. On the other hand, the optical member 90 has a return rate=10%, so the return light 1 is 10. This return light 1 is reflected by the surface of the object 1 to be measured, which has a reflectance=5%, and returns to the optical member of the photometric device 10 as return light 2=0.5.

[0046] This return light 2 passes through the optical member 90 and is received by the light receiving sensors 13b, 14b, and 15b as a received light amount 2=0.45.

[0047] A part of the return light 2 is reflected by the optical member 90 and returns to the object 1, and thereafter is repeatedly reflected between the object 1 and the optical member 90. However, since the intensity gradually decreases, this is ignored.

[0048] The sum of the received light amounts 1 and 2 at the light receiving sensors 13b, 14b, and 15b is 90.45. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by reflection from the optical member 90 and the surface reflection of the object to be measured 1, to the received light amount 1, in other words, the amount of received light increased due to the influence of multiple reflections, is 0.45 / 90=0.5%.

[0049] Next, using the schematic diagram of Figure 4 (B), we will consider what happens when the light to be measured 2 is incident on the photometric device 10 with the dimming member 40 inserted in the optical path of the light to be measured 2 in front of the optical member 90 (between the object to be measured 1 and the optical member 90).

[0050] In Fig. 4(B), the object to be measured 1 and optical member 90 are the same as in Fig. 4(A). The light-reducing member 40 has a transmittance of 5% and a reflectance of 2%. This light-reducing member 40 corresponds to a thin-film filter made of chromium oxide film. Fig. 5(A) shows the transmittance of the thin-film filter made of chromium oxide film, and Fig. 5(B) shows the reflectance. The average transmittance in the visible light range (380nm to 780nm) is 5%, and the average reflectance is 2%.

[0051] Under these conditions, when the incident light from the object 1 (=100) enters the photometric device 10, the light that passes through the light-attenuating member 40 and the optical member 90 is received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 1 = 4.5. The light reflected by the optical member 90 returns to the object 1 via the light-attenuating member 40 (return light 1 = 0.03). The light that enters from the object 1 and is reflected by the light-attenuating member 40 also returns to the object 1 (return light 3 = 2.00). The return lights 1 and 3 that return to the object 1 are reflected by the surface of the object 1, become return light 2 = 0.101, pass through the light-attenuating member 40 again, and enter the optical member 90, and are received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 2 = 0.00456.

[0052] The sum of the received light amounts 1 and 2 at the light-receiving sensors 13b, 14b, and 15b is 4.504556. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by reflection from the optical member 90 and the surface reflection of the object to be measured 1, to the received light amount 1, in other words, the amount of received light increased due to the influence of multiple reflections, is 0.00456 / 4.5=0.1%.

[0053] Comparing the case where the light-reducing member 40 shown in FIG. 4(A) is not inserted in the optical path with the case where the light-reducing member 40 shown in FIG. 4(B) is inserted, the increase in the amount of received light due to the influence of multiple reflection is 0.5% and 0.1%, a difference of 0.4%. When the light-reducing member 40 is inserted, the return light 1 from the optical member 90 passes through the light-reducing member 40 twice and reaches the light-receiving sensors 13b, 14b, and 15b. Since the return light passes through the light-reducing member 40 twice, the intensity of the return light is reduced. On the other hand, the reflected light (return light 3) from the light-reducing member 40 is added, but the intensity is lower than that of the return light 1 in FIG. 4(A).

[0054] Next, as shown in the schematic diagram of Fig. 6(A), a non-glare type object to be measured 1 was used to consider the state of the measured light 2 when the light-reducing member 40 was not inserted in the optical path. The reflectance of the object to be measured 1 was set to 1 percent. The transmission rate and return rate of the optical member 90 were set to the same as those of the optical device 90 used in Figs. 4(A) and (B).

[0055] Under these conditions, when incident light = 100 from the object to be measured 1 enters the photometric device 10, the light that passes through the optical member 90 is received by the light-receiving sensors 13b, 14b, and 15b as received light amount 1 = 90. Also, the light reflected by the optical member 90 returns to the object to be measured 1 (return light 1 = 10). This return light 1 is reflected by the surface of the object to be measured 1, becomes return light 2 = 0.1, enters the optical member 90 again, and is received by the light-receiving sensors 13b, 14b, and 15b as received light amount 2 = 0.09.

[0056] The sum of the received light amounts 1 and 2 at the light receiving sensors 13b, 14b, and 15b is 90.09. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by reflection from the optical member 90 and the surface reflection of the object to be measured 1, to the received light amount 1, in other words, the amount of received light increased due to the influence of multiple reflections, is 0.09 / 90=0.10%.

[0057] Next, the state in which the light to be measured 2 is incident on the photometric device 10 with the dimming member 40 inserted in the optical path of the light to be measured 2 in front of the optical member 90 (between the object to be measured 1 and the optical member 90) will be considered using the schematic diagram of Figure 6 (B).

[0058] In Fig. 6B, the DUT 1 and the optical member 90 are the same as those in Fig. 6A. The light-reducing member 90 has a transmittance of 5% and a reflectance of 2%.

[0059] Under these conditions, when the incident light from the object 1 to be measured = 100 is incident on the photometric device 10, the light that passes through the light-attenuating member 40 and the optical member 90 is received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 1 = 4.5. The light reflected by the optical member 90 returns to the object 1 to be measured via the light-attenuating member 40 (return light 1 = 0.03). The light that is incident from the object 1 to be measured and reflected by the light-attenuating member 40 also returns to the object 1 to be measured (return light 3 = 2.00). The return lights 1 and 3 that return to the object 1 to be measured are reflected by the surface of the object 1 to become return light 2 = 0.020, pass through the light-attenuating member 40 again, and enter the optical member, and are received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 2 = 0.00091.

[0060] The sum of the received light amounts 1 and 2 at the light-receiving sensors 13b, 14b, and 15b is 4.500911. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by reflection from the optical member 90 and the surface reflection of the object to be measured 1, to the received light amount 1, in other words, the amount of received light increased due to the influence of multiple reflections, is 0.00091 / 4.5=0.02%.

[0061] Comparing the state shown in FIG. 6(A) in which a non-glare type object to be measured 1 is used and the light-reducing member 40 is not inserted in the optical path with the state shown in FIG. 6(B) in which a non-glare type object to be measured 1 is used and the light-reducing member 40 is inserted in the optical path, the increase in the amount of received light due to the effects of multiple reflections is 0.10% and 0.02%, a difference of 0.08%.

[0062] Next, the relationship between the calibration light source and the object 1 to be measured will be considered.

[0063] When the calibration light source and the DUT 1 are of the same type, no absolute value error occurs with (inserted) / without (non-inserted) the ND filter 40. Therefore, no deviation (linearity error) in the measurement value occurs when switching between inserting and removing the ND filter 40.

[0064] Here, the "absolute value error" and the "linearity error" will be explained.

[0065] "Absolute value error" refers to the error relative to the "true value" of luminance and chromaticity. The "true value" is often the value measured using a high-precision standard photometric device (such as a spectrophotometer).

[0066] The causes of the absolute value error include the degree of mismatch with the color matching functions of the XYZ filters, differences in measurement geometry (aperture angle), etc. In the case of luminance, for example, an absolute value error of <±2% is set as the product specification of the photometric device 10.

[0067] Linearity error is an error that cannot ensure continuity of measured values ​​from low to high luminance. When "gamma measurement" is performed on a smartphone, the luminance and chromaticity are measured while continuously changing the brightness from low luminance (low gradation) to high luminance (high gradation).

[0068] In this case, the brightness of the light source and the measured luminance value must be a linear function, as shown by the dashed line in FIG. 7. Linearity errors include distortion and steps, as shown by the solid line in the figure. Linearity distortion occurs due to the light receiving sensors 13b, 14b, and 15b and electrical processing. Steps in linearity are caused by changes in the amplification factor in electrical processing and the insertion and removal of the ND filter 40. In the case of luminance values, for example, a linearity error of <±0.2% is set as the product specification of the photometric device 10. Hereinafter, step-type linearity errors are referred to as linearity errors (ND steps).

[0069] On the other hand, when the calibration light source and the object to be measured 1 are of different types, the results shown in Figures 4(A)(B) and Figures 6(A)(B) show that the absolute value error without the ND filter 40 (abbreviated as "no ND") is -0.4%, and the absolute value error with the ND filter 40 (abbreviated as "with ND") is -0.08%, and a linearity error (ND step) of +0.32% occurs.

[0070] in particular, (1) When calibrated using a glare type light source Non-ND calibration factor: Knon = incident light / received light = 100 / 90.45 With ND Calibration coefficient: Knd = incident light / received light amount = 100 / 4.50456 The measured value of glare type object 1 calibrated with this calibration factor is: Measurement value without ND = amount of light received × calibration coefficient without ND = 90.45 × 100 / 90.45 = 100 (absolute value error 0%) Measurement value with ND = amount of light received x calibration coefficient with ND = 4.50456 x 100 / 4.50456 = 100 (absolute value error 0%) Measurement value difference with / without ND (with ND - without ND) = 100-100 = 0 (linearity error (ND step) 0%) On the other hand, the measured value of the non-glare type test object 1 is Measurement value without ND = amount of light received × calibration coefficient without ND = 90.09 × 100 / 90.45 = 99.602 (absolute value error -0.4%) Measurement value with ND = Amount of light received x Calibration coefficient with ND = 4.50091 x 100 / 4.50456 = 99.919 (absolute value error -0.08%) Measurement difference with / without ND (with ND - without ND) = 99.919 - 99.602 = 0.3170 (linearity error (ND step) + 0.32%) (2) When calibrated using a non-glare type light source In this case, the opposite occurs to when calibration is performed using a glare-type light source, and the measurement value of glare-type object 1 has an absolute value error of +0.4% without ND and +0.08% with ND, and a linearity error (ND step) of -0.32%. (3) Relationship with the specifications of the photometric device (the accuracy required by the customer) The absolute value error that occurs in the above example (-0.4% without ND, -0.08% with ND) is small compared to the product specifications (±2%) and is therefore not a problem. However, the linearity error (ND step) of +0.32% is a problem because it is larger than the product specifications (±0.2%).

[0071] In this way, depending on whether the object to be measured 1 is glare or non-glare, in other words, depending on the difference in the surface reflection characteristics of the object to be measured 1, a linearity error (ND step) occurs when the light reducing member 40 is inserted or removed. <Solution> As shown in Figures 8(A) and (B), a light-attenuating member 40 having a reflective member on its front surface, i.e., the surface on the side of the object to be measured 1, was used, and the state of the measured light 2 was considered in the same manner as in Figures 4(A) and (B) and Figures 6(A) and (B).

[0072] A glare with a reflectance of 5% is used as the object to be measured 1, and the intensity of the incident light is set to 100. The transmission rate of the optical member 90 of the photometric device 10 is set to 90%, and the return rate is set to 10%.

[0073] Fig. 8(A) is a schematic diagram in a state where the light-reducing member 40 is not inserted in the optical path of the measured light 2. Since the conditions of the measured object 1 and the optical member 90 are the same as those in Fig. 4(A), the received light amount 1 = 90, the received light amount 2 = 0.45, and the sum of the received light amount 1 and the received light amount 2 = 90.45. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by reflection from the optical member 90 and surface reflection of the measured object 1, to the received light amount 1, in other words, the amount of received light increased due to the influence of multiple reflection = 0.45 / 90 = 0.5%.

[0074] 8(B) is a schematic diagram of a state in which the light-reducing member 40 having a reflecting member on its surface is inserted into the optical path of the measured light 2. The transmittance of the light-reducing member 40 is set to 5%, and the reflectance is set to 10%, which is equal to the return rate of the optical member 90.

[0075] Under these conditions, when the incident light from the object 1 (=100) enters the photometric device 10, the light that passes through the light-attenuating member 40 and the optical member 90 is received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 1 = 4.5. The light reflected by the optical member 90 returns to the object 1 via the light-attenuating member 40 (return light 1 = 0.03). The light that enters from the object 1 and is reflected by the light-attenuating member 40 also returns to the object 1 (return light 3 = 10.00). The return lights 1 and 3 that return to the object 1 are reflected by the surface of the object 1, become return light 2 = 0.501, pass through the light-attenuating member 40 again, and enter the optical member 90, and are received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 2 = 0.02256.

[0076] The sum of the received light amounts 1 and 2 at the light-receiving sensors 13b, 14b, and 15b is 4.5225564. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by reflection from the optical member 90 and the surface reflection of the object to be measured 1, to the received light amount 1, in other words, the amount of received light increased due to the influence of multiple reflections, is 0.02256 / 4.5=0.5%.

[0077] Comparing the case shown in FIG. 8(A) where the light-reducing member 40 is not inserted with the case shown in FIG. 8(B) where the light-reducing member 40 is inserted, the increase in the amount of received light due to the influence of multiple reflections is the same value of 0.5% in both cases.

[0078] Next, as shown in the schematic diagram of FIG. 9(A), a non-glare type object 1 was used to consider the state of the measured light when the light-reducing member 40 was not inserted in the optical path. The reflectance of the object 1 was set to 1 percent. The transmittance and return rate of the optical member 90 were set to the same as those of the optical device 90 used in FIG. 6(A). Since the conditions of the object 1 and the optical member 90 are the same as those in FIG. 6(A), the received light amount 1 = 90, the received light amount 2 = 0.09, and the sum of the received light amount 1 and the received light amount 2 = 90.09. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by the reflection of the optical member and the surface reflection of the object 1, to the received light amount 1, in other words, the amount of received light increased by the influence of multiple reflection = 0.09 / 90 = 0.10%.

[0079] 9(B) is a schematic diagram of a state in which the light attenuating member 40 is inserted into the optical path of the measured light 2. The light attenuating member 40 is the same as that in FIG. 8(B), and has a transmittance of 5% and a reflectance of 10%, which is equal to the return rate of the optical member 90.

[0080] Under these conditions, when incident light=100 from the object to be measured 1 enters the photometric device 10, the light that passes through the light-attenuating member 40 and the optical member 90 is received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 1=4.5. The light reflected by the optical member 90 returns to the object to be measured 1 via the light-attenuating member 40 (return light 1=0.03). The light that enters from the object to be measured 1 and is reflected by the light-attenuating member 40 also returns to the object to be measured 1 (return light 3=10.00). The return light 1 and 3 that return to the object to be measured 1 are reflected by the surface of the object to be measured 1, become return light 2=0.100, pass through the light-attenuating member 40 again, and enter the optical member 90, and are received by the light-receiving sensors 13b, 14b, and 15b as the amount of received light 2=0.00451.

[0081] The sum of the received light amounts 1 and 2 at the light-receiving sensors 13b, 14b, and 15b is 4.504511. Therefore, the ratio of the received light amount 2, which is the amount of received light caused by reflection from the optical member 90 and the surface reflection of the object to be measured 1, to the received light amount 1, in other words, the amount of received light increased due to the influence of multiple reflections, is 0.00451 / 4.5=0.1%.

[0082] Comparing the case shown in FIG. 9(A) where the light-reducing member 40 is not inserted with the case shown in FIG. 9(B) where the light-reducing member 40 is inserted, the increase in the amount of received light due to the influence of multiple reflections is the same value of 0.1% in both cases.

[0083] As can be seen from this, by forming a reflective member with a reflectance of 10% in the dimming member 40, the difference in the amount of received light that increases due to the effects of multiple reflections with and without ND becomes the same in both the glare and non-glare cases.

[0084] Next, the relationship between the calibration light source and the object 1 to be measured will be considered.

[0085] When the calibration light source and the DUT 1 are of the same type, no absolute value error occurs with or without the ND filter 40. Therefore, no linearity error (ND step) occurs when switching between inserting and removing the ND filter.

[0086] On the other hand, when the calibration light source and the object to be measured 1 are of different types, the results shown in Figures 8(A)(B) and Figures 9(A)(B) show that the absolute value error without the ND filter is -0.4%, and the absolute value error with the ND filter is -0.4%, and no linearity error (ND step) occurs.

[0087] in particular, (1) When calibrated using a glare type light source Non-ND calibration factor: Knon = incident light / received light = 100 / 90.45 With ND Calibration coefficient: Knd = incident light / received light amount = 100 / 4.52256 The measured value of glare type object 1 calibrated with this calibration factor is: Measurement value without ND = amount of light received x calibration coefficient without ND = 90.45 x 100 / 90.45 = 100 (absolute value error 0%) Measurement value with ND = amount of light received x calibration coefficient with ND = 4.52256 x 100 / 4.52256 = 100 (absolute value error 0%) Measurement value difference with / without ND (with ND - without ND) = 100-100 = 0 (linearity error (ND step) 0%) On the other hand, the measured value of the non-glare type test object 1 is Measurement value without ND = amount of light received × calibration coefficient without ND = 90.09 × 100 / 90.45 = 99.602 (absolute value error -0.4%) Measurement value with ND = amount of light received x calibration coefficient with ND = 4.50451 x 100 / 4.52256 = 99.601 (absolute value error -0.4%) Measurement value difference with / without ND (with ND - without ND) = 99.601 - 99.602 = 0.001 (linearity error (ND step) + 0%) (2) When calibrated using a non-glare type light source In this case, the opposite occurs to when calibration is performed using a glare-type light source. The absolute value error for the measurement value of glare-type DUT 1 is +0.4% without ND and +0.4% with ND, but no linearity error (ND step) occurs (0%). (3) Relationship with the specifications of the photometric device (the accuracy required by the customer) The absolute value error that occurs in the above example (-0.4% without ND, -0.4% with ND) is small compared to the specification (±2%), so it is not a problem. Also, the linearity error (ND step) is 0%, so it is not a problem.

[0088] In this way, by providing a reflective member with a return rate equivalent to that of the optical member 90 inside the photometric device 10 on the side of the measured object 1, linearity error (ND step) when the light reducing member 40 is switched between insertion and removal can be suppressed.

[0089] Here, an example of a method for measuring the transmission rate and return rate of the optical member 90 will be described.

[0090] For two photometric devices A and B, suppose that the transmission rate of the optical member 90 of the photometric device A is Top1 and the return rate of the optical member 90 is Rop1, and the transmission rate of the optical member 90 of the photometric device B is Top2 and the return rate of the optical member 90 is Rop2. Transmittance rate of the optical member 90 of the photometric device A: Top1=1-Rop1 Return rate of optical member 90 of photometric device A: Rop1 It becomes. (1) First, the sensitivity ratio C of two photometric devices A and B is calculated, and the ratio of the transmittance of photometric device A to that of photometric device B is calculated.

[0091] That is, as shown in FIG. 10A, when light of intensity E is irradiated from light source K to photometric device A and photometric device B, the light intensity V10 of photometric device A and the light intensity V20 of photometric device B are V10=E×Top1 V20=E×Top2 The sensitivity ratio C of the two photometric devices is C=V10 / V20=Top1 / Top2 It becomes. (2) Next, a half mirror with known transmittance and reflectance is used to obtain the measurement value.

[0092] 10B, a half mirror H with transmittance Thm and reflectance Rhm is placed between the light source K and the photometric device A. The return light from the photometric device A is specularly reflected by the half mirror H and is measured by the photometric device B.

[0093] At this time, the light intensity V11 of the photometric device A and the light intensity V21 of the photometric device B are V11 = E × Thm × Top1 V21=E×Thm×Rop1×Rhm×Top2 In V21, (E×Thm×Rop1) is the return light from the photometric device A.

[0094] If we calculate E from V11 and V21 above, we get E=V11 / (Thm×Top1)=V21 / (Thm×Rop1×Rhm×Top2) Therefore, the return rate Rop1 of the optical member 90 of the photometric device A can be calculated from this formula as follows: Rop1=(V21 / V11)×(1 / Rhm)×(Top1 / Top2)=(V21 / V11)×(1 / Rhm)×C The transmittance of the optical member 90 of the photometric device A is calculated as Top1=1-Rop1.

[0095] Next, the optimum value of the reflectance of the reflective member on the surface of the light reducing member 40 is obtained.

[0096] The incident light is E, the reflectance of the DUT 1 is RDUT, the transmission rate and return rate of the optical member 90 are Top and Rop, respectively, and the transmittance and reflectance of the light-reducing member 40 are Tnd and Rnd, respectively.

[0097] When the attenuation member 40 is not inserted in the optical path, Received light amount 1=E×Top, Received light amount 2=E×Rop×RDUT×Top On the other hand, when the attenuation member 40 is inserted in the optical path, Received light amount 1=E×Tnd×Top, Received light amount 2=E×Tnd×Rop×Tnd×RDUT×Tnd×Top Received light amount 3=E×Rnd×RDUT×Tnd×Top It is.

[0098] Here, the ratio of light received = light received with ND ÷ light received without ND = ND transmittance... Equation [1] When , the linearity error (ND step) becomes 0.

[0099] If we insert the total amount of light received with and without ND and the ND transmittance Tnd into equation [1] and rearrange it, we get {(E×Top)+(E×Rop×RDUT×Top)}×Tnd =(E×Tnd×Top)+(E×Tnd×Rop×Tnd×RDUT×Tnd×Top)+(E×Rnd×RDUT×Tnd×Top) It becomes. When this equation is solved for the reflectance Rnd of the light reducing member 40, Rnd = Rop(1-Tnd^2) Equation [2] It becomes.

[0100] When the linearity error (ND step) is allowed up to ±Eerr %, the allowable width of the reflectance Rnd of the light reducing member 40 is given by ΔRnd0=Eerr / RDUT.

[0101] Here, assuming that the linearity error is <±0.2% and the reflectance of most smartphones is 5% or less, the allowable range of the reflectance (Rnd) of the dimming member 40 is: ΔRnd0=Eerr / RDUT=0.002 / 0.05=0.04 From the above, the preferred reflectance of the light reducing member 40, that is, the reflectance of the reflecting member, is Optimal reflectance (Rnd0)±4%=Rop×(1-Tnd^2)±4% It becomes. A specific example of calculating the reflectance is as follows, for example, for the conditions of the photometric device 10: -Return rate of internal optical components 90 Rop=10% The transmittance Tnd of the light attenuating member 40 is 5%. When The optimal reflectance of the dimming material (reflective material) is Rnd0=Rop×(1-Tnd^2) = 0.1×(1-0.05^2) = 9.4% In order to achieve a linearity error (ND step) of 0.2% or less for most smartphones (reflectance of 5% or less), it is best to set the reflectance of the light-reducing member (reflective member) to 5.4% to 13.4%.

[0102] When the light-reducing member 40 is a thin film filter, the reflecting member may be configured with a thin film integrally formed on its surface. It is particularly preferable to control the reflectance with the thin film on the front side, that is, on the side of the object under test 1. The film configuration also affects the transmittance, so a film configuration that provides appropriate levels of both transmission and reflection is required.

[0103] The reflecting member may be formed of the surface of a glass absorption filter, or a separate reflecting member may be formed integrally with the light reducing member 40.

[0104] Alternatively, the reflecting member may be configured as a separate component separate from the light reducing member 40, and the reflecting member may be disposed in a state spaced apart from the light reducing member 40. An embodiment in which the reflecting member is configured as a separate component separate from the light reducing member 40 will be described later.

[0105] 11A shows the transmittance in the visible light region (380 to 780 nm) of ND filter 40 made of a thin film filter whose thin film is a niobium oxide film. The average transmittance is 5%.

[0106] 11(B) shows the reflectance in the visible light region of ND filter 40 consisting of three types of thin film filters: niobium oxide film 1, niobium oxide film 2, and niobium oxide film 3. The average reflectance of the thin film filter with niobium oxide film 1 is 10%, and the average reflectance of each of the thin film filters with niobium oxide films 2 and 3 is 5%.

[0107] By combining such niobium oxide films to form a multi-layer film, the reflectance can be controlled.

[0108] 12(A), (B), and (C) show the transmittance in the visible light region of ND filter 40 made of a glass absorption filter, the reflectance when a single layer of anti-reflection coating is formed, and the reflectance when there is no anti-reflection coating and only a protective coating. In the case of FIG. 12(A), the average transmittance is 5%, in the case of FIG. 12(B), the average reflectance is 1.5%, and in the case of FIG. 12(C), the average reflectance is 4.5%.

[0109] As described above, according to this embodiment, the occurrence of linearity error (ND step), the magnitude of which varies depending on the characteristics of the object 1 such as the surface reflectance, can be prevented by a reflecting member formed integrally with the ND filter 40 or a reflecting member configured as a separate part from the ND filter 40. In other words, regardless of the characteristics of the object 1, the difference in measurement value caused by this linearity error (ND step), that is, the difference between the measurement value when the ND filter 40 is not inserted in the optical path of the light to be measured and the measurement value when it is inserted, can be corrected by the reflecting member. [Variation 1] 13, in this modification, 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. Also, condenser lenses 19a to 19c are disposed between the exit end of the bundle fiber 30 and each color filter.

[0110] The ND filter 40, the inserting / removing 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 substantially 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. 13, the electrical processing units 16a, 16b, 16c, and the control unit 17 are omitted.

[0111] 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.).

[0112] 13, a part of the light under measurement 2 from the object under measurement 1 that has passed through the objective optical system 11 returns to the object under measurement 1 side by the reflecting member of the ND filter 40. By adjusting the reflectance of the reflecting member of the ND filter 40, the occurrence of linearity errors (ND steps) can be prevented.

[0113] 13, the objective optical system 11 is configured to be front telecentric, like the photometric device 10 according to the first embodiment shown in Fig. 1. In the case of a front telecentric configuration, a large amount of light reflected by the surface of the object 1 returns to the photometric device 10.

[0114] That is, in the case of front telecentricity, as shown by S1 to S3 in Fig. 14(A), light returning to the side of the object 1 under test at 0 degrees is specularly reflected by the surface of the object 1 under test and returns to the photometric device 10 at 0 degrees. Light returning to the side of the object 1 under test at +2.5 degrees is reflected by the object under test and returns to the photometric device 10 at -2.5 degrees. In other words, since it is front telecentric, light of all angle components returns to the photometric device 10. Note that the light attenuation member 40 and the insertion / removal device 50 are omitted in Fig. 14.

[0115] On the other hand, in the case of an optical system that is not telecentric, such as a typical camera lens, the light rays around the measurement area are angled as shown in FIG. 14(B), and therefore do not return to the photometry device 10. [Variation 2] This modified example is provided with a viewfinder optical system that allows the measurer to visually recognize the periphery of the area to be measured.

[0116] That is, as shown in Fig. 15, a mirror M for bending a part of the optical path is disposed between the objective optical system 11 and the incident end 30a 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 Fig. 15, symbols S1 and S2 denote slits.

[0117] If the ND filter 40 is disposed in front of the mirror M, the ND filter 40 is inserted and removed depending on the brightness of the object to be measured 1, making it difficult to see. For this reason, it is preferable that the ND filter 40 be disposed behind the mirror M.

[0118] Since this modification is almost the same as the first modification except that the objective optical system 11 is not front telecentric and includes a finder optical system 60 and mirrors M, S1 and S2, a description thereof will be omitted. Also, in Fig. 15, the condenser lenses 19a, 19b, and 19c behind the bundle fiber 30 are omitted. Also, a diffusion plate 20 may be used in place of the bundle fiber 30. [Variation 3] In this modified example, as shown in Fig. 16, 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 ND filter 40.

[0119] Since the configuration is almost the same as that of the first embodiment shown in Fig. 1 except that the objective optical system 11 is not present, a description thereof will be omitted. Note that a fiber bundle 30 may be used in place of the diffusion plate 20. [Variation 4] In this modification, the configuration of the colorimetric optical system 13 in the photometric device 10 of the first embodiment shown in FIG. 1 is changed.

[0120] That is, as shown in Fig. 17, 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 substantially the same as that of the first embodiment shown in FIG. 1, and therefore a description thereof will be omitted.

[0121] Instead of the diffusion plate 20, a fiber bundle 30 may be used. [Variation 5] 18, in this modification, a reflecting member 45, which is a separate part from the ND filter 40, is disposed in front of the ND filter 40 (on the side of the object to be measured 1). In addition, the ND filter 40 and the reflecting member 45 are simultaneously inserted into and removed from the optical path of the light to be measured 2 by a single common inserting / removing device 51.

[0122] An example of the reflective member 45 is transparent glass. Figures 19(A), (B), and (C) respectively show the transmittance of transparent glass in the visible light region, the reflectance when a single layer of anti-reflection film is formed, and the reflectance when there is only a protective film without an anti-reflection film. The average transmittance in the case of Figure 19(A) is 95%, the average reflectance in the case of Figure 19(B) is 1.5%, and the average reflectance in the case of Figure 19(C) is 4.5%. The ND filter 40 may be a thin film filter with low reflectance.

[0123] The configuration other than the ND filter 40, the reflecting member 45, and the insertion / removal device 51 is substantially the same as that of the first embodiment shown in FIG. [Variation 6] In this modified example, as shown in FIG. 20, a reflective member 45, which is a separate part from the ND filter 40, is disposed in front of the light attenuating member 40 (toward the object to be measured 1), and the ND filter 40 and the reflective member 45 are inserted and removed in synchronization with the optical path of the light to be measured 2 by different insertion / removal devices 52 and 53, respectively.

[0124] The configuration other than the ND filter 40, the reflecting member 45, and the inserting / removing devices 52 and 53 is substantially the same as that of the first modified example shown in FIG. [ND filter insertion / removal control] 21 is a flowchart for explaining a method for controlling insertion and removal of the ND filter 40, which is performed in the photometric device 10 according to the embodiment 1. This control is performed by the control unit 17.

[0125] 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 ND filter 40 is inserted in the optical path (on) or retracted (off).

[0126] 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.

[0127] If the received light data is not smaller than threshold value A in step S03 (NO in step S03), the ND filter 40 is inserted into the optical path in step S06, and then the process returns to step S01 to obtain the received light data again.

[0128] If the ND filter 40 is inserted in 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.

[0129] If the light reception data is not greater than threshold value B in step S08 (NO in step S08), the ND filter 40 is retracted from the optical path in step S11, and then the process returns to step S01 to obtain the light reception data again. [Embodiment 2] In the embodiment 1 (including various modified examples) described above, the linearity error (ND step) between the measurement value when the ND filter 40 is not inserted in the optical path of the measured light 2 and the measurement value when it is inserted, which occurs when the reflectance of the measured object 1 is different, is corrected by the reflective member, thereby making it possible to obtain an appropriate measurement value regardless of differences in the characteristics of the measured object 1.

[0130] In the second embodiment, the linearity error (ND step) is corrected by calculation using a calibration coefficient (corresponding to a correction coefficient).

[0131] The overall configuration of the calibration system is shown in Fig. 22. This calibration system includes a photometric device 10, an information processing device 300 such as a personal computer, and an object 1 to be measured.

[0132] The photometric device 10 has a cylindrical lens barrel portion 10a at the tip side for capturing the light 2 to be measured from the object to be measured 1, and further has a communication portion 10b at the rear side for communicating measurement data, control signals, etc. with the information processing device 300.

[0133] In this embodiment, the photometric device 10 of embodiment 1 shown in Figure 1 is used as the internal configuration of the photometric device 10, but any of the photometric devices 10 of variants 1 to 6 shown in Figures 13, 15 to 18, and 20 may also be used.

[0134] The internal configuration of the photometric device 10 is the same as that of the first embodiment, but the reflectance of the ND filter 40 is not limited, and a thin film filter, a glass absorption filter, or the like that is generally used as an ND filter may be used. As in the first embodiment, the ND filter 40 is inserted into or removed from the optical path of the light 2 to be measured according to the brightness of the object 1 to be measured. Specifically, the ND filter 40 is inserted into the optical path when the amount of light 2 to be measured is greater than a predetermined amount of light.

[0135] 23 shows a detailed configuration of the control unit 17. The control unit 17 includes a CPU 171, a ROM 172, a RAM 173, a storage unit 174, and the like.

[0136] The CPU 171 operates according to an operation program to comprehensively control the entire photometric device 10. For example, when measuring the object 1 under test, it receives signals from the electrical processing units 16a-16c, performs correction as necessary, and calculates a measurement value. In this embodiment, during user calibration performed based on an instruction from the user of the photometric device 10, it performs processing such as calculation of a calibration coefficient, the details of which will be described later.

[0137] The ROM 172 is a memory that stores the operation program and other data. The RAM 173 is a memory that provides a working area when the CPU 171 operates according to the operation program. It also stores the measurement values ​​such as luminance, chromaticity, etc., which are the results of calculations.

[0138] The storage unit 174 is made up of a storage medium such as a flash ROM or FeRAM, and stores various data such as calibration coefficients when the photometric device 10 is factory calibrated at the time of shipment, calibration coefficients obtained by user calibration, and predetermined setting values.

[0139] Next, the calculations for determining the measurement values ​​(tristimulus values) performed by the control unit 17 will be described.

[0140] Generally, when calculating tristimulus values ​​(X, Y, Z) from the light reception data (count value) obtained from the output of the light receiving sensors 13b, 14b, and 15b, the control unit 17 performs calculations as shown in the flowcharts of Figures 24(A) and (B). This is because individual variations occur due to variations in the internal reflectance of the photometric device 10, and individual variations occur due to changes in the amount of light caused by inserting and removing the ND filter 40 and variations in the reflectance of the ND filter 40, and it is necessary to perform calculations as shown in the flowcharts of Figures 24(A) and (B) to correct the values.

[0141] FIG. 24(A) shows the calculation process when the ND filter 40 is not inserted in the optical path, in which the count value is multiplied by the ND conversion factory calibration coefficient N (without ND) in step S21, and further multiplied by the factory calibration coefficient M in step S22 to obtain the tristimulus values.

[0142] FIG. 13B shows the calculation process when the ND filter 40 is inserted in the optical path, in which the count value is multiplied by the ND conversion factory calibration coefficient N (with ND) in step S31, and further multiplied by the factory calibration coefficient M in step S32 to obtain the tristimulus values.

[0143] The “ND conversion factory calibration coefficient N (with ND)” in step S31 is a calibration coefficient for correcting the difference between the presence and absence of the ND filter 40, which occurs due to the difference between the reflectance of the ND filter 40 and the internal reflectance of the photometric device 10.

[0144] Specifically, it is a calibration coefficient for making a correction so that the measurement data when the ND filter 40 is inserted in the optical path and when it is not inserted match using a reference light source. If the amount of light 2 to be measured is less than a predetermined amount of light, the ND filter 40 is not inserted in the optical path, and so such a correction is not necessary. For this reason, the "ND conversion factory calibration coefficient N (without ND)" in step S21 in FIG. 11A is a unit matrix.

[0145] The factory calibration coefficient M is a calibration coefficient used when calibration is performed at a factory using a reference light source before product shipment so that the output of the photometric device 10 matches the output (reference value) when a reference light source is measured using a reference device. The ND conversion factory calibration coefficient N (with ND), the ND conversion factory calibration coefficient N (without ND), and the factory calibration coefficient M are written in the memory unit or the like of the photometric device 10.

[0146] By calculating the tristimulus values ​​using the factory calibration coefficient M, it is possible to obtain predetermined values ​​when measuring an object 1 having the same surface reflectance as the light source used during factory calibration.

[0147] Next, a case will be considered in which a customer's object 1 having a surface reflectance different from that of the reference light source is to be measured.

[0148] Even if a photometric device 10 that has been matrix calibrated as described above is used, when a customer's object 1 with a different surface reflectance is measured, the tristimulus values ​​will deviate from the specified values ​​due to the difference between the calibration light source and the surface reflectance of the object 1.

[0149] For this reason, many photometric devices are equipped with a user calibration function. This user calibration function is a function that determines a user calibration coefficient U using a master panel that has representative characteristics of the object under test 1. Specifically, the output value (reference value) obtained when the master panel is measured using a reference device such as a spectrophotometer is compared with the output value obtained when the master panel is measured using the photometric device 10 used for measurement without the ND filter 40 inserted, and the user calibration coefficient U is determined so that the two output values ​​match.

[0150] After the user calibration coefficient U is calculated, the tristimulus values ​​are calculated using this user calibration coefficient U. Specifically, after correction is made using the factory calibration coefficient M shown in the flowcharts of Figures 24(A) and (B), calibration is performed by multiplying it by the user calibration coefficient U.

[0151] This calibration process makes it possible to obtain a predetermined value when the ND filter 40 is not inserted in the optical path. However, with user calibration alone, if the reflectance of the surface of the ND filter 40 facing the object 1 is different from the internal reflectance of the photometric device 10 (reflection of the color filters 13a, 14a, 15a and the light receiving sensors 13b, 14b, 15b), the effect of the different reflectance appears, causing a linearity error (ND step) when the ND filter is inserted or removed between the glare type object 1 and the non-glare type object. This point is as explained in the section <Problems that occur when inserting or removing the light-reducing member 40> in the first embodiment.

[0152] Therefore, in the second embodiment, in order to eliminate the above linearity error (ND step), a correction process is carried out by ND conversion user calibration, which will be described below.

[0153] Similar to the user calibration, this ND conversion user calibration coefficient is calculated by measuring using a master panel that is different from the reference light source and has representative characteristics of the object under test 1. The calculation process will be described below.

[0154] First, the master panel 1 emits light without the ND filter 40 inserted in the optical path, and the outputs from the light receiving sensors 13b, 14b, and 15b at that time are stored (count value C). At this time, if the luminance (brightness) of the master panel 1 is too high, the light receiving sensors will be saturated and appropriate ND conversion user calibration will not be possible. Therefore, the count value C at which ND conversion user calibration is performed is limited to a predetermined range.

[0155] Next, from the stored count values, the tristimulus value S when the ND filter 40 is not inserted is calculated. Un2(W,R,G,B) is calculated using the ND conversion factory calibration coefficient N (without ND) and the factory calibration coefficient M. The formula is as follows:

[0156]

number

[0157] Next, the master panel 1 is caused to emit light with the ND filter 40 inserted in the optical path, and the outputs from the light receiving sensors 13b, 14b, and 15b at that time are stored (count value C). At this time, if the luminance (brightness) of the master panel 1 is too low, the stability of the light emission of the master panel 1 is lost, making it impossible to perform appropriate ND conversion user calibration. Therefore, the count value C at which ND conversion user calibration is performed is limited to a predetermined range.

[0158] The exposure time with the ND filter 40 inserted in the optical path is set to be longer than the exposure time with the ND filter 40 not inserted in the optical path. The reason for this is that when the ND filter 40 is inserted, it becomes dark, so the exposure time is set to be longer than when the ND filter 40 is not inserted in order to increase the S / N ratio. In this case, the exposure time with the ND filter 40 inserted should be set to an exposure time that gives an S / N ratio that is approximately the same as when the ND filter 40 is not inserted.

[0159] From the stored count value, the tristimulus value S with the ND inserted is Un1(W,R,G,B) is calculated using the ND conversion factory calibration coefficient N (with ND) and the factory calibration coefficient M. The formula is as follows.

[0160]

number

[0161] And the tristimulus value S Un1(W,R,G,B) and tristimulus value S Un2(W,R,G,B) The ND conversion user calibration coefficient Un is calculated from the above, and the calculated ND conversion user calibration coefficient Un is stored in the storage unit 174 as a first correction coefficient. The ND conversion user calibration coefficient Un is calculated as follows: S Un2(W,R,G,B) ≒Un·S Un1(W,R,G,B) This is done by calculating Un by matrix calibration.

[0162] The calculation for determining the matrix calibration coefficients may be performed by a known method, but the outline thereof will be described below.

[0163] If the source RGB is a 3x3 matrix: A1 and the destination RGB is a 3x3 matrix: A2, A2=Un RGB ×A1, Un RGB =A2×A1 -1 Therefore, the inverse matrix A1 is -1 After asking for Un RGB =A2×A1 -1 From Un RGB Request.

[0164] The measurement for performing ND conversion user calibration is performed by making the object under test 1 emit light in W (white), R (red), G (green), and B (blue).

[0165] In this case, the exposure sequence is as follows: a) Fix the emission color of the DUT 1 and switch between no ND filter (not inserted) and with ND filter (inserted). For example, the order is white and no ND filter → white and with ND filter → red and no ND filter → red and with ND filter → green and no ND filter → green and with ND filter → blue and no ND filter → blue and with ND filter. b) Fix the setting with and without an ND filter, and switch the emission color. For example, the order is white without an ND filter → red without an ND filter → green without an ND filter → blue without an ND filter → white with an ND filter → red with an ND filter → green with an ND filter → blue with an ND filter.

[0166] Either the order a) or b) may be used, but taking into consideration the stability of the light emission from the DUT 1, the order a) which involves less switching of light emission is more desirable in terms of improving calibration accuracy.

[0167] The light emission control of the object under test 1 is performed by the information processing device 300. The object under test 1 emits light in a predetermined order based on a light emission instruction from the information processing device 300. The information processing device 300 and the photometric device 100 communicate with each other, and the photometric device 100 switches between inserting and removing an ND filter based on a signal from the information processing device 300.

[0168] In addition, in order to perform highly accurate calibration in as short a time as possible, it is desirable to increase the luminance (brightness) with the ND filter in place.

[0169] However, if the luminance (brightness) is increased with the ND filter present, the luminance (brightness) without the ND filter will become too high, causing the light receiving sensors 13b, 14b, and 15b to become saturated, making it impossible to perform appropriate ND conversion user calibration.

[0170] To address this issue, when the photometric device 10 detects saturation of the light receiving sensors 13b, 14b, and 15b, it transmits a detection signal to the information processing device 300, and the information processing device 300 performs control to reduce the luminance (brightness) of the object to be measured 1 to a level that does not cause saturation.

[0171] The calculation of the ND conversion user calibration coefficient Un is performed by the photometric device 10.

[0172] The flowchart in FIG. 25 shows the calculation process when tristimulus values ​​are calculated using the ND conversion user calibration coefficient Un obtained using the ND conversion user calibration function.

[0173] 25, in step S41, the count value C is multiplied by the ND conversion factory calibration coefficient N (with ND), and in step S42, it is further multiplied by the ND conversion user calibration coefficient Un. In step S43, it is further multiplied by the factory calibration coefficient M, and then in step S44, it is multiplied by the user calibration coefficient U to obtain tristimulus values.

[0174] As described above, the user calibration coefficient U is calculated based on the output when a master panel having a representative characteristic of the object to be measured 1 (in this embodiment, reflectance) is measured by a reference device and the output value when the master panel is measured by the photometric device 10 without the ND filter 40 being inserted in the optical path, and is a second correction coefficient for matching the two, and is calculated by the photometric device 10.

[0175] In this way, by correcting the count values ​​from the light receiving sensors 13b, 14b, and 15b using the ND conversion user calibration coefficient Un, it is possible to obtain a predetermined appropriate value when measuring panels for customers with different surface reflectivities, such as glare type and non-glare type, even if an ND filter 40 is used whose surface reflectivity differs from the internal reflectivity (return rate).

[0176] It is preferable to perform the operation to find the ND conversion user calibration coefficient Un consecutively with the operation to find the user calibration coefficient U, as this is less susceptible to fluctuations over time. Also, because the luminance (brightness) range in which ND conversion user calibration can be performed properly is limited, if ND conversion user calibration is performed after user calibration, the ND conversion user calibration cannot be performed properly, and the previous user calibration may become useless. For this reason, if the operation to find the ND conversion user calibration coefficient Un and the operation to find the user calibration coefficient U are performed consecutively, it is preferable to perform the ND conversion user calibration first.

[0177] However, in some cases, a specified value can be obtained by only the ND conversion user calibration Un, or by only the user calibration U, so each operation may be performed separately.

[0178] In this embodiment, the information processing device 300 has a processing mode in which only the calculation of the ND conversion user calibration coefficient Un is performed, a processing mode in which only the calculation of the user calibration coefficient U is performed, and a processing mode in which both coefficients are calculated continuously. Then, as shown in Fig. 26, a mode selection screen is displayed on the information processing device 300, and the user can select one of the modes by checking a check box or the like.

[0179] Also, ND conversion user calibration coefficients UnA, UnB... or further user calibration coefficients UA, UB... may be determined for each object under test 1 having different surface reflection characteristics, and the determined ND conversion user calibration coefficients UnA, UnB... or further user calibration coefficients UA, UB... may be stored in storage unit 174 in association with the type of object under test 1, as shown in Fig. 27. Then, the ND conversion user calibration coefficients Un to be used can be selected according to the type of object under test 1 to be measured.

[0180] Although the second embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned second embodiment.

[0181] For example, the light emission state of the object 1 to be measured is controlled by the information processing device 300, but the photometric device 10 may have a control function for controlling the light emission state of the object 1 to be measured, and the object 1 to be measured and the photometric device 10 may perform ND conversion user calibration or user calibration. Also, the photometric device 10 calculates the ND conversion user calibration coefficient Un and the user calibration coefficient U, but the information processing device 300 may calculate them and write them in the storage unit 174 of the photometric device 10. [Industrial Applicability]

[0182] 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]

[0183] 1 Object to be measured 2 Light to be measured 10 Photometering device 10a Telescope tube 10b Communication Department 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 45 Reflective material 50 Insertion / extraction device 60 Viewfinder optical system 300 Information processing device

Claims

1. a light receiving section having one or more light receiving sensors for receiving light to be measured from the object to be measured; A control means for calculating a measurement value based on an output from the light receiving sensor; a light attenuating member that is removably provided in an optical path of the light to be measured and that attenuates light incident on the light receiving unit; a correction means for correcting a difference between a measurement value calculated by the control means in a state where the light attenuation member is inserted in the optical path and a measurement value calculated by the control means in a state where the light attenuation member is not inserted in the optical path, the difference varying depending on the characteristics of the object to be measured; A photometric device comprising:

2. 2. The photometric device according to claim 1, wherein the correction means is a reflective member that is inserted into the optical path when the light attenuating member is inserted into the optical path and that retracts from the optical path when the light attenuating member is retracted from the optical path.

3. 3. A photometric device according to claim 2, wherein said reflecting member is formed integrally with said light attenuating member.

4. 3. A photometric device according to claim 2, wherein said reflecting member is made up of one or more members and is separate from said light attenuating member.

5. 5. The photometric device according to claim 1, wherein the reflectance of the reflective member is within ±4% of the optimum reflectance.

6. 2. The photometric device according to claim 1, wherein said correction means comprises control means for calculating the measurement value using a correction coefficient corresponding to the physical property of the object to be measured.

7. The photometric device according to claim 6, further comprising a storage unit for storing the correction coefficients.

8. 8. The photometric device according to claim 6, wherein the control means, based on an instruction from a user, determines an output value output from the light receiving unit when the light attenuation member is inserted in the optical path and an output value output from the light receiving unit when the light attenuation member is not inserted in the optical path, and determines the correction coefficient based on these.

9. 9. The photometric device according to claim 8, wherein an exposure time for obtaining an output value output from the light receiving unit when the light attenuation member is inserted is longer than an exposure time for obtaining an output value output from the light receiving unit when the light attenuation member is not inserted.

10. 9. The photometric device according to claim 8, wherein the correction coefficient is calculated when an output value output from the light receiving unit when the light attenuation member is inserted in the optical path and an output value output from the light receiving unit when the light attenuation member is not inserted in the optical path are within a predetermined range.

11. 8. The photometric device according to claim 7, wherein the storage section stores a plurality of correction coefficients respectively corresponding to the plurality of objects to be measured.

12. 8. The photometric device according to claim 6, wherein the characteristic of the object to be measured is a reflectance of the object to be measured.

13. A calibration system for calibrating a photometric device according to claim 8, comprising an information processing device, and when the correction coefficient according to claim 8 is a first correction coefficient, the information processing device requests the control means to obtain the first correction coefficient based on an instruction from a user, and a calibration system characterized by further requiring a second correction coefficient to be determined based on a reference value possessed by the object to be measured and an output value when the light receiving unit receives light from the object to be measured with the light attenuation member not inserted in the optical path.

14. 14. The calibration system of claim 13, further comprising a step of requesting determination of said second correction factor after requesting determination of said first correction factor.

15. A calibration system for calibrating a photometric device according to claim 8, comprising an information processing device, wherein when the correction coefficient according to claim 8 is a first correction coefficient, the information processing device performs the following steps in addition to a process of requesting the control means to obtain the first correction coefficient based on an instruction from a user: A calibration system characterized by having a mode that only requires processing to determine a second correction coefficient based on a reference value possessed by the object to be measured and an output value when the light receiving unit receives light from the object to be measured with the light attenuation member not inserted in the optical path.

16. A calibration system for calibrating a photometric device according to claim 8, comprising an information processing device, wherein when the correction coefficient according to claim 8 is a first correction coefficient, the information processing device performs the following steps in addition to a process of requesting the control means to determine a second correction coefficient based on a reference value of the object to be measured and an output value when the light receiving unit receives light from the object to be measured in a state in which the light attenuation member is not inserted in the optical path, based on an instruction from a user: A calibration system having a mode which requires only a process for determining the first correction coefficient.

17. 8. A photometric device according to claim 1, wherein said light attenuating member is inserted or removed in accordance with the brightness of an object to be measured.

18. 8. A photometric device according to claim 1, wherein said light receiving sensor is a silicon sensor.

19. 8. A photometric device according to claim 1, further comprising a wavelength selection filter provided in front of said light receiving sensor.

20. 8. A photometric device according to claim 1, 2, 6 or 7, wherein said wavelength selective filter is a thin film filter.

21. 8. A photometric device according to claim 1, 2, 6 or 7, wherein said light attenuating member comprises a thin film filter.

22. 8. A photometric device according to claim 1, further comprising a branching optical system for branching the light to be measured into a plurality of beams.

23. 8. A photometric device according to claim 1, wherein the measurement wavelength range of the light to be measured is the visible light range.

24. 8. A photometric device according to claim 1, wherein said wavelength-selective filter is a color-matching function filter.

25. 8. A photometric device according to claim 1, wherein said wavelength-selecting filter is a spectral filter, and said light-receiving sensor is a line sensor.

26. a light receiving section having one or more light receiving sensors for receiving light to be measured from the object to be measured; A control means for calculating a measurement value based on an output from the light receiving sensor; and correcting a difference between a measurement value calculated by the control means when the light attenuation member is inserted in the optical path and a measurement value calculated by the control means when the light attenuation member is not inserted in the optical path, the difference varying depending on a characteristic of the object to be measured.

27. 9. A calibration system for calibrating the photometric device according to claim 8 for each reference display color, the calibration system being characterized in that the correction coefficient is obtained by switching between inserting and removing a light attenuation member while the reference display color is fixed.

28. 9. A calibration system for calibrating a photometric device according to claim 8, characterized in that, when saturation of a light receiving sensor in the photometric device is detected during calculation of a correction coefficient, the brightness of the object to be measured is reduced.

Images