Photometric device, calibration system, calibration method and program

Abstract

To provide a photometric device and a calibration system capable of performing high accuracy calibration for suppressing errors generated by insertion and removal of a light reducing member to and from an optical path regardless of emission characteristics of a display device, and to provide a calibration method and a program.SOLUTION: The photometric device comprises: a light reducing member 40 arranged so as to be insertable to / removable from an optical path of measurement target light 2 from a display device 1; and obtaining means 17 for obtaining, in order to generate a calibration factor suppressing a measurement error between a state where the light reducing member is inserted into the optical path and a state of no insertion, a photometric value of the measurement target light in the state where the light reducing member is inserted into the optical path and a photometric value of the measurement target light in the state of no insertion. The obtaining means obtains three or more photometric values in total measured on each state when at least two or more times of switching are performed which include switching from the state where the light reducing member is inserted into the optical path to the state of no insertion and switching from the state of no insertion to the state of insertion.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] As such a photometric device, as shown in FIG. 12, a photometric device 100 is known that includes a branching optical system 120 that branches a light to be measured 201 from a display 200 into a plurality of beams (see, for example, Patent Document 1).

[0003] This photometric device includes an objective optical system 110 consisting of a convex lens, 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 a bundle of small-diameter bare fibers, which are randomly split into multiple groups (for example, three groups corresponding to the tristimulus values ​​of the color matching functions X, Y, and Z defined by the CIE (International Commission on Illumination)) on the output end (exit) side. The branching optical system 12 may be a diffusion plate.

[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 units 161a to 161c, and input as light receiving data to the control unit 162. The control unit 162 performs calculations based on the input light receiving data to calculate a measurement value.

[0006] Recently, displays with a wide luminance dynamic range are used in smartphones, etc. For this reason, the photometric device 100 is required to have the performance to measure a wide range of luminance from dark to bright when performing gamma inspection and adjustment.

[0007] 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 dimming member according to the brightness of the display 200 into the optical path of the measured light 201 emitted from the display 200 and incident on the light receiving sensor.

[0008] However, when the light-reducing member is inserted or removed to widen the dynamic range, a difference occurs in the measurement value between the inserted state and the non-inserted state.

[0009] Therefore, in order to eliminate the difference caused by inserting and removing the light-attenuating member, it is conceivable to calibrate the light measuring device. Such a calibration requires performing light measurement in two states, one with the light-attenuating member inserted in the optical path of the measured light and one without it, and generating a calibration coefficient using these light measurement values.

[0010] If the display's emission is stable, specifically if the emission cycle is constant and the emission waveform is also constant, a calibration coefficient that satisfies the required accuracy can be generated by simply measuring the above two states. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 5454675 Summary of the Invention [Problem to be solved by the invention]

[0012] However, as will be described below, the inventors' research has revealed that, for modern displays, it is sometimes difficult to ensure sufficient accuracy in the calibration coefficients.

[0013] That is, as shown in the light emission waveform in Fig. 13(A), the light emission waveform has become more complex as the functions and performance of displays have improved. For example, in the case of OLED (Organic Light-Emitting Diode) displays, light emission control that combines not only amplitude modulation but also pulse width modulation for gradation control is adopted to achieve faithful color reproduction, and light emission with high amplitude and complex waveforms has become common. In particular, in pulse width modulation, multiple pulse light emission control is performed in one frame period (vertical synchronization period), and the light emission waveform is faster than the image update period, and the waveform is steep and has high amplitude. Note that the vertical axis of the waveform shown in Fig. 13(A) is the luminance value, the horizontal axis is the time, and the vertical synchronization frequency Vsync is 60 Hz.

[0014] Moreover, in recent years, displays with a variable refresh rate (VRR) function have been developed. In these displays, the refresh rate switches dynamically and aperiodically, so that the emission waveform becomes increasingly complex, with transient responses being observed in the emission waveform starting from the switching point.

[0015] Furthermore, as shown in Fig. 13(B) showing the change in luminance value when the luminance value is measured with 1 / 60th of a second as one frame, there are instabilities such as a short-term drift in the light emission waveform that rises to the right as indicated by the arrow S1, and non-periodic steps as indicated by the arrow S2. In Fig. 13(B), the luminance value error normalized by the average luminance value Lv is shown on the vertical axis, and the frame number, that is, the time, is shown on the horizontal axis.

[0016] Drift is a gradual increase or decrease in brightness value over time, and the brightness value increases over time as indicated by arrow S1. Drift is mainly caused by heat generation from information devices, including displays. Non-periodic steps are irregular, large changes in brightness value. Non-periodic steps occur due to a combination of factors such as "temperature feedback" and "image data update cycle due to VRR support."

[0017] When using such a sensitive display, if calibration is performed for inserting and removing the light-reducing member, the calibration value will fluctuate each time calibration is performed. Therefore, the same linear characteristics cannot be obtained in the measured value when the light-reducing member is inserted and not inserted in the optical path, and a step occurs in the measured value when the light-reducing member is inserted and switched. As a result, it was found that although the dynamic range could be expanded by incorporating the light-reducing member, a problem occurred in which accurate measurement could not be achieved in the high brightness range where the light-reducing member is inserted.

[0018] This invention has been made in consideration of the above technical background, and aims to provide a photometric device, a calibration system, a calibration method, and a program that are capable of performing highly accurate calibration to suppress errors caused by inserting and removing a dimming member into the optical path, regardless of the light-emitting characteristics of the display. [Means for solving the problem]

[0019] The above object can be achieved by the following means: (1) a light-reducing member that is removably disposed in an optical path of light to be measured from a display; an acquisition means for acquiring a photometric value of the measured light when the light-attenuating member is inserted in the optical path and a photometric value of the measured light when the light-attenuating member is not inserted in the optical path, in order to generate a calibration coefficient that suppresses a measurement error between a state in which the light-attenuating member is inserted in the optical path and a state in which the light-attenuating member is not inserted; Equipped with The photometric device is characterized in that the acquisition means acquires a total of at least three or more photometric values ​​measured in each state when at least two or more switchings are made, including switching from a state in which the dimming member is inserted in the optical path to a state in which it is not inserted, and switching from a state in which it is not inserted to a state in which it is inserted, as photometric values ​​for generating the calibration coefficient. (2) The photometric device according to claim 1, further comprising a generating unit that generates the calibration coefficient using the photometric value for generating the calibration coefficient acquired by the acquiring unit. (3) A photometric device as described in paragraph 1 or 2 above, in which when there are multiple reference colors during calibration, at least one of the number of switching times or the photometric conditions is changed in accordance with the reference colors. (4) A photometric device as described in paragraph 1 or 2, in which the photometric values ​​corresponding to the state in which the light-attenuating member is inserted in the optical path and the state in which the light-attenuating member is not inserted are generated from a weighted average value. (5) A photometric device as described in the preceding paragraph 1 or 2, in which the number of times the switching is performed can be designated by a user. (6) The photometric device according to claim 1 or 2, wherein the acquisition means acquires a photometric value when a dimming member is switched between being inserted and removed while a reference color is set. (7) A photometric device as described in the preceding paragraph 1 or 2, which performs pre-photometric measurement before the acquisition means acquires a photometric value, and notifies a user of the degree of saturation. (8) A photometric device as described in paragraph 1 or 2 above, wherein acquisition of the photometric value by the acquisition means is started from a state in which a light-reducing member is not inserted in the optical path. (9) The photometric device according to the preceding paragraph 1; a generation means for generating the calibration coefficients using photometric values ​​for generating the calibration coefficients acquired by an acquisition means of the photometric device; A calibration system comprising: (10) A calibration system as described in the preceding paragraph 9, in which, when there are multiple reference colors during calibration, at least one of the number of switching times or the photometric conditions is changed in accordance with the reference colors. (11) A calibration system as described in paragraph 9 or 10 above, in which the photometric values ​​corresponding to the state where the light-attenuating member is inserted in the optical path and the state where the light-attenuating member is not inserted are generated from a weighted average value. (12) A calibration system as described in the preceding paragraphs 9 or 10, in which the number of times the switching is performed can be designated by a user. (13) A calibration system according to the preceding paragraph 9 or 10, wherein the acquisition means of the photometric device acquires a photometric value when a dimming member is switched between being inserted and removed while a reference color is set. (14) A calibration system as described in the preceding paragraph 9 or 10, which performs pre-photometry before the acquisition means of the photometric device acquires a photometric value, and notifies a user of the degree of saturation. (15) A calibration system as described in paragraph 9 or 10 above, wherein acquisition of the photometric value by the acquisition means of the photometric device is started from a state in which a light-reducing member is not inserted in the optical path. (16) A calibration method for calibrating a photometric device having a light-reducing member that is arranged so as to be insertable and removable from an optical path of light to be measured from a display, comprising the steps of: performing an acquisition step of acquiring a photometric value of the measured light in a state where the light-attenuating member is inserted in the optical path and a photometric value of the measured light in a state where the light-attenuating member is not inserted in the optical path in order to generate a calibration coefficient that suppresses a measurement error between a state where the light-attenuating member is inserted in the optical path and a state where the light-attenuating member is not inserted; In the acquisition step, the acquisition means acquires a total of at least three or more photometric values ​​obtained by measuring the light in each state when at least two or more switchings are performed, including switching from a state in which the light-reducing member is inserted in the optical path to a state in which it is not inserted and switching from a state in which it is not inserted to a state in which it is inserted, and further A calibration method comprising: performing a generation step of generating the calibration coefficients using acquired photometric values. (17) A computer of a photometric device having a light-reducing member arranged so as to be insertable and detachable from an optical path of light to be measured from a display, an acquisition step of acquiring a photometric value of the measured light in a state where the light-attenuating member is inserted in the optical path and a photometric value of the measured light in a state where the light-attenuating member is not inserted in the optical path in order to generate a calibration coefficient that suppresses a measurement error between a state where the light-attenuating member is inserted in the optical path and a state where the light-attenuating member is not inserted; Run the command, In the acquisition step, a program for causing the computer to execute a process of acquiring a total of at least three or more photometric values ​​measured in each state when at least two or more switchings are made, including switching from a state in which the dimming member is inserted in the optical path to a state in which it is not inserted, and switching from a state in which it is not inserted to a state in which it is inserted, as photometric values ​​for generating the calibration coefficient. Effect of the Invention

[0020] According to the photometric device, calibration system, and calibration method of the present invention, in order to generate a calibration coefficient, a photometric value of the measured light in a state in which a light-attenuating member is inserted in the optical path and a photometric value of the measured light in a state in which the light-attenuating member is not inserted are obtained. At least three or more photometric values ​​are obtained by measuring light in each state when at least two or more switching operations are performed, including switching from a state in which the light-attenuating member is inserted in the optical path to a state in which the light-attenuating member is not inserted and switching from a state in which the light-attenuating member is not inserted to a state in which the light-attenuating member is inserted. A calibration coefficient is generated using the obtained photometric values ​​when at least two or more switching operations are performed.

[0021] In this way, the calibration coefficient is generated using at least three or more photometric values ​​measured in each state when at least two or more switchings are performed, so that at least two photometric values ​​are obtained, at least one of the photometric value of the measured light when the light-reducing member is inserted in the optical path and the photometric value of the measured light when the light-reducing member is not inserted. Therefore, by averaging at least two photometric values, even if the photometric values ​​are on both sides of the step across the non-periodic step shown in FIG. 13(B), the influence of the non-periodic step can be suppressed. As a result, regardless of the light emission characteristics of the display, it is possible to generate a calibration coefficient with higher accuracy, and it is possible to obtain a highly accurate measurement result, especially in the high brightness range where the light-reducing member is inserted. In addition, it is possible to ensure linear continuity of the measurement value at the brightness value where the insertion and removal of the light-reducing member are switched.

[0022] According to the program of the present invention, the computer of the photometric device can be caused to execute a process of obtaining a total of at least three or more photometric values ​​measured in each state when at least two or more switching operations are performed as photometric values ​​for generating a calibration coefficient. [Brief description of the drawings]

[0023] [Figure 1] 1 is an overall configuration diagram of a calibration system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing the internal configuration of the photometric device. [Diagram 3] FIG. 2 is a block diagram showing a configuration of a control unit. [Figure 4] 4 is a flowchart for explaining an ND calibration method using the calibration system shown in FIG. [Diagram 5] 11 is a table showing an example of photometric conditions during ND calibration in this embodiment. [Figure 6] This is a diagram in which the timing of acquiring photometric values ​​is plotted in the same diagram as FIG. 13(B). [Figure 7] FIG. 11 is a diagram for explaining a measurement error remaining after ND calibration. [Figure 8]FIG. 1A is a diagram showing measurement errors in a conventional method, and FIG. 1B is a diagram showing measurement errors in the first embodiment. [Figure 9] FIG. 11 is an overall configuration diagram of a calibration system according to a second embodiment of the present invention. [Figure 10] 10 is a flowchart for explaining a method of ND calibration by the calibration system shown in FIG. 9. [Figure 11] FIG. 13 is an overall configuration diagram of a calibration system according to still another embodiment of the present invention. [Figure 12] FIG. 1 is a diagram showing the configuration of a typical tristimulus value type photometric device. [Figure 13] FIG. 1A is a diagram showing an example of an emission waveform of a display, and FIG. 1B is a diagram showing the occurrence of short-term drift and non-periodic steps in the emission waveform. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [First embodiment] In this embodiment, an example will be described in which a calibration application is used to perform calibration (matrix calibration) for the insertion and removal of a dimming member for the four display colors W (white), R (red), G (green), and B (blue) in a tristimulus value type photometric device. In the following description, the calibration application is also referred to as a "calibration app," and calibration for suppressing errors caused by the insertion and removal of a dimming member is also referred to as "ND calibration." In addition, the state regarding whether or not the dimming member is inserted into the optical path of the light to be measured is also referred to as an "ND state," the inserted state is also referred to as an "ND state," and the not inserted state is also referred to as an "ND state."

[0025] 1 is a diagram showing the overall configuration of a calibration system according to a first embodiment of the present invention. This calibration system includes a photometric device 10, an information processing device 300 such as a personal computer, and a display 1.

[0026] The information processing device 300 controls the entire calibration system. Specifically, when ND calibration is performed, the information processing device 300 controls the light emission state of the display 1 while communicating with the display 1 and the photometric device 10 based on a calibration application, and causes the photometric device 10 to obtain photometric values ​​for generating calibration coefficients and calculate and generate calibration coefficients.

[0027] FIG. 2 is a block diagram showing the internal configuration of the photometric device 10. As shown in FIG.

[0028] In FIG. 2, 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 the display surface of a display 1.

[0029] The photometric device 10 includes an objective optical system 11, a branching optical system 12, colorimetric optical systems 13-15, and a light-reducing member 40. The objective optical system 11 uses a convex lens 11a having a positive power. The branching optical system 12 uses a diffusion plate 20 having branching and diffusing functions. Note that instead of the diffusion plate 20, a bundle fiber having a branch on the exit end side as shown in FIG. 12 may be used.

[0030] 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 ±2.5 degrees of the normal to the measurement surface, which is the display surface of the display 1. A diffuser 20 is disposed behind the aperture stop 11b.

[0031] 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 insertion / removal device 50, which is a driving device, so as to be inserted into or removed from the optical path of the light to be measured 2. The insertion / removal device 50 is formed, for example, of a linear actuator. When the light-attenuating member 40 is inserted into the optical path of the light to be measured 2, the amount of the light to be measured 2 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 to be measured 2, the light to be measured 2 is incident on the diffusion plate 20 without being reduced in amount.

[0032] The light-reducing member 40 is inserted or removed depending on the brightness of the display 1. Specifically, when the display 1 is dark, it is in a retracted state, and when the display 1 is bright, it is inserted into the optical path to reduce the amount of light and prevent saturation of the light-receiving sensors 13b, 14b, and 15b. This allows the intensity of the light to be measured 2 to be within the dynamic range of the light-receiving sensors 13b, 14b, and 15b, and as a result, the dynamic range of the photometric device 10 is expanded.

[0033] 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.

[0034] As the light-reducing member 40, various types of filters can be used, such as a thin film filter, a glass absorption filter, or a porous plate. However, since a thin film filter has good flatness with respect to the spectral transmittance and is also highly reliable regardless of the environmental temperature, it is preferable to use a thin film filter as the light-reducing member 40.

[0035] The color measuring optical systems 13, 14, and 15 include wavelength selection filters 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 the wavelength selection filters.

[0036] 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.

[0037] Furthermore, the photometric device 10 includes a display unit 10b and an operation unit 10c. An operation screen, messages, etc. are displayed on the display unit 10b. The operation unit 10c is for operating the photometric device 10, and may be configured with a touch panel on the display unit 10b, or may be an operation button provided on the housing of the photometric device 10, or may be both.

[0038] 3 shows the 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.

[0039] The CPU 171 performs overall control of the entire photometric device 10 by operating according to an operation program. For example, when measuring the display 1, it receives signals from the electrical processing units 16a to 16c, performs correction using a calibration coefficient as necessary, and calculates a final measurement value. In this embodiment, during ND calibration performed at the factory at the time of shipment or during ND calibration performed by a user's instruction after shipment, it acquires photometric values ​​for generating a calibration coefficient in a state where the light-reducing member 40 is inserted in the optical path of the measured light 2 and in a state where it is not inserted, and performs processing such as generating an ND calibration coefficient using the acquired photometric values, the details of which will be described later.

[0040] The ROM 172 is a memory that stores predetermined setting values ​​and other data. The RAM 173 is a memory that provides a working area when the CPU 171 operates according to an operating program.

[0041] The memory unit 174 is composed of a storage medium such as a hard disk device or SSD, and stores various data and applications, such as the operating program of the CPU 171, photometric values ​​for generating ND calibration coefficients, the generated ND calibration coefficients, and measurement values ​​such as luminance and chromaticity after correction using the calibration coefficients.

[0042] Next, a method of ND calibration using the calibration system shown in Fig. 1 will be described with reference to the flowchart in Fig. 4. The process shown in the flowchart in Fig. 4 is executed based on an operation of a user U on the information processing device 30, and further based on a signal transmitted and received between the information processing device 300 and the display 1 or the photometric device 10. As the display 1, for example, a reference display having a light source for calibration is used.

[0043] When the user U instructs the information processing device 300 to transition to the ND calibration mode in step u10, the information processing device 300 instructs the photometric device 10 to transition to the ND calibration mode in step s10, and the photometric device 10 accepts the calibration mode in step i10.

[0044] In step s20, the information processing device 300 controls the calibration light source of the display 1, and in step d20, causes the display 1 to display a color of a preset reference value (RGB gradation, brightness). In this embodiment, the display color is one of WRGB.

[0045] Next, the information processing device 300 sends an instruction to execute pre-photometry to the photometry device 10 in step s30, and the photometry device 10 measures a pre-photometry value in step i30. The purpose of this pre-photometry is to optimize the photometry conditions when "executing reference color measurement" in step s50. It does not have to be performed if it is not necessary.

[0046] However, the emission waveform of the display 1 is complex and unstable, as shown in Figures 13(A) and (B). For example, the amount of heat generated varies depending on the display color and emission intensity, so the non-periodic characteristics (for example, the interval at which non-periodic steps occur and the amount of steps) vary for each reference value (WRGB) during ND calibration. There is also individual variation.

[0047] By measuring the emission intensity and waveform in the pre-photometry, the pulsation of the emission (ratio of peak intensity to average intensity) and instability (drift, non-periodic step) can be obtained. Then, the photometry conditions are derived based on the obtained pre-photometry information. An example is as follows. (1) From the average intensity obtained by pre-photometry, an exposure time to ensure the S / N ratio is calculated. Since the amount of light incident on the light receiving sensors 13b, 14b, and 15b differs depending on whether the light reducing member 40 is inserted or removed, the exposure time is calculated for each state in which the light reducing member 40 is inserted and not inserted into the optical path, i.e., the ND state. (2) From the peak intensity obtained by pre-photometry, the circuit gain required to avoid saturation is calculated for each ND state. (3) From the instability obtained by pre-photometry, the number of times the light-reducing member is inserted and removed to suppress the non-periodic step is calculated.

[0048] Furthermore, the degree of saturation may be derived based on the pre-photometry information and notified to the user U. Here, the degree of saturation is an index showing the ratio of the actually measured intensity to the emission intensity at which ND calibration is possible. The emission intensity at which ND calibration is possible is the intensity that can be measured without saturating the light receiving sensor when the light reducing member 40 is not inserted in the optical path. There is also a correlation with instability (for example, the amount of step).

[0049] Notifying the user U of the saturation level has the following effects.

[0050] In other words, the dynamic range of the photometric device 100 can be effectively utilized under display conditions in which the saturation degree is below 100% and as large as possible, thereby improving the calibration accuracy.

[0051] In addition, since saturation is correlated with instability, it can be used to manage the quality of Display 1 and provide feedback to the design, for example by making the saturation levels the same.

[0052] Furthermore, this process may also derive the vertical synchronization frequency Vsync of the display 1. In this case, the user U is relieved from the trouble of setting the vertical synchronization frequency Vsync.

[0053] In step u40, the user U checks the saturation notified by the photometric device 100. If the user U determines that the saturation is not appropriate (for example, over 100% or under 10%), the process may be forcibly terminated. Alternatively, the user U may return to the calibration light source control in step s20 and change and control the display conditions.

[0054] If the saturation is appropriate, the information processing device 300 is instructed to measure the reference color, and upon receiving this instruction, the information processing device 300 instructs the photometric device 10 to measure the reference color in step s50.

[0055] Upon receiving this instruction, the photometric device 10 determines in step i50 the state of the light reducing member 40 (ND state), that is, whether the light reducing member 40 is inserted in the optical path or not. Then, when either the state where the light reducing member 40 is inserted in the optical path or not is defined as ND state A, and the other state is defined as ND state B, in step i51, the photometric value is measured and obtained in ND state A. Next, in step i52, the photometric value is measured and obtained in ND state B. Photometry is basically performed at an integer multiple of the vertical synchronization period Tsync=1 / Vsync.

[0056] In step i53, it is determined whether the number of switchings, including switching from ND state B to ND state A and switching from ND state A to ND state B, has reached a preset number of times equal to or greater than 2. In this embodiment, the number of switchings is counted by counting each of switching from ND state A to ND state B and switching from ND state B to ND state A as one switching. Therefore, for example, when the light reducing member 40 is inserted into the optical path and then retracted from the optical path, the number of switchings is counted as one, and when it is inserted again, the number of switchings is counted as two in total, and thereafter, the number of switchings is incremented by one each time retraction or insertion is performed.

[0057] In step i53, if the number of switching times does not reach the predetermined number of times (NO in step i53), the process returns to step i51 to switch the ND state and perform photometry. If the number of switching times reaches the predetermined number (YES in step i53), the process proceeds to step i54.

[0058] 4, if the number of switching times has not reached a predetermined number, photometry is performed in ND state A and in ND state B, so the number of acquired photometric values ​​in ND state A will be the same as the number of photometric values ​​in ND state B. For example, if the number of switching times is three, photometry in ND state A → switching → photometry in ND state B → switching → photometry in ND state A → switching → photometry in ND state B will be performed, resulting in two photometric values ​​in ND state A and two photometric values ​​in ND state B.

[0059] However, the numbers of photometric values ​​may be different. For example, the number of switching times may be two, and photometric measurement in ND state A → switching → photometric measurement in ND state B → switching → photometric measurement in ND state A may be performed, resulting in two photometric values ​​in ND state A and one photometric value in ND state B, for a total of three. Also, for example, the number of switching times may be four, and the number of photometric values ​​in ND state A may be three and the number of photometric values ​​in ND state B may be two.

[0060] In short, it is necessary to switch at least two times and obtain two or more photometric values ​​of either ND state A or ND state B, and one or more of the other, for a total of three or more photometric values.

[0061] Returning to the flowchart of FIG. 4, in step i54, the photometric values ​​acquired for each of the ND states A and B are averaged, and this value is used as the photometric value for each ND state to be used in generating the calibration coefficient.

[0062] In this embodiment, as described above, a simple average is used to generate the photometric value for each ND state. However, by providing the following process, the influence of instability can be further reduced and accuracy can be improved.

[0063] That is, a process is performed to eliminate outliers. For example, discontinuities are extracted from the time series and those points are eliminated. Alternatively, spike-like outliers are extracted and eliminated.

[0064] In addition, the average is weighted. For example, in a time series, the amount of drift is detected, and each measurement value is weighted according to the degree of change and averaged.

[0065] In this embodiment, the number of times the dimming member 40 is inserted and removed is determined by pre-photometry, but a mode in which the user U can specify the number of times may be provided. For example, in the case of calibrating the display 1 using a stable light source, the calibration time can be shortened by setting the number of times to 1, and this can be used according to the display 1 being used. In addition, the user U can control the calibration time (number of times) and accuracy by himself / herself.

[0066] Also, steps i50 to i54 are performed by the photometric device 10 itself in the above embodiment, but the present invention is not limited to this. For example, the information processing device 300 may manage and control the steps.

[0067] In step s60, the information processing device 300 checks whether acquisition of the photometric values ​​for the four colors of WRGB is complete. If not completed (NO in step s60), the process returns to step s20 and controls the display 1 to emit light of another reference color.

[0068] In this way, the ND state is switched for each reference color to perform photometry, and there are two switching methods: a reference color priority method and an ND state priority method. The reference color priority method is a method in which the reference color is fixed and the ND state is switched, and when photometry of one reference color is completed, the ND state is switched for the next reference color. On the other hand, the ND state priority method is a method in which the ND state (for example, ND state A) is fixed, the reference color is switched, and photometry is performed, and when photometry of ND state A is completed, it is switched to and fixed in ND state B, and the reference color is switched and photometry is performed.

[0069] In this embodiment, the reference color priority method is adopted, which has the following effects.

[0070] In other words, by shortening the time difference between data for each ND state, it is possible to suppress calibration errors caused by drift. Furthermore, because the data for each ND state is continuous in time, the influence of steps can be suppressed by averaging even across non-periodicity.

[0071] On the other hand, the ND state priority method is also expected to have an effect of improving the accuracy of ND calibration. This ND state priority method is suitable for measuring instruments that have a long ND state switching time, because it can shorten the calibration time.

[0072] Returning to the flowchart of FIG. 4, when acquisition of photometric values ​​for all four colors has been completed (YES in step s60), in step s70, a command to acquire ND calibration coefficients is sent to the photometric device 10, and the photometric device 10 generates ND calibration coefficients in step i70.

[0073] As an example of generating the ND calibration coefficients, the tristimulus values ​​calculated from the photometric values ​​when the light-reducing member 40 is inserted in the optical path are S 1(W,R,G,B) The tristimulus values ​​calculated from the photometric values ​​when the light-reducing member 40 is not inserted in the optical path are S 2(W,R,G,B) Then, S 2(W,R,G,B) ≒N·S 1(W,R,G,B) The ND calibration coefficient N is calculated and generated.

[0074] The ND calibration coefficient is a calibration coefficient for calibrating an error due to the insertion and removal of the light-reducing member 40, and may be a calibration coefficient generated using photometric values ​​in a state where the light-reducing member 40 is inserted in the optical path and in a state where it is not inserted. In addition, the ND calibration may be a factory calibration performed in a factory, or a user calibration performed based on an instruction from a user U of the photometric device 10.

[0075] The information processing device 300 issues an instruction to record the ND calibration coefficients to the photometric device 10 in step s80, and then ends the control process in step s99. Upon receiving the instruction to record the ND calibration coefficients, the photometric device 10 stores the generated ND calibration coefficients in the memory unit 140 in step i80.

[0076] In this embodiment, the photometric device 1 generates the ND calibration coefficient, but the information processing device 300 may obtain the photometric values ​​of each ND state from the photometric device 10, generate the ND calibration coefficient, and transmit the generated ND calibration coefficient to the photometric device 10 for storage.

[0077] When actually measuring the light to be measured from the display 1, the obtained photometric value is corrected using the ND calibration coefficient stored in the memory unit 174 to obtain the final measurement value.

[0078] Fig. 5 is a table showing an example of photometric conditions during ND calibration in this embodiment. In the table shown in Fig. 5, the emission waveform of the reference color G (green) is the waveform shown in Fig. 13(A), and its stability is the same as that shown in Fig. 13(B). Different conditions are set for the exposure time, number of switching times, etc. depending on the reference color.

[0079] Next, the effects of this embodiment will be described with reference to FIGS. 6 to 8, taking the reference color green as an example.

[0080] Figure 6 is a diagram in which the timing of acquiring photometric values ​​is plotted on the same diagram as Figure 13(B). The insertion / removal control time for the dimming member 40 of the photometric device 10 used in the measurement is approximately 20 msec. Therefore, the photometric values ​​of ND state A and ND state B acquired by this photometric device 10 are approximately the same as the photometric values ​​at approximately every other point in the photometric values ​​shown in Figure 6.

[0081] As can be seen from the table in Figure 5, the reference color green was measured by switching 11 times between ND state A and ND state B. The circles in Figure 6 are the measured values ​​in ND state A, and the triangles are the measured values ​​in ND state B, with six of each being obtained at approximately one point interval, for a total of 12 photometric values. The combination of the first black circle and the next black triangle indicates the case where an ND calibration coefficient is generated with only one switch, and is shown as a conventional example.

[0082] If ND calibration is performed based on the photometric value obtained by this single switching, a large error will occur if the photometric value happens to cross a non-periodic step during calibration, as shown in Figure 6.

[0083] On the other hand, in the calibration system of this embodiment, even if a non-periodic step is crossed, the error can be significantly reduced by switching between ND state A and ND state B two or more times (11 times in this example) to take multiple measurements (six of each in this example) and using the average value or the like as the photometric value.

[0084] This effect will be explained using the measurement error remaining after ND calibration, that is, the insertion / removal error amount of the light-reducing member 40. Here, the insertion / removal error amount of the light-reducing member 40 is the relative error amount (denoted as ND insertion / removal error in FIG. 7) occurring in the photometric device 10 with respect to the stimulus value when switching between a state in which the light-reducing member 40 is inserted in a high luminance region (denoted as a region with ND in FIG. 7) and a state in which the light-reducing member 40 is not inserted in a low luminance region (denoted as a region without ND in FIG. 7), as shown in FIG.

[0085] FIG. 8(A) shows the ND insertion / removal error when ND calibration is performed using the conventional method. In this evaluation, a series of operations was repeated 50 times, such as finding an ND calibration value coefficient from each photometric value with one switching cycle and finding the ND insertion / removal error using the generated calibration coefficient. FIG. 8(A) plots the ND insertion / removal error for each of the 50 calibration cycles. Meanwhile, FIG. 8(B) shows the ND insertion / removal error for each of the 50 calibration cycles in the ND calibration of this embodiment, in which an ND calibration value coefficient is found from six photometric values ​​with 11 switching cycles.

[0086] 8(A) and 8(B) show the ND insertion / removal error that occurs every time calibration is performed. Comparing FIG. 8(A) and FIG. 8(B), it can be seen that the ND insertion / removal error is suppressed in this embodiment and falls within the allowable range shown by the dashed line in the figure. It can also be seen that this embodiment has a smaller amount of variation in the ND insertion / removal error, making it more stable. Therefore, it is possible to generate highly accurate calibration coefficients with good reproducibility.

[0087] Note that even if ND calibration is performed by successively switching between ND state A and ND state B, for example by continuously measuring the light in ND state A over six periods of the vertical synchronization signal, and then switching to ND state B and continuously measuring the light for the same period, the error reduction effect of this embodiment cannot be expected. In other words, even if the total exposure time is simply increased to be the same as in this embodiment, the averaging effect is low.

[0088] By setting the number of times to switch between ND state A and ND state B as follows, it is possible to achieve both "improved ND calibration accuracy" and "shortened calibration time." In other words, set the time as long as possible so that a non-periodic step is included once within the total exposure time for ND calibration. [Second embodiment] 9 is a diagram showing the overall configuration of a calibration system according to a second embodiment of the present invention. This calibration system includes a photometric device 10 and a display 1, and a user directly controls the display 1 and the photometric device 10 to perform ND calibration (Matrix calibration) for the four display colors WRGB.

[0089] The configuration of the photometric device 10 is the same as that of the photometric device 10 in the first embodiment shown in FIG. 1, and therefore a description thereof will be omitted.

[0090] Next, a method of ND calibration using the calibration system shown in Fig. 9 will be described with reference to the flowchart in Fig. 10. The process shown in the flowchart in Fig. 10 is executed based on operations by a user U on the display 1 and the photometric device 10. As the display 1, for example, a reference display that is a light source for calibration is used.

[0091] When the user U instructs the photometric device 10 to transition to the ND calibration mode in step u10, the photometric device 10 accepts the ND calibration mode in step s10.

[0092] User U controls the calibration light source (display 1) in step u20, and displays the color of the preset reference value (RGB gradation, brightness) on display 1 in step d20. It is preferable to set the brightness within a predetermined recommended intensity range. The recommended intensity is determined by the S / N ratio and dynamic range of the system.

[0093] In step u30, the user U notifies the photometric device 10 of the display color, and the photometric device 10 accepts the notification of the display color in step s30. Note that instead of notifying the display color, the photometric device 10 may have a function for identifying the display color from the photometric value. For example, if the photometric device 10 is a tristimulus value type, the display color can be easily identified from the acquired balance of XYZ. Identifying the display color leads to improved usability by eliminating operational errors.

[0094] It is also preferable that the photometric device 10 has a function to selectively accept the displayed intensity. By having the intensity information in advance, it becomes possible to measure the light under appropriate conditions, and the calibration accuracy is improved. However, this is not essential because it makes the user's settings complicated.

[0095] Furthermore, the user U instructs the photometric device 10 to measure the reference color in step u40. The notification of the display color in step u30 may be performed simultaneously with the instruction to perform measurement in step u40. The photometric device 10, which has received this instruction, determines in step s40 the ND state of the light-attenuating member 40, that is, whether the light-attenuating member 40 is inserted in the optical path or not. If the light-attenuating member 40 is inserted in the optical path (ND state), it changes the state to one where it is not inserted. If the light-attenuating member 40 is not inserted (ND state), it maintains the state as it is.

[0096] The non-ND state has the following effects. That is, because the ND state is switched twice, the ND state that is measured first is measured twice, which is more. For this reason, there is an advantage in that the calibration time can be shortened by measuring the state with the shorter exposure time (the amount of light is greater in the non-ND state) first. Furthermore, measuring the non-ND state first has the effect of improving the accuracy of determining the appropriateness for the light source emission intensity. However, it is also possible to stop at understanding the ND state without changing to the non-ND state.

[0097] Next, in steps s41 to s43, the photometry device 10 switches the ND state twice to measure and obtain the photometry value. Photometry is basically performed at an integer multiple of the vertical synchronization period Tsync=1 / Vsync.

[0098] Next, in step s44, the photometric value obtained for each ND state is used as the photometric value for each ND state to generate the calibration coefficient. Note that for ND states measured twice, the photometric value is averaged.

[0099] In step u50, the user U checks whether acquisition of photometric values ​​for the four colors of WRGB is complete. If not completed (NO in step u50), the user U returns to step u20 and controls the display 1 to emit another reference color.

[0100] If acquisition of photometric values ​​for all four colors has been completed (YES in step u50), an instruction to acquire ND calibration coefficients is sent to the photometric device 10 in step u60, and the photometric device 10 generates ND calibration coefficients in step s60.

[0101] After the user U issues an instruction to record the ND calibration coefficient to the photometric device 10 in step u70, the control process ends in step u99. Upon receiving the instruction to record the ND calibration coefficient, the photometric device 10 stores the generated ND calibration coefficient in the memory unit 140 in step s70.

[0102] According to the second embodiment, by switching the ND state twice, for example, if the drift changes linearly, the average value of two photometric values ​​in ND state A matches ND state B, thereby suppressing ND calibration errors caused by instability due to drift. This makes it possible to achieve both a reduction in ND calibration time and calibration accuracy.

[0103] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

[0104] For example, as shown in FIG. 11, a calibration application may be installed and incorporated in a display 1 equipped with a calibration light source, and the photometric device 10 may be controlled by this calibration application during ND calibration.

[0105] Further, the ND calibration for four colors (WRGB) has been described, but the present invention is not limited to this, and may be, for example, one-point calibration for only W (white). [Explanation of symbols]

[0106] 1 Display 2 Light to be measured 10 Photometering device 10b Display section 10c Control unit 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 17 Control section 20 Diffuser 40 Light-reducing material 41 Transparent plate 41a Incidence plane 41b Output surface 42, 43 Thin Film 50 Insertion / extraction device 300 Information processing device

Claims

1. a light-reducing member that is disposed so as to be insertable into and removable from an optical path of the light to be measured from the display; an acquisition means for acquiring a photometric value of the measured light when the light-attenuating member is inserted in the optical path and a photometric value of the measured light when the light-attenuating member is not inserted in the optical path, in order to generate a calibration coefficient that suppresses a measurement error between a state in which the light-attenuating member is inserted in the optical path and a state in which the light-attenuating member is not inserted; Equipped with The acquisition means acquires a total of at least three or more photometric values ​​measured in each state when at least two or more switchings are performed, including switching from a state in which the dimming member is inserted in the optical path to a state in which it is not inserted, and switching from a state in which it is not inserted to a state in which it is inserted, as photometric values ​​for generating the calibration coefficient.

2. 2. The photometric device according to claim 1, further comprising a generating unit that generates the calibration coefficient using the photometric value for generating the calibration coefficient acquired by the acquiring unit.

3. 3. The photometric device according to claim 1, wherein when there are a plurality of reference colors at the time of calibration, at least one of the number of switching times and the photometric conditions is changed in accordance with the reference colors.

4. 3. The photometric device according to claim 1, wherein the photometric values ​​corresponding to the state where the light reducing member is inserted in the optical path and the state where the light reducing member is not inserted in the optical path are generated from weighted average values.

5. 3. The photometric device according to claim 1, wherein the number of times the switching is performed can be designated by a user.

6. 3. The photometric device according to claim 1, wherein the acquisition means acquires a photometric value when a light-reducing member is switched between being inserted and removed with a reference color set.

7. 3. The photometric device according to claim 1, wherein a pre-photometric measurement is performed before the acquisition means acquires a photometric value, and the degree of saturation is notified to a user.

8. 3. The photometric device according to claim 1, wherein acquisition of the photometric value by said acquisition means is started from a state in which a light-reducing member is not inserted in the optical path.

9. The photometric device according to claim 1 ; a generation means for generating the calibration coefficients using photometric values ​​for generating the calibration coefficients acquired by an acquisition means of the photometric device; A calibration system comprising:

10. 10. The calibration system according to claim 9, wherein when there are a plurality of reference colors at the time of calibration, at least one of the number of switching times or the photometric conditions is changed in accordance with the reference colors.

11. 11. The calibration system according to claim 9, wherein the photometric values ​​corresponding to the states where the light-attenuating member is inserted in the optical path and where the light-attenuating member is not inserted are generated from weighted average values.

12. 11. The calibration system according to claim 9, wherein the number of times the switching is performed can be designated by a user.

13. 11. The calibration system according to claim 9, wherein the acquisition means of the photometric device acquires a photometric value when a light-reducing member is switched between being inserted and removed with a reference color set.

14. 11. The calibration system according to claim 9, wherein a pre-photometry is performed before the acquisition means of the photometry device acquires a photometric value, and the user is notified of the degree of saturation.

15. 11. The calibration system according to claim 9, wherein acquisition of the photometric value by the acquisition means of the photometric device is started from a state in which a light-reducing member is not inserted in the optical path.

16. A calibration method for calibrating a photometric device having a light-reducing member that is arranged so as to be insertable and removable from an optical path of light to be measured from a display, comprising: performing an acquisition step of acquiring a photometric value of the measured light in a state where the light-attenuating member is inserted in the optical path and a photometric value of the measured light in a state where the light-attenuating member is not inserted in the optical path in order to generate a calibration coefficient that suppresses a measurement error between a state where the light-attenuating member is inserted in the optical path and a state where the light-attenuating member is not inserted; In the acquisition step, the acquisition means acquires a total of at least three or more photometric values ​​obtained by measuring the light in each state when at least two or more switching operations are performed, including switching from a state in which the light-reducing member is inserted in the optical path to a state in which it is not inserted and switching from a state in which it is not inserted to a state in which it is inserted, and A calibration method comprising: performing a generation step of generating the calibration coefficients using acquired photometric values.

17. A computer of a photometric device having a light-reducing member that is arranged so as to be insertable and detachable from an optical path of light to be measured from a display, an acquisition step of acquiring a photometric value of the measured light in a state where the light-attenuating member is inserted in the optical path and a photometric value of the measured light in a state where the light-attenuating member is not inserted in the optical path in order to generate a calibration coefficient that suppresses a measurement error between a state where the light-attenuating member is inserted in the optical path and a state where the light-attenuating member is not inserted; Run the command, In the acquisition step, a program for causing the computer to execute a process of acquiring a total of at least three or more photometric values ​​measured in each state when at least two or more switchings are made, including switching from a state in which the dimming member is inserted in the optical path to a state in which it is not inserted, and switching from a state in which it is not inserted to a state in which it is inserted, as photometric values ​​for generating the calibration coefficient.

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