JPWO2018198674A1 - Optical measurement device - Google Patents

Abstract

The range of luminance that can be measured by an optical measurement device is increased without complicating the optical measurement device. In an optical measurement device, an optical sensor receives light from a display and outputs a photocurrent corresponding to the light, and an integrator integrates the photocurrent continuously over time to output an integrated signal. The required accuracy for the measurement value, the approximate brightness of the light, and the period of the time change of the brightness and the chromaticity of the light are acquired. The exposure time is determined from the required accuracy and the estimated luminance. The integration time is determined so that the integrator is not saturated and the exposure time is a common multiple of the period and the integration time. The exposure period is composed of at least one integration period, the length of the exposure period is the determined exposure time, the length of each of the at least one integration period is the determined integration time, and the integrator is at least one integration period. The integrator is controlled so as to integrate the photocurrent and output at least one integrated signal. A measurement value is calculated from at least one integrated signal.

Description

  The present invention relates to an optical measurement device.

  In an optical measurement device that measures the luminance and chromaticity of a display, an optical sensor receives light from the display and outputs a photocurrent corresponding to the received light, and an integrator integrates the output photocurrent and integrates an integrated signal. And the arithmetic unit measures the measured value from the output integrated signal. However, there is a restriction on the integration time indicating the length of the integration period during which the integrator integrates the optical signal.

  The brightness and chromaticity of the display, including the transient response, change periodically over time. For this reason, the measurement of the luminance and chromaticity of the display must be performed in synchronization with the periodic time change of the luminance and chromaticity of the display. Therefore, the integration time is limited to an integral multiple of the period of the time change of the luminance and chromaticity of the display.

  The period of the temporal change of the luminance and chromaticity of the display corresponds to the reciprocal of the frame rate or the length of the vertical synchronization (Vsync) period. For this reason, the integration time is limited to the reciprocal of the frame rate or an integral multiple of the length of the Vsync period. However, in a liquid crystal display (LCD) in which inversion driving is performed to prevent burn-in, flicker occurs in principle. For this reason, when the optical measurement device measures the luminance and chromaticity of the LCD, in order to accurately measure the luminance and chromaticity without being affected by flicker, the period of the time change of the luminance and chromaticity is set to the frame rate. , Or twice the length of the Vsync period, and the integration time is limited to an integral multiple of the period.

  In the optical measurement device, a plurality of gains can be selected in the integrator in order to widen the range of luminance that can be measured. If the exposure is not proper exposure, the selected gain is changed. For example, when the exposure is over or under the proper exposure, the gain is decreased or the gain is increased, respectively. The technique described in Patent Literature 1 is an example of such a technique, and is capable of measuring a wide range of luminance from low luminance to high luminance while realizing a high S / N ratio.

  Further, in another optical measurement device, in order to widen the range of luminance that can be measured, a neutral density filter (ND filter) can be inserted in the optical path of light incident on the optical sensor, so that the exposure exceeds the proper exposure. In some cases, a neutral density filter is inserted into the optical path to reduce the amount of light incident on the optical sensor.

JP 2005-321313 A

  However, the conventional optical measurement device has a dimming mechanism (ND mechanism) for inserting an ND filter, which has to allow a large number of gains to be selected in an integrating circuit in order to widen the range of luminance that can be measured. There was a problem that it had to be provided. For this reason, many correction values and calculations are required in order to correct for fluctuations in the environment in which the measurement is performed, individual variations in the measurement target, and the like, and a storage capacity for that is required. For example, a large number of offset / gain corrections and environmental correction values corresponding to a large number of gains have been required.

  In particular, when the light measuring device measures the luminance and chromaticity of the display, the integration time is limited as described above, so that the appropriate exposure changes according to the length of the Vsync period, and the saturation value for the luminance changes. . For this reason, the number of required gains increases, and the load on the optical measurement device increases.

  The range of luminance that can be measured with a small number of gains can be widened by increasing the gain pitch indicating the difference between two adjacent gains in the selectable small number of gains. However, when the gain pitch is increased, there arises a problem that a measurement condition in which the exposure is lower than the proper exposure occurs at the selected gain.

  The invention described below aims to solve this problem. The problem to be solved by the invention described below is to increase the range of luminance that can be measured by the optical measurement device without complicating the optical measurement device.

  In an optical measurement device, an optical sensor receives light from a display and outputs a photocurrent according to the light, and an integrator integrates the photocurrent continuously over time to output an integrated signal.

  The required accuracy for the measurement value, the approximate brightness of the light, and the period of the time change of the brightness and the chromaticity of the light are acquired.

  The exposure time is determined from the required accuracy and the estimated luminance. The integration time is determined so that the integrator is not saturated and the exposure time is a common multiple of the period and the integration time.

  The exposure period consists of at least one integration period, the length of the exposure period becomes the determined exposure time, the length of each of the at least one integration period becomes the determined integration time, and the integrator performs at least one integration period. The integrator is controlled so as to integrate the photocurrent and output at least one integrated signal.

  A measurement value is calculated from at least one integrated signal.

  According to the invention described below, the range of luminance that can be measured by the optical measurement device can be expanded without complicating the optical measurement device.

  The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

FIG. 2 is a block diagram illustrating the optical measurement device according to the first embodiment. 5 is a flowchart illustrating a measurement flow in the optical measurement device according to the first embodiment. FIG. 4 is a diagram illustrating a look-up table (LUT) for determining an exposure time from a required S / N ratio and an estimated luminance in the optical measurement device according to the first embodiment. FIG. 3 is a diagram illustrating a look-up table (LUT) for determining an integration time from a required S / N ratio, a vertical synchronization (Vsync) frequency, and an estimated luminance in the optical measurement device of the first embodiment. 5 is a timing chart illustrating an example of a display to be measured by the optical measurement device according to the first embodiment and an example of a time change of a state of an integrator provided in the optical measurement device. 5 is a timing chart illustrating an example of a display to be measured by the optical measurement device according to the first embodiment and an example of a time change of a state of an integrator provided in the optical measurement device. 5 is a timing chart illustrating an example of a temporal change in a state of the optical measurement device of the first embodiment and an integrator provided in the optical measurement device.

1. Optical Measurement Device FIG. 1 is a block diagram illustrating an optical measurement device according to the first embodiment. FIG. 2 is a flowchart illustrating a measurement flow in the optical measurement device according to the first embodiment.

  The optical measurement device 1000 illustrated in FIG. 1 measures the luminance and chromaticity of a display, and includes an optical sensor 1020, an integrator 1021, a control unit 1022, and a peripheral unit 1023. The optical measurement device 1000 may include components other than these components.

  In the optical measurement device 1000, the optical sensor 1020 receives light from the display, and outputs a photocurrent according to the received light. Further, the integrator 1021 integrates the output photocurrent and outputs an integration signal corresponding to the amount of charge accumulated by the integration. Further, control section 1022 calculates a measurement value from the output integrated signal.

  The integrator 1021 includes an integration circuit 1040, an integration circuit 1041, a switch 1042, and a switch 1043.

  The integration circuits 1040 and 1041 integrate the photocurrent. The switches 1042 and 1043 switch the integration circuit for integrating the photocurrent between the integration circuit 1040 and the integration circuit 1041 under the control of the control unit 1022. For this reason, the integrator 1021 can integrate the photocurrent continuously without interruption in time.

  The integrator 1021 may have a plurality of selectable gains. Thereby, the range of the measurable luminance is further expanded.

  The control unit 1022 is a computer that operates according to the installed program, and includes a required accuracy acquisition unit 1060, an approximate luminance acquisition unit 1061, a cycle acquisition unit 1062, an exposure time determination unit 1063, an integration time determination unit 1064, and an integrator control unit. 1065 and a calculation unit 1066. All or a part of the processing performed by the computer may be performed by hardware that does not execute the program.

  The peripheral unit 1023 includes a display unit 1080 and an operation unit 1081.

  In the measurement, steps S101 to S105 shown in FIG. 2 are executed in response to receiving a measurement command from the operator.

  In step S101, measurement conditions are acquired. The measurement condition may be obtained from an operation on a hardware switch provided in the operation unit 1081, or may be obtained from an operation performed using the operation unit 1081 on a graphical user interface (GUI) displayed on the display unit 1080. May be done.

  In acquiring the measurement condition, the required accuracy acquiring unit 1060 acquires the required S / N ratio for the measured value. The required accuracy acquiring unit 1060 receives the designation of one of the three modes, ie, the high accuracy mode, the standard mode, and the high speed mode, which correspond to the three required S / N ratios, respectively. Acquire the required S / N ratio corresponding to the mode. The method of obtaining the required S / N ratio may be changed. For example, the required accuracy acquiring unit 1060 receives the specification of one accuracy range included in the plurality of accuracy ranges respectively corresponding to the plurality of required S / N ratios, and thereby obtains the required S / N corresponding to the specified accuracy range. The N ratio may be obtained. The accuracy range is represented by, for example, “...% Or less”, “... Required accuracy other than the required S / N ratio may be obtained.

  In acquiring the measurement condition, the cycle acquiring unit 1062 acquires a Vsync time that is a length of a vertical synchronization (Vsync) period that coincides with a cycle of a temporal change in luminance and chromaticity of the display. The Vsync time is obtained from an operation performed on the GUI displayed on the display unit 1080 using the operation unit 1081. The Vsync frequency may be acquired, and the Vsync time may be acquired from the acquired Vsync frequency. The method of obtaining the Vsync time may be changed. For example, a Vsync signal may be input to the cycle acquisition unit 1062, and the cycle acquisition unit 1062 may acquire the Vsync time from the input Vsync signal. When the luminance and chromaticity of the liquid crystal display on which the inversion driving is performed are measured, instead of the Vsync time, a time twice as long as the Vsync time, which coincides with the time change cycle of the luminance and chromaticity of the liquid crystal display, is obtained. Is done.

  In the following step S102, the approximate luminance of light from the display is obtained. Step S102 may be performed simultaneously with step S101.

  In obtaining the approximate luminance, the integrator control unit 1065 controls the integrator 1021. The control is performed such that the integrator 1021 integrates the photocurrent during an initial integration period preceding a plurality of integration periods described later and outputs an initial integration signal. Further, the approximate luminance obtaining unit 1061 obtains the approximate luminance of light from the display from the initial integration signal. The initial integration period may be short. The method of obtaining the approximate luminance may be changed. One example will be described later.

  In the following step S103, measurement conditions are determined.

  In determining the measurement conditions, the exposure time determination unit 1063 determines the exposure time from the acquired required S / N ratio and the estimated luminance. The exposure time can be changed according to the required S / N. The exposure time may be determined by a function having the required S / N ratio and the estimated luminance as variables, or may be determined by a look-up table (LUT). The function is, for example, a function represented by Expression (1). F (required S / N ratio, estimated luminance) included in the equation (1) is an integer. The LUT is, for example, a look-up table for determining the exposure time from the required S / N ratio and the approximate luminance shown in FIG.

  Exposure time = Vsync time × f (required S / N ratio, estimated brightness) (1)

  In addition, when acquiring the measurement conditions, the integration time determination unit 1064 determines the maximum non-saturation integration time that is the upper limit of the appropriate integration time from which the integrator 1021 does not saturate and the S / N ratio can be secured based on the acquired approximate luminance. decide. In addition, the integration time determination unit 1064 sets the integration time and the number of repetitions such that the integration time is shorter than the determined maximum non-saturation integration time and the determined exposure time is a common multiple of the acquired Vsync time and the integration time. decide. Thus, the integration time at which the integrator 1021 is not saturated and the exposure time is a common multiple of the Vsync time and the integration time is determined.

  The integration time is desirably the longest that satisfies the above-mentioned condition, which satisfies the equations (2) and (3). The common multiple is desirably the least common multiple. As a result, the charge accumulated in the integrator 1021 increases within a range where the integrator 1021 does not saturate, and the S / N ratio is improved.

Number of repetitions = Int (exposure time / maximum non-saturation integration time) +1 (2)
Integration time = exposure time / number of repetitions (3)

  The determination of the exposure time, the determination of the maximum non-saturation integration time, and the determination of the integration time are performed in separate steps, but may be performed in the same step. For example, the integration time may be directly determined by the LUT illustrated in FIG. 4 that determines the integration time from the required S / N ratio, Vsync frequency, and the estimated luminance so as to satisfy the above-described condition.

  In the following step S104, measurement is performed.

  In the measurement, the integrator control unit 1065 controls the integrator 1021. In the control, the exposure period includes a plurality of integration periods, the number of the plurality of integration periods becomes the determined number of repetitions, the length of the exposure period becomes the determined exposure time, and the length of each of the plurality of integration periods Becomes the determined integration time, and the integrator 1021 integrates the photocurrent during a plurality of integration periods and outputs a plurality of integration signals, respectively. Thereby, measurement is performed under the determined measurement conditions.

  In the following step S105, calculation and output of the measured value are performed.

  In the calculation and output of the measurement value, the calculation unit 1066 obtains a plurality of integrated signal values indicating the magnitudes of the plurality of output integrated signals, and averages the obtained integrated signal values per unit time. , And perform necessary arithmetic processing on the value obtained by the conversion to calculate measured values of luminance and chromaticity. As a result, measured values of luminance and chromaticity are calculated from the plurality of integrated signals. The method of calculating the measured values of luminance and chromaticity may be changed. In addition, the calculation unit 1066 outputs the calculated values of the calculated luminance and chromaticity.

  According to such measurement in the optical measurement device of the first embodiment, the number of selectable gains can be reduced, the load on the optical measurement device can be reduced, and the optical measurement device can be simplified. For this reason, the range of luminance that can be measured by the optical measurement device can be expanded without complicating the optical measurement device.

2 Relationship Between Exposure Time, Integration Time, and Vsync Time Under Measurement Conditions FIGS. 5 and 6 show states of a display to be measured by the optical measurement device of the first embodiment and an integrator provided in the optical measurement device. 6 is a timing chart illustrating an example of a time change of the first embodiment.

  FIG. 5 shows an example in which the Vsync frequency of the display is high. FIG. 6 shows an example in which the Vsync frequency of the display is low.

  In the example shown in FIG. 5, an exposure period 1100 having an exposure time necessary to secure a required S / N ratio is equally divided into eight Vsync periods 1120. The Vsync time is, for example, about 1 millisecond to 2 seconds. Further, the exposure period 1100 is equally divided into five integration periods 1140. For this reason, the exposure time is a common multiple of the integration time and the Vsync time. The integration time is shorter than the maximum unsaturated integration time.

  In the example shown in FIG. 6, an exposure period 1160 having an exposure time necessary to secure a required S / N ratio is equally divided into four Vsync periods 1180. The Vsync time is, for example, about 1 millisecond to 2 seconds. Further, the exposure period 1160 is equally divided into five integration periods 1200. For this reason, the exposure time is a common multiple of the integration time and the Vsync time. The integration time is shorter than the maximum unsaturated integration time.

3. Another Example of Method for Obtaining Approximate Luminance FIG. 7 is a timing chart illustrating an example of a temporal change in the state of the optical measurement device of the first embodiment and an integrator provided in the optical measurement device.

  As shown in FIG. 7A, the state of the optical measurement device 1000 changes from the standby state 1220 to the measurement state 1240 at the timing T1 when the measurement command is received from the operator, and the exposure time has elapsed from the timing T1. At the timing T2, the state changes from the measurement state 1240 to the standby state 1260.

  Further, as shown in FIG. 7B, the state of the integrator 1021 changes from the state 1280 performing the integration circuit reset operation at the timing T1 to the state 1300 performing the integration operation at the timing T1, and at the timing T2. The state changes from the state 1300 in which the integration operation is being performed to the state 1320 in which the integration circuit reset operation is being performed. Therefore, when the optical measurement device 1000 is in the standby states 1220 and 1260, the integrator 1021 is in the states 1280 and 1320 in which the integration circuit reset operation is performed, respectively, and the optical measurement device 1000 is in the measurement state 1240. In this case, the state is 1300 in which the integration operation is performed.

  The integrator 1021 can constantly integrate the optical signal and output the integrated signal even in the states 1280 and 1320 in which the integration circuit reset operation is performed. Therefore, the integrator control unit 1065 controls the integrator 1021 so as to integrate the photocurrent during the standby integration period 1340 that repeatedly arrives and to output a standby integration signal. The approximate luminance may be obtained by regarding the standby integration period that has just arrived as the initial integration period. As a result, the approximate luminance is obtained before the timing T1 at which the measurement is started, so that the time required for the measurement is reduced. The length of the standby integration period 1340 that repeatedly arrives may be the shortest time that can be set.

  Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that innumerable modifications that are not illustrated can be assumed without departing from the scope of the present invention.

1000 Optical measurement device 1020 Optical sensor 1021 Integrator 1022 Control unit 1060 Required accuracy acquisition unit 1061 Approximate brightness acquisition unit 1062 Cycle acquisition unit 1063 Exposure time determination unit 1064 Integration time determination unit 1065 Integrator control unit 1066 Operation unit

Claims (6)

An optical sensor that receives light from the display and outputs a photocurrent according to the light,
An integrator that integrates the photocurrent continuously in time and outputs an integration signal;
A required accuracy acquisition unit for acquiring required accuracy for the measured value;
An approximate luminance obtaining unit for obtaining an approximate luminance of the light,
A period acquisition unit that acquires a period of time change of the luminance and chromaticity of the light,
An exposure time determination unit that determines an exposure time from the required accuracy and the approximate luminance,
An integration time determination unit that determines the integration time of the integrator such that the exposure time is a common multiple of the cycle and the integration time without the integrator being saturated;
An exposure period includes at least one integration period, a length of the exposure period is the exposure time, a length of each of the at least one integration period is the integration time, and the integrator is the at least one integration period. An integrator control unit that controls the integrator to integrate the photocurrent and output at least one integrated signal, respectively.
A calculation unit that calculates the measurement value from the at least one integrated signal,
An optical measurement device comprising: The integrator control unit controls the integrator so that the integrator outputs the initial integration signal by integrating the photocurrent during an initial integration period preceding the at least one integration period,
The optical measurement device according to claim 1, wherein the approximate luminance obtaining unit obtains the approximate luminance from the initial integration signal. The integrator control unit controls the integrator to output the standby integration signal by integrating the photocurrent during the standby integration period that repeatedly arrives,
The optical measurement device according to claim 2, wherein the initial integration period is a standby integration period that arrives immediately before the exposure period. The optical measurement device according to claim 1, wherein the common multiple is a least common multiple. The optical measurement device according to claim 1, wherein the exposure time can be changed according to the required accuracy. 6. The optical measurement device according to claim 1, wherein the integrator has a plurality of selectable gains.

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