WO2018198674A1

WO2018198674A1 - Light measurement device

Info

Publication number: WO2018198674A1
Application number: PCT/JP2018/013729
Authority: WO
Inventors: 増田　敏
Original assignee: コニカミノルタ株式会社
Priority date: 2017-04-27
Filing date: 2018-03-30
Publication date: 2018-11-01
Also published as: JPWO2018198674A1; JP7188382B2; KR102426522B1; KR20190133030A; TWI770161B; TW201842308A

Abstract

The present invention broadens the brightness range that can be measured by a light measurement device without making the light measurement device more complicated. In this light measurement device, a light sensor receives light from a display and outputs a photocurrent corresponding to the light. An integrator continuously integrates the photocurrent over time and outputs an integrated signal. A required measured value accuracy, approximate light brightness, and period of variation in light brightness and color over time are acquired. An exposure time is determined from the required accuracy and the approximate brightness. An integration time is determined such that the integrator is not saturated and the exposure time is a common multiple of the period and integration time. The integrator is controlled such that an exposure period includes at least one integration period, the length of the exposure period is the determined exposure time, the individual length of at least one integration period is the determined integration time, and the integrator integrates the photocurrent in at least one integration period and outputs at least one integrated signal for each integration period. A measured value is calculated from the at least one integrated signal.

Description

Optical measuring device

The present invention relates to an optical measurement device.

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

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

The period of time change of luminance and chromaticity of the display is equal 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 measuring device measures the brightness and chromaticity of the LCD, the period of the time change of the brightness and chromaticity is set to the frame rate in order to measure the correct brightness and chromaticity without being affected by flicker. It is assumed that it is twice the reciprocal of or 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, and the selected gain is changed when the exposure is not proper exposure. For example, when the exposure is over or under than the proper exposure, gain down or gain up is performed, respectively. The technique described in Patent Document 1 is an example, and a wide luminance range from low luminance to high luminance can be measured while realizing a high S / N ratio.

In another optical measurement device, in order to widen the range of brightness that can be measured, a neutral density filter (ND filter) can be inserted in the optical path of light incident on the optical sensor, and the exposure is over 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 measuring device has a dimming mechanism (ND mechanism) for inserting an ND filter, which must be able to select a large number of gains in the integrating circuit in order to widen the range of luminance that can be measured. There was a problem such as having to be provided. For this reason, in order to correct for changes in the environment in which the measurement is performed, individual variations in the measurement target, etc., many correction values and calculations are required, and a storage capacity for that is required. For example, a large number of offset / gain corrections, environmental correction values and the like corresponding to a large number of gains are required.

In particular, when the optical 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. . This increases the number of necessary gains and increases the load on the optical measurement device.

The range of luminance that can be measured with a small number of gains can also be increased by increasing the gain pitch that indicates the difference between two adjacent gains in a small number of selectable gains. However, when the gain pitch is increased, there arises a problem that a measurement condition occurs in which the exposure is under the proper exposure 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 widen the range of luminance that can be measured by the optical measurement device without complicating the optical measurement device.

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

Requirement accuracy for measurement values, approximate brightness of light, and period of time change of light brightness and chromaticity are acquired.

The exposure time is determined from the required accuracy and approximate brightness. 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 is the determined exposure time, the length of each of the at least one integration period is the determined integration time, and the integrator has at least one integration period The integrator is controlled to integrate the photocurrent and output at least one integrated signal.

Measured value is calculated from at least one integral signal.

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

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

1 is a block diagram illustrating an optical measurement device according to a first embodiment. It is a flowchart which illustrates the flow of measurement in the optical measuring device of 1st Embodiment. It is a figure which illustrates the look-up table (LUT) for determining exposure time from the request | requirement S / N ratio and approximate brightness in the optical measuring device of 1st Embodiment. It is a figure which illustrates the look-up table (LUT) for determining integration time from the request | requirement S / N ratio, a vertical-synchronization (Vsync) frequency, and approximate brightness in the optical measuring device of 1st Embodiment. It is a timing chart which illustrates the example of the time change of the state of the display used as the object of measurement by the optical measuring device of a 1st embodiment, and the integrator with which the said optical measuring device is provided. It is a timing chart which illustrates the example of the time change of the state of the display used as the object of measurement by the optical measuring device of a 1st embodiment, and the integrator with which the optical measuring device is provided. It is a timing chart which illustrates the example of the time change of the state of the optical measuring device of a 1st embodiment, and the integrator with which the said optical measuring device is equipped.

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.

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 measuring device 1000, the optical sensor 1020 receives light from the display and outputs a photocurrent corresponding 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, the control unit 1022 calculates a measurement value from the output integration signal.

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

Integration circuits

1040 and 1041 integrate the photocurrent.

Switches

1042 and 1043 switch an integration circuit that integrates the photocurrent between the integration circuit 1040 and the integration circuit 1041 in accordance with control by the control unit 1022. For this reason, the integrator 1021 can integrate the photocurrent continuously in time without interruption.

The integrator 1021 may have a plurality of selectable gains. This further expands the range of luminance that can be measured.

The control unit 1022 is a computer that operates according to an installed program, and includes a required accuracy acquisition unit 1060, an approximate luminance acquisition unit 1061, a period 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 are provided. Hardware that does not execute the program may be responsible for all or part of the processing performed by the computer.

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

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

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

In the acquisition of measurement conditions, the required accuracy acquisition unit 1060 acquires the required S / N ratio for the measured value. The requested accuracy acquisition unit 1060 is designated by accepting designation of one mode included in the three modes of the high accuracy mode, the standard mode, and the high speed mode respectively corresponding to the three required S / N ratios. The required S / N ratio corresponding to the mode is acquired. The method for obtaining the required S / N ratio may be changed. For example, the request accuracy acquisition unit 1060 receives a specification of one accuracy range included in a plurality of accuracy ranges respectively corresponding to a plurality of request S / N ratios, thereby request S / O corresponding to the specified accuracy range. You may acquire N ratio. The accuracy range is expressed by, for example, “...% or less”, “...% to. The required accuracy other than the required S / N ratio may be acquired.

In the measurement condition acquisition, the period acquisition unit 1062 acquires the Vsync time that is the length of the vertical synchronization (Vsync) period that matches the period of time change of the luminance and chromaticity of the display. The Vsync time is acquired from an operation performed using the operation unit 1081 on the GUI displayed on the display unit 1080. The Vsync frequency may be acquired, and the Vsync time may be acquired from the acquired Vsync frequency. The method for acquiring the Vsync time may be changed. For example, the Vsync signal may be input to the period acquisition unit 1062, and the Vsync time may be acquired from the Vsync signal input to the period acquisition unit 1062. When the luminance and chromaticity of a liquid crystal display that is driven in reverse are measured, instead of the Vsync time, a time that is twice the Vsync time that matches the period of time change of the luminance and chromaticity of the liquid crystal display is acquired. Is done.

In the subsequent step S102, the approximate brightness of the light from the display is acquired. Step S102 may be executed simultaneously with step S101.

In acquiring the approximate brightness, the integrator control unit 1065 controls the integrator 1021. The control is performed so 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. The approximate brightness acquisition unit 1061 acquires the approximate brightness of light from the display from the initial integration signal. The initial integration period may be short. The method of obtaining the approximate brightness may be changed. One example will be described later.

In subsequent 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 approximate brightness. 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 approximate luminance as variables, or may be determined by a look-up table (LUT). The function is a function represented by, for example, the formula (1). F (required S / N ratio, approximate brightness) included in Expression (1) is an integer. The LUT is a look-up table for determining the exposure time from the required S / N ratio and the approximate brightness shown in FIG. 3, for example.

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

Further, in the acquisition of the measurement conditions, the integration time determination unit 1064 sets the maximum desaturation integration time, which is the upper limit of an appropriate integration time that can ensure the S / N ratio without the integrator 1021 being saturated from the acquired approximate brightness. decide. In addition, the integration time determination unit 1064 sets the integration time and the number of repetitions so that the integration time is shorter than the determined maximum unsaturated integration time, and the determined exposure time is the common multiple of the acquired Vsync time and integration time. decide. As a result, the integration time in 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 preferably the longest condition that satisfies the above-mentioned conditions that satisfy the expressions (2) and (3). The common multiple is preferably the least common multiple. As a result, the charge accumulated in the integrator 1021 increases within a range where the integrator 1021 is not saturated, and the S / N ratio is improved.

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

The determination of the exposure time, the determination of the maximum unsaturated 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 an LUT that determines the integration time from the required S / N ratio, the Vsync frequency, and the approximate luminance so as to satisfy the above-described condition, as shown in FIG.

In the subsequent step S104, measurement is performed.

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

In the subsequent step S105, the measurement value is calculated and output.

In the calculation and output of the measurement value, the calculation unit 1066 acquires a plurality of integration signal values respectively indicating the magnitudes of the output plurality of integration signals, and calculates the average value of the acquired plurality of integration signal values per unit time. Then, the necessary calculation processing is performed on the value obtained by the conversion, and the measured values of luminance and chromaticity are calculated. Thereby, the measured values of luminance and chromaticity are calculated from the plurality of integrated signals. The method of calculating the measurement values of luminance and chromaticity may be changed. In addition, the computing unit 1066 outputs computed brightness and chromaticity computation values.

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 measuring device can be expanded without complicating the optical measuring device.

2 Relationship between exposure time, integration time, and Vsync time under measurement conditions Each of FIGS. 5 and 6 shows a display to be measured by the optical measurement device of the first embodiment and a state of an integrator provided in the optical measurement device. It is a timing chart which illustrates the example of the time change of.

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

In the example illustrated in FIG. 5, an exposure period 1100 having an exposure time necessary for ensuring 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. 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 illustrated in FIG. 6, an exposure period 1160 having an exposure time necessary to ensure the 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 time change in the state of the optical measurement device according to the first embodiment and the 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 timing T2, the measurement state 1240 changes to the standby state 1260.

Further, as shown in FIG. 7B, the state of the integrator 1021 changes from the state 1280 in which the integration circuit reset operation is performed at the timing T1 to the state 1300 in which the integration operation is performed, and at the timing T2. The state changes from the state 1300 in which the integration operation is performed to the state 1320 in which the integration circuit reset operation is performed. Accordingly, the integrator 1021 is in the

state

1280 and 1320 in which the integration circuit reset operation is being performed when the optical measurement device 1000 is in the

standby state

1220 and 1260, respectively, and the optical measurement device 1000 is in the measurement state 1240. In this case, the integration operation is being performed 1300.

The integrator 1021 can always 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. For this reason, the integrator control unit 1065 controls the integrator 1021 to integrate the photocurrent and output the standby integration signal in the standby integration period 1340 that repeatedly arrives, and the approximate luminance acquisition unit 1061 The approximate luminance may be acquired by regarding the standby integration period that has just arrived as the initial integration period. As a result, the approximate luminance is acquired before the timing T1 at which the measurement is started, so that the time required for the measurement is shortened. The length of the standby integration period 1340 that repeatedly arrives may be the shortest settable time.

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 countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

1000 Optical Measuring Device 1020 Optical Sensor 1021 Integrator 1022 Control Unit 1060 Required Accuracy Acquisition Unit 1061 Approximate Luminance Acquisition Unit 1062 Period Acquisition Unit 1063 Exposure Time Determination Unit 1064 Integration Time Determination Unit 1065 Integrator Control Unit 1066 Operation Unit

Claims

A photosensor that receives light from the display and outputs a photocurrent according to the light;
An integrator that continuously integrates the photocurrent in time and outputs an integrated signal;
A request accuracy acquisition unit for acquiring the request accuracy for the measurement value;
An approximate brightness acquisition unit for acquiring the approximate brightness of the light;
A period acquisition unit that acquires a period of time change in luminance and chromaticity of the light;
An exposure time determination unit that determines an exposure time from the required accuracy and the approximate brightness;
An integration time determining unit that determines an integration time of the integrator 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 exposure time, the 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 controller for controlling the integrator so as to integrate the photocurrent and output at least one integral signal,
A computing unit for computing the measured value from the at least one integrated signal;
An optical measurement device comprising:
The integrator control unit controls the integrator so that the integrator integrates the photocurrent and outputs an initial integration signal in an initial integration period preceding the at least one integration period;
The optical measurement device according to claim 1, wherein the approximate brightness acquisition unit acquires the approximate brightness 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 apparatus according to claim 2, wherein the initial integration period is a standby integration period that arrives immediately before the exposure period.
The optical measurement apparatus according to claim 1, wherein the common multiple is a least common multiple.
The optical measurement apparatus according to claim 1, wherein the exposure time can be changed according to the required accuracy.
The optical measuring device according to claim 1, wherein the integrator has a plurality of selectable gains.