TW201842308A - Optical measurement apparatus - Google Patents

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

Light measuring device

The present invention relates to a light measuring device.

In a light measuring device for measuring the brightness and chromaticity of a display, a light sensor receives light from the display and outputs a photocurrent corresponding to the received light, and an integrator integrates the output photocurrent to output an integrated signal The calculation section measures the measured value based on the output integral signal. Among them, there is a limitation on the integration time of the length of the integration period during which the integrator integrates the optical signal.

The brightness and chromaticity of the display include transient response, which changes periodically over time. Therefore, the measurement of the brightness and chromaticity of the display has to be performed in synchronization with the periodic time changes of the brightness and chromaticity of the display. Therefore, the integration time is limited to an integer multiple of the period of the temporal change in brightness and chrominance of the display.

The period of the temporal change of the brightness and chrominance of the display is consistent with the length of the reciprocal of the frame rate or the vertical synchronization (Vsync) period. For this reason, the integration time is limited to the inverse of the frame rate or an integer multiple of the length of the Vsync period. Among them, in principle, a liquid crystal display (LCD) that performs reverse driving for preventing burns may flicker. Therefore, in the case where the light measuring device measures the brightness and chromaticity of the LCD, in order to measure the correct brightness and chromaticity without being affected by flicker, the period of time change of the brightness and chromaticity is regarded as a frame. The reciprocal of the rate is twice or the length of the Vsync period is twice. The integration time is limited to an integer multiple of the period.

In the light measuring device, in order to increase the range of measurable brightness, a gain can be selected in the integrator, and the selected gain can be changed in the case of improper exposure. For example, when the exposure is over or under an appropriate exposure, the gain is decreased or the gain is increased, respectively. The technology described in Patent Document 1 is an example, and a wide brightness range from low brightness to high brightness can be measured while achieving a high S / N ratio.

In addition, in other light measuring devices, in order to increase the range of measurable brightness, a neutral gray filter (ND filter) can be inserted into the light path of the light incident on the light sensor. In the case of exposure, a neutral grayscale filter is inserted into the light path to reduce the amount of light incident on the light sensor. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-321313

[Problems to be solved by the invention]

Among the conventional light measuring devices, in order to increase the range of measurable brightness, there are problems in that a large number of gains must be selected in the integration circuit, and a light reduction mechanism for inserting an ND filter has to be provided ( ND agency). For this reason, in order to correct for changes in the environment in which the measurement is performed, individual variability of the measurement target, etc., a large number of correction values and calculations are required, and a memory capacity for this is required. For example, a large number of offsets, gain corrections, environmental correction values, and the like are required corresponding to a large number of gains, respectively.

In particular, when the light measuring device measures the brightness and chromaticity of the display, the integration time is limited as described above, so the appropriate exposure varies with the length of the Vsync period, and the saturation value with respect to the brightness changes. For this reason, the number of necessary gains is increased, and the load applied to the optical measurement device is increased.

It is also possible to increase the gain pitch by selecting a small number of gains, thereby increasing the range of brightness that can be measured through a small number of gains. The gain pitch shows the difference between two adjacent gains. Among them, when the gain pitch is increased, such a problem occurs that the measurement conditions for the underexposure and the proper exposure occur in 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 in which the light measuring device can measure the brightness without complicating the light measuring device. [Technical means to solve the problem]

In a light measuring device, a light sensor receives light from a display and outputs a photocurrent corresponding to the light. The integrator continuously integrates the photocurrent over time and outputs an integrated signal.

Obtain the required accuracy of the measurement value, the estimated brightness of the light, and the period of time change of the brightness and chromaticity of the light.

Determine the exposure time according to the required accuracy and estimated brightness. The integration time is determined such that the integrator is not saturated and the exposure time becomes a common multiple of the period and integration time.

The integrator is controlled such that the exposure period is formed by at least one integration period, the length of the exposure period becomes the determined exposure time, and the individual length of the at least one integration period becomes the determined integration time. The photocurrent is integrated, and at least one integrated signal is output respectively.

Calculate the measured value based on at least one integral signal. [Compared with the efficacy of the prior art]

According to the invention described below, the range in which the light measuring device can measure the brightness can be increased without complicating the light measuring device.

The objects, features, solutions and advantages of the present invention will become clearer with the following detailed description and drawings.

1 Optical measurement device FIG. 1 is a block diagram showing the 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 light measuring device 1000 shown in FIG. 1 measures the brightness and chromaticity of a display, and includes a light sensor 1020, an integrator 1021, a control unit 1022, and a peripheral portion 1023. The optical measurement device 1000 may include components other than these components.

In the light measuring device 1000, a light sensor 1020 receives light from a display and outputs a photocurrent corresponding to the received light. In addition, the integrator 1021 integrates the output photocurrent, and outputs an integration signal corresponding to the amount of charge accumulated through the integration. In addition, the control unit 1022 calculates the measured value based on the outputted integral signal.

The integrator 1021 includes an integrating circuit 1040, an integrating circuit 1041, a switcher 1042, and a switcher 1043.

Integrating circuits 1040 and 1041 integrate the photocurrent. The switches 1042 and 1043 switch the integration circuit integrating the photocurrent between the integration circuit 1040 and the integration circuit 1041 according to the control under the control unit 1022. To this end, the integrator 1021 can integrate the photocurrent in time without interruption.

The integrator 1021 may have a plurality of selectable gains. This can further increase the range of measurable brightness.

The control unit 1022 is a computer that operates in accordance with the installed program, and includes a required accuracy acquisition unit 1060, an estimated brightness 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 calculation department 1066. It is not necessary for the hardware of the program to perform all or part of the processing that the computer is responsible for.

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

In response to the reception of a measurement command from the operator, the measurement system executes steps S101 to S105 shown in FIG. 2.

The measurement conditions are acquired in step S101. The measurement conditions can be obtained from the operation of the hardware switch provided in the operation unit 1081 or from the operation performed by the operation unit 1081 on a graphical user interface (GUI) displayed on the display unit 1080.

For the acquisition of the measurement conditions, the required accuracy acquisition unit 1060 acquires a required S / N ratio for the measured value. The requested accuracy acquisition unit 1060 accepts the designation of one of the three modes such as the high-accuracy mode, the standard mode, and the high-speed mode corresponding to the three required S / N ratios, and acquires the corresponding mode. The required S / N ratio. The method of obtaining the required S / N ratio can also be changed. For example, the request accuracy acquisition unit 1060 may accept the designation of one accuracy range included in the plurality of accuracy ranges corresponding to the plurality of required S / N ratios, thereby obtaining the request S / corresponding to the specified accuracy range. N ratio. The accuracy range is expressed by, for example, "...% or less", "...% to ...%", and the like. The required accuracy other than the required S / N ratio can also be obtained.

In the acquisition of the measurement conditions, the cycle acquisition unit 1062 acquires a Vsync time, which is the length of a vertical synchronization (Vsync) period that coincides with a period in which the luminance and chromaticity of the display change over time. The Vsync time is obtained from an operation performed on the GUI displayed on the display portion 1080 by the operation portion 1081. The Vsync frequency can also be obtained, and the Vsync time can be obtained from the obtained Vsync frequency. The method of obtaining the Vsync time can also be changed. For example, a Vsync signal may be input to the cycle obtaining unit 1062, and the cycle obtaining unit 1062 may obtain a Vsync time based on the input Vsync signal. When measuring the brightness and chrominance of a liquid crystal display that is driven in the reverse direction, instead of the Vsync time, a time twice as long as the Vsync time corresponding to the cycle of time changes in the brightness and chrominance of the liquid crystal display is obtained.

Next, in step S102, the estimated brightness of the light from the display is obtained. Step S102 and step S101 may be performed simultaneously.

Upon obtaining the estimated brightness, the integrator control unit 1065 controls the integrator 1021. The control is performed as follows: the integrator 1021 integrates the photocurrent during the initial integration period before the plurality of integration periods described later, and outputs an initial integration signal. The estimated brightness acquisition unit 1061 obtains the estimated brightness of the light from the display from the initial integration signal. It doesn't matter if the initial credit period is short. The method of obtaining the estimated brightness can also be changed. One example will be described later.

Next, in step S103, measurement conditions are determined.

In determining the measurement conditions, the exposure time determination unit 1063 determines the exposure time based on the obtained required S / N ratio and the estimated brightness. The exposure time can be changed according to the required S / N. The exposure time can be determined by making the required S / N ratio and the estimated brightness as a function of variables, or by using a lookup table (LUT). This function is, for example, a function represented by Expression (1). F (required S / N ratio, estimated brightness) contained in the formula (1) is an integer. This LUT is, for example, a lookup table for determining the exposure time based on the required S / N ratio and estimated brightness shown in FIG. 3.

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

In addition, upon the acquisition of the measurement conditions, the integration time determination unit 1064 determines the maximum unsaturated integration time based on the obtained estimated brightness. This maximum unsaturated integration time is not saturated by the integrator 1021 and can ensure proper integration of the S / N ratio. The upper limit of time. The integration time determination unit 1064 determines 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 a common multiple of the obtained Vsync time and integration time. Thereby, the integration time in which the integrator 1021 is not saturated and the exposure time becomes a common multiple of the Vsync time and the integration time is determined.

The integration time is preferably the longest one that satisfies the conditions described in Expressions (2) and (3). The common multiple is preferably the least common multiple. This makes it possible to increase the electric charge accumulated in the integrator 1021 in a range where the integrator 1021 is not saturated, thereby improving the S / N ratio.

Number of repetitions = Int (exposure time / maximum unsaturated integration time) + 1 ... (2) Integration time = exposure time / repeated times ... (3)

Although the determination of the exposure time, the determination of the maximum unsaturated integration time, and the determination of the integration time are performed in different programs, they can also be performed in the same program. For example, the integration time can also be determined directly by using the LUT shown in FIG. 4 to determine the integration time based on the required S / N ratio, Vsync frequency, and estimated brightness in a manner that meets the aforementioned conditions.

Then, in step S104, measurement is performed.

For measurement, the integrator control unit 1065 controls the integrator 1021. The control is performed as follows: the exposure period is formed by 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 individual lengths of the plurality of integration periods After the integration time is determined, the integrator 1021 integrates the photocurrent during a plurality of integration periods, and outputs a plurality of integration signals, respectively. Thereby, the measurement is performed under the determined measurement conditions.

Next, in step S105, calculation and output of the measured value are performed.

In the calculation and output of the measured values, the calculation unit 1066 obtains a plurality of integral signal values each indicating the size of the plurality of output integral signals, and converts the average value of the obtained plurality of integral signal values into a value per unit time. The required calculation processing is performed on the value obtained through conversion, and calculation is performed on the measured values of brightness and chromaticity. Thereby, the measured values of brightness and chromaticity are calculated based on a plurality of integrated signals. The calculation method of the measured values of brightness and chromaticity can also be changed. The calculation unit 1066 also outputs calculated values of brightness and chromaticity.

In such a measurement according to the optical measurement device according to the first embodiment, the number of selectable gains can be reduced, the load applied to the optical measurement device can be reduced, and the optical measurement device can be simplified. Therefore, it is possible to increase the range in which the light measuring device can measure the brightness without complicating the light measuring device.

2 Relationship between exposure time, integration time, and Vsync time in measurement conditions Each of FIGS. 5 and 6 is provided with a display which is an object to be measured under the optical measurement device of the first embodiment and the optical measurement device An example of the time variation of the state of the integrator is shown.

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 shown in FIG. 5, an exposure period 1100 having an exposure time required to ensure the required S / N ratio is divided into eight Vsync periods 1120 equally. The Vsync time is, for example, about 1 millisecond to 2 seconds. In addition, the exposure period 1100 is equally divided into five integration periods 1140. For this reason, the exposure time becomes 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 required to ensure a required S / N ratio is divided into four Vsync periods 1180 by an equal amount. The Vsync time is, for example, about 1 millisecond to 2 seconds. In addition, the exposure period 1160 is equally divided into five integration periods 1200. For this reason, the exposure time becomes 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 the method of obtaining the estimated brightness FIG. 7 is a timing chart showing an example of the time variation of the state of the optical measurement device and the integrator provided in the optical measurement device according to the first embodiment.

As shown in FIG. 7 (a), the state of the optical measurement device 1000 changes from the standby state 1220 to the measurement state 1240 at a time point T1 when a measurement command is received from the operator, and from the measurement state 1240 at a time point T2 when the exposure time elapses from the time point T1. Change to standby state 1260.

In addition, as shown in FIG. 7 (b), the state of the integrator 1021 changes from the state 1280 where the integration circuit reset operation is performed to the state 1300 where the integration operation is performed at the time point T1, and changes from the state 1300 where the integration operation is performed at the time point T2. The state 1320 is for resetting the integrating circuit. Therefore, when the integrator 1021 series optical measuring device 1000 is in the standby state 1220 and 1260, it is in the states 1280 and 1320 to perform the resetting operation of the integrating circuit, and when the optical measuring device 1000 is in the measuring state 1240, it is to perform the integrating operation. Of the state 1300.

The integrator 1021 is in a state of 1280 and 1320 for resetting the integration circuit. It can also integrate the optical signal at all times, and can output the integration signal. For this reason, the integrator control unit 1065 may also control the integrator 1021 to integrate the photocurrent during the repeated standby integration period 1340 and output the standby integration signal. The estimated brightness acquisition unit 1061 will be immediately before the exposure period. The coming standby integration period is regarded as the initial integration period and the estimated brightness is obtained. Thereby, the estimated brightness is obtained before the time point T1 at which measurement is started, so the time required for measurement is shortened. The length of the repeating standby integration period 1340 may be the shortest time that can be set.

Although the invention has been described in detail, the above description is illustrative in all aspects, and the invention is not limited by them. Countless modification examples which are not illustrated should be conceived without departing from the scope of the invention.

1000‧‧‧ light measuring device

1020‧‧‧Light Sensor

1021‧‧‧ Integrator

1022‧‧‧Control Department

1060‧‧‧Required Accuracy Acquisition Department

1061‧‧‧Estimated brightness acquisition department

1062‧‧‧cycle acquisition department

1063‧‧‧Exposure time determination department

1064‧‧‧Credit time decision department

1065‧‧‧Integrator Control Department

1066‧‧‧Calculation Department

[Fig. 1] A block diagram showing a light measuring device according to a first embodiment. [FIG. 2] A flowchart showing a measurement flow in the optical measurement device according to the first embodiment. [FIG. 3] A diagram showing a lookup table (LUT) for determining the exposure time based on the required S / N ratio and the estimated brightness in the optical measurement device according to the first embodiment. [Fig. 4] A diagram showing a lookup table (LUT) for determining the integration time according to the required S / N ratio, vertical synchronization (Vsync) frequency, and estimated brightness in the optical measurement device according to the first embodiment. . [FIG. 5] A timing chart showing an example of a time change of the state of the display which is the measurement target under the optical measurement device according to the first embodiment and the state of the integrator provided in the optical measurement device. [Fig. 6] A timing chart showing an example of a time change of the state of a display which is a measurement target under the optical measurement device according to the first embodiment and the state of an integrator provided in the optical measurement device. [FIG. 7] A timing chart showing an example of the time variation of the state of the optical measurement device and the integrator provided in the optical measurement device according to the first embodiment.

Claims (6)

An optical measuring device includes: (1) a light sensor that receives light from a display and outputs a photocurrent corresponding to the light; (2) an integrator that continuously integrates the photocurrent in time and outputs an integrated signal; Requirement accuracy for measured values; Estimated brightness acquisition section to obtain the estimated brightness of the aforementioned light; Period acquisition section to obtain the period of time change of the brightness and chromaticity of the light; Exposure time determination section based on the required accuracy and the estimated brightness Determine the exposure time; the integration time determination unit determines the integration time of the integrator so that the integrator is not saturated, the exposure time becomes a common multiple of the period and the integration time; the integrator control unit controls the integrator to, The exposure period is made up of at least one integration period, the length of the exposure period becomes the exposure time, and the individual length of the at least one integration period becomes the integration time. The photocurrent is integrated to output at least one integrated signal, respectively; and the calculation unit calculates the measured value based on the at least one integrated signal. The optical measurement device according to item 1, wherein: the integrator control unit controls the integrator so that the integrator integrates the photocurrent during an initial integration period before the at least one integration period, and outputs an initial integration signal, the foregoing The estimated brightness acquisition unit obtains the estimated brightness from the initial integration signal. The optical measuring device according to item 2, wherein: the integrator control unit controls the integrator to integrate the photocurrent during a repeating standby integration period, and outputs an integration signal during standby, the initial integration period is between The standby integration period immediately before the aforementioned exposure period. The optical measurement device according to any one of items 1 to 3, wherein the common multiple is a least common multiple. The light measuring device according to any one of items 1 to 3, wherein the exposure time can be changed in accordance with the required accuracy. The optical measurement device according to any one of items 1 to 3, wherein the integrator has a plurality of selectable gains.