Display light measurement device and light measurement method, data processing device, and program

Abstract

The present invention comprises: a stimulus value acquisition means (4) for receiving light of a display and continuously acquiring intensities corresponding to stimulus values at a fixed time interval; a setting means (5) for setting, as a period of interest, a light amount fluctuation cycle of the display; a determination means (72) for setting, as a variable, a time of a response function which indicates impulse response characteristics corresponding to a visual stimulus response, and changing and determining the time of the response function in accordance with the period of interest set by the setting means (5); and a digital filtering means (73) for performing, using the response function in which the time has been determined by the determination means (72), digital filtering on continuous data of the stimulus value intensities acquired by the stimulus value acquisition means (4) and thereby generating data on which the visual stimulus response has been superimposed.

Description

Display light measurement device and light measurement method, data processing device and program

[0001] The present invention relates to a display light measurement device that measures light from a display, and in particular to a display light measurement device and light measurement method, a data processing device, and a program that are suitable for measuring flicker, which is the amount of flicker visible to the eye on a display.

[0002] As display functions and performance improve, light-emitting waveforms are becoming more complex. For example, in the case of OLED (Organic Light-Emitting Diode) displays, light-emitting 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, complex waveforms is becoming common. In particular, pulse-width modulation performs multiple pulse light-emitting control within one frame period (vertical synchronization cycle), and the light-emitting waveform is faster than the image update cycle, resulting in a steep waveform with high amplitude.

[0003] In recent years, displays with a variable refresh rate (VRR) function have been developed. The refresh rate of these displays changes dynamically and aperiodically, resulting in increasingly complex emission waveforms, such as transient responses observed in the emission waveform starting from the switching point.

[0004] As light-emitting waveforms become more complex, flicker (visible flickering) becomes more apparent, posing a quality issue for displays.

[0005] A known example of an optical measurement device that measures visible flicker on a display is a display color analyzer (one example is the CA-410 manufactured by Konica Minolta, Inc.). Such a display color analyzer has an internal optical sensor that acquires fluctuations in stimulus values ​​and measures flicker values.

[0006] There are two main methods for acquiring stimulus values: a sequential acquisition method that acquires instantaneous values, and an integral acquisition method that acquires integral values ​​over a set period of time. The sequential acquisition method excels in speed, while the integral method excels in low-luminance measurement performance.

[0007] The JEITA method is a common method for measuring flicker that occurs in displays. However, while this method is effective for measuring simple light-emitting waveforms such as those of liquid crystal displays (LCDs), it is not suitable for complex waveforms, as the measured values ​​do not match those of the human eye.

[0008] Therefore, as a measurement method for the complicated light emission waveform, there is a method defined in the IEC standard "62341-6-3" of Non-Patent Document 1.

[0009] This standard derives stimulus values ​​that take into account the temporal response of the eye by convolving the acquired continuous stimulus values ​​with the temporal contrast sensitivity function (TCSF), which indicates the eye's sensitivity characteristics to light emission frequency, and then derives a flicker index from these stimulus values.

[0010] The specific processing steps are as follows: (1) Continuously acquire stimulus values ​​from the illuminated display. (2) Perform a discrete Fourier transform (DFT) on the acquired data to convert it into a frequency spectrum. (3) Convolve the obtained frequency spectrum with TCSF to superimpose the eye characteristics. (4) Perform an inverse Fourier transform (iDFT) to generate stimulus values ​​with TCSF superimposed. (5) Calculate the maximum value (Max) - minimum value (Min) / average value (Ave) of the stimulus value data with TCSF superimposed, and use this as an index of the amount of flicker.

[0011] However, this method uses a digital Fourier transform (DFT, iDFT) that is based on the assumption that the input waveform is periodic and synchronized, and incorporating this digital Fourier transform into a flicker measurement method poses the following problem: If the measurement time does not match (is not an integer multiple of) the period of the light emission waveform (for example, the Vsync period), the light intensity values ​​at the leading and trailing ends of the acquired waveform will not match, resulting in significant distortion of the superimposed stimulus value and large errors in the flicker value.

[0012] To address this issue, a method has been proposed in which continuous data of stimulus intensity is subjected to digital filtering using a response function that represents the impulse response characteristic equivalent to the visual stimulus response, thereby generating data with the visual stimulus response superimposed, and then using this data to measure flicker. This method eliminates restrictions on measurement time and makes it possible to obtain distortion-free superimposed stimulus values ​​(i.e., stimulus value response characteristics).

[0013] IEC standard “62341-6-3”

[0014] However, in flicker measurement using the digital filter, when measuring a periodic light emission waveform with abrupt changes in luminance, spike-like noise may occur in the superimposed stimulus value. This situation is shown in Figures 6(A) and 6(B).

[0015] Figure 6(A) shows the light emission waveform of a display operating under the driving condition of a vertical synchronization signal (Vsync) frequency of 29.126 Hz, where the light emission control is a hybrid control of pulse width modulation and amplitude modulation, and the number of pulses in the pulse width modulation is 4. Figure 6(B) is a graph of the superimposed stimulus value after digital filtering. As shown in Figure 6(B), spike-like noise has occurred in the superimposed stimulus value.

[0016] Specifically, in digital filtering, when the response function crosses a steep fluctuation in light intensity, an offset occurs in the output value after filtering. As a result, there is an issue that, depending on the light emission waveform, accurate flicker measurement cannot be performed even with digital filtering, making this a measurement method with low robustness.

[0017] This invention has been made in view of the above technical background, and aims to provide a display light measurement device, light measurement method, data processing device, and program that can obtain superimposed stimulus values ​​that suppress the generation of spike-like noise even when digital filtering is performed on the steep light emission waveform of a display, thereby ensuring measurement accuracy and enabling highly robust flicker measurement.

[0018] The above object is achieved by the following means: (1) A display light measurement device comprising: stimulus value acquisition means for receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at regular time intervals; setting means for setting a light intensity fluctuation period of the display as a period of interest; determination means for changing and determining the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response as a variable, and changing the time of the response function in accordance with the period of interest set by the setting means; and digital filter processing means for performing digital filtering on the continuous data of stimulus value intensity acquired by the stimulus value acquisition means using the response function whose time has been determined by the determination means, to generate data on which the visual stimulus response is superimposed. (2) A display light measurement device comprising: a stimulus value acquisition means that receives light from a display and continuously acquires an intensity corresponding to a stimulus value at regular time intervals; and a digital filtering means that performs digital filtering on the continuous data of stimulus value intensity acquired by the stimulus value acquisition means using a response function that represents an impulse response characteristic corresponding to a visual stimulus response, to generate data on which the visual stimulus response is superimposed, wherein, when a light intensity fluctuation period of the display is set as a period of interest, a time of the response function used in the digital filtering is determined in accordance with the period of interest. (3) A display light measurement device according to the preceding paragraph 1 or 2, wherein the time of the response function is an integer multiple of the period of interest. (4) A display light measurement device according to any of the preceding paragraphs 1 to 3, which converts the unit time of either the time resolution of the response function or the acquisition period of the stimulus value by the stimulus value acquisition means. (5) A display light measurement device according to any of the preceding paragraphs 1 to 4, which changes the acquisition period of the stimulus value in accordance with the period of interest. (6) A display light measurement device according to any one of the preceding paragraphs 1 to 5, wherein the response function is generated by inverse Fourier transform from the frequency characteristics of the eye, and the frequency resolution and the number of data of the frequency characteristics of the eye are adjusted so as to obtain a desired time before the inverse Fourier transform.(7) A display light measurement method including: a stimulus value acquisition step of receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at regular time intervals; a setting step of setting a light intensity fluctuation period of the display as a period of interest; a determination step of setting the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response as a variable, and changing and determining the time of the response function according to the period of interest set in the setting step; and a digital filter processing step of performing digital filtering on the continuous data of stimulus value intensity acquired by the stimulus value acquisition step using the response function whose time has been determined in the determination step, to generate data on which the visual stimulus response is superimposed. (8) A display light measurement method comprising: a stimulus value acquisition step of receiving light from a display and continuously acquiring intensities corresponding to stimulus values ​​at regular time intervals; and a digital filtering step of performing digital filtering on the continuous data of stimulus value intensities acquired in the stimulus value acquisition step using a response function representing an impulse response characteristic corresponding to a visual stimulus response to generate data on which the visual stimulus response is superimposed, wherein, when a light intensity fluctuation period of the display is set as a period of interest, a time of the response function used in the digital filtering is determined according to the period of interest. (9) A display light measurement method according to claim 7 or 8, wherein the time of the response function is an integer multiple of the period of interest. (10) A display light measurement method according to any of paragraphs 7 to 9, wherein a unit time of either a time resolution of the response function or an acquisition period of stimulus values ​​by the stimulus value acquisition means is converted. (11) A display light measurement method according to any of paragraphs 7 to 10, wherein the acquisition period of the stimulus values ​​is changed according to the period of interest. (12) A display light measurement method according to any one of the preceding paragraphs 7 to 11, wherein the response function is generated by inverse Fourier transform from the frequency characteristics of the eye, and the frequency resolution and the number of data of the frequency characteristics of the eye are adjusted so as to obtain a desired time before the inverse Fourier transform.(13) A data processing device comprising: a receiving means for receiving continuous data of stimulus value intensity obtained by receiving light from a display and continuously acquiring intensity corresponding to a stimulus value at regular time intervals; a setting means for setting the light intensity fluctuation period of the display as a period of interest; a determining means for setting the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response as a variable and changing and determining the time of the response function in accordance with the period of interest set by the setting means; and a digital filter processing means for performing digital filtering on the continuous data of stimulus value intensity received by the receiving means using the response function whose time has been determined by the determining means, and generating data on which the visual stimulus response is superimposed. (14) A data processing device comprising: a receiving means for receiving continuous data of stimulus value intensity obtained by receiving light from a display and continuously acquiring intensities corresponding to stimulus values ​​at regular time intervals; and a digital filtering means for performing digital filtering on the continuous data of stimulus value intensity received by the receiving means using a response function representing an impulse response characteristic corresponding to a visual stimulus response to generate data on which the visual stimulus response is superimposed, wherein, when a light intensity fluctuation period of the display is set as a period of interest, a time of the response function used in the digital filtering is determined in accordance with the period of interest. (15) The data processing device according to paragraph 13 or 14, wherein the time of the response function is an integer multiple of the period of interest. (16) The data processing device according to any of paragraphs 13 to 15, which converts the unit time of either the time resolution of the response function or the acquisition period of the stimulus value. (17) The data processing device according to any of paragraphs 13 to 16, which changes the acquisition period of the stimulus value in accordance with the period of interest. (18) A data processing device according to any one of the preceding paragraphs 13 to 17, wherein the response function is generated by inverse Fourier transform from the frequency characteristics of the eye, and the frequency resolution and the number of data of the frequency characteristics of the eye are adjusted so as to obtain a desired time before the inverse Fourier transform.(19) A program for causing a computer to execute the following steps: a receiving step for receiving continuous data of stimulus value intensity obtained by receiving light from a display and continuously acquiring intensity corresponding to a stimulus value at regular time intervals; a setting step for setting the light intensity fluctuation period of the display as a period of interest; a determining step for setting the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response as a variable, and changing and determining the time of the response function according to the period of interest set in the setting step; and a digital filtering step for performing digital filtering on the continuous data of stimulus value intensity received by the receiving step using the response function whose time has been determined by the determining step, to generate data on which the visual stimulus response is superimposed. (20) A program causing a computer to execute the following steps: a receiving step of receiving continuous data of stimulus value intensity obtained by receiving light from a display and continuously acquiring intensities corresponding to stimulus values ​​at regular time intervals; and a digital filtering step of applying digital filtering to the continuous data of stimulus value intensity received by the receiving step using a response function representing an impulse response characteristic corresponding to a visual stimulus response, to generate data on which the visual stimulus response is superimposed; and causing the computer to execute a process of determining a time of the response function used in the digital filtering process in accordance with a period of interest, where the period of variation in light intensity of the display is a period of interest. (21) The program according to paragraph 19 or 20, wherein the time of the response function is an integer multiple of the period of interest. (22) The program according to any of paragraphs 19 to 21, causing the computer to execute a process of converting a unit time of either the time resolution of the response function or the acquisition period of the stimulus values. (23) The program according to any one of the preceding paragraphs 19 to 22, which causes the computer to execute a process of changing the acquisition period of the stimulus values ​​in accordance with the period of interest, using the acquisition period of the stimulus values ​​as a variable. (24) The program according to any one of the preceding paragraphs 19 to 23, which generates the response function by performing an inverse Fourier transform on the frequency characteristics of the eye, and adjusts a frequency resolution and a number of data points of the frequency characteristics of the eye so that they correspond to a desired time before the inverse Fourier transform.

[0019] The display light measurement device, light measurement method, and data processing device according to the present invention receive light from a display and continuously acquire intensities corresponding to stimulus values ​​at regular time intervals. The continuous data of stimulus value intensities is then digitally filtered using a response function that represents impulse response characteristics corresponding to a visual stimulus response. In this digital filtering, the time of the response function is determined based on the period of light intensity fluctuation of the display, which is the period of interest. Therefore, the superimposed stimulus value generated by the digital filtering matches the average luminance value over the period going back in time from the current time to the response function time. This makes it possible to avoid offsets even in steep light emission waveforms and obtain superimposed stimulus values ​​with reduced spike-like noise. Using this superimposed stimulus value enables highly robust flicker measurement while ensuring measurement accuracy.

[0020] According to the program of the present invention, continuous data of stimulus value intensity obtained by receiving light from a display and continuously acquiring intensities corresponding to stimulus values ​​at regular time intervals is received, and when digital filtering is performed on the received continuous data of stimulus value intensity using a response function that represents an impulse response characteristic corresponding to a visual stimulus response, the program can cause a computer to execute a process of determining the time of the response function in accordance with the light intensity fluctuation period of the display, which is a period of interest.

[0021] 1 is a block diagram showing the configuration of a display light measurement system according to a first embodiment of the present invention; FIG. 2 is a waveform diagram showing an example of an impulse response characteristic corresponding to a visual stimulus response; (A) is a diagram showing an example of an emission waveform of a display, (B) is a waveform diagram of a response function used, and (C) is a waveform diagram of superimposed stimulus value data generated by digital filter processing; FIG. 3 is a block diagram showing the configuration of a display light measurement device according to a second embodiment of the present invention; FIG. 4 is a waveform diagram showing an example of the frequency characteristic of the eye; and FIG. 5 is a diagram for explaining the conventional problem, where (A) is a diagram showing an example of an emission waveform of a display, and (B) is a waveform diagram of superimposed stimulus value data generated by digital filter processing.

[0022] 1 is a block diagram showing the functional configuration of a display light measurement system (hereinafter simply referred to as an optical measurement system) 10 that uses a data processing device according to an embodiment of the present invention.

[0023] As shown in FIG. 1, the optical measurement system 10 includes a measurement head 20, a personal computer (PC) 30 as a data processing device, an operation unit 11 for the PC, and a display unit 12.

[0024] The measurement head 20 includes a light collecting unit 2 , a light path branching unit 3 , and a stimulus value acquiring unit 4 .

[0025] The light collecting unit 2 is made up of a collecting lens and the like, and collects light emitted from a display, which is the object to be measured.

[0026] The optical path branching unit 3 branches the optical path of the light condensed by the condensing unit 2 into three. <Acquisition of stimulus values> The stimulus value acquisition unit 4 uses the three branched optical paths created by the optical path branching unit 3 and includes an optical sensor (X) 41a, an optical sensor (Y) 41b, and an optical sensor (Z) 41c that receive light from each optical path, and an output unit 42. The output of the optical sensors 41a to 41c is continuously acquired by the output unit 42 at regular time intervals corresponding to the sampling frequency, and has the function of converting this into continuous data of stimulus value intensity. The output of the optical sensor (Y) 41b is also used for flicker measurement.

[0027] The optical sensors 41a to 41c may be tristimulus value direct reading types or spectroscopic types. The converted stimulus values ​​include, for example, luminance, chromaticity (xy), and tristimulus values ​​expressed as XYZ. Filtering may be performed to remove noise during the continuous data conversion of stimulus values. For example, moving average processing using previous and following data may be applied.

[0028] Although not shown, the output unit 42 includes three current integration circuits, one for each of the three optical sensors 41a to 41c, and three A / D converters, one downstream of each current integration circuit. In this embodiment, the output unit 42 acquires data from each of the optical sensors 41a to 41c using an integration method in the current integration circuits. The integration method has an excellent S / N ratio, which can improve measurement accuracy. On the other hand, the integration method has the disadvantage that it cannot acquire data as quickly as the sequential method, but this is not a problem when used to measure flicker because human visual response is slow.

[0029] In this embodiment, in consideration of the S / N characteristics of the optical sensors 41a to 41c, the output of each optical sensor 41a to 41c is acquired at a cycle of, for example, 333.3 μsec. The data acquisition cycle may be changed depending on the type of display to be measured and its driving conditions. For example, if the driving conditions are amplitude modulation drive, the speed may be set low to prioritize S / N, and if the driving conditions are PWM modulation drive, the speed may be set high.

[0030] The PC 30 functionally comprises a period of interest setting unit 5 and a flicker value derivation unit 7. <Setting of Period of Interest> The period of interest setting unit 5 sets a period of interest, which will be described later, in order to improve the measurement stability (robustness) of flicker measurement. Since frequency and period are inextricably linked, a configuration may be adopted in which the period of interest is automatically calculated and set by setting a frequency of interest. In this embodiment, the setting is performed based on instructions from the user to the PC 30. Alternatively, as will be described later, a light waveform frequency detection unit may be provided and the period of interest may be set based on the detection results of the frequency detection unit.

[0031] The period of interest is the period of fluctuation in the light intensity of the display. If the frequency of the vertical synchronization signal (Vsync) is 29.126 Hz, the period of interest can be set to the Vsync period (1 / 29.126 Hz), or a different period can be set. For example, selecting the period at which the amount of fluctuation in light intensity is at its maximum can also achieve the effect of suppressing spike noise. Specifically, if the Vsync frequency is 29.126 Hz, the light emission control is hybrid control using pulse width modulation and amplitude modulation, and the number of pulses in pulse width modulation is 4, the period during which pulse width modulation control is implemented will be the period at which the amount of fluctuation in light intensity is at its maximum, and this period can be set to 1 / (29.126 × 4) = 8.583 usec.

[0032] The flicker value derivation unit 7 measures flicker using the data output from the optical sensor (Y) 41b and acquired by the output unit 42, by a method described later, and includes a response storage unit 71, a response function determination unit 72, a digital filter processing unit 73, and a flicker derivation unit 74. <Storage of response function> The response storage unit 71 stores a response function that represents an impulse response characteristic that corresponds to a visual stimulus response.

[0033] An example of an impulse response characteristic corresponding to a visual stimulus response is shown in Figure 2. The response period to be memorized is sufficient if it is long enough for the eye response to converge. The eye response generally converges after 0.5 seconds.

[0034] The visual stimulus response, which is a sensory characteristic, is highly dependent on the individual (person), the environment, and the display being measured. For this reason, multiple response functions may be stored in the response storage unit 31, and different response functions may be used depending on the conditions. Furthermore, the response storage unit 31 may be configured so that the user can store (register) response functions.

[0035] Examples of parameters on which the visual stimulus response depends include the measurement area of ​​the stimulus value acquisition unit 20, luminance, color, gender, age, ambient luminance, individual, etc. The response function may be selected by manual setting by the user or automatically selected by the optical measurement device 1. For example, when color is used as a parameter, automatic selection can be achieved by utilizing the stimulus value acquired for flicker measurement. As another example, a sensor may be provided in the optical measurement device 1, and the current measurement color may be checked by the sensor and automatically switched.

[0036] The response memory unit 31 does not have to be built into the data processing device 3, but may be external. In this case, the response function can be acquired from the external response memory unit 31 and processed. <Determination of Response Function> The response function determination unit 72 uses the time (also referred to as the response function time) of a response function selected from multiple response functions stored in the response memory unit 71 as a variable, and changes and determines the time according to the period of interest set by the period of interest setting unit 5. In this embodiment, it is desirable to set the time of the response function as an integer multiple of the period of interest. This ensures that the average luminance value over the period going back from the current time by the response function time matches at any time during digital filtering by the digital filtering unit 73. This makes it possible to avoid offsets even in steep waveforms and eliminate spike-like noise that occurs in the superimposed stimulus value. The time of the response function is desirably derived according to the following formula (1), with a lower limit set taking into account the reaction time of the eye. This makes it possible to set the time of the response function so as to shorten the invalid period (see the explanation of digital filtering described below) under measurement conditions that avoid noise.

[0037] Response function time ≒ period of interest × (natural number) ≒ period of interest × RoundUp (response time lower limit value / period of interest) Equation (1) In this example, the response time lower limit value was set to 0.5 seconds, and the response function time was 0.515 seconds.

[0038] The method for determining the response function time is not limited to the above. For example, the user may select and determine from among the magnifications that make the response function time equal to or greater than the lower limit value. As another example, the user may simply specify and determine the magnification. The selection of the magnification may also be changed in accordance with the response characteristics used in flicker measurement.

[0039] To achieve digital filtering, it is essential that the time resolution of the response function and the period during which stimulus values ​​are acquired match. Therefore, it is desirable that the response function determination unit 72 also have a function for converting the time resolution of the response function as a preprocessing step for digital filtering. In this embodiment, the response function previously stored in the response storage unit 71 is converted to 333 μsec, the same as the stimulus value period, using linear interpolation. Note that the time interval matching method is not limited to this, and multidimensional interpolation may also be used. Furthermore, the interpolation target may be continuous stimulus value data. <Digital Filtering> The digital filtering unit 73 receives continuous data of stimulus value intensity acquired by the output unit 42 of the stimulus value acquisition unit 4, acquires a response function with a determined time from the response function determination unit 72, and performs digital filtering on the received continuous data of stimulus value intensity using the acquired response function to generate data with a visual stimulus response superimposed thereon (hereinafter referred to as superimposed stimulus value data).

[0040] To perform digital filtering, stimulus value data for at least the response period is required. The superimposed stimulus value data to be generated begins after the response period, and the period before that is invalid due to missing data. To reduce this missing data period, in this embodiment, the impulse response period is set to 0.5 seconds or less, which is the time required for the eye's response to converge. Digital filtering is performed using only the response portion of 0.5 seconds or less.

[0041] The timing of performing the digital filter processing is not limited, and it may be performed after the acquisition of consecutive stimulus values ​​has been completed, or the acquired stimulus values ​​may be processed sequentially even if the acquisition of all data has not been completed. <Deriving Flicker Value> The flicker derivation unit 74 derives a flicker index using the superimposed stimulus value data generated by the digital filter processing unit 73.

[0042] In this embodiment, as an example, (Max-Min) / Ave is derived for the entire time range of the superimposed stimulus value data and converted into an index value (percent flicker). More preferably, the time range for deriving the index value can be set under synchronized conditions, that is, to an integer multiple of the light emission period, to reduce measurement errors. Note that synchronization methods include, but are not limited to, a method using an external synchronization signal or a method in which the user inputs a synchronization frequency.

[0043] Furthermore, the method for deriving the flicker index is not limited to the above method, and other methods of derivation of the index, such as a method of deriving an area ratio (Flicker Index using the IES method), etc. <Others> The operation unit 11 is used by the user to input data and perform other operations on the optical measurement device 1 via the PC 10.

[0044] The display unit 14 displays, via the PC 10, the optical waveform acquired by the output unit 42, the flicker value derived by the flicker value derivation unit 7, and the like.

[0045] Furthermore, the process of setting the period of interest by the period of interest setting unit 5, the process of changing and determining the time of the response function by the response function determination unit 72, the digital filter process by the digital filter processing unit 73, the process of deriving the flicker index by the flicker derivation unit 74, etc. are executed by a processor mounted on the PC 30 operating in accordance with an operating program stored in a memory unit (not shown).

[0046] Furthermore, in the first embodiment described above, the optical measurement system 10 is configured to include the measurement head 20 and the data processing device 30. However, a single display optical measurement device (hereinafter simply referred to as the optical measurement device) may also include the functions of the measurement head 20 and the data processing device 30. In this case, the user may write the setting of the target period directly into the optical measurement device, or the optical measurement device may be connected to a PC via communication and written via the PC. <Effects of the First Embodiment> Figure 3(C) shows the superimposed stimulus value data generated by the digital filter processing unit 73. Note that Figure 3(A) shows the display light emission waveform when the Vsync frequency is 29.126 Hz, light emission control is hybrid control of pulse width modulation and amplitude modulation, and the number of pulses in pulse width modulation is 4, and Figure 3(B) shows the response function used.

[0047] According to the superimposed stimulus value data of FIG. 3(C), it can be confirmed that the spike-like noise observed in the conventional method and shown in FIG. 6(B) has been eliminated.

[0048] In other words, according to this embodiment, by setting the time of the response function to an integer multiple of the period of interest, the average luminance value in the original data before digital filtering (specifically, the period going back from the current time to the response function time) will match at any time of the superimposed stimulus value data. As a result, even if steep stimulus value data is input, offset can be avoided, making it possible to measure flicker with high accuracy. [Second Embodiment] Figure 4 is a block diagram showing the functional configuration of an optical measurement device 1 according to one embodiment of the present invention. This optical measurement device 1 is configured as a stimulus value direct-reading type luminance measurement device and has the function of controlling the stimulus value acquisition period.

[0049] The optical measurement device 1 includes, within a single device, a stimulus value acquisition unit 4, a period of interest setting unit 5, a sampling period determination unit 6, and a flicker value derivation unit 7. The flicker value derivation unit 7 also includes a frequency characteristic storage unit 75, a response conversion unit 76, a response function determination unit 72, a digital filter processing unit 73, and a flicker derivation unit 74.

[0050] The stimulus value acquisition unit 4 includes one optical sensor (Y) 43 that receives light from the display, and an output unit 44 that continuously acquires the output of the optical sensor 43 at a sampling period determined by the sampling period determination unit 6. In this embodiment, a successive approximation method that allows high-speed sampling is used as the acquisition method. <Setting of the period of interest> The period of interest setting unit 5 sets the period of interest. The period of interest may be set based on input by the user via the PC 13, but in this embodiment, a frequency detection unit 51 is provided, and the optical measurement device 1 sets the period corresponding to the frequency detected by this frequency detection unit 51 as the period of interest.

[0051] Specifically, pre-photometry is performed on the display before actual photometry, and the frequency detection unit 51 performs a discrete Fourier transform (DFT) on the data obtained by pre-photometry to convert it into a frequency spectrum, and then frequency analyzes the spectrum to derive a fluctuating frequency, and sets the period corresponding to the fluctuating frequency as the period of interest. Note that the detection of the frequency of interest by the frequency detection unit 51 is not limited to this method. For example, the fluctuating period (frequency) may be directly determined by waveform analysis such as autocorrelation rather than spectral analysis. In this example, 29 Hz is detected as the frequency of interest, and the corresponding period of interest is set. <Determining the Sampling Period> The sampling period determination unit 6 determines the period for acquiring stimulus values.

[0052] In the first embodiment, the time length of the response function can only be adjusted using the stimulus value acquisition period as a basic unit. Therefore, there is a limit to the degree of matching between the response function time and the target period, and a slight error may remain. To further reduce this error, in this embodiment, the sampling period determination unit 6 is provided with a function for varying the stimulus value acquisition period, and the acquisition period is determined according to the target period, and the output unit 44 acquires stimulus values ​​under the determined conditions.

[0053] In this embodiment, the acquisition period is determined to be 1 / natural number times the response function time derived by the above-mentioned formula (1) (note that the response function time is already a time that depends on the period of interest by formula (1)). Specifically, it follows formula (2) below.

[0054] Acquisition period ≒ Response function time / natural number ≒ Response function time / RoundDown (Response function time / basic acquisition period) ... Equation (2) When the response time lower limit is set to 0.5 seconds and the response function time is calculated using equation (1), it becomes 0.51724 seconds. Furthermore, when the basic acquisition period is set to 250 μsec (4 kHz), equation (2) becomes Acquisition period ≒ 0.51724 seconds / RoundDown {0.51724 seconds / (1 / 4000 Hz)} = 250.117 usec (3998.13 Hz).

[0055] The method for determining the acquisition period is not limited to the above. Since the period of interest is matched with the response function time by Equation (1), the effect of reducing the matching error can also be obtained by setting the acquisition period to 1 / natural number times the period of interest, as in Equation (3).

[0056] Acquisition period ≒ Period of interest / Natural number ≒ Period of interest / RoundDown (Period of interest / Basic acquisition period) Formula (3) Furthermore, the matching method may be rounding up, rounding off, etc. instead of rounding down. <Storage of eye frequency characteristics> In the first embodiment, the response storage unit 71 is configured to store a response function that represents an impulse response characteristic that corresponds to a visual stimulus response.

[0057] In contrast, in the second embodiment, the frequency characteristics of the eye are stored in a frequency characteristic storage unit 75, and the frequency characteristics of the eye are converted into an impulse response by a response conversion unit 76. This combination of these two components provides a configuration that performs the same function as the response storage unit 71 of the first embodiment.

[0058] The characteristics of the eye have been widely studied, and many TCSFs have been reported for their time response. For example, the literature "De Lange, H. Journal of the Optical Society of America, 1958 48, 777-785" explains the differences for each brightness.

[0059] To utilize the results of such research, in this embodiment, the frequency characteristics of the eye, such as the TCSF, are stored in the frequency characteristic storage unit 75. The response transformation unit 76 performs an inverse Fourier transform on these frequency characteristics to convert them into impulse response characteristics (response functions) that correspond to visual stimulus responses.

[0060] Figure 5 shows an example of the frequency characteristics of the eye used in this embodiment. By preparing the frequency characteristics to be used in the conversion in advance according to the following conditional expression, the time resolution of the response function can be set to a desired value. Generating a response function by conversion can minimize errors when the frequency characteristics are expressed by a mathematical formula.

[0061] Maximum frequency = 1 / (2 x time resolution of response function) Frequency resolution = maximum frequency / N (N = arbitrary) For example, if the time resolution of the response function is 250 μsec, prepare frequency spectrum data up to 2 kHz. If the frequency pitch is 0.1 Hz (N = 10), the number of spectrum data will be 20,001 (including DC value).

[0062] As in the first embodiment, a plurality of frequency characteristics may be prepared and used separately. Alternatively, the configuration may be such that the user can store (register) the frequency characteristics of the eye in the frequency characteristic storage unit 71, or an arbitrary frequency characteristic may be automatically selected. <Determination of Response Function Time, Digital Filter Processing, and Deriving Flicker Value> The response function determination unit 72 uses the time of a response function selected from the plurality of frequency characteristics stored in the frequency characteristic storage unit 71 and converted by the response conversion unit 76 as a variable, and changes and determines the time according to the period of interest set by the period of interest setting unit 5. The determination method is the same as in the first embodiment. If the time of the response function has already been determined by the sampling period determination unit 6 or the like, the already determined value may be used.

[0063] The digital filter processing unit 73 receives the continuous data of stimulus value intensity acquired by the output unit 42 of the stimulus value acquisition unit 4, acquires the response function for which time has been determined from the response function determination unit 72, and performs digital filtering on the received continuous data of stimulus value intensity using the acquired response function to generate superimposed stimulus value data.

[0064] The time data of the impulse response (response function) generated by the transformation in the response transformer 76 is often sufficiently longer than the response period of the eye (approximately 0.5 seconds). For example, if the frequency characteristics are stored in 0.1 Hz increments, the response data generated by the inverse Fourier transform will be 10 seconds. In digital filter calculations, as described in Example 1, the impulse response period is directly linked to the length of the invalid period of the superimposed stimulus value data. In this embodiment, to suppress the invalid period, only the first 0.5 seconds or less of the transformed response data is used for filtering (see FIG. 3B).

[0065] The derivation of the flicker index by the flicker derivation unit 74 is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0066] Furthermore, each of the processes, such as the setting of the period of interest by the period of interest setting unit 5, the determination of the sampling period by the sampling period determination unit, the conversion of the eye's frequency characteristics into an impulse response by the response conversion unit 76, the determination of the response function time by the response function determination unit 72, the digital filtering by the digital filtering processing unit 73, and the derivation of the flicker index by the flicker derivation unit 74, may be executed by a processor included in the optical measurement device 1 operating in accordance with an operating program stored on a recording medium included in the optical measurement device 1. <Effects of the Second Embodiment> The same effects as those of the first embodiment can be achieved. That is, by setting the time of the response function to an integer multiple of the period of interest, the average luminance value in the original data before digital filtering (specifically, the period going back in time from the current time to the response function time) coincides at any time in the superimposed stimulus value data. As a result, offset can be avoided even when steep stimulus value data is input, enabling highly accurate flicker measurement.

[0067] This application claims priority from Japanese Patent Application No. 2022-55696, filed on March 30, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0068] The present invention can be used for measuring light from a display, etc.

[0069] REFERENCE SIGNS LIST 1 Display light measurement device 2 Light collecting unit 3 Light path branching unit 4 Stimulus value acquisition unit 41a to 41c, 43 Light sensor 42, 44 Output unit 5 Target period setting unit 51 Frequency detection unit 6 Sampling period determination unit 7 Flicker value derivation unit 71 Response storage unit 72 Response function determination unit 73 Digital filter processing unit 74 Flicker derivation unit 75 Frequency characteristic storage unit 76 Response conversion unit 10 Light measurement system 11 Operation unit 12 Display unit 13 Personal computer 20 Measurement head 30 Data processing device

Claims

1. a stimulus value acquiring means for receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at a constant time interval; A setting means for setting a light amount fluctuation period of the display as a period of interest; a determining means for determining the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response as a variable, the time of the response function being changed in accordance with the period of interest set by the setting means; a digital filter processing means for performing digital filtering on the continuous data of the stimulus value intensity acquired by the stimulus value acquisition means using a response function whose time has been determined by the determination means, to generate data on which the visual stimulus response is superimposed; A display light measurement device comprising:

2. a stimulus value acquiring means for receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at a constant time interval; a digital filter processing means for performing digital filtering on the continuous data of the stimulus value intensity acquired by the stimulus value acquisition means using a response function that represents an impulse response characteristic corresponding to a visual stimulus response, to generate data on which the visual stimulus response is superimposed; Equipped with A display light measuring device that determines the time of the response function used in digital filter processing according to a period of interest that corresponds to a period of interest in which the period of interest is a light amount fluctuation period of the display.

3. 3. The display light measuring device according to claim 1, wherein the time of the response function is an integer multiple of the period of interest.

4. 3. The display light measurement device according to claim 1, wherein the unit time of either the time resolution of the response function or the acquisition period of the stimulus value by the stimulus value acquisition means is converted.

5. The display light measurement device according to claim 1 or 2, wherein an acquisition cycle of the stimulus value is changed in accordance with the target cycle.

6. The response function is generated by inverse Fourier transform from the frequency characteristics of the eye, 3. The display light measurement device according to claim 1, wherein a frequency resolution and a number of data items are adjusted so that the frequency characteristics of the eye are in a desired time before inverse Fourier transform.

7. a stimulus value acquisition step of receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at a constant time interval; A setting step of setting a light amount fluctuation period of the display as a period of interest; a determining step of changing and determining the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response in accordance with the period of interest set in the setting step, the time of the response function being a variable; a digital filter processing step of performing digital filter processing on the continuous data of the stimulus value intensity acquired in the stimulus value acquisition step using the response function whose time is determined in the determination step, to generate data on which the visual stimulus response is superimposed; A display light measurement method comprising:

8. a stimulus value acquisition step of receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at a constant time interval; a digital filter processing step of performing digital filtering on the continuous data of the stimulus value intensity acquired by the stimulus value acquisition step using a response function that represents an impulse response characteristic corresponding to a visual stimulus response, thereby generating data on which the visual stimulus response is superimposed; Including, A display light measuring method, in which, when a period of fluctuation in the amount of light of the display is a period of interest, a time of the response function used in digital filter processing is determined according to the period of interest.

9. 9. The display light measuring method according to claim 7, wherein the time of the response function is an integer multiple of the period of interest.

10. 9. The display light measuring method according to claim 7, further comprising converting the unit time of either the time resolution of the response function or the acquisition period of the stimulus value by the stimulus value acquisition means.

11. The display light measuring method according to claim 7 or 8, wherein an acquisition cycle of the stimulus value is changed in accordance with the target cycle.

12. The response function is generated by inverse Fourier transform from the frequency characteristics of the eye, 9. The display light measuring method according to claim 7, wherein a frequency resolution and a number of data items of the frequency characteristics of the eye are adjusted before inverse Fourier transform so as to obtain a desired time.

13. a receiving means for receiving continuous data of the stimulus value intensity obtained by receiving light from the display and continuously acquiring the intensity corresponding to the stimulus value at a constant time interval; A setting means for setting a light amount fluctuation period of the display as a period of interest; a determining means for determining the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response as a variable, the time of the response function being changed in accordance with the period of interest set by the setting means; a digital filter processing means for performing digital filtering on the continuous data of the stimulus value intensity received by the receiving means using a response function whose time has been determined by the determining means, to generate data on which the visual stimulus response is superimposed; A data processing device comprising:

14. a receiving means for receiving continuous data of the stimulus value intensity obtained by receiving light from the display and continuously acquiring the intensity corresponding to the stimulus value at a constant time interval; a digital filter processing means for performing digital filtering on the continuous data of the stimulus value intensity received by the receiving means using a response function that represents an impulse response characteristic corresponding to a visual stimulus response, to generate data on which the visual stimulus response is superimposed; Equipped with a data processing device that determines a time of the response function used in digital filter processing in accordance with a period of interest that corresponds to a period of variation in the amount of light of the display;

15. 15. The data processing apparatus according to claim 13, wherein the time of the response function is an integer multiple of the period of interest.

16. 15. The data processing apparatus according to claim 13, wherein the unit time of either the time resolution of the response function or the acquisition period of the stimulus value is converted.

17. 15. The data processing apparatus according to claim 13, wherein the cycle for acquiring the stimulus value is changed in accordance with the cycle of interest.

18. The response function is generated by inverse Fourier transform from the frequency characteristics of the eye, 15. The data processing device according to claim 13, wherein the frequency characteristics of the eye are adjusted in frequency resolution and data number so as to have a desired time before inverse Fourier transform.

19. a receiving step of receiving continuous data of stimulus value intensity obtained by receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at a constant time interval; A setting step of setting a light amount fluctuation period of the display as a period of interest; a determining step of changing and determining the time of a response function representing an impulse response characteristic corresponding to a visual stimulus response in accordance with the period of interest set in the setting step, the time of the response function being a variable; a digital filter processing step of performing digital filter processing on the continuous data of the stimulus value intensity received in the receiving step using the response function whose time has been determined in the determining step, to generate data on which the visual stimulus response is superimposed; A program for causing a computer to execute the following.

20. a receiving step of receiving continuous data of stimulus value intensity obtained by receiving light from a display and continuously acquiring an intensity corresponding to a stimulus value at a constant time interval; a digital filter processing step of performing digital filtering on the continuous data of the stimulus value intensity received by the receiving step using a response function that represents an impulse response characteristic corresponding to a visual stimulus response, to generate data on which the visual stimulus response is superimposed; on the computer, A program for causing the computer to execute a process of determining a time of the response function used in digital filter processing in accordance with a period of interest that is a period of variation in the amount of light of the display.

21. 21. The program according to claim 19, wherein the time of the response function is an integer multiple of the period of interest.

22. 21. The program according to claim 19, which causes the computer to execute a process of converting a unit time of either a time resolution of the response function or an acquisition period of the stimulus value.

23. 21. The program according to claim 19, causing the computer to execute a process of setting the acquisition period of the stimulus value as a variable and changing the acquisition period of the stimulus value in accordance with the period of interest.

24. The response function is generated by inverse Fourier transform from the frequency characteristics of the eye, 21. The program according to claim 19, wherein the frequency characteristics of the eye are adjusted in frequency resolution and data number so as to have a desired time before inverse Fourier transform.