KR20230003205A - Optical waveform measuring device and measuring method - Google Patents

Abstract

Detection means 13 for detecting a candidate for the light quantity fluctuation frequency of the measurement object 100, frequency determination means 14 for determining a light quantity fluctuation frequency based on the detected light quantity fluctuation frequency candidate, and the determined light quantity fluctuation frequency Based on this, measurement condition determination means 15 for determining measurement conditions for optical waveform measurement and acquisition means 16 for acquiring the optical waveform of the measurement target under the determined measurement conditions are provided. The measurement condition determination means 15 determines the sampling frequency and measurement points at which the measurement time is an integer multiple of the cycle of the light amount fluctuation frequency determined by the frequency determination means 14.

Description

Optical waveform measuring device and measuring method

This invention relates to an optical waveform measurement device and measurement method for measuring the optical waveform of a measurement object such as a display.

In general, a display of a personal computer or the like updates an image at the cycle of the vertical synchronizing signal (Vsync), so that the screen has luminance fluctuations at the cycle of the vertical synchronizing signal. In addition, when the display is a liquid crystal display device (LCD), since inversion driving in which the polarity is switched between odd frames and even frames is employed, the luminance fluctuation cycle of the screen becomes twice as low frequency.

As an optical measuring instrument for measuring the basic performance of such a display, for example, a display color analyzer (CA-410 manufactured by Konica Minolta Co., Ltd. as an example) is known. Such a display color analyzer has an optical sensor inside and can measure not only color and luminance, but also light waveform and flicker.

There are broadly two types of methods for acquisition of light quantity: a sequential acquisition method for obtaining an instantaneous value, and an integral acquisition method for acquiring an integral value for a determined time. The sequential acquisition method is characterized by excellent high-speed performance, while the integration method is excellent in low luminance measurement performance.

In addition, as a means for realizing the characteristics of the acquired waveform, there is a frequency filter process. In the filter process, a desired weight is given to the acquired waveform for each frequency component constituting the waveform. For example, in the case of a low pass filter (LPF), a high pass frequency is attenuated with respect to a signal frequency. Accordingly, high-frequency noise can be reduced, and a smooth signal waveform can be reproduced. As another example, when a temporal contrast sensitivity function (TCSF) is used for a filter, a waveform corresponding to human visual characteristics can be reproduced.

In a conventional optical waveform measuring device, a waveform of a measurement period prepared in advance in a system is acquired, or a user inputs measurement points and a waveform of a time period corresponding to the points is acquired.

Discrete Fourier transform (DFT) processing is performed on the acquired waveform, and the acquired waveform is converted into a frequency spectrum. A filter having an arbitrary frequency characteristic is reflected on the obtained frequency spectrum. Specifically, weighting is performed by multiplying for each frequency. By performing an inverse Fourier transform (IDFT) on the weighted frequency spectrum, a filtered waveform is obtained.

Further, fast Fourier transform is known as an algorithm for reducing the arithmetic processing of discrete Fourier transform and inverse Fourier transform. Fast Fourier Transform has a limitation that the number of data can only handle powers of 2 (number of data = 2d). The number of measurement points at the time of waveform acquisition is often multiplied by a power of 2 in order to reduce the computational load of discrete Fourier transform and inverse Fourier transform.

Further, Patent Literature 1 discloses a technique for determining a measurement time value by performing high-speed scanning in an optical measuring device (spectrometer) having an array detector, and enabling synchronization of temporally discontinuous illumination light sources.

US Patent Publication No. 2005-0103979

Here, if the measurement time does not match the cycle of the light emission waveform (for example, the Vsync period) (when it is not an integer multiple), the light quantity values at the front end and the rear end of the obtained waveform do not match. Therefore, many frequency components related to the measurement time are generated in the frequency spectrum. The frequency component related to the measurement time is 1/measurement time x n, that is, the frequency and its harmonics that make the measurement time one cycle.

If filter processing is performed on this frequency spectrum, the waveform after filter processing (inverse Fourier transform after weighting) has a problem that the front end and rear end of the waveform are greatly distorted.

As a countermeasure for this, a method of deleting the leading and trailing ends of the waveform after filtering is known. However, in this method, data loss occurs, so there is a possibility that time domain information necessary for trigger measurement or the like cannot be obtained. There is, but the convenience is not good.

As another countermeasure, a method of using a window function that sets data ends to the same value is disclosed. In this method, the acquisition waveform is multiplied by a window function, and discrete Fourier transform is performed on it. After that, the waveform subjected to weighting and inverse Fourier transformation is divided by a window function, and a waveform after filtering is created.

However, even in this method, a problem arises in that the waveform is greatly distorted because the error in measurement expands when the window function is divided.

In addition, Patent Literature 1 does not have a description of optical waveform measurement or a description of the above problems related to optical waveform measurement, and therefore, even if Patent Literature 1 is referred to, the above problems cannot be solved.

This invention was made in view of such a technical background, and an object of the present invention is to provide an optical waveform measuring device and measuring method capable of reducing distortion of a waveform after filtering.

The above object is achieved by the following means.

(1) detecting means for detecting a candidate for the frequency of light quantity fluctuation of the object to be measured; frequency determining means for determining a frequency for fluctuation in the quantity of light based on the candidate for the frequency for fluctuating light quantity detected by the detecting means; a measurement condition determining means for determining a measurement condition for optical waveform measurement based on a light amount fluctuation frequency, and acquisition means for acquiring an optical waveform of a measurement target under the measurement condition determined by the measurement condition determining means, wherein the measurement wherein the condition determination means determines the sampling frequency and measurement points at which the measurement time is an integer multiple of the cycle of the light quantity fluctuation frequency determined by the frequency determination means.

(2) The detecting means acquires waveform data of light quantity fluctuation by preliminary measurement before measuring the light waveform, and acquires frequency spectrum data by performing Fourier transform processing on the waveform data, and in the frequency spectrum data, intensities are adjacent to each other. The optical waveform measuring device according to the preceding item 1, which detects a candidate for the light quantity fluctuation frequency based on a frequency serving as a singularity larger than the frequency.

(3) The optical waveform measuring device according to 1 or 2 above, wherein the frequency determining unit determines the candidate for the minimum frequency among the candidates for the light quantity variation frequency as the light quantity variation frequency.

(4) a selection unit capable of allowing a user to select one of the light quantity variation frequency candidates detected by the detection unit, wherein the frequency determination unit sets the candidate selected by the user by the selection unit as the light quantity variation frequency; The optical waveform measuring device according to item 1 or item 2 to be determined.

(5) An input unit capable of inputting a light quantity variation frequency by a user is provided, and the frequency determination unit includes a candidate closest to the light quantity variation frequency input by the input unit, among the light quantity variation frequency candidates detected by the detecting unit. The optical waveform measuring device according to the preceding paragraph 1 or 2, which determines as the light amount fluctuation frequency.

(6) The detecting unit detects a candidate for the light quantity fluctuation frequency by complementation using an intensity of a frequency adjacent to a frequency that is a singularity having an intensity greater than an adjacent frequency in the frequency spectrum data, instrumentation.

(7) The detection unit acquires waveform data of light quantity fluctuation by preliminary measurement before optical waveform measurement, and detects a candidate for the light quantity fluctuation frequency by an autocorrelation method for the waveform data. Device.

(8) The optical waveform measuring device according to any one of 1 to 7 above, wherein the wave number of the optical waveform acquired by the acquisition unit changes according to the light amount fluctuation frequency.

(9) Filter processing means for filtering the optical waveform acquired by the acquisition means is provided, the measured points are m times the number of powers of 2 (m is an integer), and the measured points are different before and after the filter processing from 1 to 1 above. The optical waveform measuring device according to any one of item 8 above.

(10) The optical waveform measuring device according to 9 above, wherein the optical waveform before filtering by the filter processing means is averaged in units of m units and then filtered.

(11) a detection step in which the detection means detects a candidate for the light quantity fluctuation frequency of the measurement object, and a frequency determination step in which the frequency determination means determines the light quantity fluctuation frequency based on the light quantity fluctuation frequency candidate detected in the detection step; A determination step in which the measurement condition determination means determines the measurement conditions for optical waveform measurement based on the light amount fluctuation frequency determined in the frequency determination step, and the optical waveform of the measurement target is acquired under the measurement conditions determined in the measurement condition determination step. and an acquisition step for determining a sampling frequency and measurement points at which a measurement time is an integer multiple of a period of a light amount fluctuation frequency determined in the frequency determination step, in the measurement condition determining step.

(12) In the detecting step, waveform data of light quantity fluctuation is obtained by preliminary measurement before optical waveform measurement, and frequency spectrum data is acquired by performing Fourier transform processing on the waveform data, and in the frequency spectrum data, intensities are adjacent to each other. The optical waveform measuring method according to the preceding item 11, wherein a candidate for the light quantity fluctuation frequency is detected based on a frequency serving as a singularity greater than the frequency.

(13) The optical waveform measurement method according to 11 or 12 above, wherein, in the frequency determining step, the candidate for the minimum frequency among the candidates for the light quantity variation frequency is determined as the light quantity variation frequency.

(14) The optical waveform measurement method according to 11 or 12 above, wherein, in the frequency determination step, the candidate selected by the user by the selection means is determined as the light quantity variation frequency among the light quantity variation frequency candidates detected in the detection step.

(15) In the frequency determining step, according to the preceding item 11 or 12, among the candidates for the light quantity variation frequency detected by the detection step, the candidate closest to the light quantity variation frequency input by the user through the input means is determined as the light quantity variation frequency. The optical waveform measurement method described.

(16) In the detection step, the light waveform according to the preceding item 12 for detecting a candidate for the light amount fluctuation frequency by complementation using the intensity of a frequency adjacent to a frequency that is a singularity having an intensity greater than an adjacent frequency in the frequency spectrum data. instrumentation method.

(17) In the detection step, the optical waveform measurement described in the preceding item 11, in which waveform data of light quantity fluctuation is obtained by preliminary measurement before optical waveform measurement, and a candidate for light quantity fluctuation frequency is detected by an autocorrelation method for the waveform data. Way.

(18) The optical waveform measurement method according to any one of 11 to 17 above, wherein the wave number of the optical waveform acquired in the acquisition step changes according to the light amount fluctuation frequency.

(19) A filter processing step for filtering the optical waveform acquired in the acquisition step, wherein the measured points are m times the number of powers of 2 (m is an integer), and the measured points are different before and after the filter processing from the preceding items 11 to 11 The optical waveform measurement method according to any one of the preceding items 18.

(20) The optical waveform measuring method according to the above item 19, wherein the optical waveforms before the filtering in the filtering step are averaged in m units and then filtered.

According to the invention described in the preceding paragraphs (1) and (11), while detecting a candidate for the light quantity fluctuation frequency of the measurement object, determining the light quantity fluctuation frequency based on the detected candidate, and measuring the light quantity fluctuation frequency based on the determined light quantity fluctuation frequency. Since time determines the sampling frequency and the number of measurement points that are integer multiples of the period of the light quantity fluctuation frequency determined above, distortion-free waveforms can be obtained even if any frequency filter processing is performed, and the frequency to be measured is not known. Even if not, errors can be minimized.

In addition, a flicker index based on the IEC standard (Project No. 62341-6-3, 5.2.1 Flicker https://webstore.iec.ch/publication/31171) can be accurately and easily derived. In short, in the IEC standard, the flicker value is a value obtained by calculating (maximum value - minimum value)/average value for a waveform filtered by TCSF. However, in order to derive this flicker value, an accurate filtered waveform is required. In addition, since a light amount fluctuation period is required for derivation of the average value, it can be easily derived by using the present invention.

According to the inventions described in the preceding items (2) and (12), waveform data of light quantity fluctuation is obtained by preliminary measurement before optical waveform measurement, and frequency spectrum data is obtained by performing Fourier transform processing on the waveform data, and in the frequency spectrum data , Since a candidate for the light quantity fluctuation frequency is detected based on a frequency that becomes a singularity having a greater intensity than the adjacent frequency, it is possible to detect a candidate corresponding to the actual light quantity fluctuation frequency of the measurement object, and furthermore, a light quantity fluctuation frequency with high accuracy. can decide

According to the inventions described in the preceding paragraphs (3) and (13), since the candidate for the minimum frequency among candidates for the light quantity fluctuation frequency is determined as the light quantity fluctuation frequency, the light quantity fluctuation frequency can be easily extracted.

According to the inventions described in the preceding paragraphs (4) and (14), since the candidate selected by the user among the detected light quantity variation frequency candidates is determined as the light quantity variation frequency, the light waveform of the frequency of interest to the user can be measured with high precision. there is.

According to the inventions described in the preceding paragraphs (5) and (15), among the detected light quantity variation frequency candidates, the candidate closest to the light quantity variation frequency input by the user is determined as the light quantity variation frequency, so that the user is interested in the vicinity of the frequency. The optical waveform of can be measured with high precision.

According to the inventions described in the preceding paragraphs (6) and (16), candidates for light quantity fluctuation frequencies are detected by supplementing using the intensity of a frequency that is a singularity whose intensity is greater than that of an adjacent frequency in frequency spectrum data and an adjacent frequency. , it is possible to determine the light intensity fluctuation frequency with high precision.

According to the inventions described in the preceding paragraphs (7) and (17), waveform data of light quantity fluctuation is obtained by preliminary measurement before light waveform measurement, and candidates for light quantity fluctuation frequencies are detected by the autocorrelation method for this waveform data. , the preliminary measurement time can be shortened.

According to the inventions described in the preceding items (8) and (18), since the wave number of the acquired light waveform changes according to the light amount fluctuation frequency, waveform distortion can be reduced and period matching error can be reduced.

According to the inventions described in the preceding items (9) and (19), since the measurement points are m times the number of powers of 2 (m is an integer), and the measurement points are different before and after the filter process, an increase in wave number can be avoided.

According to the inventions described in the preceding paragraphs (10) and (20), since the filter processing is performed after averaging the light waveforms before the filter processing in units of m, noise of the waveform after the filter processing can be reduced.

1 is a block diagram showing the functional configuration of an optical waveform measuring device according to an embodiment of the present invention.
Fig. 2 is a flow chart showing a process for detecting a candidate for a light quantity fluctuation frequency and determining a light quantity fluctuation frequency.
3 is a diagram showing an example of spectral data that is a result of spectral analysis of acquired waveform data.
4 is a diagram for explaining one method of determining measurement conditions.
5 is a diagram for explaining another method of determining measurement conditions.
Fig. 6 shows waveforms after filtering, where (A) is a conventional waveform and (B) is a waveform in the present embodiment.
Fig. 7 is a diagram showing a display screen in the case of displaying a candidate list of light amount fluctuation frequencies on a display unit and allowing the user to make a selection.
Fig. 8 is a diagram showing a display screen in the case where a user inputs a design value of a light amount fluctuation frequency.
Fig. 9 is a configuration diagram showing another embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described based on drawing.

1 is a block diagram showing the functional configuration of an optical waveform measurement device 1 according to an embodiment of the present invention.

As shown in FIG. 1 , the optical waveform measurement device 1 includes a light receiving unit 11, a data processing unit 12, a candidate detection unit 13, a frequency determination unit 14, a measurement condition determination unit 15 ), an optical waveform acquisition unit 16, a filter processing unit 17, a display unit 18, and the like.

The light receiving unit 11 receives light from a measurement target 100 such as a display and is provided with a light receiving sensor. The data processing unit 12 performs predetermined processing such as amplification on the light-received data from the light-receiving unit 11 . The candidate detection unit 13 detects a candidate for the light quantity variation frequency based on the light reception data processed by the data processing unit 12, and the frequency determination unit 14 determines the light quantity variation frequency from among the detected candidates.

The measurement condition determination unit 15 determines the sampling frequency and measurement points based on the light amount fluctuation frequency determined by the frequency determination unit 14. In this embodiment, the sampling frequency at which the measurement time becomes an integer multiple of the period of the determined light amount fluctuation frequency and the number of measurement points are determined.

The optical waveform acquisition unit 16 acquires an optical waveform with the sampling frequency and measurement points determined by the measurement condition determination unit 15, the filter processing unit 17 filters the acquired optical waveform, and the display unit 18 filters the acquired light waveform. The measurement results after processing are displayed.

Next, the operation of the optical waveform measurement device 1 will be described.

When the user sets the optical waveform measurement device 1 at the measurement position and instructs the measurement start by depressing the measurement start button displayed on the display unit 18 or the like, the light receiving unit 11 transmits data from the measurement target 100 such as the display. Receive measurement light. The received light is input to the candidate detection unit 13 after predetermined data processing such as amplification is performed in the data processing unit 12.

The candidate detection unit 13 detects candidates for the light quantity variation frequencies of the measurement target 100 (hereinafter also referred to as candidate frequencies), and the frequency determination unit 14 determines the light quantity variation frequencies from the detected candidate frequencies.

An example of the process of detecting the candidate frequency and determining the light amount fluctuation frequency is shown in the flowchart of FIG. 2 . In this embodiment, as an example of a method of detecting candidate frequencies, a method of detecting candidate frequencies based on waveform data of light amount fluctuation obtained by preliminary measurement is used. A frequency equal to or higher than the threshold may be used as a candidate frequency.

In the flow chart of FIG. 2 , when the process is started in step S01, light from the measurement target 100 is received by preliminary measurement (pre-measurement), and waveform data of light amount fluctuation is acquired (step S02). Next, candidate frequencies are extracted (detected) (step S03). Specifically, spectrum analysis is performed on the previously acquired waveform data (step S31). In order to shorten the preliminary measurement time, the frequency resolution may be set sparsely in the spectrum analysis in the preliminary measurement.

Fig. 3 shows an example of spectrum data as a result of spectrum analysis. In the example of FIG. 3, a case in which the frequency resolution is set to 2 Hz is exemplified. In addition, in the example of FIG. 2, 14 Hz and 16 Hz, 30 Hz and 32 Hz, 46 Hz and 48 Hz, and 60 Hz and 62 Hz of the spectrum data are frequencies whose intensity is greater than adjacent frequencies, that is, singularities. It is considered that the actual candidate frequency at which the intensity peaks in the vicinity of the singularity exists.

After returning to the flow chart of FIG. 2 and extracting the singularity as shown in the spectrum data of FIG. 3 (step S32), the frequency is detailed by complementary processing using the strength of the frequency adjacent to the frequency serving as the singularity (step S32). S33). The detailing of the frequency by supplementation is not limited, but may be carried out by, for example, center of gravity detection.

By refinement of the frequency, the frequency at which the intensity actually peaks is obtained, and the frequency obtained is listed as a candidate frequency. Candidate frequencies include the fundamental wave and its harmonics.

Next, a light amount change frequency is determined from among the listed light amount change frequency candidates (step S04). As an example of a specific determination method, the minimum frequency among the candidates is determined as the light amount change frequency (step S41), and the process of detecting the candidate frequency and determining the light amount change frequency is ended (step S05).

Thus, in this embodiment, waveform data of light amount fluctuation is acquired by pre-measurement (preliminary measurement) before optical waveform measurement, frequency spectrum data is obtained by Fourier transform processing of the waveform data, and in the frequency spectrum data, intensity Since a candidate for the light quantity fluctuation frequency is detected based on a frequency that becomes a singularity greater than the adjacent frequency, it is possible to detect a candidate corresponding to the actual light quantity fluctuation frequency of the measurement object, and further to determine the light quantity fluctuation frequency with high precision. can In addition, when the candidate of the minimum frequency is determined as the light quantity variation frequency among the light quantity variation frequency candidates, the light quantity variation frequency can be easily extracted.

Based on the thus determined light quantity fluctuation frequency, the measurement condition determination section 15 determines the sampling frequency and measurement points.

The relational expression of the measurement conditions to be satisfied is shown in [Equation 1] below.

[Equation 1]

Measurement time T = measurement points c/sampling frequency fs ≒ wave number n/light intensity fluctuation frequency fv

(However, n and c are natural numbers)

As the measurement conditions, the wave number n, the measurement point c, and the sampling frequency fs are determined so as to maximally satisfy the relationship represented by [Equation 1] above. In short, determine the sampling frequency fs and measurement points c at which the measurement time T becomes an integer multiple (n/fv) of the period of the light amount fluctuation frequency fv.

The error of the period matching degree (= c/fs - n/fv) is preferably less than 1/10 of the period of the light amount change due to the reproducibility (distortion amount) of the waveform after filtering, and it is adapted to a smooth waveform with a small amount of noise. Considering that, it is more preferable to set it to 1/30 or less. Determination of each parameter can be realized by having a lookup table in the system.

An example of measurement condition determination in the successive acquisition method for obtaining an instantaneous value regarding the acquisition of light quantity is shown below. As for the sequential sampling frequency fs, the frequency that can be selected is determined by the system. For the fs, as shown on the left side of FIG. 4, n and c satisfying the above [Equation 1] are selected. Since the sequential method can realize high-speed sampling, generally fs >> fv, so the measurement point c tends to become large.

^[ Select wavenumbers n, m, and d that satisfy Equation 1]. By adding not only the conventional condition m = 1 but also m ≥ 2 to the condition, the degree of freedom of the selectable wavenumber n is increased. If only the conventional condition m = 1, since fs ≥ fv, the wave number n or the measurement point c satisfying the above [Equation 1] becomes a very large value. As a result, an increase in measurement time and an increase in computational load occur, and the advantages of fast Fourier transform cannot be obtained.

The reason why fast Fourier transform is established when m ≠ 1 is described later in “Filter processing function”. Since the m value means the rate of reduction of the effective sampling frequency for the waveform after filtering, a smaller value is preferable (described later in "Filter processing function"). For example, in the case where the system upper limit frequency is 2700 Hz,

Light quantity fluctuation frequency fv: 30 Hz → wave number n: 16, measurement points c: 14336 (m = 7, d = 11), sampling frequency fs: 2700 Hz

Light intensity fluctuation frequency fv: 24 Hz → wave number n: 11, measurement points c: 12288 (m = 3, d = 12), sampling frequency fs: 27000 Hz

becomes

An example of measurement condition determination in an integration method for obtaining an integral value of time determined for acquisition of light quantity is shown below. Although it is difficult to speed up the sampling frequency fs of the integration method, the frequency setting is generally highly flexible and can be arbitrarily set. Therefore, as the measurement condition, as shown in the left part of FIG. 5, c and fs that satisfy the above [Equation 1] are selected for the reference wavenumber n.

When fast Fourier transform is used for calculation, the measurement point c is c = m × 2 ^d (m, d: natural number), and as shown in the right part of FIG. 5, the above [Equation 1 ] to select n, m, d that satisfy Here, the value of m is preferably set to m = 1 for the following reasons.

・In the case of the integration method, since there is a degree of freedom in fs, the lengthening of the measurement time does not occur easily even in m = 1

・When m ≥ 2, the effective sampling frequency of the waveform after filtering is lower than that of the acquired waveform (described later in "Filter processing function")

The wave number n is changed depending on the light amount fluctuation frequency in order to maintain a high fs near the upper limit of the system. By changing the wave number n according to the frequency of light quantity fluctuation, it is possible to reduce waveform distortion and reduce periodic matching error.

An example of measurement conditions is shown below. For example, in the case where the system upper limit frequency is 2700 Hz,

Light intensity fluctuation frequency fv: 30 Hz → wave number n: 12, measurement points c: 1024 (m = 1, d = 10), sampling frequency fs: 2560 Hz

Light intensity fluctuation frequency fv: 24 Hz → wave number n: 18, measurement points c: 2048 (m = 1, d = 11), sampling frequency fs: 2731.667 Hz

Under the measurement conditions determined in this way, an optical waveform is acquired. Since the measurement of the light waveform is carried out in a conventional manner, detailed explanations are omitted.

After acquisition of the optical waveform, the filter processing unit 17 performs filter processing on the acquired optical waveform. In the case of processing by ordinary Discrete Fourier Transform (DFT) or Inverse Fourier Transform (IDFT), and in the case of m = 1 by Fast Fourier Transform, the filter processing is the same as before.

Fast Fourier transform and filter processing in the case of m ≥ 2 will be described below. That is, preprocessing is required for the acquired waveform prior to fast Fourier transform processing. In the preprocessing, measurement data (array of c pieces) is averaged every m pieces from the head data or thinned, and the number of data is compressed to 1/m pieces. Fast Fourier transform (DFT) processing, weighting, and inverse fast Fourier transform (IDFT) processing are performed on these ^2d pieces of compressed data to generate a waveform after filtering.

The above-described compression of the number of data is equivalent to setting the effective sampling frequency fs of the waveform after filtering to 1/m with respect to the acquired waveform. Therefore, the value of m needs to be small enough not to affect the reproducibility of the waveform after filtering. However, since fs ≥ fv in the case of the sequential type, the effect of the value of m on the reproduction of the waveform is low. By compressing the number of data to 1/m in this way, the measurement score is different before and after the filter process, and an increase in the number of waves can be avoided. In addition, since the waveform before the filtering process is averaged in units of m before the filtering process is performed, the noise of the waveform after the filtering process can be reduced.

The waveform after the filtering process is shown in FIG. 6 . (A) in the figure is a conventional waveform, and (B) is a waveform in the present embodiment. In the present embodiment, since the measurement conditions are set to match the light amount fluctuation frequency, distortion is suppressed especially at the front end and the rear end of the waveform compared to the conventional example.

Thus, in this embodiment, a candidate for the light quantity variation frequency of the measurement target 100 is detected, a light quantity variation frequency is determined based on the detected candidate, and the measurement time is determined based on the determined light quantity variation frequency. Since the sampling frequency and the number of measurement points that are integer multiples of the cycle of the light intensity fluctuation frequency are determined, distortion-free waveforms can be acquired even if any frequency filter processing is performed, and even if the frequency to be measured is not already known, errors can be minimized. In addition, a flicker index based on the IEC standard can be accurately and easily derived. In short, in the IEC standard, the flicker value is a value obtained by calculating (maximum value - minimum value)/average value for a waveform filtered by TCSF. However, in order to derive this flicker value, an accurate filtered waveform is required. In addition, since a light amount fluctuation period is required for derivation of the average value, it can be easily derived by using the present invention.

In the above-described embodiment, an example in which the candidate of the minimum frequency is determined as the light quantity variation frequency among a plurality of candidate frequencies has been shown, but the method of determining the light quantity variation frequency is not limited to this. In particular, when a user such as a designer of a display measures a light waveform for confirmation, it is considered that the user is aware of the light amount fluctuation frequency.

For this reason, as shown in Fig. 7, a list of detected candidate frequencies may be displayed on the display unit 18 together with a message such as "Please select a frequency", and the user may select a desired candidate. In the example of Fig. 7, four candidate frequencies are displayed, indicating that the checked candidate frequency of 15.36 Hz is selected. When one of the candidate frequencies is selected, the selected candidate frequency is determined as the light quantity variation frequency.

In this way, by allowing the user to select a candidate and determining the candidate frequency selected by the user as the light quantity fluctuation frequency, the light waveform of the frequency of interest to the user can be measured with high precision.

In addition, a singular point shown in the spectral data of FIG. 3 obtained as a result of spectrum analysis in preliminary measurement may be displayed as a candidate frequency, and the user may select it. In this case, the light quantity variation frequency closest to the selected singularity is determined as the light quantity variation frequency that is the basis for determining the frequency resolution. However, it is preferable that the candidate list to be displayed is a list of candidate frequencies after refinement by supplementation in that accurate candidate frequencies can be displayed.

Alternatively, instead of displaying a list of candidate frequencies, as shown in FIG. 8, the input box 18a is displayed along with a message such as "Please select a frequency" and the user directly inputs the design value of the light quantity fluctuation frequency. do. In this case, among the candidate frequencies, a candidate frequency closest to the input frequency is determined as the light quantity variation frequency. In this way, even when the user inputs the light quantity variation frequency and the candidate frequency closest to the input light quantity variation frequency is determined as the light quantity variation frequency, the light waveform near the frequency of interest to the user can be measured with high precision. There is an effect.

Further, in the above embodiment, waveform data of light quantity fluctuation is obtained by preliminary measurement before optical waveform measurement, and frequency spectrum data is acquired by performing Fourier transform processing on the obtained waveform data, and in the frequency spectrum data, the intensity is an adjacent frequency. Although an example of detecting a candidate frequency based on a frequency serving as a larger singularity has been described, other methods may be used for detecting the candidate frequency.

For example, the fluctuation period (frequency) may be directly obtained by obtaining waveform data of light amount fluctuation by preliminary measurement before measuring the optical waveform and analyzing the acquired waveform data. An example thereof is an autocorrelation method for waveform data. This autocorrelation method is a method of extracting periodicity of data and detecting a candidate frequency by calculating a correlation coefficient between waveform data of light quantity fluctuation and data shifted in time from the waveform data. As another method, a period extraction method using feature points of waveform data by an image analysis technique may be used.

The detection of the light amount fluctuation frequency by analyzing the waveform data has the effect of shortening the preliminary measurement time, but increases the computational load.

As mentioned above, although one embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the candidate detector 13 may be configured using a function of a conventional optical waveform measurement device that obtains frequency spectrum data by performing Fourier transform processing on waveform data of light quantity fluctuations, or a dedicated circuit for detecting candidates is separately provided. It may be constituted by forming.

In addition, as shown in FIG. 9 , the optical waveform measurement device may be constituted by the personal computer 200 . In this case, the personal computer 200 obtains the light reception data of the measurement target 100 from the conventional optical waveform measuring device 300, thereby detecting candidate frequencies, determining the light amount fluctuation frequency, determining measurement conditions, and the like. You can do it.

Further, the optical waveform measurement step does not need to be continuously performed with the frequency detection step, the frequency determination step, and the measurement condition determination step. For example, the frequency detection step, the frequency determination step, and the measurement condition determination step may be performed first to obtain measurement condition data, and then only light measurement may be performed using the acquired measurement conditions.

In addition, the determined measurement conditions may be recorded and saved in the optical waveform measuring device or an external recording device (for example, a personal computer) connected to the optical waveform measuring device. By recording and saving the measurement conditions, when the optical waveform measurement is needed again, it is possible to omit the processes of detecting the light quantity fluctuation frequency candidate, determining the light quantity fluctuation frequency, and determining the measurement conditions. time can be shortened.

This application accompanies the claim of priority of Japanese Patent Application No. 2020-095517 of the Japanese patent application for which it applied on June 1, 2020, The content of the disclosure constitutes a part of this application as it is.

The present invention can be used when measuring the light waveform of a measurement object such as a display.

1: Optical waveform measurement device
11: light receiving unit
13: candidate detection unit
14: frequency determining unit
15: measurement condition determining unit
16: filter processing unit
17: optical waveform acquisition unit
18: display
100: measurement object
200: personal computer

Claims (20)

detection means for detecting a candidate for a frequency of light quantity fluctuation of a measurement object;
frequency determination means for determining a light quantity variation frequency based on the light quantity variation frequency candidate detected by the detection means;
measurement condition determination means for determining a measurement condition for optical waveform measurement based on the light amount fluctuation frequency determined by the frequency determination means;
Acquisition means for acquiring the optical waveform of the measurement target under the measurement conditions determined by the measurement condition determination means;
to provide,
wherein the measurement condition determination means determines the sampling frequency and measurement points at which the measurement time is an integer multiple of the cycle of the light amount fluctuation frequency determined by the frequency determination means. According to claim 1,
The detecting means is
Acquiring waveform data of light amount fluctuation by preliminary measurement before optical waveform measurement,
obtaining frequency spectrum data by performing Fourier transform processing on the waveform data;
In the frequency spectrum data, the optical waveform measurement device detects a candidate for the light amount fluctuation frequency based on a frequency that becomes a singularity having an intensity greater than an adjacent frequency. According to claim 1 or 2,
The optical waveform measurement device according to claim 1 , wherein the frequency determining means determines a candidate of the smallest frequency among the candidates for the light quantity variation frequency as the light quantity variation frequency. According to claim 1 or 2,
a selection unit capable of allowing a user to select one of the candidates for the light amount fluctuation frequency detected by the detection unit;
wherein the frequency determination means determines the candidate selected by the user by the selection means as the light quantity fluctuation frequency. According to claim 1 or 2,
An input means through which a user can input a light quantity variation frequency;
wherein the frequency determination unit determines, as the light quantity variation frequency, a candidate closest to the light quantity variation frequency input by the input unit, among the light quantity variation frequency candidates detected by the detection unit. According to claim 2,
The optical waveform measurement device according to claim 1, wherein the detecting means detects a candidate for the light amount fluctuation frequency by complementation using an intensity of a frequency adjacent to a frequency that is a singularity having an intensity greater than an adjacent frequency in the frequency spectrum data. According to claim 1,
The detecting means is
Acquiring waveform data of light amount fluctuation by preliminary measurement before optical waveform measurement,
An optical waveform measuring device that detects a candidate for a light amount fluctuation frequency by an autocorrelation method for the waveform data. According to any one of claims 1 to 7,
The wave number of the light waveform acquired by the acquisition unit changes according to the light amount fluctuation frequency. According to any one of claims 1 to 8,
a filter processing means for filtering the optical waveform acquired by the acquisition means;
wherein the measurement points are m times the number of powers of 2 (m is an integer), and the measurement points are different before and after filter processing. According to claim 9,
The optical waveform measuring device, wherein the filter processing is performed after averaging the optical waveforms before filtering by the filter processing unit in units of m units. a detection step in which the detection means detects a candidate for the frequency of light quantity fluctuation of the measurement object;
a frequency determination step in which a frequency determination means determines a light quantity variation frequency based on the light quantity variation frequency candidate detected in the detection step;
a determination step in which measurement condition determination means determines measurement conditions for optical waveform measurement based on the light amount fluctuation frequency determined by the frequency determination step;
an acquisition step of acquiring an optical waveform of a measurement target under the measurement conditions determined by the measurement condition determination step;
to provide,
In the measurement condition determining step, the sampling frequency and measurement points are determined such that the measurement time is an integer multiple of the period of the light amount fluctuation frequency determined by the frequency determining step. According to claim 11,
In the detection step,
Acquiring waveform data of light amount fluctuation by preliminary measurement before optical waveform measurement,
obtaining frequency spectrum data by performing Fourier transform processing on the waveform data;
In the frequency spectrum data, a candidate for a light amount fluctuation frequency is detected based on a frequency that becomes a singularity having an intensity greater than an adjacent frequency. According to claim 11 or 12,
In the frequency determining step, the candidate for the minimum frequency among the candidates for the light quantity variation frequency is determined as the light quantity variation frequency. According to claim 11 or 12,
In the frequency determination step, a candidate selected by the user by the selection means is determined as the light quantity variation frequency among the light quantity variation frequency candidates detected in the detection step. According to claim 11 or 12,
In the frequency determination step, among the candidates for the light quantity variation frequency detected in the detection step, a candidate closest to the light quantity variation frequency input by the user through the input means is determined as the light quantity variation frequency. According to claim 12,
In the detection step, a candidate for a light amount fluctuation frequency is detected by complementation using an intensity of a frequency adjacent to a frequency that is a singularity having an intensity greater than an adjacent frequency in the frequency spectrum data. According to claim 11,
In the detection step,
Acquiring waveform data of light amount fluctuation by preliminary measurement before optical waveform measurement,
An optical waveform measuring method comprising detecting a candidate for a light amount fluctuation frequency by an autocorrelation method for the waveform data. According to any one of claims 11 to 17,
The optical waveform measuring method according to claim 1 , wherein the wavenumber of the optical waveform acquired in the acquisition step changes according to the light amount fluctuation frequency. According to any one of claims 11 to 18,
a filter processing step of filtering the optical waveform acquired by the acquisition step;
wherein the measurement points are m times the number of powers of 2 (m is an integer), and the measurement points are different before and after filter processing. According to claim 19,
An optical waveform measurement method of averaging the optical waveforms before filtering by the filter processing step in m units and then filtering them.

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