Measuring device, measuring method, and program

Abstract

To provide a measurement device capable of estimating, a change of an object whose change is not constant, on the basis of a speckle pattern, in a condition in which, a time interval of measurement is restricted.SOLUTION: A measurement device comprises: a radiation part for generating coherent light; a measurement part for receiving by a plurality of pixels, light of a speckle pattern which is generated by interference of diffuse light which is generated by reception of the coherent light on a scatterer, then detecting a pixel whose luminance change amount indicating a change of a luminance value detected by receiving the light of the speckle pattern by each pixel, is a predetermined detection object luminance change amount, then, generating event data including; a position of the detected pixel; a code value indicating a change direction of the luminance change amount of the pixel; and a detection time indicating a time when detection is performed; and a calculation processing part for calculating a physical amount indicating a change of the scatterer, on the basis of the event data.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a measuring device, a measuring method, and a program for measuring changes in a speckle pattern, for example.

Background Art

[0002] When coherent light such as laser light is irradiated onto an object having fine irregularities on its reflecting surface or an object causing internal scattering, scattered light is generated from the object in response to the coherent light, and a pattern resulting from the interference of the generated scattered light can be observed. This pattern is called a speckle pattern, and at each point of the speckle pattern, light and dark occur due to the constructive and destructive interference caused by the superposition of a plurality of scattered lights.

[0003] When the phase difference of the scattered light changes with the deformation or movement of the object, the speckle pattern also changes. Therefore, by measuring the temporal change of the speckle pattern, it is possible to estimate the temporal change of the fine shape of the object, the temporal change of the movement amount, and the like. The measurement method using the speckle pattern is used in various applications such as medical sensors such as blood flow meters and speed meters for machine control in addition to material measurement. For example, in a laser Doppler blood flow meter, a light receiving intensity signal is detected by a light receiving element from the light of a speckle pattern generated by the interference between the light scattered by red blood cells moving in a blood vessel and the light scattered by stationary living tissue when laser light is irradiated from above the skin. The speed of the red blood cells passing through the blood vessel is calculated from the frequency of the detected light receiving intensity signal, and the blood flow rate and pulse are estimated from the calculated speed of the red blood cells.

[0004] By taking a photograph with an image sensor such as a CCD (Charge Coupled Device), a speckle pattern can be observed two-dimensionally. However, when photographing a scatterer with a very high frequency of the received light intensity signal like the above-mentioned speckle pattern of blood flow, an image sensor with a high frame rate corresponding to the high frequency is required. Generally, image sensors have a problem that the higher the frame rate and the higher the resolution, the higher the price. High-frame-rate image sensors and high-resolution image sensors have a problem that they are strongly affected by noise due to insufficient light quantity.

[0005] For example, in the technique disclosed in Non-Patent Document 1, that is, in a blood flow meter using the laser speckle blood flow imaging method, by using a measurement method of a speckle pattern using an image sensor with a general frame rate, the problems regarding the price and noise of the above-mentioned image sensor are solved. In a blood flow meter using the laser speckle blood flow imaging method, the image data obtained by the image sensor indicates the result of integrating the received light intensity signal within the exposure time for each pixel. Since the frequency of the received light intensity signal in real time becomes higher as the blood flow velocity is faster, there is a tendency that the variation of the integrated value becomes smaller. In a blood flow meter using the laser speckle blood flow imaging method, this tendency is utilized to acquire image data multiple times and compare them, and based on the comparison result, it is possible to obtain the blood flow volume according to the amount of variation between the image data.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when measuring a speckle pattern using an image sensor with a general frame rate, as in the technology disclosed in Non-Patent Document 1 above, when measuring an object whose frequency of the light reception intensity signal is high, such as the blood flow described above, multiple continuous measurements are required. Therefore, there is a problem that it is difficult to perform measurement under conditions where there are restrictions on the time interval of measurement, such as so-called real-time measurement. When using an image sensor with a general frame rate, since multiple continuous measurements are required, there is a problem that it is difficult to perform accurate measurement when the ratio of changes occurring in the object to be measured is not a constant ratio.

[0008] In view of the above circumstances, an object of the present invention is to provide a technology capable of estimating changes in an object with non-constant changes based on a speckle pattern under conditions where there are restrictions on the time interval of measurement.

Means for Solving the Problems

[0009] One aspect of the present invention is a measuring device including: an irradiation unit that generates coherent light; a measuring unit that receives light of a speckle pattern generated by interference of scattered light generated when a scatterer receives the coherent light with a plurality of pixels, and detects a pixel having a luminance change amount indicating a change in luminance value for each of the pixels receiving the light of the speckle pattern, and generates event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the detected time; and a calculation processing unit that calculates a physical quantity indicating a change in the scatterer based on the event data.

[0010] One aspect of the present invention is to generate coherent light, receive the light of the speckle pattern generated by the interference of the scattered light generated when the scatterer receives the coherent light by a plurality of pixels, and each of the pixels receives the light of the speckle pattern and detects the change in the luminance value indicating the change in the detected luminance amount is a measurement method for detecting a pixel having a luminance change amount of a detection target determined in advance, generating event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the detected time, and calculating a physical quantity indicating the change of the scatterer based on the generated event data.

[0011] One aspect of the present invention is to receive the light of the speckle pattern generated by the interference of the scattered light generated when the scatterer receives the coherent light by a plurality of pixels, and each of the pixels receives the light of the speckle pattern and detects the change in the luminance value indicating the change in the detected luminance amount is a measurement step for detecting a pixel having a luminance change amount of a detection target determined in advance, generating event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the detected time, and a calculation processing step for calculating a physical quantity indicating the change of the scatterer based on the event data, which is a program for causing a computer to execute.

Advantages of the Invention

[0012] According to the present invention, it becomes possible to estimate the change of an object whose change is not constant based on the speckle pattern under the condition that there is a restriction on the time interval of measurement.

Brief Description of the Drawings

[0013]

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Embodiments for Carrying Out the Invention

[0014] (First Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a measuring device 1 in the first embodiment and a scatterer 30 that is the measurement target of the measuring device 1. The scatterer 30 includes a moving scatterer 31 that moves in part, and can be any object as long as it is an object that receives coherent light and generates scattered light. For example, the scatterer 30 is a human body, and the moving scatterer 31 is blood flowing in the blood vessels of the human body.

[0015] The measurement device 1 includes an irradiation unit 11, a measurement unit 12, and a calculation processing unit 13. The irradiation unit 11 includes a light source that generates laser light which is coherent light, and the light source generates the laser light at a constant light intensity. The irradiation unit 11 diffusely scatters the generated laser light in a planar shape by an optical element provided therein, and irradiates the scattered laser light 40 onto the scatterer 30. Here, the optical element provided inside the irradiation unit 11 may be any optical element as long as it can diffuse the laser light. For example, it may be a convex lens disposed at a position where the laser light generated by the light source is diffused.

[0016] In FIG. 1, the scattered light 50 indicates the scattered light generated when the portion of the scatterer 30 excluding the moving scatterer 31, that is, the stationary portion, receives the laser light 40, and the scattered light 51 indicates the scattered light generated when the moving scatterer 31 receives the laser light 40. When the moving scatterer 31 is not moving, the scattered light 51 will be included in the scattered light 50. In this case, a speckle pattern will be generated due to the interference of the scattered light 50. On the other hand, when the moving scatterer 31 is moving, the scattered light 51 is generated, and a change will occur in the speckle pattern due to the interference between the scattered light 50 and the scattered light 51.

[0017] The measurement unit 12 is, for example, an event camera equipped with an event-based vision sensor, and includes a light receiving unit 21 and an event detection unit 23. The light receiving unit 21 is arranged at a position where it can receive the light of the speckle pattern generated by the interference of the scattered lights 50 and 51. The light receiving unit 21 includes, for example, a plurality of pixels 22-1 to 22-n arranged in a rectangular shape to form the light receiving surface of the light receiving unit 21. Here, n can be any value as long as it is an integer of 2 or more. For a general event camera, n is a value in the range of tens of thousands to hundreds of thousands. In FIG. 1, as an example, an example where n = 54, that is, an example where the light receiving unit 21 includes 54 pixels 22-1 to 22-54 arranged in 6 rows and 9 columns is shown, and the first and the last pixels among them are respectively labeled with the symbols "22-1" and "22-n". When each of the pixels 22-1 to 22-n receives the light of the speckle pattern generated by the interference of the scattered lights 50 and 51, it outputs a luminance value indicating the intensity of the light of the speckle pattern measured at each position. Hereinafter, when indicating any one of the pixels 22-1 to 22-n, the pixel is referred to as pixel 22 without indicating the branch number of the symbol.

[0018] The event detection unit 23 asynchronously detects the amount of luminance change indicating the change in the luminance value output by each of the pixels 22-1 to 22-n. The event detection unit 23 further generates event data including the position of the detected pixel 22, a symbol value indicating the change direction of the amount of luminance change, and a detection time indicating the detected time when it detects a pixel 22 having a predetermined amount of luminance change of the detection target among the detected amounts of luminance change. Here, the position of the pixel 22 is, for example, a position indicated by coordinate data represented by the row and column positions with the position of the pixel 22-1 as the origin, that is, (0,0). The position of the pixel one row below the same column of the pixel 22-1 is indicated as coordinate data (1,0), and the position of the pixel one column to the right of the same row of the pixel 22-1 is indicated as coordinate data (0,1). The symbol value indicating the change direction of the amount of luminance change is, for example, a value that becomes "+1" when the luminance value changes from a small value to a large value, and becomes "-1" when the luminance value changes from a large value to a small value.

[0019] Here, the relationship between the amount of luminance change detected by the event detection unit 23 and the light reception intensity signal that causes a change in the speckle pattern will be described. The light reception intensity signal is a signal obtained by arranging in time series the light intensity values of the light of the speckle pattern measured at a certain position. There is a relationship that as the change in the speckle pattern increases, the frequency of the light reception intensity signal also increases. The luminance values detected by each of the pixels 22-1 to 22-n indicate the intensity of the light of the speckle pattern measured at each position. By arranging the luminance values detected by each in time series, the light reception intensity signals of the speckle pattern measured at each position of the pixels 22-1 to 22-n can be obtained. Here, let the light reception intensity signal measured at a certain one pixel 22 be I(t) (where in I(t), t is the time, and I(t) is the luminance value detected by the pixel 22 at time t). For example, if the luminance value detected by the pixel 22 at time t1 is I(t1), and the luminance value detected by the pixel 22 at time t2, which is the detection time immediately after time t1, is I(t2), the event detection unit 23 will detect, at time t2, the amount of luminance change log(I(t2)) - log(I(t1)) represented by the difference in the logarithmic values of the luminance values. Here, the base of log(·) is "e", and hereinafter, when referring to "logarithm", it is assumed to be the natural logarithm with the base "e". The event detection unit 23 detects the sign of the result of the calculation of log(I(t2)) - log(I(t1)) as the sign of the sign value. Hereinafter, when generalizing the formula for the amount of luminance change log(I(t2)) - log(I(t1)) and showing the amount of luminance change at time t by a formula, it is shown by the formula Δ(log(I(t)).

[0020] Based on the event data output by the event detection unit 23, the calculation processing unit 13 calculates a physical quantity indicating the change of the scatterer 30. Hereinafter, four methods for calculating the moving speed of the moving scatterer 31 included in the scatterer 30 as the physical quantity indicating the change of the scatterer 30 will be described.

[0021] (The First Method by the Measuring Apparatus of the First Embodiment) While referring to FIG. 2, a first method by the measuring device 1 in the first embodiment will be described. FIG. 2 is a flowchart showing the flow of the first method by the calculation processing unit 13. It is assumed that the following is done as a premise for starting the processing of the flowchart in FIG. 2. The irradiation unit 11 is installed at a fixed position and direction, and irradiates the measurement region with the laser beam 40. Here, the measurement region is, for example, the region of the scatterer 30 where the moving scatterer 31 exists. The light receiving unit 21 of the measurement unit 12 receives the light of the speckle pattern generated by the interference of the scattered lights 50 and 51 by the pixels 22-1 to 22-n.

[0022] The event detection unit 23 asynchronously detects the amount of luminance change indicating the change in the luminance value output from each of the pixels 22-1 to 22-n. The event detection unit 23 pre-stores a predetermined detection threshold value in an internal storage area. When detecting the amount of luminance change, the event detection unit 23 refers to the internal storage area and determines whether the detected amount of luminance change is equal to or greater than the detection threshold value. When the event detection unit 23 determines that the detected amount of luminance change is equal to or greater than the predetermined detection threshold value, the event detection unit 23 detects the pixel 22 corresponding to the amount of luminance change as a pixel having the predetermined detection target amount of luminance change. The event detection unit 23 generates event data for the detected pixel 22, that is, event data including the position of the pixel 22, a sign value indicating the change direction of the amount of luminance change, and the detection time, and outputs the generated event data to the calculation processing unit 13.

[0023] As described above, when the moving scatterer 31 included in the scatterer 30 is not moving, all of the scatterer 30 is in a stationary state. In this case, since the scattered light 51 is included in the scattered light 50, only the scattered light 50 is generated. The irradiation unit 11 irradiates the laser light 40 with a constant light intensity in a certain direction as described above. That is, the laser light 40 irradiated by the irradiation unit 11 does not change even as time passes. Therefore, the speckle pattern generated by the interference of the scattered light 50 also does not change even as time passes. In this case, since the luminance values output by each of the pixels 22-1 to 22-n by receiving the light of the speckle pattern do not change, the event detection unit 23 detects a luminance change amount of "0" from any of the pixels 22-1 to 22-n. However, in reality, since noise and the like exist, the luminance change amount detected by the event detection unit 23 may not become "0", but does not exceed the detection threshold. Therefore, in this case, the event detection unit 23 does not output event data.

[0024] On the other hand, when the moving scatterer 31 included in the scatterer 30 is moving, the speckle pattern changes due to the interference between the scattered light 50 generated when the stationary portion other than the moving scatterer 31 of the scatterer 30 receives the laser light 40 and the scattered light 51 generated when the moving scatterer 31 receives the laser light 40. When the speckle pattern changes, the luminance values detected by the pixels 22-1 to 22-n corresponding to the position where the change in the speckle pattern occurs change. When the event detection unit 23 detects a luminance change amount from the luminance values output by the pixels 22-1 to 22-n, and determines that the detected luminance change amount is a luminance change amount equal to or greater than a predetermined detection threshold, the event detection unit 23 generates and outputs event data regarding the pixel 22 corresponding to the luminance change amount.

[0025] The processing flow will be described below according to the flowchart of FIG. 2. The calculation processing unit 13 captures the event data asynchronously output by the event detection unit 23 (step Sa1). The calculation processing unit 13 counts the number of event data per unit time for each of the pixels 22-1 to 22-n based on the position of the pixel 22 included in each of the event data and the detection time (step Sa2).

[0026] When the moving speed of the moving scatterer 31 increases, the change in the speckle pattern becomes larger. When the change in the speckle pattern becomes larger, the frequency of the received light intensity signal becomes higher. When the frequency of the received light intensity signal becomes higher, the number of event data per unit time also increases. Therefore, a large number of event data per unit time indicates that the moving speed of the moving scatterer 31 is fast, and the relative moving speed of the moving scatterer 31 can be indicated by the amount of event data.

[0027] The position of each of the pixels 22-1 to 22-n can be associated with any position of the scatterer 30. The calculation processing unit 13 outputs the number of event data per unit time for each of the pixels 22-1 to 22-n as a value indicating the relative moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n (step Sa3).

[0028] (Second Method by the Measuring Device of the First Embodiment) With reference to FIGS. 3 and 4, the second method by the measuring device 1 in the first embodiment will be described. When the second method is performed, a detection threshold value identical to the detection threshold value stored in the internal storage area of the event detection unit 23 is stored in advance in the internal storage area of the calculation processing unit 13.

[0029] FIG. 3 is a flowchart showing the flow of the second method by the calculation processing unit 13. Note that the premise for starting the processing of the flowchart in FIG. 3 is the same as the premise of the above-described first method. The calculation processing unit 13 captures the event data asynchronously output by the event detection unit 23 (step Sb1). The calculation processing unit 13 multiplies the code value included in the captured event data by the detection threshold value stored in the internal storage area to calculate a multiplication value for each event data (step Sb2). For each of the pixels 22-1 to 22-n, the calculation processing unit 13 integrates the multiplication values corresponding to the detection times before the current detection time for each detection time, and calculates an integrated value for each detection time (step Sb3).

[0030] For example, the calculation processing unit 13 calculates the integrated value for each detection time of each of the pixels 22-1 to 22-n as follows. In the calculation processing unit 13, an integration start time is determined in advance. The calculation processing unit 13 sequentially captures the event data of a certain pixel 22 whose detection time is after the integration start time. Here, assume that the detection times included in the plurality of event data of the pixel 22 sequentially captured by the calculation processing unit 13 are t1, t2,... in order from the earliest time. However, t1, t2,... are times after the integration start time.

[0031] When the calculation processing unit 13 captures the event data at the detection time t1 of the pixel 22, it calculates the multiplication value corresponding to the detection time t1 by the process of step Sb2. Since there is no multiplication value corresponding to the detection time before the detection time t1 and after the integration start time, the calculation processing unit 13 uses the calculated multiplication value corresponding to the detection time t1 as the integration value at the detection time t1 of the pixel 22. Next, when the calculation processing unit 13 captures the event data at the detection time t2 of the pixel 22, it calculates the multiplication value corresponding to the detection time t2 by the process of step Sb2. The calculation processing unit 13 adds the calculated multiplication value corresponding to the detection time t2 to the integration value at the detection time t1 of the pixel 22, and uses the added value as the integration value at the detection time t2 of the pixel 22. In this way, every time the calculation processing unit 13 captures the event data of the pixel 22, it repeats adding the multiplication value corresponding to the detection time included in the captured event data to the integration value at the previous detection time, and calculates the integration value for each detection time of the pixel 22. The calculation processing unit 13 performs the same operation for all pixels 22-1 to 22-n, and calculates the integration value for each detection time of each of the pixels 22-1 to 22-n.

[0032] FIG. 4 is a diagram showing an example of the integration value for each detection time of a certain pixel 22 calculated by the calculation processing unit 13 in the form of a bar graph. In the bar graph shown in FIG. 4, the horizontal axis represents the detection time, and the vertical axis represents the integration value calculated by the calculation processing unit 13. Since the event data output by the event detection unit 23 is asynchronous, the intervals of the detection times in the bar graph are not at regular intervals. Since the integration value is obtained by adding a value obtained by multiplying the detection threshold by the signed value of "-1" or "+1", it becomes a quantization value with the magnitude of the detection threshold as the step width. In this case, the change in the bar graph shown in FIG. 4 includes an error corresponding to the quantization by the magnitude of the detection threshold, but it can be regarded as the temporal change when the luminance change amount Δ(log(I(t))) at the pixel 22 is integrated in the time direction, that is, log(I(t)) measured at the position of the pixel 22.

[0033] The calculation processing unit 13 calculates each received light intensity signal I(t) from log(I(t)) for each of the pixels 22-1 to 22-n. The calculation processing unit 13 calculates the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n from the frequency of the received light intensity signal I(t) calculated for each of the pixels 22-1 to 22-n, for example, by the method using a laser Doppler blood flowmeter shown in the following Reference 1 (step Sb4).

[0034] [Reference 1: K.K. Kousei, Optimedia, "38·7 Laser Speckle Blood Flow Imaging Method", [online], [searched on August 18, 2021], Internet <https: / / optipedia.info / laser / handbook / laser-handbook-9th-section / 38-7 / >]

[0035] That is, the calculation processing unit 13 of the second method calculates a multiplication value by multiplying a sign value indicating the change direction of the amount of luminance change included in the event data by a detection threshold value. For each of the pixels 22-1 to 22-n, the calculation processing unit 13 calculates, for each detection time, a value obtained by integrating the multiplication values corresponding to the detection times before the current detection time as an integrated value for each detection time. Based on the calculated integrated values for each detection time of each of the pixels 22-1 to 22-n, the calculation processing unit 13 performs a process of calculating the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n.

[0036] The moving speed calculated by the calculation processing unit 13 by the above-described second method is a relative moving speed, which is the same as that of the first method. However, in the case of the first method, if there is variation in the amount of event data generated at each detection time due to external factors such as noise, detection delay depending on the light amount of the laser light 40, and bandwidth shortage in the light receiving unit 21 and the event detection unit 23 when a large amount of event data is generated at one time, variation will also occur in the calculated moving speed. In contrast, in the second method, an integrated value obtained by integrating in the time direction a multiplication value obtained by multiplying a sign value by a detection threshold is calculated, and a light reception intensity signal I(t) corresponding to each of the pixels 22-1 to 22-n is calculated. Therefore, in the second method, a relative moving speed with reduced influence of the above-described external factors can be calculated.

[0037] Note that the calculation processing unit 13 may perform filtering processing on the bar graph of the integrated values for each detection time of the pixel 22 shown in FIG. 4 to generate a curve indicated by the sign 100, and regard the change of the generated curve as log(I(t)) measured at the position of the pixel 22. Thereby, it is possible to reduce the error due to quantization and calculate the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n.

[0038] (The Third Method by the Measuring Apparatus of the First Embodiment) With reference to FIGS. 5 and 6, the third method by the measuring apparatus 1 in the first embodiment will be described. When the third method is performed, the value of the detection threshold stored in advance in the internal storage area of the event detection unit 23 is determined in advance as follows. The event detection unit 23 detects in advance the maximum value and the minimum value from the luminance values detected when each of the pixels 22-1 to 22-n of the light receiving unit 21 receives the light of the speckle pattern. The event detection unit 23 calculates the absolute value of the difference between the maximum value and the minimum value of the luminance values detected in advance, and stores the calculated absolute value of the difference in the internal storage area in advance as the detection threshold.

[0039] FIG. 5 is a graph showing an example of the change in the luminance value detected when a certain pixel 22 receives the light of the speckle pattern. The horizontal axis represents time, and the vertical axis represents the luminance value. The magnitude of the detection threshold is the length from the maximum value to the minimum value of the luminance value indicated by reference numeral 110. In this case, the event detection unit 23 generates event data for the pixel 22 because the amount of luminance change detected from the pixel 22 is equal to or greater than the detection threshold at the time of the peak of reference numeral 121 where the luminance value changes from the maximum value to the minimum value and at the time of the peak of reference numeral 122 where the luminance value changes from the minimum value to the maximum value.

[0040] The peak of reference numeral 121 indicates the state where the interference of the scattered lights 50 and 51 is weakest, and the peak of reference numeral 122 indicates the state where the interference of the scattered lights 50 and 51 is strongest. Therefore, the occurrence interval between the peak of reference numeral 121 and the peak of reference numeral 122 indicates the frequency of the received light intensity signal I(t) measured at the position of the pixel 22. Note that the graph of FIG. 5 is an example shown to explain in what cases event data is generated when the absolute value of the difference between the maximum value and the minimum value of the luminance value is used as the detection threshold. The graph of the actual speckle pattern light becomes a graph in which light and dark patterns appear periodically.

[0041] FIG. 6 is a flowchart showing the flow of the third method by the calculation processing unit 13. Note that the premise for starting the processing of the flowchart in FIG. 6 is the same as the premise of the above-described first method. The calculation processing unit 13 captures the event data asynchronously output by the event detection unit 23 (step Sc1). The calculation processing unit 13 measures the generation interval of the event data for each of the pixels 22-1 to 22-n from the detection time of the captured event data (step Sc2). The calculation processing unit 13 calculates the frequency of the light reception intensity signal I(t) corresponding to each of the pixels 22-1 to 22-n based on the measured generation interval of the event data for each of the pixels 22-1 to 22-n (step Sc3). The calculation processing unit 13 calculates and outputs the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n from the frequency of the light reception intensity signal I(t) corresponding to each of the pixels 22-1 to 22-n, for example, by the method using the laser Doppler blood flow meter shown in the above-mentioned reference 1 (step Sc4).

[0042] That is, the calculation processing unit 13 of the third method calculates the generation interval of the event data for each of the pixels 22-1 to 22-n based on the detection time included in the event data. The calculation processing unit 13 calculates the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n based on the calculated generation interval of the event data for each of the pixels 22-1 to 22-n.

[0043] In the third method, event data is generated only when the received light intensity signal I(t) reaches its peak as described above. Therefore, the frequency of the received light intensity signal I(t) can be directly calculated from the interval between the occurrences of event data. As a result, it is not necessary to count the number of event data as in the first method or obtain an integrated value as in the second method, and it becomes possible to calculate the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n with a smaller amount of calculation than the first and second methods. In the third method, since the frequency of the received light intensity signal I(t) measured at each position of the pixels 22-1 to 22-n is calculated, the absolute moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n can be calculated instead of calculating the relative moving speed as in the first method or the second method.

[0044] Note that in the above-described third method, it is assumed that there is no variation in each of the maximum value and the minimum value of the luminance values detected by each of the pixels 22-1 to 22-n, and the absolute value of the difference between the maximum value and the minimum value among the luminance values detected by each of the pixels 22-1 to 22-n receiving the light of the speckle pattern is used as a common detection threshold for all the pixels 22-1 to 22-n. On the other hand, when there is variation in each of the maximum value and the minimum value of the luminance values detected by each of the pixels 22-1 to 22-n, the event detection unit 23 may detect the maximum value and the minimum value of the luminance values in advance for each of the pixels 22-1 to 22-n, and use the absolute value of the difference between the maximum value and the minimum value of the luminance values corresponding to each of the pixels 22-1 to 22-n as an individual detection threshold for each of the pixels 22-1 to 22-n.

[0045] (Fourth Method by the Measuring Apparatus of the First Embodiment) While referring to Fig. 7, a fourth method by the measuring device 1 in the first embodiment will be described. The fourth method is assumed to be applicable when the area of the moving scatterer 31 included in the scatterer 30 is sufficiently large. When the area of the moving scatterer 31 included in the scatterer 30 is sufficiently large, the light of the speckle pattern in the portion where the pattern has changed due to the interference of the scattered lights 50 and 51 can be received by many pixels 22-1 to 22-n of the light receiving unit 21. In this case, from the event data detected by the event detection unit 23, an image indicating the intensity of the light of the speckle pattern measured at the positions of the light receiving surface of the light receiving unit 21, that is, the pixels 22-1 to 22-n, is generated for each detection time, and by comparing the images at two different detection times, the temporal change of the speckle pattern can be detected.

[0046] Fig. 7 is a flowchart showing the flow of the fourth method by the calculation processing unit 13. Note that the premise for starting the processing of the flowchart in Fig. 7 is the same as the premise of the above-described first method. The calculation processing unit 13 captures the event data asynchronously output by the event detection unit 23 (step Sd1). For each of the pixels 22-1 to 22-n, the calculation processing unit 13 integrates the code values corresponding to the detection times before the current detection time for each detection time, and calculates the integrated value for each detection time (step Sd2). Note that in the fourth method, the procedure for the calculation processing unit 13 to integrate the code values is the same as the procedure for integrating the multiplication values in the second method, except that the integration target changes from the multiplication value to the code value.

[0047] The calculation processing unit 13 generates image data for each detection time by using, as pixel values, the integrated values for each of the calculated pixels 22-1 to 22-n (step Sd3). In the second method, the integrated value is a value obtained by integrating the multiplication value obtained by multiplying the sign value by the detection threshold, and the change in the integrated value for each detection time of each of the pixels 22-1 to 22-n is regarded as log(I(t)) obtained by integrating Δlog(I(t)) in each of the pixels 22-1 to 22-n. On the other hand, the integrated value for each detection time of each of the pixels 22-1 to 22-n calculated by the fourth method indicates the degree of light intensity of the speckle pattern. Therefore, in step Sd3, the image represented by the image data at the detection time t generated by the calculation processing unit 13 is an image indicating the degree of light intensity of the speckle pattern at the detection time t.

[0048] The calculation processing unit 13 calculates the cross-correlation between the image data at two different arbitrarily selected detection times (step Sd4). If a peak occurs in the cross-correlation calculated by the calculation processing unit 13, the position where the peak occurs indicates the amount of movement of the speckle pattern between the two different detection times. The calculation processing unit 13 divides the position of the peak obtained by the cross-correlation, that is, the amount of movement of the speckle pattern, by the time difference between the two different detection times to calculate the speed of the speckle pattern, that is, the overall speed of the moving scatterer 31 (step Sd5).

[0049] That is, the calculation processing unit 13 of the fourth method calculates, for each of the pixels 22-1 to 22-n, as the pixel value of the pixels 22-1 to 22-n for each detection time, the value obtained by integrating the sign values included in the event data corresponding to the detection times before the current detection time for each detection time. The calculation processing unit 13 generates image data for each detection time based on the calculated pixel values, and calculates the moving speed of the moving scatterer 31 based on the generated image data at two different detection times.

[0050] In the above-described fourth method, the amount of movement of the speckle pattern is calculated by calculating the cross-correlation of the image data at two different detection times. However, the amount of movement of the speckle pattern may be calculated by a method other than cross-correlation, for example, pattern matching.

[0051] In the above-described fourth method, in step Sd2, the calculation processing unit 13 integrates the code values corresponding to the detection times before the current detection time for each of the pixels 22-1 to 22-n for each detection time, and calculates the integrated value for each detection time. On the other hand, the calculation processing unit 13 may generate image data having the code values of the event data corresponding to each of the pixels 22-1 to 22-n for each detection time as pixel values. In this case, the calculation processing unit 13 generates image data with the pixel values of the pixels 22-1 to 22-n for which there is no event data corresponding to the detection time for which the image data is to be generated set to "0". Therefore, the pixel values of the image data generated by the calculation processing unit 13 are either "-1", "0", or "+1".

[0052] Since the image represented by the image data generated by the calculation processing unit 13 does not perform integration as in the above-described fourth method, although the difference in intensity is not as distinct as the image data generated by the fourth method, it is an image showing the degree of light intensity of the speckle pattern at the detection time. Therefore, the calculation processing unit 13 can calculate the amount of movement of the speckle pattern by comparing the image data at two different detection times. Note that the comparison method for the image data at two different detection times may be the cross-correlation used in the above-described fourth method, or a method other than cross-correlation, for example, pattern matching. The calculation processing unit 13 can calculate the speed of the speckle pattern, that is, the overall speed of the moving scatterer 31, by dividing the calculated amount of movement by the time difference between the two different detection times.

[0053] In the measuring device 1 of the first embodiment described above, the irradiation unit 11 generates coherent light. The measuring unit 12 receives the light of the speckle pattern generated by the interference of the scattered lights 50 and 51 generated when the scatterer 30 receives the coherent light, by a plurality of pixels 22-1 to 22-n, and detects pixels 22-1 to 22-n having a luminance change amount of a detection target, which is a predetermined luminance change amount indicating a change in the luminance value detected by each of the pixels 22-1 to 22-n receiving the light of the speckle pattern. The event data including the positions of the detected pixels 22-1 to 22-n, the sign value indicating the change direction of the luminance change amount of the pixels 22-1 to 22-n, and the detection time indicating the time of detection is generated. The calculation processing unit 13 calculates the velocity of the movement of the position of the moving scatterer 31 corresponding to each of the pixels 22-1 to 22-n, or the moving velocity of the moving scatterer 31, based on the event data generated by the measuring unit 12.

[0054] A frame camera equipped with a general image sensor outputs the luminance value integrated in each pixel for each frame. In the frame camera, the integration time, that is, the exposure time and the dynamic range of the signal are the same for all pixels. Therefore, when there are very bright pixels and very dark pixels, white blooming, black crushing, quantization error, etc. will occur. When the brightness of the scene changes drastically due to the influence of illumination or the like, white blooming and black crushing may occur without being able to adjust the exposure time.

[0055] In contrast, as described above, an event camera outputs event data asynchronously each time the amount of luminance change of each pixel exceeds a detection threshold. Therefore, problems such as blooming, black crush, and quantization error do not occur. Since the event data output by the event camera is asynchronously output data, it is very sparse data compared to the image data output by a frame camera. Therefore, the memory capacity required to store the event data can be small, and the transmission capacity required to transmit the event data can also be small. Because the event data is very sparse data, an event camera can suppress the costs such as the amount of computation and power consumption required for imaging processing and data processing to be very low compared to a frame camera.

[0056] For example, when attempting to achieve a time resolution equivalent to that of the image data output by a frame camera in event data, it is possible to achieve this with event data having a capacity much smaller than the capacity of the image data output by the frame camera. In other words, if event data with a capacity equivalent to the capacity of the image data output by the frame camera is collected, a very high time resolution can be obtained. For these reasons, by using an event camera, it is possible to perform stable, low-cost, and very high-time-resolution measurements in an environment with low light or an environment with drastic lighting changes.

[0057] In the measuring device 1 of the first embodiment, an event camera having the above advantages is applied to the measuring unit 12 as compared with a frame camera. Therefore, it is not necessary to perform continuous measurements a plurality of times as in the case of a frame camera, and in the measuring device 1, it is possible to measure the change of an object whose change is not constant based on a speckle pattern under conditions where there are restrictions on the time interval of measurement, such as so-called real-time measurement.

[0058] In the above-described first embodiment, the planar laser beam 40 diffused by the irradiation unit 11 is irradiated onto the scatterer 30. In contrast, the position of an optical element such as a convex lens provided inside the irradiation unit 11 may be adjusted so that the irradiation unit 11 irradiates a specific location on the scatterer 30 with a spot laser beam, that is, a non-diffused laser beam. As the optical element provided inside the irradiation unit 11, for example, a cylindrical lens or the like may be applied so that the irradiation unit 11 irradiates the scatterer 30 with a linear laser beam. As the irradiation unit 11, a projector including a light source that generates a laser beam may be applied so that a laser beam of an arbitrary pattern is irradiated at an arbitrary timing.

[0059] Depending on the performance of the event camera applied to the measurement unit 12, if the luminance values change in a large number of pixels 22-1 to 22-n at once, the bandwidth in the light receiving unit 21 and the event detection unit 23 may be insufficient, and not all event data can be output to the calculation processing unit 13. In such a case, the laser beam 40 irradiated by the irradiation unit 11 is made into a spot laser beam, a linear laser beam, or a laser beam of an arbitrary pattern as described above, and the range of irradiation of the laser beam 40 is narrowed, or the laser beam 40 is irradiated to another location on the scatterer 30 at different timings, thereby eliminating the bandwidth shortage in the light receiving unit 21 and the event detection unit 23.

[0060] The laser beam 40 irradiated by the irradiation unit 11 is made into a spot laser beam and adjusted to irradiate only a minute range of the scatterer 30, for example, a range corresponding to the area of the light receiving surface of one pixel 22, so that the light of the speckle pattern is measured only by one pixel 22. In this case, by performing triangulation based on the irradiation position of the irradiation unit 11 and the position of the pixel 22, the position in the three-dimensional space where the laser beam 40 is irradiated on the scatterer 30 can be calculated. Therefore, by measuring while shifting the irradiation position of the laser beam 40, the position in the three-dimensional space of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n and the moving speed of the moving scatterer 31 when the moving scatterer 31 is moving at a constant speed can be calculated.

[0061] As the irradiation unit 11, an apparatus that irradiates a raster-scan type laser such as a MEMS (Micro Electro Mechanical Systems) laser projector may be applied. In this case, the irradiation unit 11 irradiates the laser beam 40 at a single point of the scatterer 30, and changes the irradiation target of the laser beam 40 one by one so as to raster-scan the scatterer 30 with the laser beam 40. The event detection unit 23 of the measurement unit 12 is configured to generate event data only when constructive interference occurs due to the interference of the scattered lights 50 and 51. Specifically, in the event detection unit 23, the absolute value of the difference between the minimum value and the maximum value of the luminance value is set as the detection threshold, and event data is generated only when the luminance value changes from the minimum value to the maximum value and a luminance change amount equal to or greater than the detection threshold is detected. Thereby, the calculation processing unit 13 can detect the interval during which constructive interference occurs from the generation interval of the event data in each of the pixels 22-1 to 22-n. The calculation processing unit 13 can calculate the frequency of the received light intensity signal measured at each position of the pixels 22-1 to 22-n from the detected interval, and can calculate the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n. In this case, since the laser beam 40 is irradiated to only one point of the scatterer 30 at a time, the range of the pixels 22-1 to 22-n in which the change in the luminance value occurs is also limited, and a large amount of event data does not occur at once, and it is also possible to avoid processing crashes due to the generation of a large amount of event data that may occur when irradiating the laser beam 40 over a wide range at once. In addition, compared with the case of irradiating the laser beam 40 over a wide range at once, it is also possible to measure a large area with a low-power laser. Also, by arbitrarily controlling the timing of moving from one irradiation position to the next using a raster scan type laser irradiation device capable of arbitrarily controlling the scan speed, it becomes possible to match the timing of the sleep of the event sensor with the timing of the movement of the irradiation position, and to detect only the events due to the change in speckle without detecting the events generated by the movement of the irradiation position. In a general event sensor, after detecting an event at each pixel, the next event detection is performed after a certain sleep period, so the events based on the luminance change occurring during the sleep period are not detected. The sleep period and the irradiation position movement timing may be set in advance, or may be dynamically controlled using a synchronization device. Alternatively, for a similar laser irradiation device, a process of classifying the events based on the change in the irradiation position and the events due to the change in speckle may be performed in the calculation processing unit 13. For example, when changing the irradiation position every T seconds, the events occurring at the period T can be regarded as those due to the change in the irradiation position. Alternatively, for a series of event groups occurring during the irradiation period for each pixel, the events for a certain period at the beginning and the end can be regarded as those due to the change in the irradiation position.

[0062] (Second Embodiment) FIG. 8 is a block diagram showing the measuring device 1a in the second embodiment and the scatterer 32 which is the measurement target of the measuring device 1a. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and different components will be described below. The scatterer 32 in the second embodiment may be any object as long as it is an object that deforms in shape as time passes and generates scattered light when receiving coherent light.

[0063] The measurement device 1a includes an irradiation unit 11a, a measurement unit 12, a calculation processing unit 13a, an optical branching unit 14, and an optical focusing unit 15. The irradiation unit 11a is obtained by adjusting the position of the optical element provided inside the irradiation unit 11 of the first embodiment from the position where the laser light is diffused to the position where the laser light travels straight. The laser light 41 that travels straight is generated as coherent light with a constant light intensity and irradiated. The optical branching unit 14 branches the optical path from the irradiation point of the laser light 41 of the irradiation unit 11a to the light receiving surface of the light receiving unit 21 of the measurement unit 12 into two optical paths so that an optical path difference occurs. In FIG. 8, as an example, the optical branching unit 14 shows a configuration in which the laser light 41 irradiated by the irradiation unit 11a is branched so that an optical path difference occurs and the two laser lights 42 and 43 are irradiated onto the scatterer 32.

[0064] When the scatterer 32 receives the laser light 42, the scattered light 52 is irradiated in the direction of the light receiving surface of the light receiving unit 21. When the scatterer 32 receives the laser light 43, the scattered light 53 is irradiated in the direction of the light receiving surface of the light receiving unit 21. The optical focusing unit 15 focuses the two optical paths branched by the optical branching unit 14, that is, focuses the scattered light 52 and the scattered light 53, and forms an image of the speckle pattern generated by the interference of the focused scattered lights 52 and 53 on the light receiving surface of the light receiving unit 21. As the optical focusing unit 15, for example, a convex lens or the like is applied. However, as long as the speckle pattern can be imaged on the light receiving surface of the light receiving unit 21, an optical element other than the convex lens may be used.

[0065] FIG. 9 is a diagram showing the configurations of four optical systems as examples of the optical systems applied to the optical branching unit 14 and the optical focusing unit 15. It is a diagram that quotes the diagram parts of the four optical systems shown in FIGS. 31·34 of Reference 2 shown below and is labeled for the purpose of explaining the configuration of the optical system. For convenience of explanation, the order of the figures is shown reversed from FIGS. 31·34 of Reference 2.

[0066] [Reference 2: Kousei Co., Ltd., Optimedia, "31·3 Speckle", [online], [searched on August 18, 2021], Internet <https: / / optipedia.info / laser / handbook / laser-handbook-7th-section / 31-3 / >]

[0067] (Configuration of optical branching section applying two-beam method) FIG. 9(a) is an example of an optical branching section 14 that branches one laser beam 41 shown in FIG. 8 into two laser beams 42 and 43, and is an optical system called the two-beam method. In FIG. 9(a), the half mirror 61, the mirrors 62 and 64, and the convex lenses 63 and 65 are optical elements included in the optical branching section 14. In FIG. 9(a), as an example of the light focusing section 15, an example including a convex lens 15a is shown, and the same example is also shown in FIGS. 9(b) to 9(d). In FIG. 9(a), the scatterer 32 before its shape is deformed is shown as the scatterer 32-1, and the scatterer 32 after its shape is deformed is shown as the scatterer 32-2.

[0068] The positional relationship in which the convex lenses 63, 65, and 15a and the mirrors 62 and 64 are arranged is as follows. The angle formed by the optical axis 66 of the convex lens 15a and the optical axis 67 which is the direction in which the laser beam is reflected by the mirror 62 and is the optical axis of the convex lens 63 is the same as the angle formed by the optical axis 66 and the optical axis 68 which is the direction in which the laser beam is reflected by the mirror 64 and is the optical axis of the convex lens 65, and the optical axes 66, 67, and 68 are arranged so as to intersect on the surface of the scatterer 32-1 before deformation. The angle formed by the optical axes 67 and 68 is determined to be larger than the opening angle of the convex lens 15a. The convex lens 15a is arranged such that its optical axis is perpendicular to the light receiving surface of the light receiving unit 21 of the measuring unit 12, and is located between the scatterers 32-1 and 32-2 and the light receiving unit 21, and at a position where the speckle pattern is imaged on the light receiving surface of the light receiving unit 21.

[0069] The half mirror 61 and the mirrors 62 and 64 are arranged such that the laser beam 41 irradiated by the irradiation unit 11a is reflected by the half mirror 61 and reaches the mirror 62, and the laser beam 41 passes through the half mirror 61 and reaches the mirror 64. The half mirror 61 and the mirrors 62 and 64 are arranged so that an optical path difference occurs in the optical path from the irradiation point of the irradiation unit 11a to the light receiving surface of the light receiving unit 21.

[0070] By arranging as described above, the laser beam 41 irradiated by the irradiation unit 11a branches into a laser beam that is reflected by the half mirror 61 and reaches the mirror 62 and a laser beam that passes through the half mirror 61 and reaches the mirror 64. The mirror 62 reflects the received laser beam in the direction of the optical axis 67, and the reflected laser beam is diffused by the convex lens 63 and irradiated onto the scattering bodies 32-1 and 32-2. The mirror 64 reflects the received laser beam in the direction of the optical axis 68, and the reflected laser beam is diffused by the convex lens 65 and irradiated onto the scattering bodies 32-1 and 32-2. For example, the laser beam 42 irradiated by the optical branching unit 14 in FIG. 8 corresponds to the laser beam diffused by the convex lens 63, and the laser beam 43 corresponds to the laser beam diffused by the convex lens 65. Hereinafter, the laser beam diffused by the convex lens 63 is referred to as the laser beam 42, and the laser beam diffused by the convex lens 65 is referred to as the laser beam 43.

[0071] The scattered light generated when the scattering body 32-1 before deformation receives the laser beam 42 is defined as scattered light 52-1, and the scattered light generated when the scattering body 32-2 after deformation receives the laser beam 42 is defined as scattered light 52-2. Similarly, the scattered light generated when the scattering body 32-1 before deformation receives the laser beam 43 is defined as scattered light 53-1, and the scattered light generated when the scattering body 32-2 after deformation receives the laser beam 43 is defined as scattered light 53-2. The scattered lights 52-1, 52-2, 53-1, and 53-2 are condensed by the convex lens 15a and reach the light receiving surface of the light receiving unit 21.

[0072] The scattered light 52-1 and 53-1 generated from the scatterer 32-1 before deformation is light generated by laser light irradiated from two directions with an optical path difference. When the scattered light 52-1 and 53-1 interfere, a speckle pattern reflecting the phase difference caused by the optical path difference is imaged on the light receiving surface of the light receiving unit 21. Here, assume that a deformation occurs such that the surface of the scatterer 32-1 to be measured, that is, the surface irradiated with the laser light 42 and 43, moves in the direction indicated by the arrow of reference numeral 39a and becomes the scatterer 32-2. Hereinafter, such displacement due to deformation is referred to as in-plane displacement, which is a displacement parallel to the surface to be measured. The scattered light 52-2 and 53-2 of the scatterer 32-2 after deformation is also light generated by laser light irradiated from two directions with an optical path difference. When the scattered light 52-2 and 53-2 interfere, a speckle pattern reflecting the phase difference caused by the optical path difference and the amount of displacement when deforming from the scatterer 32-1 to the scatterer 32-2 is imaged on the light receiving surface of the light receiving unit 21.

[0073] (Configuration of Optical Branching Unit Applying Reference Light Method) The optical system shown in Fig. 9(b) is an optical system called the reference light method. Also in Fig. 9(b), the scatterer 32 before deformation is shown as the scatterer 32-1, and the scatterer 32 after deformation is shown as the scatterer 32-2. Also in the reference light method, the scattered light generated when the scatterer 32-1 receives laser light is defined as the scattered light 52-1, and the scattered light generated when the scatterer 32-2 receives laser light is defined as the scattered light 52-2. In the reference light method, unlike the above-described two-beam method, instead of irradiating the scatterers 32-1 and 32-2 with two laser lights, one of the laser lights is irradiated to the scatterers 32-1 and 32-2, and the other of the laser lights is irradiated as reference light to the light receiving surface of the light receiving unit 21.

[0074] In Fig. 9(b), the convex lens 71, the half mirror 72, and the mirror 73 are optical elements included in the optical branching unit 14. The mirror 73 is arranged such that the reflecting surface of the mirror 73 is perpendicular to the direction in which the laser beam 41 irradiated by the irradiation unit 11a travels straight. The half mirror 72 is arranged at a position inclined by 45 degrees with respect to the direction in which the laser beam 41 irradiated by the irradiation unit 11a travels straight. The convex lens 71 is arranged such that its optical axis coincides with the direction in which the laser beam 41 travels straight. A convex lens 15a, which is an example of the light focusing unit 15, is arranged such that its optical axis is perpendicular to the light receiving surface of the light receiving unit 21 of the measuring unit 12. The convex lens 15a is arranged at a position where a speckle pattern is imaged on the light receiving surface of the light receiving unit 21 by condensing the scattered light 52-1 and 52-2 that passes through the half mirror 72 and reaches there.

[0075] By arranging as described above, the laser beam 41 irradiated by the irradiation unit 11a is diffused by the convex lens 71, and the diffused laser beam 41 is reflected by the half mirror 72 and branches into the laser beam traveling in the direction of the scatterers 32-1 and 32-2 and the laser beam that passes through the half mirror 72 and reaches the mirror 73. Hereinafter, the laser beam that passes through the half mirror 72 and reaches the mirror 73 is referred to as the reference light. The scattered light 52-1 and 52-2 generated when the scatterers 32-1 and 32-2 receive the laser beam travel in the direction of the half mirror 72, pass through the half mirror 72, are condensed by the convex lens 15a, and reach the light receiving surface of the light receiving unit 21. On the other hand, the reference light is reflected by the mirror 73 in the direction of the half mirror 72, further reflected by the half mirror 72, travels in the direction of the convex lens 15a, is condensed by the convex lens 15a, and reaches the light receiving surface of the light receiving unit 21.

[0076] When the scattered light 52-1 and the reference light reach the light-receiving surface of the light-receiving unit 21, the scattered light 52-1 and the reference light interfere with each other, and a speckle pattern reflecting the phase difference caused by the optical path difference between the scattered light 52-1 and the reference light is formed on the light-receiving surface of the light-receiving unit 21. Here, assume that the scatterer 32-1 undergoes a deformation such that it moves in the direction indicated by the arrow of reference numeral 39b and becomes the scatterer 32-2. Hereinafter, such a displacement due to deformation is referred to as an out-of-plane displacement, which is a displacement not parallel to the surface to be measured of the scatterer 32-1, that is, the surface irradiated with the laser light reflected by the half mirror 72. After the deformation from the scatterer 32-1 to the scatterer 32-2, when the scattered light 52-2 and the reference light reach the light-receiving surface of the light-receiving unit 21, the scattered light 52-2 and the reference light interfere with each other, and a speckle pattern reflecting the phase difference caused by the optical path difference between the scattered light 52-2 and the reference light and the amount of displacement during the deformation from the scatterer 32-1 to the scatterer 32-2 is formed on the light-receiving surface of the light-receiving unit 21.

[0077] (Configuration of optical branching unit applying two-aperture method) The optical system shown in Fig. 9(c) is an optical system called the two-aperture method. Also in Fig. 9(c), the scatterer 32 before deformation is shown as the scatterer 32-1, and the scatterer 32 after deformation is shown as the scatterer 32-2. Also in the two-aperture method, the scattered light generated when the scatterer 32-1 receives the laser light is defined as the scattered light 52-1, and the scattered light generated when the scatterer 32-2 receives the laser light is defined as the scattered light 52-2. In the two-aperture method, by disposing a multi-aperture plate 82 having slits at two locations in the middle of the optical path from the irradiation point of the laser light 41 of the irradiation unit 11a to the light-receiving surface of the light-receiving unit 21 of the measurement unit 12, two optical paths with an optical path difference are generated.

[0078] The convex lens 81 and the multi-aperture plate 82 are optical elements included in the optical branching unit 14. The convex lens 81 is arranged such that its optical axis coincides with the direction in which the laser beam 41 irradiated by the irradiation unit 11a travels straight. A convex lens 15a, which is an example of the light focusing unit 15, is arranged such that its optical axis 83 is perpendicular to the light receiving surface of the light receiving unit 21 of the measurement unit 12 and the plane of the flat portion of the multi-aperture plate 82. The convex lens 15a is arranged at a position where a speckle pattern is imaged on the light receiving surface of the light receiving unit 21 by condensing the scattered light 52-1 and 52-2 that passes through the multi-aperture plate 82. The multi-aperture plate 82 is arranged such that the plane of the flat portion is parallel to the light receiving surface of the light receiving unit 21, and further arranged such that the distances from the position intersecting the optical axis 83 to each of the two slits are equal.

[0079] By arranging as described above, the laser beam 41 irradiated by the irradiation unit 11a is diffused by the convex lens 81, and the diffused laser beam 41 is irradiated onto the scatterers 32-1 and 32-2. The scattered light 52-1 and 52-2 generated when the scatterers 32-1 and 32-2 receive the diffused laser beam 41 will have an optical path difference due to diffraction when passing through the two slits of the multi-aperture plate 82. The scattered light 52-1 and 52-2 that have passed through the two slits of the multi-aperture plate 82 are condensed by the convex lens 15a and reach the light receiving surface of the light receiving unit 21.

[0080] When the scattered light 52-1 reaches the light-receiving surface of the light-receiving unit 21 through the two optical paths with an optical path difference caused by the double aperture plate 82, a speckle pattern reflecting the phase difference caused by the optical path difference is imaged on the light-receiving surface of the light-receiving unit 21. Here, assume that a deformation occurs such that the surface of the measurement target of the scatterer 32-1, that is, the surface irradiated with the laser light diffused by the convex lens 81, moves in the direction indicated by the arrow of reference numeral 39c and becomes the scatterer 32-2. That is, assume that in the scatterer 32-1, in-plane displacement similar to the two-beam method shown in FIG. 9(a) occurs. In this case, when the scattered light 52-2 reaches the light-receiving surface of the light-receiving unit 21 through the two optical paths with an optical path difference caused by the double aperture plate 82, a speckle pattern reflecting the phase difference caused by the optical path difference and the displacement amount when deforming from the scatterer 32-1 to the scatterer 32-2 is imaged on the light-receiving surface of the light-receiving unit 21.

[0081] (Configuration of optical branching unit applying lateral shift method) The optical system shown in FIG. 9(d) is an optical system called the lateral shift method. In the lateral shift method, a biprism 92 is arranged in the middle of the optical path from the irradiation point of the laser light 41 of the irradiation unit 11a to the light-receiving surface of the light-receiving unit 21 of the measurement unit 12, thereby generating two optical paths with an optical path difference. The convex lens 91 and the biprism 92 are optical elements included in the optical branching unit 14. The convex lens 91 is arranged such that its optical axis 93 coincides with the direction in which the laser light 41 irradiated by the irradiation unit 11a travels straight. The biprism 92 is a so-called compound prism, and is a prism having a triangular prism shape with an isosceles triangle cross-section having an apex angle close to 180 degrees. The biprism 92 is arranged such that the surface including the base of the isosceles triangle shape is parallel to the light-receiving surface of the light-receiving unit 21. A convex lens 15a, which is an example of the light focusing unit 15, is arranged such that its optical axis is perpendicular to the light-receiving surface of the light-receiving unit 21 of the measurement unit 12 and the surface including the base of the isosceles triangle shape of the biprism 92, and intersects the side including the apex angle of the isosceles triangle shape. The convex lens 15a is arranged at a position where the scattered lights 52-1 and 52-2 that pass through the biprism 92 and reach are focused and a speckle pattern is imaged on the light-receiving surface of the light-receiving unit 21.

[0082] By arranging as described above, the laser beam 41 irradiated by the irradiation unit 11a is diffused by the convex lens 91, and the diffused laser beam is irradiated onto the scatterer 32. The scattered light 52 generated when the scatterer 32 receives the laser beam passes through the biprism 92. When the scattered light 52 passes through the biprism 92, due to the optical action of the biprism 92, as shown in FIG. 9(d), on the surface of the measurement target irradiated with the laser beam of the scatterer 32, a double image 32D of the scatterer 32 is formed at a slightly displaced position. Here, the light that forms the double image 32D and is generated by the biprism 92 is defined as the double image light 52D. An optical path difference will occur between the scattered light 52 and the double image light 52D due to the optical action of the biprism 92. The scattered light 52 that has passed through the biprism 92 and the double image light 52D generated by the biprism 92 are condensed by the convex lens 15a and reach the light receiving surface of the light receiving unit 21.

[0083] When the scattered light 52 and the double image light 52D reach the light receiving surface of the light receiving unit 21, a speckle pattern reflecting the phase difference generated by the optical path difference will be imaged on the light receiving surface of the light receiving unit 21. Here, assume that in the scatterer 32, an out-of-plane displacement deformation as shown in the case of the reference light method in FIG. 9(b) occurs, that is, a displacement in which the scatterer 32 is not parallel to the surface of the measurement target. In this case, when the scattered light 52 and the double image light 52D reach the light receiving surface of the light receiving unit 21, a speckle pattern reflecting the phase difference generated by the optical path difference and the displacement amount due to the deformation of the scatterer 32 will be imaged on the light receiving surface of the light receiving unit 21.

[0084] By using the optical branching unit 14 to which any of the optical systems shown in FIGS. 9(a) to 9(d) is applied, the speckle pattern generated by the scatterer 32-1 before deformation and the speckle pattern generated by the scatterer 32-2 after deformation can be obtained. When the square of the difference between the two speckle patterns before and after deformation is calculated, interference fringes can be obtained. The light and dark of the obtained interference fringes depend on the displacement amount when the scatterer 32 is deformed. It becomes darkest when the displacement amount is an integer multiple of the wavelength of the laser beam 41, and becomes brightest when the displacement amount is a half-integer multiple of the wavelength of the laser beam 41. One interference fringe indicates the same displacement amount. When the surface of the scatterer 32 is continuous, the interference fringes can be regarded as contour lines with the altitude replaced by the displacement amount. Therefore, in the region where the interval of the interference fringes is fine, it indicates that the change in the displacement amount is large and the shape of the scatterer 32 changes rapidly. In the region where the interval of the interference fringes is coarse, it indicates that the change in the displacement amount is small and the shape of the scatterer 32 changes gently. In this way, by receiving the speckle pattern corresponding to the measurement region by the pixels 22-1 to 22-n of the light receiving unit 21 of the measurement unit 12 and comparing before and after the deformation of the shape of the scatterer 32, the displacement amount of the position of the scatterer 32 corresponding to each of the pixels 22-1 to 22-n generated along with the deformation of the shape of the scatterer 32 can be estimated.

[0085] (Processing by the measuring device of the second embodiment) With reference to FIG. 10, the processing by the measuring device 1a in the second embodiment will be described. FIG. 10 is a flowchart showing the flow of processing by the calculation processing unit 13a. Here, the optical system of the two-beam method shown in FIG. 9(a) is applied as the optical branching unit 14, and a convex lens 15a is applied as the light focusing unit 15. The processing by the measuring device 1a will be described.

[0086] On the premise that the processing of the flowchart in FIG. 10 is started, it is assumed that the following is done. The irradiation unit 11a generates the laser beam 41 and outputs it to the optical branching unit 14. In the optical branching unit 14, the half mirror 61 branches the laser beam 41 irradiated by the irradiation unit 11a into the laser beam reaching the mirror 62 and the laser beam reaching the mirror 64. The mirror 62 reflects the received laser beam in the direction of the optical axis 67, and the reflected laser beam is diffused by the convex lens 63 to become the laser beam 42. The mirror 64 reflects the received laser beam in the direction of the optical axis 68, and the reflected laser beam is diffused by the convex lens 65 to become the laser beam 43. The laser beam 42 and the laser beam 43 are irradiated onto the scatterer 32. The scattered light 52 generated when the scatterer 32 receives the laser beam 42 and the scattered light 53 generated when the scatterer 32 receives the laser beam 43 are condensed by the convex lens 15a. The scattered light 52 condensed by the convex lens 15a and the scattered light 53 interfere with each other, so that a speckle pattern is generated in the pixels 22-1 to 22-n on the light receiving surface of the light receiving unit 21.

[0087] When the shape of the scatterer 32 is not deformed, no change occurs in the scattered light 52 and the scattered light 53, so the speckle pattern generated in the pixels 22-1 to 22-n on the light receiving surface of the light receiving unit 21 also does not change. In this case, since the luminance values output by each of the pixels 22-1 to 22-n receiving the light of the speckle pattern do not change, the event detection unit 23 detects a luminance change amount of "0" from any of the pixels 22-1 to 22-n. However, actually, since noise and the like exist, the luminance change amount detected by the event detection unit 23 may not become "0", but does not exceed the detection threshold value. Therefore, in this case, the event detection unit 23 also does not output event data.

[0088] On the other hand, when the shape of the scatterer 32 is deformed, the scattered light 52 and the scattered light 53 will change according to the displacement amount when the shape of the scatterer 32 is deformed. Therefore, the speckle pattern will change according to the changes in the scattered light 52 and the scattered light 53. When the speckle pattern changes, the luminance values detected by the pixels 22-1 to 22-n corresponding to the position where the change in the speckle pattern occurs will change. When the event detection unit 23 detects a luminance change amount from the luminance values output by the pixels 22-1 to 22-n, and determines that the detected luminance change amount is equal to or greater than a predetermined detection threshold, the event detection unit 23 generates and outputs event data for the pixel 22 corresponding to the luminance change amount.

[0089] Hereinafter, the processing flow will be described according to the flowchart of FIG. 10. The calculation processing unit 13a captures the event data asynchronously output by the event detection unit 23 (step Se1). The calculation processing unit 13a counts the number of event data for each of the pixels 22-1 to 22-n within a predetermined time based on the position of the pixel 22 and the detection time included in each of the event data (step Se2).

[0090] The calculation processing unit 13a generates image data with the number of event data for each of the pixels 22-1 to 22-n as pixel values (step Se3). As described above, the light and dark of the interference fringes obtained by calculating the square of the difference between the two speckle patterns before and after deformation depend on the displacement amount when the shape of the scatterer 32 is deformed. The bright part of the interference fringes has a large luminance change amount before and after the deformation of the scatterer 32, so the event data increases. On the other hand, in the dark part of the interference fringes, since the luminance change amount before and after the deformation of the scatterer 32 is small, the event data decreases or there is no event data. Therefore, the image represented by the image data generated by the calculation processing unit 13a is an image showing the change in the interference fringes.

[0091] As described above, in the region where the interference fringe interval is fine, it indicates that the displacement amount is large and the scatterer 32 changes rapidly. In the region where the interference fringe interval is coarse, it indicates that the displacement amount is small and the scatterer 32 changes gently. The calculation processing unit 13a performs frequency analysis on the generated image data to calculate the fineness of the interference fringe interval at each position of the pixels 22-1 to 22-n. The calculation processing unit 13a calculates the displacement amount at the position of the scatterer 32 corresponding to each of the pixels 22-1 to 22-n from the fineness of the interference fringe interval at each position of the calculated pixels 22-1 to 22-n (step Se4).

[0092] In the cases of FIGS. 9(a) and (c), that is, when each of the two-beam method and the two-aperture method is applied, the calculation processing unit 13a calculates the displacement amount of the scatterer 32 in the directions of reference numerals 39a and 39c in FIGS. 9(a) and (c), that is, in the direction parallel to the surface of the scatterer 32 to be measured. In the case of FIG. 9(b), that is, when the reference light method is applied, the calculation processing unit 13a calculates the displacement amount of the scatterer 32 in the direction of reference numeral 39b in FIG. 9(b), that is, in the direction not parallel to the surface of the scatterer 32 to be measured. In the case of FIG. 9(d), that is, in the case of the lateral shift method, the calculation processing unit 13a calculates the inclination with respect to the direction of the displacement between the scatterer 32 and the double image 32D caused by the deformation due to the out-of-plane displacement of the scatterer 32 as the displacement amount of the scatterer 32. Therefore, when the displacement amount between the scatterer 32 and the double image 32D is sufficiently small, the displacement amount calculated by the calculation processing unit 13a indicates the differential value of the out-of-plane displacement of the scatterer 32. Which optical system among FIGS. 9(a) to (d) is applied to the optical branching unit 14 is appropriately determined according to which direction of the displacement amount of the scatterer 32 is to be detected.

[0093] In the measuring device 1a of the second embodiment described above, the irradiation unit 11a generates coherent light that irradiates the scatterer 32 whose shape is deformed. The optical branching unit 14 branches the optical path from the irradiation unit 11a to the plurality of pixels 22-1 to 22-n of the measuring unit 12 into two optical paths so that an optical path difference occurs. The light focusing unit 15 focuses the two optical paths branched by the optical branching unit 14 and forms a speckle pattern on the plurality of pixels 22-1 to 22-n included in the measuring unit 12. The measuring unit 12 receives the light of the speckle pattern generated by the interference of the scattered light 52 and 53 generated when the scatterer 32 receives the coherent light by the plurality of pixels 22-1 to 22-n, and each of the pixels 22-1 to 22-n receives the light of the speckle pattern and detects a pixel 22-1 to 22-n having a luminance change amount of a detection target whose luminance change amount indicating the change in the detected luminance value is predetermined, and outputs event data including the positions of the detected pixels 22-1 to 22-n, a sign value indicating the change direction of the luminance change amount of the pixels 22-1 to 22-n, and a detection time indicating the detected time. The calculation processing unit 13a generates image data having the number of event data for each of the pixels 22-1 to 22-n within a predetermined time as pixel values, and calculates the displacement amount generated along with the deformation of the scatterer 32 based on the generated image data.

[0094] With the above configuration, when the shape of the scatterer 32 is deformed, an optical path difference corresponding to the amount of displacement when the shape of the scatterer 32 is deformed is added in the two optical paths branched by the optical branching section 14, and a phase difference of the added optical path differences occurs. Therefore, a change corresponding to the generated phase difference appears in the speckle pattern formed by the light focusing section 15 on the plurality of pixels 22-1 to 22-n. Accordingly, by generating image data having the number of event data corresponding to each of the pixels 22-1 to 22-n as pixel values, the image of the generated image data is an image showing the change in the speckle pattern before and after the deformation of the shape of the scatterer 32 depending on the fineness of the interference fringe interval. The calculation processing unit 13a can calculate the amount of displacement when the shape of the scatterer 32 is deformed from the fineness of the interference fringe interval by performing frequency analysis on the generated image data. In the generation of image data based on the event data by the calculation processing unit 13a, since it is not necessary to acquire continuous image data a plurality of times like a frame camera, the measuring device 1a can estimate the change in an object whose change is not constant based on the speckle pattern under conditions where there is a restriction on the time interval of measurement, such as so-called real-time measurement.

[0095] In the above second embodiment, the convex lens 71 in FIG. 9(b), the convex lens 81 in FIG. 9(c), and the convex lens 91 in FIG. 9(d) are assumed to be included in the optical branching section 14. On the other hand, the optical branching section 14 may not include the convex lenses 71, 81, and 91, and the position of the optical element provided inside the irradiation section 11a may be adjusted so that the irradiation section 11a irradiates the diffused laser light.

[0096] In the above-described second embodiment, the optical branching unit 14 branches the optical path from the irradiation unit 11a to the plurality of pixels 22-1 to 22-n of the measurement unit 12 into two paths so that an optical path difference occurs, regardless of which of the optical systems shown in FIGS. 9(a) to 9(d) is applied. On the other hand, the optical branching unit 14 may branch the optical path from the irradiation unit 11a to the plurality of pixels 22-1 to 22-n of the measurement unit 12 into three or more optical paths so that an optical path difference occurs. In this case, the light focusing unit 15 focuses the three or more optical paths branched by the optical branching unit 14 and forms a speckle pattern on the pixels 22-1 to 22-n included in the measurement unit 12.

[0097] In the above-described first and second embodiments, when the event detection unit 23 determines that the amount of change in the luminance of a certain pixel 22 is equal to or greater than a predetermined detection threshold value, the event detection unit 23 detects the pixel 22 corresponding to the amount of change in luminance as a pixel 22 having a predetermined amount of change in luminance of a detection target. On the other hand, when the event detection unit 23 determines that the amount of change in the luminance of a certain pixel 22 is greater than a predetermined detection threshold value, the event detection unit 23 may detect the pixel 22 corresponding to the amount of change in luminance as a pixel 22 having a predetermined amount of change in luminance of a detection target. However, in this case, in the configuration in which the absolute value of the difference between the maximum value and the minimum value of the luminance values of the pixels 22-1 to 22-n shown in the first embodiment is used as the detection threshold value, in order to make a correct determination, the absolute value of the difference between the maximum value and the minimum value of the luminance values is not directly used as the detection threshold value, but it is necessary to use, as the detection threshold value, a value obtained by subtracting a minute value corresponding to the determination accuracy of the event detection unit 23 from the absolute value of the difference between the maximum value and the minimum value of the luminance values.

[0098] When the scatterer 30 of the measurement device 1 according to the first embodiment described above is, for example, a human body and the moving scatterer 31 is, for example, blood, it can also be said to be a measurement device for measuring blood flow, and it can also be said to be an observation device for observing blood flow. When the scatterer 32 of the measurement device 1a according to the second embodiment is, for example, a human body, it can also be said to be a measurement device for measuring a change in the shape of the human body, and it can also be said to be an observation device for observing a change in the shape of the human body.

[0099] The calculation processing units 13 and 13a in the above-described first and second embodiments may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to realize it. Here, the “computer system” shall include hardware such as an OS and peripheral devices. Further, the “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, etc., and a storage device such as a hard disk built in a computer system. Furthermore, the “computer-readable recording medium” also includes a medium that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and a volatile memory inside a computer system that becomes a server or a client in that case, which holds a program for a certain period of time. Also, the above program may be for realizing a part of the above-described functions, and may further be realized in combination with a program already recorded in the computer system for realizing the above-described functions, or may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0100] As described above, the embodiments of this invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and designs and the like within the scope not departing from the gist of this invention are also included.

Explanation of Reference Numerals

[0101] 1... Measuring device, 11... Irradiation unit, 12... Measuring unit, 13... Calculation processing unit, 21... Light receiving unit, 22-1 to 22-n... Pixels, 23... Event detection unit, 30... Scattering body, 31... Moving scattering body

Claims

1. An irradiation unit that generates coherent light; A measurement unit that receives, by a plurality of pixels, light of a speckle pattern generated by interference of scattered light generated when a human body receives the coherent light, and detects a change in a luminance value indicating a change in the luminance of each of the pixels that receives the light of the speckle pattern, and detects a pixel having a change in luminance amount of the detection target that is predetermined, and generates event data including the position of the detected pixel, a sign value indicating a change direction of the change in luminance amount of the pixel, and a detection time indicating the detected time; A calculation processing unit that calculates a physical quantity indicating a change in the human body based on the event data; Comprising: The human body includes blood flowing in blood vessels of the human body; The calculation processing unit: Calculates, as a physical quantity indicating a change in the human body, a blood movement speed at a position of the human body corresponding to each of the pixels based on the number of pieces of event data for each of the pixels per predetermined unit time; A measuring device.

2. An irradiation unit that generates coherent light; A measurement unit that receives, by a plurality of pixels, light of a speckle pattern generated by interference of scattered light generated when a human body receives the coherent light, and detects a change in a luminance value indicating a change in the luminance of each of the pixels that receives the light of the speckle pattern, and detects a pixel having a change in luminance amount of the detection target that is predetermined, and generates event data including the position of the detected pixel, a sign value indicating a change direction of the change in luminance amount of the pixel, and a detection time indicating the detected time; A calculation processing unit that calculates a physical quantity indicating a change in the human body based on the event data; Comprising: The human body includes blood flowing in blood vessels of the human body; The measurement unit: Determines whether each of the pixels has a change in luminance amount of the detection target based on the change in luminance amount corresponding to each of the pixels and a predetermined detection threshold value; The calculation processing unit: A multiplication value is calculated by multiplying a sign value indicating the change direction of the amount of luminance change included in the event data by the detection threshold value. For each of the pixels, for each detection time, a value obtained by integrating the multiplication values corresponding to the detection times before the detection time is calculated as an integrated value for each detection time. Based on the integrated values for each detection time of each of the calculated pixels, the blood movement speed at the position of the human body corresponding to each of the pixels is calculated as a physical quantity indicating the change of the human body. Measuring device.

3. An irradiation unit that generates coherent light, A measuring unit that receives light of a speckle pattern generated by interference of scattered light generated when a human body receives the coherent light with a plurality of pixels, and each of the pixels receives the light of the speckle pattern and detects a change in luminance value indicating a change in luminance amount. The measuring unit detects a pixel having a luminance change amount of a detection target determined in advance, and generates event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the detected time. A calculation processing unit that calculates a physical quantity indicating a change in the human body based on the event data. Comprising The human body includes blood flowing through blood vessels of the human body. The measuring unit Based on the amount of luminance change corresponding to each of the pixels and a detection threshold value determined based on an absolute value of a difference between a maximum value and a minimum value of luminance values detected by the pixel from the light of the speckle pattern, which is a predetermined detection threshold value, it is determined whether each of the pixels is a pixel having a luminance change amount of the detection target. The calculation processing unit Based on the detection time included in the event data, the occurrence interval of the event data for each pixel is calculated. Based on the calculated occurrence interval of the event data for each pixel, the blood movement speed at the position of the human body corresponding to each of the pixels is calculated as a physical quantity indicating the change of the human body. Measuring device.

4. An irradiation unit that generates coherent light, A measuring unit that receives the light of the speckle pattern generated by the interference of the scattered light generated when the human body receives the coherent light with a plurality of pixels, and detects a pixel having a luminance change amount indicating a change in the luminance value for each of the pixels that receive the light of the speckle pattern, and generates event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the time of detection. An arithmetic processing unit that calculates a physical quantity indicating a change in the human body based on the event data. Comprising The human body includes blood flowing through the blood vessels of the human body. The arithmetic processing unit Generates image data for each detection time based on the sign value included in the event data, and calculates the blood movement speed as a physical quantity indicating a change in the human body based on the image data at two different detection times generated. Measuring device.

5. An irradiation unit that generates coherent light, A measuring unit that receives the light of the speckle pattern generated by the interference of the scattered light generated when the human body receives the coherent light with a plurality of pixels, and detects a pixel having a luminance change amount indicating a change in the luminance value for each of the pixels that receive the light of the speckle pattern, and generates event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the time of detection. An arithmetic processing unit that calculates a physical quantity indicating a change in the human body based on the event data. Comprising An optical branching unit that branches a plurality of optical paths so that an optical path difference occurs in the optical paths from the irradiation unit to the plurality of pixels of the measuring unit. An optical focusing unit that focuses the plurality of optical paths branched by the optical branching unit and forms the speckle pattern on the plurality of pixels included in the measuring unit. The human body is a human body whose shape is deformed. The arithmetic processing unit Generates image data having the number of event data for each pixel within a predetermined time as pixel values, and calculates the displacement amount caused by the deformation of the human body as a physical quantity indicating a change in the human body based on the generated image data. Measuring device.

6. The irradiation unit generates coherent light. The measurement unit receives the light of the speckle pattern generated by the interference of the scattered light generated when the human body receives the coherent light, by a plurality of pixels, the measurement unit detects a pixel having a luminance change amount indicating a change in the luminance value detected by each of the pixels receiving the light of the speckle pattern, the luminance change amount being a luminance change amount of a detection target determined in advance, the measurement unit generates event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the detected time, the calculation processing unit calculates a physical quantity indicating the change of the human body based on the generated event data, the human body contains blood flowing through the blood vessels of the human body, the calculation processing unit calculates, as a physical quantity indicating the change of the human body, the blood flow velocity at the position of the human body corresponding to each of the pixels, based on the number of the event data for each pixel per unit time determined in advance, Measurement method.

7. The irradiation unit generates coherent light, the measurement unit receives the light of the speckle pattern generated by the interference of the scattered light generated when the human body receives the coherent light, by a plurality of pixels, the measurement unit detects a pixel having a luminance change amount indicating a change in the luminance value detected by each of the pixels receiving the light of the speckle pattern, the luminance change amount being a luminance change amount of a detection target determined in advance, the measurement unit generates event data including the position of the detected pixel, a sign value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the detected time, the calculation processing unit calculates a physical quantity indicating the change of the human body based on the generated event data, the human body contains blood flowing through the blood vessels of the human body, the measurement unit determines whether or not each of the pixels has a luminance change amount corresponding to the detection target, based on the luminance change amount corresponding to each of the pixels and a detection threshold value determined in advance, The calculation processing unit calculates a multiplication value by multiplying a sign value indicating a change direction of the luminance change amount included in the event data by the detection threshold value, and for each of the pixels, for each detection time, a value obtained by integrating the multiplication values corresponding to the detection times before the detection time is calculated as an integrated value for each detection time, and based on the integrated value for each detection time of each of the calculated pixels, the blood movement speed at the position of the human body corresponding to each of the pixels is calculated as a physical quantity indicating a change in the human body. Measurement method. **Claim 8**: A program for causing a computer to function as the measurement device according to any one of Claims 1 to 5.

Images