JP2023059422A - Measurement device, measurement method, and program - Google Patents

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

The present invention relates to, for example, a measuring device, a measuring method, and a program for measuring changes in speckle patterns.

When coherent light such as laser light is irradiated onto an object with fine unevenness on the reflecting surface or an object that causes internal scattering, the object receives the coherent light and scatters light, resulting in a pattern derived from the interference of the scattered light. can be observed. This pattern is called a speckle pattern, and light and dark occur at each point of the speckle pattern due to strengthening and weakening due to superimposition of a plurality of scattered lights.

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 in the speckle pattern, it is possible to estimate the temporal change in the fine shape of the object, the temporal change in the amount of movement, and the like. Measurement methods using speckle patterns are used in various applications such as medical sensors such as blood flowmeters and speedometers for machine control, in addition to material measurement. For example, in a laser Doppler blood flowmeter, a laser beam is irradiated from above the skin, and a speckle pattern of light generated by interference between the light scattered by red blood cells moving in blood vessels and the light scattered by stationary living tissue is used. A light-receiving intensity signal is detected by a light-receiving element. The velocity of red blood cells passing through the blood vessel is calculated from the frequency of the detected received light intensity signal, and the blood flow rate and pulse rate are estimated from the calculated velocity of red blood cells.

A speckle pattern can be two-dimensionally observed by photographing with an image sensor such as a CCD (Charge Coupled Device). However, in the case of imaging a scatterer in which the frequency of the received light intensity signal is extremely high, such as the above speckle pattern of blood flow, an image sensor with a high frame rate corresponding to the height of the frequency is required. In general, image sensors have the problem that the higher the frame rate and the higher the resolution, the higher the price. A high frame rate image sensor and a high resolution image sensor have a problem that they are strongly affected by noise due to insufficient amount of light.

For example, the technique disclosed in Non-Patent Document 1, that is, the blood flow meter using the laser speckle blood flow imaging method, uses a speckle pattern measurement method using a general frame rate image sensor. solves the above-mentioned problems related to image sensor price and noise. In a blood flowmeter using a laser speckle blood flow imaging method, image data obtained by an image sensor indicates the result of integrating the received light intensity signal within the exposure time for each pixel. The faster the blood flow, the higher the frequency of the received light intensity signal in real time. A blood flow meter using laser speckle blood flow imaging utilizes this tendency, acquires image data multiple times and compares them. It makes it possible to ask for

OMEGAWAVE, INC., “2D laser blood flow imaging device, OMEGAZONE 2D Laser Blood Flow Imager, measurement principle”, [online], [searched on August 18, 2021], Internet <http://www.omegawave .co.jp/products/oz/principle.shtml>

However, as in the technique disclosed in Non-Patent Document 1 above, when measuring a speckle pattern using an image sensor with a general frame rate, the frequency of the received light intensity signal is high like the blood flow described above. In the case of measuring an object that is different in size, continuous measurement is required a plurality of times. Therefore, there is a problem that it is difficult to perform measurements such as so-called real-time measurements under conditions where the time interval of measurements is restricted. When using an image sensor with a general frame rate, multiple continuous measurements are required. Therefore, accurate measurement is required if the rate of change occurring in the object to be measured is not a constant rate. is difficult.

In view of the above circumstances, it is an object of the present invention to provide a technology capable of estimating the change of an object whose change is not constant, based on the speckle pattern, under the condition that the measurement time interval is restricted.

In one aspect of the present invention, a speckle pattern light generated by interference between an irradiation unit that generates coherent light and scattered light generated by a scatterer receiving the coherent light is received by a plurality of pixels, and the pixels detects a pixel having a luminance change amount indicating a change in the luminance value detected by receiving light of the speckle pattern, and having a predetermined detection target luminance change amount, and the position of the detected pixel; a measurement unit for generating event data including a code value indicating the direction of change of the luminance change amount of the pixel and a detection time indicating the detection time; and a physical quantity indicating a change in the scatterer based on the event data. and a calculation processing unit that calculates .

In one aspect of the present invention, coherent light is generated, speckle pattern light generated by interference of the scattered light generated by a scatterer receiving the coherent light is received by a plurality of pixels, and each of the pixels is A pixel having a luminance change amount indicating a change in luminance value detected by receiving the light of the speckle pattern has a predetermined detection target luminance change amount, and a position of the detected pixel and a position of the pixel are detected. generating event data including a code value indicating a change direction of the luminance change amount and a detection time indicating a detection time, and calculating a physical quantity indicating a change in the scatterer based on the generated event data; , is the measurement method.

In one aspect of the present invention, a plurality of pixels receive speckle pattern light generated by interference of scattered light generated by a scatterer receiving coherent light, and each of the pixels receives the speckle pattern light. A pixel having a predetermined amount of luminance change to be detected is detected, and the position of the detected pixel and the direction of change of the amount of luminance change of the pixel are detected. and a detection time indicating the detection time, and a calculation processing step of calculating a physical quantity indicating the change of the scatterer based on the event data It is a program for executing

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 the time interval of measurement is restricted.

2 is a block diagram showing the internal configuration and scatterers of the measuring device of the first embodiment; FIG. 9 is a flow chart showing the flow of processing of the first method performed by the calculation processing unit of the first embodiment; It is a flowchart which shows the flow of the process of the 2nd method which the calculation process part of 1st Embodiment performs. 9 is a graph showing an example of changes in the integrated value calculated by the calculation processing unit in the second method performed by the calculation processing unit of the first embodiment; 10 is a graph for explaining the relationship between the magnitude of the detection threshold set in the event detection unit and the position of the peak detected by the event detection unit in the third method performed by the calculation processing unit of the first embodiment; It is a flow chart which shows a flow of processing of the 3rd method which a calculation processing part of a 1st embodiment performs. It is a flow chart which shows a flow of processing of the 4th method which a calculation processing part of a 1st embodiment performs. It is a block diagram which shows the internal structure and scatterer of the measuring device of 2nd Embodiment. It is a figure which shows the example of the optical system applied to the light branching part of 2nd Embodiment, and a light converging part. 9 is a flow chart showing the flow of processing by a calculation processing unit according to the second embodiment;

(First embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION 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 and a scatterer 30 to be measured by the measuring device 1 according to the first embodiment. The scatterer 30 partially includes a moving scatterer 31 and may be any 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 through blood vessels of the human body.

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 with a constant light intensity. The irradiating unit 11 diffuses the generated laser light in a plane by an internal optical element, and irradiates the scatterer 30 with the diffused laser light 40 . Here, the optical element provided inside the irradiation unit 11 may be any optical element as long as it diffuses the laser light. It is a convex lens.

In FIG. 1, the scattered light 50 indicates the scattered light generated by the portion of the scatterer 30 excluding the moving scatterer 31, that is, the stationary portion receiving the laser beam 40. The scattered light 51 is the moving scattered light. Scattered light caused by body 31 receiving laser light 40 is shown. If the moving scatterer 31 is not moving, the scattered light 51 will be included in the scattered light 50, and in this case, interference of the scattered light 50 will produce a speckle pattern. On the other hand, when the moving scatterer 31 is moving, scattered light 51 is generated, and interference between the scattered light 50 and the scattered light 51 causes a change in the speckle pattern.

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 speckle pattern light generated by the interference of the scattered lights 50 and 51 . The light receiving section 21 includes, for example, a plurality of pixels 22-1 to 22-n arranged in a rectangular shape to form a light receiving surface of the light receiving section 21. As shown in FIG. Here, n may be an arbitrary value as long as it is an integer of 2 or more, and in the case of a general event camera, n is a value of tens of thousands to hundreds of thousands. Note that FIG. 1 shows an example of n=54, that is, an example in which the light receiving unit 21 includes 54 pixels 22-1 to 22-54 arranged in 6 rows×9 columns. The first and last pixels are indicated with reference numerals "22-1" and "22-n", respectively. 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. do. Hereinafter, when any one of the pixels 22-1 to 22-n is indicated, it will be referred to as the pixel 22 without indicating the branch number of the code.

The event detection unit 23 asynchronously detects a luminance change amount indicating a change in luminance value output from each of the pixels 22-1 to 22-n. Further, when the event detecting unit 23 detects a pixel 22 having a predetermined detection target luminance change amount, the event detection unit 23 detects the position of the detected pixel 22 and the change direction of the luminance change amount. Event data is generated that includes a code value indicating the event and a detection time indicating the time of detection. Here, the position of the pixel 22 is, for example, the position indicated by the coordinate data represented by the position of the row and column with the position of the pixel 22-1 as the origin, that is, (0, 0). is shown as coordinate data (1, 0), and the position of the pixel one row right in the same row of pixel 22-1 is shown as coordinate data (0, 1). It will be. The code value indicating the change direction of the luminance change amount is, for example, "+1" when the luminance value changes from a small value to a large value, and "-" when the luminance value changes from a large value to a small value. 1”.

Here, the relationship between the luminance change amount detected by the event detection unit 23 and the received light intensity signal that causes the speckle pattern to change will be described. The received light intensity signal is a signal obtained by arranging light intensity values of speckle pattern light measured at a certain position in time series. There is a relationship that the frequency of the received light intensity signal increases as the change in the speckle pattern increases. The luminance value detected by each of the pixels 22-1 to 22-n indicates the light intensity of the speckle pattern measured at each position. By arranging the luminance values detected by each in time series, A received light intensity signal of the speckle pattern measured at each position of the pixels 22-1 to 22-n is obtained. Here, let the received light intensity signal measured at one pixel 22 be I(t) (in I(t), t is time, and I(t) is the pixel 22 at time t). is the luminance value to be detected). For example, 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 detects the luminance change amount log(I(t ₂ ))−log(I(t ₁ )) represented by the difference between the logarithms of the luminance values at time t ₂ It will be. Here, the base of log(·) is “e”, and hereinafter, “logarithm” 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(t ₂ ))−log(I(t ₁ )) as the sign of the code value. Hereinafter, when generalizing the formula of the amount of change in brightness log(I(t ₂ ))−log(I(t ₁ )) and expressing the amount of change in brightness at time t by the formula, Δ(log(I(t)) It shall be shown by the formula

The calculation processing unit 13 calculates physical quantities indicating changes in the scatterers 30 based on the event data output by the event detection unit 23 . Four methods for calculating the moving speed of the moving scatterer 31 included in the scatterer 30 as a physical quantity indicating the change of the scatterer 30 will be described below.

(First method by the measuring device of the first embodiment)
A first method by the measuring device 1 according to the first embodiment will be described with reference to FIG. 2 . FIG. 2 is a flow chart showing the flow of the first method by the calculation processing unit 13. As shown in FIG. As a premise for starting the processing of the flow chart of FIG. 2, it is assumed that the following has been performed. The irradiation unit 11 is installed at a fixed position and direction, and irradiates the measurement area with the laser light 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 measuring unit 12 receives speckle pattern light generated by interference of the scattered lights 50 and 51 by the pixels 22-1 to 22-n.

The event detection unit 23 asynchronously detects a luminance change amount indicating a change in luminance value output from each of the pixels 22-1 to 22-n. The event detection unit 23 stores a predetermined detection threshold value in an internal storage area in advance, and upon detecting a luminance change amount, refers to the internal storage area, and determines whether the detected luminance change amount is equal to or greater than the detection threshold value. It is determined whether or not it is the amount of change. When the event detection unit 23 determines that the detected amount of luminance change is equal to or greater than a predetermined detection threshold, the event detection unit 23 has a predetermined amount of luminance change to be detected for the pixel 22 corresponding to the amount of luminance change. detected as a pixel with 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 code value indicating the change direction of the luminance change amount, and the detection time, and calculates the generated event data. Output to the processing unit 13 .

As described above, when the moving scatterer 31 included in the scatterer 30 is not moving, the scatterer 30 is all stationary. In this case, the scattered light 51 is included in the scattered light 50, so only the scattered light 50 is generated. As described above, the irradiation unit 11 irradiates the laser beam 40 in a certain direction with a certain light intensity. That is, the laser beam 40 emitted by the irradiation unit 11 does not change over time. Therefore, the speckle pattern caused by the interference of the scattered light 50 also does not change over time. In this case, since the luminance value output by each of the pixels 22-1 to 22-n upon receiving the light of the speckle pattern does not change, the event detection unit 23 detects the light from any of the pixels 22-1 to 22-n A luminance change amount of "0" is detected. However, in reality, noise or the like exists, so the amount of change in brightness detected by the event detection unit 23 may not be "0", but it never exceeds the detection threshold. Therefore, in this case, the event detector 23 does not output any event data.

On the other hand, when the moving scatterer 31 included in the scatterer 30 is moving, the scattered light 50 generated by the stationary portion of the scatterer 30 other than the moving scatterer 31 receiving the laser beam 40 and the moving scattering Interference with the scattered light 51 generated when the body 31 receives the laser light 40 changes the speckle pattern. When the speckle pattern changes, the luminance values detected by the pixels 22-1 to 22-n corresponding to the positions where the speckle pattern changes are changed. When the event detection unit 23 detects the amount of luminance change from the luminance values output by the pixels 22-1 to 22-n, it determines that the detected amount of luminance change is equal to or greater than a predetermined detection threshold. Then, event data relating to the pixel 22 corresponding to the luminance change amount is generated and output.

The flow of processing will be described below according to the flowchart of FIG. The calculation processing unit 13 takes in 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 event data and the detection time (step Sa2).

As the moving speed of the moving scatterer 31 increases, the speckle pattern changes more. As the speckle pattern changes more, the frequency of the received light intensity signal increases. As the frequency of the received light intensity signal increases, the number of event data per unit time also increases. Therefore, a large number of event data per unit time means that the moving speed of the moving scatterer 31 is high, and the amount of event data changes the relative moving speed of the moving scatterer 31. can indicate the size of

The position of each of pixels 22-1 through 22-n can be associated with any position of scatterer 30. FIG. The calculation processing unit 13 calculates the number of event data per unit time for each of the pixels 22-1 to 22-n by calculating the moving scatterer 31 at the position of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n. (step Sa3).

(Second method using the measuring device of the first embodiment)
A second method by the measuring device 1 according to the first embodiment will be described with reference to FIGS. 3 and 4. FIG. Note that when the second method is performed, a detection threshold having the same value as the detection threshold stored in the storage area inside the event detection section 23 is stored in advance in the storage area inside the calculation processing section 13 .

FIG. 3 is a flow chart showing the flow of the second method by the calculation processing unit 13. As shown in FIG. Note that the premise for starting the processing of the flowchart of FIG. 3 is the same as the premise for the first method described above. The calculation processing unit 13 takes in 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 the multiplied value for each event data (step Sb2). For each of the pixels 22-1 to 22-n, the calculation processing unit 13 integrates the multiplied values corresponding to the detection times before the detection time, and calculates the integrated value for each detection time (step Sb3).

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 section 13, the integration start time is determined in advance. The calculation processing unit 13 sequentially acquires event data of one pixel 22 whose detection time is after the integration start time. Here, it is assumed that the detection times included in the plurality of event data of the pixels 22 sequentially captured by the calculation processing unit 13 are t ₁ , t ₂ , . However, t ₁ , t ₂ , . . . are times after the integration start time.

When the calculation processing unit 13 takes in the event data of the pixel 22 at the detection time _t1 , it calculates the multiplication value corresponding to the detection time _t1 by the process of step Sb2. Since there is no multiplied value corresponding to the detection time before the detection time _t1 and after the integration start time, the calculation processing unit 13 calculates the multiplied value corresponding to the calculated detection time _t1 to the pixel 22. is the integrated value at the detection time _t1 . Next, when the calculation processing unit 13 takes in the event data of the pixel 22 at the detection time _t2 , it calculates the multiplication value corresponding to the detection time _t2 by the process of step Sb2. The calculation processing unit 13 adds the multiplied value corresponding to the calculated detection time _t2 to the integrated value of the detection time _t1 of the pixel 22, and the added value is the integrated value of the detection time _t2 of the pixel 22. do. In this manner, the calculation processing unit 13 adds the multiplication value corresponding to the detection time included in the captured event data to the integrated value of the previous detection time every time the event data of the pixel 22 is captured. is repeated to calculate an integrated value for each detection time of the pixel 22 . The calculation processing unit 13 performs similar calculations for all the pixels 22-1 to 22-n, and calculates integrated values for each detection time of each of the pixels 22-1 to 22-n.

FIG. 4 is a bar graph showing an example of integrated values for each detection time of one pixel 22 calculated by the calculation processing unit 13 . In the bar graph shown in FIG. 4 , the horizontal axis is the detection time, and the vertical axis is the integrated value calculated by the calculation processing unit 13 . Since the event data output by the event detection unit 23 is asynchronous, the detection time interval of the bar graph is not constant. Since the integrated value is obtained by multiplying the code value "-1" or "+1" by the detection threshold, it becomes a quantized value with a step width equal to the magnitude of the detection threshold. In this case, the change in the bar graph shown in FIG. 4 includes an error quantized by the magnitude of the detection threshold. , i.e. log(I(t)) measured at the pixel 22 position.

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 pixel 22 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 a method using a laser Doppler blood flowmeter shown in Reference 1 below. The movement speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of -1 to 22-n is calculated (step Sb4).

[Reference 1: Kokyo Co., Ltd., Optipedia, “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/>]

That is, the calculation processing unit 13 of the second method calculates a multiplied value by multiplying the code value indicating the change direction of the luminance change amount included in the event data by the detection threshold. 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 multiplied values corresponding to detection times before the detection time as an integration value for each detection time. . The calculation processing unit 13 calculates moving scattering at the positions of the scatterer 30 corresponding to each of the pixels 22-1 to 22-n based on the calculated integrated value for each detection time of each of the pixels 22-1 to 22-n. This means that the process of calculating the moving speed of the body 31 is performed.

The moving speed calculated by the calculation processing unit 13 by the above second method is a relative moving speed as in the first method. However, in the case of the first method, external factors such as noise, detection delay depending on the amount of light of the laser beam 40, and band shortage in the light receiving unit 21 and the event detection unit 23 when a large amount of event data is generated at once. If there is variation in the amount of event data generated at each detection time, the calculated moving speed will also vary. On the other hand, in the second method, the multiplied value obtained by multiplying the code value by the detection threshold value is integrated in the time direction to calculate the integrated value, and the received light corresponding to each of the pixels 22-1 to 22-n is calculated. Calculate the intensity signal I(t). Therefore, in the second method, it is possible to calculate a relative moving speed that is less affected by the above external factors.

Note that the calculation processing unit 13 generates a curve indicated by reference numeral 100 by performing filtering processing on the bar graph of the integrated value for each detection time of the pixel 22 shown in FIG. may be regarded as log(I(t)) measured at the position of . This makes it possible to reduce errors 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.

(Third method by the measuring device of the first embodiment)
A third method by the measurement device 1 according to the first embodiment will be described with reference to FIGS. 5 and 6. FIG. It should be noted that when the third technique is performed, the value of the detection threshold stored in advance in the storage area inside the event detection unit 23 is predetermined as follows. The event detection unit 23 preliminarily detects the maximum value and the minimum value from luminance values detected by each of the pixels 22-1 to 22-n of the light receiving unit 21 receiving speckle pattern light. The event detection unit 23 calculates the absolute value of the difference between the maximum value and the minimum value of luminance values detected in advance, and stores the calculated absolute value of the difference in advance in an internal storage area as a detection threshold.

FIG. 5 is a graph showing an example of change in luminance value detected by one pixel 22 receiving speckle pattern light, where the horizontal axis is time and the vertical axis is luminance value. The magnitude of the detection threshold is the length from the maximum luminance value to the minimum luminance value indicated by reference numeral 110 . In this case, the event detection unit 23 determines whether the pixel 22 Since the amount of change in luminance detected from 1 is greater than or equal to the detection threshold, event data for the pixel 22 is generated.

The peak 121 indicates the weakest interference of the scattered lights 50 and 51 , and the peak 122 indicates the strongest interference of the scattered lights 50 and 51 . Therefore, the interval between the peaks 121 and 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 and minimum luminance values is used as the detection threshold. , the light graph of the actual speckle pattern becomes a graph in which light and dark patterns appear periodically.

FIG. 6 is a flow chart showing the flow of the third method by the calculation processing unit 13. As shown in FIG. Note that the premise for starting the processing of the flowchart of FIG. 6 is the same as the premise for the first method described above. The calculation processing unit 13 takes in 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 received light intensity signal I(t) corresponding to each of the pixels 22-1 to 22-n based on the measured occurrence intervals of the event data for each of the pixels 22-1 to 22-n. Calculate (step Sc3). The calculation processing unit 13 calculates the pixel 22 from the frequency of the received light intensity signal I(t) corresponding to each of the pixels 22-1 to 22-n, for example, by the method using a laser Doppler blood flowmeter shown in Reference 1 above. The moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of -1 to 22-n is calculated and output (step Sc4).

That is, the calculation processing unit 13 of the third method calculates the occurrence intervals of the event data for each of the pixels 22-1 to 22-n based on the detection times included in the event data. The calculation processing unit 13 calculates 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 occurrence interval of the event data for each of the pixels 22-1 to 22-n. is calculated.

In the third method, as described above, event data is generated only at the time when the received light intensity signal I(t) peaks. Therefore, the frequency of the received light intensity signal I(t) can be directly calculated from the occurrence interval of the event data. Therefore, it is not necessary to count the number of event data as in the first method or to obtain an integrated value as in the second method. It becomes possible to calculate the moving speed of the moving scatterer 31 at the position of the scatterer 30 corresponding to each of -1 to 22-n. The third method calculates the frequency of the received light intensity signal I(t) measured at each position of the pixels 22-1 to 22-n. Instead of calculating the relative moving speed, 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.

It should be noted that the above-described third technique assumes that there is no variation in the maximum and minimum luminance values detected by the pixels 22-1 to 22-n. The absolute value of the difference between the maximum value and the minimum value among the luminance values detected by receiving the light of the speckle pattern is used as a detection threshold common to all the pixels 22-1 to 22-n. there is On the other hand, if there are variations in the maximum and minimum luminance values detected by each of the pixels 22-1 to 22-n, the event detection unit 23 detects , the maximum and minimum luminance values are detected in advance, and the absolute values of the differences between the maximum and minimum luminance values corresponding to each of the pixels 22-1 to 22-n are calculated for the pixels 22-1 to 22-n. There may be separate detection thresholds for each of n.

(Fourth method by the measuring device of the first embodiment)
A fourth method by the measurement device 1 according to the first embodiment will be described with reference to FIG. 7 . The fourth method is assumed to be applied when the area of the moving scatterer 31 included in the scatterer 30 is sufficiently large. If 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 is changed due to the interference of the scattered lights 50 and 51 is distributed to many pixels 22 of the light receiving unit 21. -1 to 22-n can receive light. In this case, from the event data detected by the event detection unit 23, an image indicating the degree of light intensity of the speckle pattern measured at the light receiving surface of the light receiving unit 21, that is, at the positions of the pixels 22-1 to 22-n is detected. By generating the images for each time and comparing the images at two different detection times, it is possible to detect temporal changes in the speckle pattern.

FIG. 7 is a flow chart showing the flow of the fourth method by the calculation processing unit 13. As shown in FIG. The premise for starting the processing of the flowchart of FIG. 7 is the same as the premise for the first method described above. The calculation processing unit 13 takes in 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 code values corresponding to detection times before the detection time, and calculates an integrated value for each detection time (step Sd2). In the fourth method, the procedure for the calculation processing unit 13 to integrate the code values is the procedure for integrating the multiplication values in the second method, except that the target of integration is changed from the multiplication value to the code value. It is the same procedure as

The calculation processing unit 13 uses the calculated integrated value for each detection time for each of the pixels 22-1 to 22-n as the pixel value, and generates image data for each detection time (step Sd3). In the second method, the integrated value is a value obtained by multiplying the sign value by the detection threshold, and the integrated value changes at each detection time for each of the pixels 22-1 to 22-n. Δlog(I(t)) in each of 22-1 to 22-n was regarded as integrated log(I(t)). On the other hand, the integrated value for each detection time for 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 showing the intensity of the light of the speckle pattern at the detection time t.

The calculation processing unit 13 calculates the cross-correlation between two arbitrarily selected image data at different detection times (step Sd4). When the cross-correlation calculated by the calculation processing unit 13 has a peak, the position of the peak indicates the amount of movement of the speckle pattern between two different detection times. The calculation processing unit 13 divides the position of the peak obtained by cross-correlation, i.e., the amount of movement of the speckle pattern, by the time difference between two different detection times to obtain the speed of the speckle pattern, i.e., the moving scatterer 31 is calculated (step Sd5).

That is, for each of the pixels 22-1 to 22-n, the calculation processing unit 13 of the fourth method integrates the code values included in the event data corresponding to the detection time before the detection time for each detection time. values are calculated as pixel values of the pixels 22-1 to 22-n at each detection time. The calculation processing unit 13 generates image data for each detection time from 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. Become.

In the above 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. The movement amount of the speckle pattern may be calculated by pattern matching or the like.

In the above fourth method, in step Sd2, the calculation processing unit 13 integrates the code values corresponding to the detection times before the detection time for each of the pixels 22-1 to 22-n. , an integrated value is calculated for each detection time. On the other hand, the calculation processing unit 13 may generate image data whose pixel values are code values of event data corresponding to each of the pixels 22-1 to 22-n at each detection time. In this case, the calculation processing unit 13 generates image data by setting the pixel values of the pixels 22-1 to 22-n for which event data corresponding to the detection time for which image data is to be generated are "0". Therefore, the pixel value of the image data generated by the calculation processing unit 13 is one of "-1", "0", and "+1".

Since the image represented by the image data generated by the calculation processing unit 13 is not integrated as in the above-described fourth method, the difference in intensity is not as clear as in the image data generated by the fourth method. Although not shown, the image shows the intensity of the light of the speckle pattern at the detection time. Therefore, the calculation processing unit 13 can calculate the movement amount of the speckle pattern by comparing the image data at two different detection times. Note that the method of comparing image data at two different detection times may be the cross-correlation used in the fourth method described above, or a method other than cross-correlation, such as pattern matching. The calculation processing unit 13 can calculate the speed of the speckle pattern, that is, the speed of the entire moving scatterer 31 by dividing the calculated movement amount by the time difference between two different detection times.

In the measurement device 1 of the first embodiment described above, the irradiation unit 11 generates coherent light. The measurement unit 12 receives speckle pattern light generated by interference of the scattered lights 50 and 51 generated when the scatterer 30 receives the coherent light by the plurality of pixels 22-1 to 22-n, and the pixels 22- Detect pixels 22-1 to 22-n having a luminance change amount to be detected, in which a luminance change amount indicating a change in luminance value detected by each of pixels 1 to 22-n receiving speckle pattern light is predetermined. event data including the positions of the detected pixels 22-1 to 22-n, code values indicating the direction of change in luminance variation of the pixels 22-1 to 22-n, and detection time indicating the detection time. Generate. Based on the event data generated by the measurement unit 12, the calculation processing unit 13 calculates the speed of movement of the position of the moving scatterer 31 corresponding to each of the pixels 22-1 to 22-n, or the movement of the moving scatterer 31. Calculate speed.

A frame camera equipped with a general image sensor outputs a luminance value integrated in each pixel for each frame. In a frame camera, the integration time, that is, the exposure time and the dynamic range of the signal are the same for all pixels. Therefore, if there are very bright pixels and very dark pixels, blown-out highlights, blocked-up shadows, quantization errors, and the like will occur. If the brightness of the scene changes drastically due to lighting effects, etc., the exposure time may not be adjusted, resulting in blown-out highlights and blocked-up shadows.

On the other hand, the event camera asynchronously outputs event data each time the amount of change in brightness of each pixel exceeds the detection threshold as described above. Therefore, problems such as blown-out highlights, blocked-up shadows, and quantization errors do not occur. Since the event data output by the event camera is data output asynchronously, it is very sparse data compared to the image data output by the frame camera. Therefore, the memory capacity required for storing the event data can be reduced, and the transmission capacity required for transmitting the event data can be reduced. Since the event data is very sparse data, the event camera can keep costs such as the amount of calculation and power consumption required for image processing and data processing much lower than those of the frame camera.

For example, when trying to achieve the same temporal resolution in event data as the temporal resolution of image data output by a frame camera, it is possible to achieve event data with a much smaller volume than the volume of image data output by the frame camera. It is possible. In other words, if event data with a volume equivalent to the volume of image data output by the frame camera is collected, a very high temporal resolution can be obtained. For these reasons, by using an event camera, it is possible to perform measurements stably, at low cost, and with a very high temporal resolution in an environment with a small amount of light or an environment where the illumination changes rapidly.

In the measurement device 1 of the first embodiment, the measurement unit 12 is an event camera that has the advantages described above compared to a frame camera. Therefore, unlike a frame camera, it is not necessary to continuously measure multiple times. can be measured based on the speckle pattern.

In the above-described first embodiment, the scatterer 30 is irradiated with the planar laser beam 40 obtained by diffusing the laser beam from the irradiation unit 11 . On the other hand, by adjusting the position of an optical element such as a convex lens provided inside the irradiation unit 11, the irradiation unit 11 emits a spot laser beam, that is, a non-diffused laser beam to a specific portion of the scatterer 30. You may make it irradiate to. For example, a cylindrical lens or the like may be used as an optical element provided inside the irradiation unit 11 so that the irradiation unit 11 irradiates the scatterer 30 with linear laser light. A projector having a light source that generates laser light may be used as the irradiation unit 11 to irradiate the laser light of an arbitrary pattern at an arbitrary timing.

Depending on the performance of the event camera applied to the measurement unit 12, if a large number of pixels 22-1 to 22-n change in luminance value at once, the bands in the light receiving unit 21 and the event detection unit 23 become insufficient, and all event data cannot be output to the calculation processing unit 13 in some cases. In such a case, the laser light 40 emitted by the irradiation unit 11 is the spot laser light, the linear laser light, or the laser light having an arbitrary pattern as described above, and the irradiation range of the laser light 40 is narrowed down. Alternatively, by irradiating the laser beam 40 on different parts of the scatterer 30 at different timings, it is possible to eliminate the band shortage in the light receiving unit 21 and the event detection unit 23 .

The laser beam 40 irradiated by the irradiation unit 11 is used as a spot laser beam, and is irradiated only to a small range of the scatterer 30, for example, a range of the width of the light receiving surface of one pixel 22, and a speckle pattern is formed by only one pixel 22. of light is measured. 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 in 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 scatterer 31 move at a constant speed. It becomes possible to calculate the moving speed of the moving scatterer 31 in the case where

As the irradiation unit 11, a raster scan type laser irradiation device such as a MEMS (Micro Electro Mechanical Systems) laser projector may be applied. In this case, the irradiation unit 11 irradiates the laser light 40 at one point on the scatterer 30 and changes the irradiation destination of the laser light 40 point by point so that the laser light 40 raster scans the scatterer 30 . The event detection unit 23 of the measurement unit 12 generates event data only when constructive interaction 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 when the luminance value changes from the minimum value to the maximum value, Event data is generated only when a luminance change amount is detected. Accordingly, the calculation processing unit 13 can detect the interval at which constructive interaction due to interference occurs from the interval at which event data is generated 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 intervals. It becomes possible to calculate the moving speed of the moving scatterer 31 at the position of the scatterer 30 where the scatterer 30 is located. In this case, since only one point of the laser beam 40 is irradiated onto the scatterer 30 at a time, the range of the pixels 22-1 to 22-n in which the brightness value changes is also limited, and a large amount of event data is generated at once. In addition, it is possible to avoid processing failures due to generation of a large amount of event data that may occur when a wide range is irradiated with the laser beam 40 at once. In addition, it is possible to measure a large area with a low-power laser, as compared with the case of irradiating a wide range with the laser beam 40 at once.
In addition, by using a raster scan type laser irradiation device that can arbitrarily control the scanning speed and arbitrarily controlling the timing of moving from one irradiation position to the next irradiation position, the dormancy timing of the event sensor and the irradiation position can be adjusted. It is also possible to match the movement timing and detect only the event due to the speckle change without detecting the event caused by the irradiation position movement. Since a general event sensor detects an event in each pixel and then detects the next event after a certain sleep period, an event based on a luminance change occurring during the sleep period is not detected. The sleep period and the irradiation position movement timing may be set in advance, or may be dynamically controlled using a synchronizer. Alternatively, for a similar laser irradiation device, the calculation processing unit 13 may perform a process of classifying an event based on a change in irradiation position and an event due to a change in speckle. For example, when the irradiation position is changed every T seconds, an event that occurs at the period T can be caused by the irradiation position change. Alternatively, for a series of events that occur during the irradiation period for each pixel, events for a certain period at the beginning and end can be caused by changing the irradiation position.

(Second embodiment)
FIG. 8 is a block diagram showing a measuring device 1a and a scatterer 32 to be measured by the measuring device 1a according to the second embodiment. In the second embodiment, the same reference numerals are assigned to the same configurations as in the first embodiment, and the different configurations will be described below. The scatterer 32 in the second embodiment may be any object, for example, as long as it changes its shape over time and receives coherent light to generate scattered light.

The measurement device 1 a includes an irradiation section 11 a , a measurement section 12 , a calculation processing section 13 a , a light branching section 14 and a light converging section 15 . The irradiating section 11a is obtained by adjusting the position of the optical element provided inside in the irradiating section 11 of the first embodiment from a position that diffuses the laser light to a position that allows the laser light to travel straight. It is generated as coherent light with a constant light intensity and irradiated. The light branching unit 14 branches the optical path from the irradiation point of the laser beam 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 light branching unit 14 splits the laser light 41 emitted by the irradiation unit 11a so as to cause an optical path difference, and irradiates the scatterer 32 with two laser beams 42 and 43. showing.

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 directed in the direction of the light receiving surface of the light receiving unit 21. is irradiated to The light converging section 15 converges the two optical paths branched by the light branching section 14, that is, converges the scattered light 52 and the scattered light 53, and receives the speckle pattern generated by the interference of the converged scattered lights 52 and 53. An image is formed on the light receiving surface of the portion 21 . For example, a convex lens or the like is applied as the light converging section 15 , but an optical element other than the convex lens may be used as long as the speckle pattern can be imaged on the light receiving surface of the light receiving section 21 .

FIGS. 9A and 9B are diagrams showing configurations of four optical systems as examples of the optical system applied to the light branching section 14 and the light converging section 15, which are shown in FIGS. FIG. 2 is a diagram citing parts of diagrams of four optical systems shown in FIG. 31 and 34 of Reference 2 are shown in a different order for convenience of explanation.

[Reference 2: Kokyo Co., Ltd., Optipedia, “31.3 Speckle”, [online], [searched on August 18, 2021], Internet <https://optipedia.info/laser/handbook/ laser-handbook-7th-section/31-3/>]

(Structure of optical splitter applying two-beam method)
FIG. 9A shows an example of the optical splitter 14 that splits the single laser beam 41 shown in FIG. 8 into two laser beams 42 and 43, which is an optical system called a two-beam method. In FIG. 9A, a half mirror 61, mirrors 62 and 64, and convex lenses 63 and 65 are optical elements included in the light branching section 14. In FIG. FIG. 9A shows an example including a convex lens 15a as an example of the light converging portion 15, and FIGS. 9B to 9D show similar examples. In FIG. 9A, the scatterer 32 before shape deformation is indicated as scatterer 32-1, and the scatterer 32 after shape deformation is indicated as scatterer 32-2.

The positional relationship between the convex lenses 63, 65, 15a and the mirrors 62, 64 is as follows. The angle between the optical axis 66 of the convex lens 15a and the optical axis 67 of the convex lens 63 which is the direction in which the laser beam is reflected by the mirror 62 and the optical axis 66 and the mirror 64 reflect the laser beam. and the angle formed by the optical axis 68, which is the optical axis of the convex lens 65, coincides, and the optical axis 66, the optical axis 67, and the optical axis 68 intersect on the surface of the scatterer 32-1 before deformation. are arranged to The angle formed by the optical axis 67 and the optical axis 68 is determined to be larger than the aperture angle of the convex lens 15a. The convex lens 15a has its optical axis perpendicular to the light-receiving surface of the light-receiving unit 21 of the measuring unit 12, and is positioned between the scatterers 32-1 and 32-2 and the light-receiving unit 21, and receives light from the light-receiving unit 21. It is arranged at a position where the speckle pattern is imaged on the surface.

The half mirror 61 and the mirrors 62 and 64 are arranged so that the laser beam 41 emitted by the irradiation unit 11 a 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 . placed in The half mirror 61 and the mirrors 62 and 64 are arranged so that an optical path difference is generated in the optical path from the irradiation point of the irradiation section 11 a to the light receiving surface of the light receiving section 21 .

By arranging as described above, the laser light 41 emitted by the irradiation unit 11a is divided into laser light that is reflected by the half mirror 61 and reaches the mirror 62, and laser light that is transmitted through the half mirror 61 and reaches the mirror 64. and branch off. The mirror 62 reflects the received laser light in the direction of the optical axis 67, and the reflected laser light is diffused by the convex lens 63 and irradiated onto the scatterers 32-1 and 32-2. The mirror 64 reflects the received laser light in the direction of the optical axis 68, and the reflected laser light is diffused by the convex lens 65 and applied to the scatterers 32-1 and 32-2. For example, the laser light 42 irradiated by the light branching unit 14 in FIG. 8 corresponds to the laser light diffused by the convex lens 63 , and the laser light 43 corresponds to the laser light diffused by the convex lens 65 . The laser light diffused by the convex lens 63 is hereinafter referred to as laser light 42 , and the laser light diffused by the convex lens 65 is hereinafter referred to as laser light 43 .

Scattered light 52-1 is the scattered light generated when the scatterer 32-1 before deformation receives the laser light 42, and scattered light generated when the scatterer 32-2 after the deformation receives the laser light 42 is scattered. Let it be light 52-2. Similarly, the scattered light generated by the scatterer 32-1 before deformation caused by receiving the laser light 43 is the scattered light 53-1, and the scattered light generated by the scatterer 32-2 after deformation by receiving the laser light 43 Let the light be 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 section 21. FIG.

Scattered lights 52-1 and 53-1 generated from the scatterer 32-1 before deformation are light generated by laser light irradiated from two directions with an optical path difference, and the scattered lights 52-1 and 53-1 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 by the interference of the . Here, the surface of the scatterer 32-1 to be measured, that is, the surface irradiated with the laser beams 42 and 43 is deformed to move in the direction indicated by the arrow 39a and becomes the scatterer 32-2. Suppose Hereinafter, displacement due to such deformation is referred to as in-plane displacement, which is displacement parallel to the surface to be measured. Scattered lights 52-2 and 53-2 of the scatterer 32-2 after deformation are also lights generated by laser lights irradiated from two directions with an optical path difference, and the scattered lights 52-2 and 53-2 are A speckle pattern reflecting the optical path difference and the phase difference caused by the displacement amount when the scatterer 32-1 transforms into the scatterer 32-2 due to interference is imaged on the light receiving surface of the light receiving unit 21. become.

(Configuration of optical splitter applying reference light method)
The optical system shown in FIG. 9B is an optical system called a reference light method. Also in FIG. 9B, the scatterer 32 before shape deformation is indicated as scatterer 32-1, and the scatterer 32 after shape deformation is indicated as scatterer 32-2. In the reference light method, the scattered light generated by the scatterer 32-1 receiving the laser beam is referred to as the scattered light 52-1, and the scattered light generated by the scatterer 32-2 receiving the laser light is referred to as the scattered light 52-2. and In the reference beam method, unlike the two beam method described above, two laser beams are applied to the scatterers 32-1 and 32-2, but one of the laser beams is directed to the scatterers 32-1 and 32-2. The light receiving surface of the light receiving unit 21 is irradiated with the other laser light as the reference light.

In FIG. 9B, a convex lens 71, a half mirror 72, and a mirror 73 are optical elements included in the light branching section . The mirror 73 is arranged so that the reflecting surface of the mirror 73 is perpendicular to the direction in which the laser beam 41 emitted 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 emitted 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 light 41 travels straight. A convex lens 15 a , which is an example of the light converging section 15 , is arranged such that its optical axis is perpendicular to the light receiving surface of the light receiving section 21 of the measuring section 12 . The convex lens 15a is arranged at a position where the speckle pattern is formed on the light receiving surface of the light receiving section 21 by condensing the scattered lights 52-1 and 52-2 arriving after passing through the half mirror 72. FIG.

By arranging as described above, the laser beam 41 emitted 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 to form the scatterers 32-1 and 32-2. and a laser beam that passes through the half mirror 72 and reaches the mirror 73 . Hereinafter, the laser light that passes through the half mirror 72 and reaches the mirror 73 will be referred to as reference light. Scattered lights 52-1 and 52-2 generated by the scatterers 32-1 and 32-2 receiving the laser light travel in the direction of the half mirror 72, pass through the half mirror 72, and are condensed by the convex lens 15a. It reaches the light receiving surface of the light receiving section 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, proceeds in the direction of the convex lens 15a, and is condensed by the convex lens 15a to form the light receiving surface of the light receiving unit 21. to reach

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 interferes with the reference light, resulting in an optical path difference between the scattered light 52-1 and the reference light. A speckle pattern reflecting the phase difference is imaged on the light receiving surface of the light receiving unit 21 . Here, assume that the scatterer 32-1 is deformed to move in the direction indicated by the arrow 39b and becomes the scatterer 32-2. Hereinafter, displacement due to such deformation is referred to as out-of-plane displacement, which is displacement that is not parallel to the surface of the scatterer 32-1 to be measured, that is, the surface irradiated with the laser beam reflected by the half mirror 72. FIG. After the scatterer 32-1 transforms into 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 interferes with the reference light. As a result, a speckle pattern reflecting the optical path difference between the scattered light 52-2 and the reference light and the phase difference caused by the displacement amount when the scatterer 32-1 transforms into the scatterer 32-2 is formed on the light receiving unit 21. image is formed on the light-receiving surface of .

(Structure of optical branching section to which two-aperture method is applied)
The optical system shown in FIG. 9C is an optical system called a two-aperture method. Also in FIG. 9C, the scatterer 32 before its shape is deformed is shown as a scatterer 32-1, and the scatterer 32 after its shape is deformed is shown as a scatterer 32-2. In the two-aperture method as well, the scattered light generated when the scatterer 32-1 receives the laser light is called the scattered light 52-1, and the scattered light generated when the scatterer 32-2 receives the laser light is called the scattered light 52-2. and In the two-aperture method, a double-aperture plate 82 having two slits is placed in the middle of the optical path from the irradiation point of the laser beam 41 of the irradiation unit 11a to the light-receiving surface of the light-receiving unit 21 of the measurement unit 12. Generate two optical paths with an optical path difference.

A convex lens 81 and a double aperture plate 82 are optical elements included in the light branching section 14 . The convex lens 81 is arranged such that its optical axis coincides with the direction in which the laser light 41 emitted by the irradiation unit 11a travels straight. The convex lens 15 a , which is an example of the light converging section 15 , is arranged so that its optical axis 83 is perpendicular to the light receiving surface of the light receiving section 21 of the measuring section 12 and the planar surface of the double aperture plate 82 . The convex lens 15a is arranged at a position where the speckle pattern is formed on the light receiving surface of the light receiving unit 21 by condensing the scattered lights 52-1 and 52-2 that have passed through the double aperture plate . The double aperture plate 82 is arranged so that the surface of the flat portion is parallel to the light receiving surface of the light receiving section 21, and furthermore, the distance from the position intersecting the optical axis 83 to each of the two slits is uniform. are arranged as follows.

By arranging as described above, the laser light 41 emitted by the irradiation section 11a is diffused by the convex lens 81, and the diffused laser light 41 is irradiated to the scatterers 32-1 and 32-2. Scattered lights 52-1 and 52-2 generated by receiving the diffused laser light 41 by the scatterers 32-1 and 32-2 are diffracted when passing through the two slits of the double aperture plate 82. there will be a difference. The scattered lights 52-1 and 52-2 that have passed through the two slits of the double aperture plate 82 are condensed by the convex lens 15a and reach the light receiving surface of the light receiving section 21. FIG.

When the scattered light 52-1 reaches the light receiving surface of the light receiving section 21 through the two optical paths with the optical path difference caused by the double aperture plate 82, a speckle pattern reflecting the phase difference caused by the optical path difference is formed on the light receiving section 21. image is formed on the light-receiving surface of . Here, the surface of the scatterer 32-1 to be measured, that is, the surface irradiated with the laser beam diffused by the convex lens 81 is deformed to move in the direction indicated by the arrow 39c. Suppose it becomes 2. That is, in the scatterer 32-1, it is assumed that the same in-plane displacement as in 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 two optical paths with an optical path difference caused by the double aperture plate 82, the optical path difference and the scatterer 32-1 to the scatterer 32-2 A speckle pattern reflecting the phase difference caused by the amount of displacement when deformed is imaged on the light-receiving surface of the light-receiving unit 21 .

(Structure of optical branching section to which lateral shift method is applied)
The optical system shown in FIG. 9D is an optical system called a 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 beam 41 of the irradiation unit 11a to the light receiving surface of the light receiving unit 21 of the measurement unit 12, thereby separating two optical paths having an optical path difference. Generate. A convex lens 91 and a biprism 92 are optical elements included in the light branching section 14 . The convex lens 91 is arranged such that its optical axis 93 coincides with the direction in which the laser beam 41 emitted by the irradiation unit 11a travels straight. The biprism 92 is a so-called biprism, and is a triangular prism whose cross section is an isosceles triangle having an apex angle close to 180 degrees. The biprism 92 is arranged such that the plane including the base of the isosceles triangle is parallel to the light receiving surface of the light receiving section 21 . The convex lens 15a, which is an example of the light converging unit 15, has its optical axis perpendicular to the light receiving surface of the light receiving unit 21 of the measuring unit 12 and the plane including the base of the isosceles triangle shape of the biprism 92. It is arranged so as to intersect the side including the apex angle of the triangular shape. The convex lens 15a is arranged at a position where the speckle pattern is formed on the light receiving surface of the light receiving section 21 by condensing the scattered lights 52-1 and 52-2 that have passed through the biprism 92 and arrived.

By arranging as described above, the laser light 41 emitted by the irradiation unit 11 a is diffused by the convex lens 91 , and the diffused laser light is applied to the scatterer 32 . Scattered light 52 generated by the scatterer 32 receiving the laser light is transmitted through the biprism 92 . When the scattered light 52 is transmitted through the biprism 92, due to the optical action of the biprism 92, as shown in FIG. A double image 32D of the scatterer 32 is formed at the shifted position. Here, the light that forms the double image 32D and is generated by the biprism 92 is referred to as double image light 52D. The optical action of the biprism 92 causes an optical path difference between the scattered light 52 and the double image light 52D. The scattered light 52 transmitted 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 section 21 .

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 caused by the optical path difference is imaged on the light receiving surface of the light receiving unit 21. Become. Here, it is assumed that the scatterer 32 undergoes deformation of the out-of-plane displacement shown in the case of the reference light method in FIG. 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 caused by the displacement amount due to the optical path difference and the deformation of the scatterer 32 is received. An image is formed on the light receiving surface of the portion 21 .

By using the optical splitter 14 to which any one of the optical systems shown in FIGS. 9A to 9D is applied, the speckle pattern generated by the scatterer 32-1 before deformation and A speckle pattern produced by 32-2 will be obtained. Interference fringes can be obtained by calculating the square of the difference between the two speckle patterns before and after deformation. The brightness of the obtained interference fringes depends on the amount of displacement when the scatterer 32 is deformed. It is brightest when it is a half-integer multiple of . One interference fringe indicates the same amount of displacement, and if the surface of the scatterer 32 is continuous, the interference fringe can be regarded as a contour line in which the altitude is replaced by the amount of displacement. Therefore, in the region where the interference fringe interval is small, the change in the displacement amount is large, indicating that the shape of the scatterer 32 is rapidly changing. 32 shows that the shape is gradually changing. In this way, the speckle patterns corresponding to the measurement area are received by the pixels 22-1 to 22-n of the light receiving unit 21 of the measuring unit 12, and the shape of the scatterer 32 is compared before and after the deformation, whereby scattering It is possible to estimate the displacement amount of the position of the scatterer 32 corresponding to each of the pixels 22-1 to 22-n caused by the deformation of the shape of the scatterer 32. FIG.

(Processing by the measuring device of the second embodiment)
Processing by the measuring device 1a in the second embodiment will be described with reference to FIG. FIG. 10 is a flow chart showing the flow of processing by the calculation processing unit 13a. 9A is applied as the light branching unit 14, and the convex lens 15a is applied as the light converging unit 15. Processing will be explained.

As a prerequisite for starting the processing of the flowchart of FIG. 10, it is assumed that the following has been performed. The irradiation unit 11 a generates a laser beam 41 and outputs it to the light branching unit 14 . In the light splitting section 14 , the half mirror 61 splits the laser light 41 emitted by the irradiation section 11 a into laser light reaching the mirror 62 and laser light reaching the mirror 64 . The mirror 62 reflects the received laser light in the direction of the optical axis 67 , and the reflected laser light is diffused by the convex lens 63 to become the laser light 42 . The mirror 64 reflects the received laser light in the direction of the optical axis 68 , and the reflected laser light is diffused by the convex lens 65 to become the laser light 43 . The scattering medium 32 is irradiated with the laser light 42 and the laser light 43 . Scattered light 52 generated by the scatterer 32 receiving the laser light 42 and scattered light 53 generated by the scatterer 32 receiving the laser light 43 are collected by the convex lens 15a. Interference between the scattered light 52 and the scattered light 53 condensed by the convex lens 15a produces a speckle pattern in the pixels 22-1 to 22-n on the light receiving surface of the light receiving section 21. FIG.

When the shape of the scatterer 32 is not deformed, the scattered light 52 and the scattered light 53 do not change, 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 changes. do not. In this case, since the luminance value output by each of the pixels 22-1 to 22-n upon receiving the light of the speckle pattern does not change, the event detection unit 23 detects the light from any of the pixels 22-1 to 22-n A luminance change amount of "0" is detected. However, in reality, noise or the like exists, so the amount of change in brightness detected by the event detection unit 23 may not be "0", but it never exceeds the detection threshold. Therefore, in this case, the event detector 23 does not output any event data.

On the other hand, when the shape of the scatterer 32 is deformed, the scattered light 52 and the scattered light 53 change according to the amount of displacement when the shape of the scatterer 32 is deformed. Therefore, the speckle pattern changes according to 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 positions where the speckle pattern changes are changed. When the event detection unit 23 detects the amount of luminance change from the luminance values output by the pixels 22-1 to 22-n, it determines that the detected amount of luminance change is equal to or greater than a predetermined detection threshold. Then, event data for the pixel 22 corresponding to the luminance change amount is generated and output.

The flow of processing will be described below according to the flowchart of FIG. The calculation processing unit 13a takes in 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 included in each event data and the detection time. (step Se2).

The calculation processing unit 13a generates image data having the number of event data of each of the pixels 22-1 to 22-n as a pixel value (step Se3). As described above, the brightness of the interference fringes obtained by calculating the square of the difference between the two speckle patterns before and after deformation depends on the amount of displacement when the shape of the scatterer 32 is deformed. A bright portion of the interference fringes has a large amount of change in luminance before and after the scatterer 32 is deformed, so there is a large amount of event data. On the other hand, in the dark portion of the interference fringes, the luminance change amount before and after the scatterer 32 is deformed is small, so the event data is small or does not exist. Therefore, the image represented by the image data generated by the calculation processing unit 13a is an image showing changes in the interference fringes.

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

In the case of FIGS. 9A and 9C, that is, when the two-beam method and the two-aperture method are applied, the calculation processing unit 13a performs the That is, the amount of displacement of the scatterer 32 in the direction parallel to the surface of the scatterer 32 to be measured is calculated. In the case of FIG. 9B, that is, when the reference light method is applied, the calculation processing unit 13a calculates the scatterer in the direction of reference numeral 39b in FIG. 32 displacement amounts are calculated. In the case of FIG. 9D, that is, in the case of the lateral displacement method, the calculation processing unit 13a calculates the inclination of the scatterer 32 with respect to the direction of 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. Calculated as displacement. 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. FIG. Which optical system of FIGS. 9A to 9D is applied to the light branching unit 14 is appropriately determined depending on which direction of the displacement amount of the scatterer 32 is to be detected.

In the measuring apparatus 1a of the second embodiment described above, the irradiation unit 11a generates coherent light with which the scatterer 32 whose shape is deformed is irradiated. The optical splitter 14 splits 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 optical paths so that an optical path difference occurs. The light converging section 15 converges the two optical paths branched by the light branching section 14 to image a speckle pattern on a plurality of pixels 22-1 to 22-n provided in the measuring section 12. FIG. The measurement unit 12 receives speckle pattern light generated by interference of the scattered lights 52 and 53 generated by the scatterer 32 receiving the coherent light by the plurality of pixels 22-1 to 22-n, and the pixels 22- Detect pixels 22-1 to 22-n having a luminance change amount to be detected, in which a luminance change amount indicating a change in luminance value detected by each of pixels 1 to 22-n receiving speckle pattern light is predetermined. event data including the positions of the detected pixels 22-1 to 22-n, code values indicating the direction of change in luminance variation of the pixels 22-1 to 22-n, and detection time indicating the detection time. Output. The calculation processing unit 13a generates image data whose pixel value is the number of event data for each of the pixels 22-1 to 22-n within a predetermined period of time, and based on the generated image data, calculates the number of scatterers 32. Calculate the amount of displacement caused by the deformation.

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 to the two optical paths branched by the light branching unit 14 . , the phase difference of the added optical path difference will occur. Therefore, the speckle pattern imaged by the light converging unit 15 on the plurality of pixels 22-1 to 22-n changes according to the phase difference. Therefore, by generating image data whose pixel value is the number of event data corresponding to each of the pixels 22-1 to 22-n, the image of the generated image data is scattered due to the fineness of the intervals of the interference fringes. The result is an image showing the change in speckle pattern before and after deformation of the body 32 shape. By frequency-analyzing the generated image data, 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 interval of the interference fringes. In the generation of image data based on event data by the calculation processing unit 13a, unlike a frame camera, it is not necessary to acquire image data continuously a plurality of times. It becomes possible to estimate the change of an object whose change is not constant based on the speckle pattern under the condition that the time interval of is restricted.

In the above-described second embodiment, the convex lens 71 in FIG. 9B, the convex lens 81 in FIG. 9C, and the convex lens 91 in FIG. On the other hand, the light branching unit 14 does not include the convex lenses 71, 81, and 91, and adjusts the position of the optical element provided inside the irradiation unit 11a so that the irradiation unit 11a irradiates diffused laser light. You may make it

In the above-described second embodiment, the light branching unit 14 has a plurality of beams from the irradiation unit 11a to the measurement unit 12, regardless of which of the optical systems shown in FIGS. 9A to 9D is applied. The optical path leading to the pixels 22-1 to 22-n is branched into two so that an optical path difference occurs. On the other hand, 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 three or more optical paths so that optical path differences occur. can be In this case, the light converging unit 15 converges three or more optical paths branched by the light branching unit 14 to form speckle patterns on the pixels 22-1 to 22-n included in the measuring unit 12. Become.

In the first and second embodiments described above, when the event detection unit 23 determines that the luminance change amount of a certain pixel 22 is equal to or greater than a predetermined detection threshold value, the event detection unit 23 corresponds to the luminance change amount. A pixel 22 having a predetermined amount of change in luminance to be detected is detected as a pixel 22 having a luminance change amount to be detected. On the other hand, when the event detection unit 23 determines that the luminance change amount of a certain pixel 22 exceeds a predetermined detection threshold value, the event detection unit 23 determines in advance the pixel 22 corresponding to the luminance change amount. The pixel 22 having the luminance change amount to be detected may be detected. 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, correct determination is performed. Therefore, instead of using the absolute value of the difference between the maximum and minimum luminance values as the detection threshold value, the absolute value of the difference between the maximum and minimum luminance values is used to determine the accuracy of the determination of the event detection unit 23. It is necessary to set a value obtained by subtracting a minute value corresponding to , as a detection threshold.

The measuring device 1 of the first embodiment described above can be said to be a measuring device for measuring blood flow when the scatterer 30 is, for example, a human body, and the moving scatterer 31 is, for example, blood. It can also be called an observation device that observes the flow. If the scatterer 32 is, for example, a human body, the measuring device 1a of the second embodiment can also be called a measuring device for measuring changes in the shape of the human body, and can be called an observation device for observing changes in the shape of the human body. can also

The calculation processing units 13 and 13a in the first and second embodiments described above may be realized by a computer. In that case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in this recording medium may be read into a computer system and executed. It should be noted that the "computer system" referred to here includes hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible discs, magneto-optical discs, ROMs and CD-ROMs, and storage devices such as hard discs incorporated in computer systems. Furthermore, "computer-readable recording medium" means a medium that dynamically retains a program for a short period of time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It may also include something that holds the program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in that case. Further, the program may be for realizing a part of the functions described above, or may be capable of realizing the functions described above in combination with a program already recorded in the computer system. It may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design and the like are included within the scope of the gist of the present invention.

Reference Signs List 1 measuring device, 11 irradiation unit, 12 measurement unit, 13 calculation processing unit, 21 light receiving unit, 22-1 to 22-n pixels, 23 event detection unit, 30 scatterer, 31 movement scatterer

Claims (8)

an illumination unit that generates coherent light;
Light of a speckle pattern generated by interference of scattered light generated by a scatterer receiving the coherent light is received by a plurality of pixels, and luminance detected by each of the pixels receiving the light of the speckle pattern. detecting a pixel having a predetermined amount of luminance change to be detected, the position of the detected pixel and a code value indicating the direction of change of the amount of luminance change of the pixel; a measurement unit that generates event data including a detection time indicating the time of detection;
a calculation processing unit that calculates a physical quantity indicating a change in the scatterer based on the event data;
A measuring device comprising the scatterer comprises a moving mobile scatterer;
The calculation processing unit is
moving speed of the moving scatterer at the position of the scatterer corresponding to each of the pixels based on the number of the event data for each pixel per predetermined unit time as a physical quantity indicating the change of the scatterer calculate,
The measuring device according to claim 1. the scatterer comprises a moving mobile scatterer;
The measuring unit
Determining whether each of the pixels is a pixel having the luminance change amount to be detected based on the luminance change amount corresponding to each of the pixels and a predetermined detection threshold;
The calculation processing unit is
A code value indicating the change direction of the luminance change amount included in the event data is multiplied by the detection threshold to calculate a multiplied value, and for each of the pixels, for each detection time, A value obtained by integrating the multiplied values corresponding to the detection times is calculated as an integrated value for each of the detection times, and corresponding to each of the pixels based on the integrated value for each of the detection times calculated for each of the pixels. calculating the moving speed of the moving scatterer at the position of the scatterer as a physical quantity indicating the change of the scatterer;
The measuring device according to claim 1. the scatterer comprises a moving mobile scatterer;
The measuring unit
determined based on the amount of change in brightness corresponding to each of the pixels, and a predetermined detection threshold, which is an absolute value of a difference between the maximum value and the minimum value of the brightness values detected by the pixel from the light of the speckle pattern; Determining whether each of the pixels is a pixel having the luminance change amount to be detected,
The calculation processing unit is
calculating an occurrence interval of the event data for each pixel based on the detection time included in the event data; calculating a moving speed of the moving scatterer at the position of the scatterer as a physical quantity indicating a change of the scatterer;
The measuring device according to claim 1. the scatterer comprises a moving mobile scatterer;
The calculation processing unit is
image data for each detection time is generated based on the code value included in the event data, and the moving speed of the moving scatterer is calculated based on the generated image data at two different detection times; Calculated as a physical quantity that indicates changes in the body,
The measuring device according to claim 1. an optical branching unit that branches an optical path from the irradiation unit to the plurality of pixels of the measurement unit into a plurality of optical paths so that an optical path difference occurs;
a light converging unit that converges the plurality of optical paths branched by the light branching unit and forms an image of the speckle pattern on the plurality of pixels included in the measurement unit;
The scatterer is a scatterer whose shape is deformable,
The calculation processing unit is
generating image data whose pixel value is the number of event data for each pixel within a predetermined time period; Calculated as a physical quantity that indicates the change in
The measuring device according to claim 1. produce coherent light,
A speckle pattern of light generated by interference of scattered light generated by a scatterer receiving the coherent light is received by a plurality of pixels,
Detecting a pixel having a predetermined amount of luminance change to be detected, wherein the amount of luminance change indicating a change in luminance value detected by each of the pixels receiving the light of the speckle pattern is determined in advance;
generating event data including the position of the detected pixel, a code value indicating the change direction of the luminance change amount of the pixel, and a detection time indicating the detection time;
calculating a physical quantity indicating a change in the scatterer based on the generated event data;
measurement method. A speckle pattern of light generated by interference of scattered light generated by a scatterer receiving coherent light is received by a plurality of pixels, and each pixel receives and detects a luminance value of the speckle pattern of light. detecting a pixel having a predetermined amount of luminance change to be detected, the position of the detected pixel, a code value indicating the direction of change of the amount of luminance change of the pixel, a measurement step of generating event data including a detection time indicating the time when the
a calculation processing step of calculating a physical quantity indicating a change in the scatterer based on the event data;
A program that causes a computer to run

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