RU2485459C1 - Method to measure time intervals between radiation pulses - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: in the method for measurement of time intervals between radiation pulses each of pulses generated by an investigated object is introduced into the appropriate light guide, the opposite ends of light guides are arranged in the form of a matrix, its image with the help of an optical system including a rotary mirror is moved along a photosensitive surface of a photodetector, on which light marks are fixed. Time intervals are determined between marks as a quotient from division of distances between them into a speed of image scan, at the same time the time intervals are broken into two parts: the first one, common for all intervals (delay time T_spec), the value of which is by 1 mcs lower than the time of development of the investigated process, produced by calculation, and the second one, requiring measurement for each interval ΔT_ik, where i, k - numbers of a column and a line of the light guide image in the matrix. At the moment T_spec a light signal is generated, sent with the help of light guides into corner points of the matrix and fixed with the help of a digital recorder, and this signal is delayed relative to the start one by the specified value, radiation pulses are fixed in the same frame from light guides at the completing stage of the process, as well as time marks generated with the specified frequency, using the coordinates of corner points of the light guide matrix, and also knowing the number of columns m and lines n in it, through calculation they determine coordinates of all light guides at the moment T_spec, the difference of coordinates ΔX_ik is defined along the direction of image scan for each light guide at the moment of radiation of light pulses by them and at the moment T_spec. At the same time a recorder based on CCD-matrix is used, coordinates of light marks are coordinates of a pixel in the light guide image, which accumulated the maximum charge, using time marks, the speed of image scan is determined, intervals ΔT_jk are found as the quotient from division of the appropriate difference of coordinates into the speed of scan, the sought for time intervals T_ik are defined as a sum of intervals T_spec+ΔT_ik.

EFFECT: reduced error of measurements.

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Description

The proposed method can be applied in the field of measurement technology in the study of single fast-flowing physical processes accompanied by light and infrared radiation, in particular the formation of light pulses with a duration of about 0.2 μs, the number of which in the studied object, which is a source of light pulses, can reach a value of about 10 ³ .

The formation of light pulses occurs at the initial and final stages of the process under study, the duration of which is several tens of microseconds and can be estimated in advance with an error of the order of 1 microsecond.

At the initial stage, simultaneously with the electrical signal initiating the process, several light pulses are formed, which are used as reference points. The formation of light pulses at the end of the process occurs at different points on the surface of the investigated object in an interval not exceeding a few microseconds.

The task is to fix the spatio-temporal structure of light pulses and, during processing of the resulting picture, measure the development time intervals of the investigated physical process from its beginning to the formation of each light pulse at the final stage.

Currently, this problem is being solved using high-speed photographic recorders of the SFR type [1] (prototype) in the following way: each of the light pulses generated by the test object is introduced into the corresponding fiber, the opposite ends of the fibers are placed in a bar in the form of a matrix with a certain number of columns (rows) ) and rows (optical fibers in a row), the image of the matrix with optical fibers using an optical system that includes a mirror rotating at a given speed, is moved along the photosensitive surface of the photodetector the camera, fix the light marks formed on the photosensitive surface of the photodetector at the initial and final stages of the process under study, measure the distance between the mark that defines the beginning of the process, and the marks formed at the end of the process, determine the time intervals as the quotient of dividing the distances between the marks by the image scan speed .

To implement this method, a high-speed photochronographic recorder (SFR) is used [1], in which a photographic film is used as a photodetector that detects pulses of optical radiation.

Figure 1 shows a photochronogram of an experiment on the study of a fast-flowing physical process obtained using SFR on photographic film.

Accepted designations:

1 - marks from light pulses that determine the beginning of the process under study, from optical fibers located in the middle of the rows indicated by letters from a to f;

2 - marks from light pulses generated at the end of the process, transmitted along the optical fibers located in rows indicated by letters from a to f in the matrix;

3 - the interval on the film in the sweep direction ΔX ₁ between the mark that defines the beginning of the process for the first row of optical fibers and the mark from the light pulse generated at the end of the process and transmitted to the first optical fiber of the row indicated by the letter a in figure 1.

After measuring the size of the interval 3 ΔX ₁ using the photographic imprint of the working frame and knowing the scanning speed of the image on the film V _times , we find the desired time interval by the formula:

Similar actions are performed with respect to marks from light pulses transmitted by other light guides 1 and 2 formed at the beginning and at the end of the process under study.

It should be noted the following:

- with typical development times of the investigated process of 10 ² μs and an image scan speed of about 3 mm / μs, the length of the working frame on the film is about 300 mm, which makes it impossible to use photodetectors with a sensitive surface of smaller sizes when recording intervals 3 in this way;

- a photographic print of the working frame for processing convenience is performed with an increase of 5 or more times, with marks 1 and 2 fixing the radiation of the fiber, in shape representing an ellipse with a large axis elongated along the scan direction of the image, the size of which is several mm, do not always have sharp borders; as the coordinates of marks 1 and 2, take its border or center, determined by the operator by eye, which gives a significant error in determining the coordinate.

The disadvantage of the above method for determining time intervals is a significant error in their determination, ranging from 1 to 2% of the recorded interval 3, which is associated with inaccuracy in determining the speed of rotation of the mirror at the time of registration, deformation of film and photo paper during development and drying, error in determining the coordinates of marks and etc.

The second disadvantage of this method is the long time taken to obtain the measurement results, due to the need for the development of film and further work on extracting information from the resulting work frame, such as obtaining enlarged prints of work frames on photo paper, manually measuring the distances 3 between the marks and etc.

The technical result of the invention is to reduce the measurement error of time intervals by 2-10 times (depending on the presence or absence of time stamps on the film) and to reduce the processing time of recorded information from tens of hours to several minutes.

The technical result in the proposed method for measuring time intervals between radiation pulses is achieved by the fact that each of the light pulses generated by the object under study is introduced into the corresponding fiber, the opposite ends of the fibers are placed in a bar in the form of a matrix with a certain number of columns (rows) and rows (fibers in row), the image of the matrix with optical fibers using an optical system including a mirror rotating at a given speed, is moved along the photosensitive surface of the photodetector ka, light marks are formed on the photosensitive surface of the photodetector formed at different stages of the process under study, they determine the time intervals between the marks as the quotient of dividing the distances between them by the image scan speed, the desired time intervals are divided into two parts: the first, common for all intervals (time delay T _ass ), the value of which is 1 μs less than the development time of the process under study, obtained by calculation based on the available information about it, and the second, individual and require measurements for each interval ΔT _ik , where i, k are the column and row numbers of the image of the fiber in the matrix, which is of the order of 1 μs, at the moment T, the _{backside is} formed, transmitted via fiber optics to the corner points of the matrix, and the light signal is recorded using a digital recorder, delayed with respect to the start-up by a predetermined amount, the radiation pulses from the optical fibers at the final stage of the process and time stamps formed at a given frequency are recorded in the same frame using the coordinates of the corner points of the optical fiber matrix, as well as knowing the quantity GUT column m and row n therein, calculated by determining the coordinates of all the optical fibers at the time T _ass, determined by the difference coordinate ΔH _Ik along the image scan direction for each of the optical fibers at the time of radiation of the light pulses and time T _butt, while in a digital a light signal recorder is used a registrar in which the CCD matrix is a radiation-sensitive element, and the coordinates of the light marks are the pixel coordinates in the image of the light guide that has accumulated the maximum an insulating charge, using timestamps determined speed image scanning interval? T are _Ik as the quotient corresponding to the difference of coordinates on the scanning speed determined by the required time intervals T _Ik as the sum of intervals T +? T _{ass Ik.}

Figure 2 shows an illustration of the process of finding the interval T _ik on the example of one fiber.

Accepted designations:

4 - time stamp on the left side of the frame;

5 - time stamp on the right side of the frame;

6 - four marks from the light signal, delayed in relation to the start signal by the value of T _ass and transmitted using optical fibers to the corner points of the matrix;

7 - the estimated position of the image of the fiber on the photosensitive surface of the CCD matrix with coordinate X _{Tzad ik} ;

8 - mark from the light pulse formed at the final stage of the process under study, having the coordinate X _{slave ik} ;

ΔХ _iк is the interval on the photosensitive surface of the CCD matrix between the image of the fiber at the moment T _ass and at the final stage of the process.

The method is implemented as follows:

- the desired time interval between the beginning and the end of the process, found by calculation on the basis of the available information, is divided into two parts: the first, the value of which is 1 μs less than the calculated (delay time T _back ), and the second ( _{ΔТ iк} ), which requires measurement;

- at the moment T, the _{butt is} formed, transmitted using optical fibers to the corner points of the matrix and four points 6 are recorded with a digital recorder from the light signal delayed by the value of T _rear relative to the start signal, the 8 point from the light pulse generated in the same frame is fixed at the final stage of the process under study, having the coordinate X _{slave ik} , as well as time stamps formed with a given frequency,

- using the coordinates of the corner points 6 of the matrix of optical fibers, as well as knowing the number of columns (m) and rows (n) in it, calculate the coordinate 7 of the optical fiber at the moment T _ass by the formula:

where X ₁ and X ₃ are the coordinates of the light marks from the optical fibers 6 located at the left and right upper corner points of the fiber matrix, X ₂ is the coordinate of the light marks from the optical fiber 6 located at the lower left corner point of the matrix, in pixels,

i, k are the column and row numbers of the matrix in which the fiber is located: 1≤i≤m, 1≤k≤n;

- determine the coordinate difference ΔX _ik along the scan direction of the image for each of the optical fibers at the moment they emit light pulses and at the moment T _ass according to the formula:

where X _{slave ik} is the coordinate of the mark from the light pulse 8 formed at the final stage of the process under study, X _{Tzad ik} is the calculated coordinate of the image of the optical fiber 7 on the photosensitive surface of the CCD matrix at the time T _ass ;

- determine the scan speed of the image V _rafts on the surface of the photodetector, for which they determine the coordinate X of the _{left mark} 4 and X of the _{right mark of} 5 time _stamps in the left and right parts of the frame and the number of periods p between them and, knowing the value of the period of the marks of the T _mark , find the sweep speed images in units of pixels in microseconds by the formula:

- determine the time intervals ΔT _ik by the formula:

- find the desired interval T _ik from the beginning of the process to the exit of radiation from the optical fiber 8, located in the column and row with numbers i and k, respectively:

Figure 3 shows the working frame obtained by studying the process described in the present application for the case of thirteen optical fibers arranged in one row (row number i = 1 for all optical fibers and the number of optical fiber in the row are within 1≤k≤13).

Accepted designations:

9 - time stamps formed with a given frequency;

10 - marks from the light signal delayed in relation to the start signal by the value of T _ass = 29 μs and transmitted using the optical fibers to the upper and lower points of a number of optical fibers;

11 - marks from thirteen light pulses formed at the final stage of the investigated process.

The table shows the results of mathematical programming of the image of the working frame shown in figure 3, by the formulas (2) - (6).

The average value of the measured time intervals was 30.53 μs, and the standard deviation was 0.02 μs.

As a light pulse recorder based on a CCD matrix, a digital pulsed light radiation recorder was used [2].

The proposed method for measuring time intervals allowed to reduce the measurement error by 2-10 times (depending on the presence or absence of time stamps on the film) and reduce the processing time of information from tens of hours to several minutes.

LITERATURE

1. A.S. Dubovik. Photographic registration of fast processes. M., "Science", 1984, p. 51.

2. Digital recorder of pulsed light radiation. Utility Model Patent No. 54478, publ. 06/27/2006.

Row number (i) Fiber number in row (k) Time interval _Tik , μs one one 30.51 one 2 30.51 one 3 30.48 one four 30.54 one 5 30.53 one 6 30.52 one 7 30.54 one 8 30.56 one 9 30.51 one 10 30.49 one eleven 30.57 one 12 30.54 one 13 30.52 Average value 30.53 Standard deviation 0.02

Claims (1)

A method for measuring time intervals between radiation pulses, namely, that each of the light pulses generated by the object under study is introduced into the corresponding fiber, the opposite ends of the fibers are placed in a bar in the form of a matrix with a certain number of columns (rows) and rows (fibers in a row) , the image of the matrix with optical fibers using an optical system that includes a mirror rotating at a given speed, is moved along the photosensitive surface of the photodetector, fixed on a photosensitive of the surface of the photodetector, the light marks formed at different stages of the process under study determine the time intervals between the marks as the quotient of dividing the distances between them by the image scan speed, characterized in that the desired time intervals are divided into two parts: the first, common for all intervals (time delay T _ass) whose magnitude is less than 1 microsecond of time the test process obtained by calculation based on the information about it, and a second individual measuring and requiring to every? T interval _ik, where i, k - the image column and row numbers fiber in a matrix, having the order of 1 microsecond, the time T _back is formed, is transmitted via the optical fibers in the corner of the matrix points and fixed via the digital logger light signal delayed by relative to the start-up by a given value, the radiation pulses from the optical fibers at the final stage of the process and time stamps, formed at a given frequency, using the coordinates of the corner points of the optical fiber matrix, and also knowing the number of columns are recorded in the same frame m and row n therein, calculated by determining the coordinates of all the optical fibers at the time T _ass, determined by the difference coordinate ΔH _ik along the image scan direction for each of the optical fibers at the moment of light pulse emission and the moment T _butt, while in a digital recorder light signals are used by a registrar in which the CCD matrix is a radiation-sensitive element, and the coordinates of the pixels are taken as the coordinates of the pixel in the image of the fiber with the maximum electric series, using timestamps, determine the scan rate of the image, find the intervals ΔT _ik as the quotient of the division of the corresponding coordinate difference by the scan speed, determine the desired time intervals T _ik as the sum of the intervals T _back + ΔT _ik .

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