RU2265227C2 - Passive method for detecting optical objects and photo-detector for realization of said method - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: prior to detection of optical object, dimensions and position of direction diagram of photo-detector are determined and recorded in computer memory, zone of optical blocking is set by dimensions and position of direction diagram of only the photo-detector, passive-action photo-detector without light source is used, while dynamic range of light flows in blocking zone is used, 60 dB, dynamic range of levels of optical signals of photo-diode 26 dB, optical object is registered by position of time characteristics, photo-diode signal, characteristic sign of object is determined on basis of position of time characteristics of photo-diode signal in negative or positive areas of signal values, appropriately passive or active. Photo-detector has optical block, including spherical lens and diaphragm, photo-diode, electronic board of photo-detector, including transformer for transformation of current from photo-diode to voltage, amplifier and comparator, also has base, on which input window is positioned and on which optical block, electronic board, electronic board of signals generator and electronic board of curtain control are positioned together with socket for connection to computer and indicator.

EFFECT: possible detection of optical objects without using an additionally light source with higher precision; excluded influence of daylight level changes on precision of measurements in broad dynamic range of daylight levels; possible detection of passive shadow-giving, and active, emitting, optical objects; possible determination of shape of objects and presence of accompanying fragments; possible detection of objects with optical signals of different value; higher reliability; simplified adjustment of device prior to measurements; possible portable variant of device; decreased deployment time under field conditions.

2 cl, 8 dwg

Description

The invention relates to measuring equipment and can be used in measuring systems when registering optical objects at a given point, when examining their shape and the nature of optical radiation in the infrared wavelength range.

The closest analogue to the claimed method is a method for detecting optical objects (1), which provides for the use of an optical emitter (illuminator) in addition to a photodetector. The illuminator creates an optical barrier or optical blocking area located between the illuminator and the photodetector. When the detection object is in the optical blocking zone, the optical radiation is interrupted between the illuminator and the photodetector and the moment of interruption of the optical radiation is recorded.

The disadvantages of this method are the use of additional optical radiation from the illuminator, the loss of information about the detection object itself, its features, the effect of changes in daylight levels on the measurement accuracy. In the zone of optical blocking, with an increase in the level of daylight from reflected solar radiation, to maintain the accuracy of the measurement, it is necessary to increase the power of the illuminator, since the luminous flux, falling into the blocking zone, changes the response threshold of the signal level comparator. In addition, the disadvantages include the complexity of the mutual tuning of the optical systems of the illuminator and the photodetector, the uncertainty introduced by the interference of the signal level comparators at the time of interruption of the optical radiation from the illuminator.

The inventive method allows you to:

- detect optical objects without the use of an additional illuminator with higher registration accuracy due to the use of a calibrated radiation pattern of the photodetector itself;

- detect objects with different optical signals.

The inventive method allows you to determine the shape, type of optical object, the presence of the object accompanying fragments.

This is achieved by the fact that in the claimed method, which includes the use of a photodetector based on a photo diode with linear light characteristic, an electronic computer (computer) with an indicator, before detecting an optical object, the dimensions and position patterns of the photodetector device are determined and stored in a computer, set the optical blocking zone with the dimensions and position of the radiation patterns of only the photodetector, use a passive photodetector without an illuminator moreover, the dynamic range of the light fluxes falling into the blocking zone is used, 60 dB, the dynamic range of the optical signal levels is 26 dB, the optical object is registered by the position of the temporal characteristics of the photodiode signal, the characteristic feature of the object is determined by the location of the photodiode signal in the negative or positive regions of the signal values, respectively passive or active.

The closest analogue to the claimed device are photodetectors (2), included in the devices FEB-4SM, FEB-5, FEB-6, FEB-7 of the Nizhny Tagil Institute of Metal Testing.

The disadvantages of the above photodetectors are: the obligatory presence of illuminators for their operation, the difficulty of setting up two optical systems of the illuminator and a photodetector to create an optical blocking zone, a negative effect on the measurement of changes in daylight levels, stationarity, low reliability and accuracy of measurements due to uncertainty introduced by interference signal level comparators at the time of interruption of radiation from the illuminator.

The inventive photodetector allows to solve the following tasks:

- increase the accuracy of registration of optical objects;

- increase the reliability of registration of optical objects;

- simplify device setup before measurements;

- make the device in the form of a portable structure;

- increase mobility, reduce the deployment time of the device in the field;

- ensure the operation of the device in a wide range of daylight conditions.

The solution of the tasks is achieved by the fact that the base with which the input window is combined is introduced into the photodetector device containing an optical unit, including a spherical lens, an aperture and a photodiode, an electronic board of the photodetector device, including a converter for converting current from the photodiode to voltage, an amplifier and a comparator and on which the optical unit, the electronic boards of the photodetector, signal former and the curtain control board, the computer connection connector and the indicator are placed ohm, as well as a direct current amplifier and a circuit for coupling the levels to which the constant components of the voltage are supplied from the output of the converter, and the voltage from the output of the direct current amplifier is supplied to a comparator, from the output of which the signals are sent to the curtain control board, designed to attenuate the light flux, amplifiers with a linear change in the transfer coefficient, to which through the signal separation element the variable voltage components from the converter are supplied, to the other input of which voltage from the output of the interface circuit of the levels and the output of which the signals are fed to the input of the amplifier with a switchable transmission coefficient, a filter for forming a passband and a terminal amplifier.

Figure 1 shows the design of the photodetector, where indicated:

1 - electronic board of the photodetector;

2 - electronic board of the signal shaper;

3 - base;

4 - optical block;

5 - input window;

6 - connection connector;

7 - electronic control board curtain;

8 - direction parallel to the trajectories of the objects;

9 - direction perpendicular to the trajectories of the movement of objects.

Figure 2 shows the location of the elements of the optical unit with a photodiode, where indicated:

10 - curtain;

11 - aperture;

12 - spherical lens;

13 - photodiode;

14 - connector with the electronic board of the photodetector.

Figure 3 shows the radiation patterns of the photodetector, where indicated:

15 is a radiation pattern of a device in a plane perpendicular to the paths of movement of objects;

16 is the width of the radiation pattern of the device;

17 is a radiation pattern of a device in a plane parallel to the trajectories of objects;

18 is the height of the radiation pattern of the device.

Figure 4 shows the structural diagram of the photodetector, where indicated:

1 - electronic board of the photodetector;

2 - electronic board of the signal shaper;

7 - electronic control board curtain;

10 - curtain;

11 - aperture;

12 - spherical lens;

13 - photodiode;

19 - converter;

20 is a signal separation element;

21 is a diagram of a pairing of levels;

22 - DC amplifier of the photodiode;

23 - amplifiers with a linear change in the gain;

24 - switchable amplifier;

25 - filter;

26 - terminal amplifier;

27 is a comparator.

Figure 5 shows graphs explaining the operation of automatic gain control (AGC) of the photodetector, where is indicated:

28 is a graph of the dependence of the signal voltages and with at the input of the amplifier with a linear change in the gain 23 from the levels of the constant components of the voltage u _n at the output of the converter;

29 is a graph of the dependence of the gain K _{n of the} photodetector on the levels of the constant voltage components u _n at the output of the converter. As the coordinates, the voltages u _n and u _c are chosen, respectively, the constant and variable components of the voltages at the output of the converter.

Figure 6 shows a structural diagram of a photodetector with a computer and an indicator, where indicated:

30 - photodetector;

31 - computers;

32 - indicator.

Figure 7 shows the temporal characteristics of the signals of the photodiode, where indicated:

33 - voltage of the photodiode signals from passive objects located in the negative region of the signal values at the output of the photodetector;

34 - voltage signals of the photodiode from active objects located in the positive range of signal values at the output of the photodetector.

On Fig shows the temporal characteristics of the signals of the photodiode in the presence of accompanying object fragments, where indicated:

35 - voltage signals of the photodiode from the fragments accompanying the object at the output of the photodetector.

The inventive method for detecting optical objects is as follows. The photodetector 30 is calibrated, i.e. determine the sizes 16, 18 and the position of the radiation patterns (perpendicular and parallel to the movement of objects). The dimensions and position patterns of the device are recorded in the memory of the computer 31.

The photodetector 30 is positioned so that the optical objects fall into the blocking zone, and the paths of the objects are perpendicular to the plane of the diagram 15. Using connector 6, the photodetector is connected to a computer 31 and an indicator 32 and connected to the network. Due to daylight, at the moment, a constant component of the voltage of the photodiode signal u _n arises at the output of the converter 19, which in the AGC system, including a level conjugation circuit 21 and an amplifier with a linear change in the transmission coefficient of the photodiode 23 signal, automatically controls the gain of the photodetector, providing a given output photodiode signal level. Thanks to the action of the AGC system, the influence of daylight on the measurement accuracy is excluded. When moving, optical objects, falling into the blocking zone, modulate the luminous flux in amplitude, causing optical signals. The dynamic range of optical signals depends on the size of optical objects, the magnitude and nature of the radiation, the degree of their distance from the photodetector, and is 26 dB. To detect optical objects with different optical signals, the control voltage of the switchable amplifier 24 is preselected. The control voltage of the switchable amplifier 26 allows you to change the gain of the signals of the photodetector 20 times, which is equivalent to the dynamic range of the optical signals of 26 dB. For large optical signals, the gain of the photodetector using the control voltage is reduced, and for small optical signals it is increased, maintaining a certain level of the output photodiode signals in the entire dynamic range of existing optical signals.

When optical objects get into the blocking zone, the photodiode 13 generates currents that are different from the level of intrinsic noise. The magnitude of the photodiode currents depends on the magnitude of the optical signals and on the levels of light fluxes. The action of the AGC system and the control of the gain of the switchable amplifier 24 provide a certain level of signals of the photodiode at the output of the photodetector. The currents of the photodiode 13, converting to voltage u _c , are amplified at the input of the amplifier with a linear change in the transmission coefficient and fed to the output of the photodetector, then to the computer 31 and indicator 32. The indicator 32 is the screen of the computer monitor. Using the computer program, the photodiode signals are converted into digital form and stored for further processing in the computer memory for the purpose of subsequent display of the graphs of these signals on the computer monitor screen.

On the screen of the indicator 32 there are temporary characteristics of the signals of the photodiode. For active emitting objects, the temporal characteristics of the photodiode signals are located in the positive range of signal values 34, for passive objects that create a “shadow”, the temporal characteristics of the photodiode signals are located in the region of negative signal values 33. The amplitudes of the negative signals are currently proportional to the linear dimensions of the object in the direction perpendicular to the movement. Determining the type of object occurs by visual observation of the shape of the negative temporal characteristics of the photodiode signal in a time scale. In the presence of fragments accompanying the object, the temporal characteristics of the photodiode signals can be located both in the positive and negative ranges of signal values 35. The duration of the photodiode signals depends on the speed of the object: the higher the speed of the optical object, the shorter the duration of the photodiode signal. To obtain the undistorted waveform of the photodiode, a wide passband of amplifiers, including a converter, is used.

The design of the photodetector is as follows. The electronic board of the photodetector 1 is connected via cable to the electronic board of the signal conditioning instrument 2. Both electronic boards and the optical unit 4 are fixed to the base 3. The connector 6 is fixed to the same base 3 and the cable is connected to the electronic circuit board of the signal conditioning instrument 2. Input window 5 It is structurally combined with base 3 and forms a single whole with it. On the electronic control board for the shutter 7, there are elements that control the shutter 10. Using a connector 14, a photodiode 13 connects to the electronic board of the photodetector 1. The focal length of the spherical lens 12 together with the diaphragm 11 and the input window 5 form the dimensions of the radiation patterns of the photodetector 15, 17 .

The inventive photodetector operates as follows. In accordance with the daylight conditions, the light fluxes collected by the spherical lens 12, amplitude modulated by optical objects falling into the blocking zone, having passed through the diaphragm 11, are transmitted to the photodiode 13 in the form of optical signals. Changing the daylight conditions leads to the fact that the light flux entering the blocking zone changes in the dynamic range of 60 dB. The photodiode 13 under the influence of optical signals generates currents, which in the Converter 19 are converted to voltage u. The voltages u from the output of the converter 19 are supplied to the signal separation element 20. The constant voltage components u _n are supplied to the interface circuit of the levels 21 and the DC amplifier 22. The voltage u _{n is} used in the AGC system to control the gain of the claimed device. The AGC system consists of a coupling circuit of levels 21 and an amplifier with a linear change in the transmission coefficient of the signal of the photodiode 23. The variable voltage components u _c are fed to the input of an amplifier with a linear change in the transmission coefficient 23, which consists of three broadband amplifiers connected in series with a linear dependence of the transmission coefficients from control voltages supplied to it from the output of the leveling circuit 21.

Graph 28 shows a linear increase in voltage u _c from increasing voltage u _n . Graph 29 shows a linear decrease in the gain K _{n of the} photodetector with increasing voltage u _n . The increase in voltage u _n is associated with an increase in luminous flux. Thus, an increase in the photodiode signals caused by an increase in the light flux is compensated by a decrease in the gain K _{n of the} photodetector due to the action of the AGC system. The signals from the output of the amplifier 23 are fed to the input of the amplifier with a switchable transmission coefficient 24. The second input of the amplifier 24 receives the control voltage of the transmission coefficient, which decreases or increases the transmission coefficient of the amplifier 24 when the levels of optical signals increase or decrease in the dynamic range of 26 dB. The filter 25 forms the passband of the photodetector. The terminal amplifier 26 provides the necessary power of the photodiode signals at the output of the photodetector. The voltage from the output of the DC amplifier 22 is supplied to a comparator 27, from the output of which the control voltage is supplied to the electronic control board for the shutter 7. When direct sunlight enters the blocking zone, the shutter 10 automatically activates, weakening the light flux. The return of the curtain 10 to its initial state occurs automatically.

In addition to registering signals from optical objects, the claimed photodetector allows you to further examine their shape, determine the type and characteristic features of optical objects and their fragments. These properties of the photodetector were obtained for the first time; they allow us to study and analyze optical objects in detail.

Technical solutions underlying the construction of a photodetector for the implementation of the proposed method, made at the current level of development of electronics using domestic element base. The inventive device is part of and modifications to the system of the initial speed meter FEB 2I45 of the Nizhny Novgorod Research Institute of Instrument Engineering.

Bibliographic data

1. Hermann Schreiber "Infrared rays in electronics", Moscow, 2001, p. 94.

2. Advertising NTIIM SKB measuring equipment, Photoelectric speed meters, 622015, Nizhny Tagil, Gagarin St., 29.

Claims (2)

1. A passive method for detecting optical objects, including the use of a photodetector based on a photo diode with a linear light characteristic, an electronic computer with an indicator, characterized in that before detecting an optical object, determine the size and position of the radiation patterns of the photodetector and enter into computer memory, set the optical blocking zone with the dimensions and position of radiation patterns of only the photodetector, use a passive photodetector actions without a illuminator, use the dynamic range of light fluxes falling into the blocking zone, 60 dB, use the dynamic range of optical signals 26 dB, register the optical object by the position of the temporal characteristics of the photodiode signal, determine the location of the temporal characteristics of the photodiode signal in the negative or positive ranges of signal values characteristic feature of the object, respectively passive or active. 2. A photodetector for detecting optical objects, comprising an optical unit including a spherical lens and an aperture, a photodiode, an electronic board including a converter for converting current from a photodiode to voltage, an amplifier and a comparator, characterized in that it contains a base with which the input a window and on which an optical unit is placed, a curtain control board with a curtain control circuit designed to attenuate the light flux, an electronic board, a connection connector for connecting with a computer and an indicator, as well as a DC amplifier and a circuit for interfacing the levels to which the constant components of the voltage are supplied from the output of the converter, and the voltage from the output of the DC amplifier is supplied to a comparator, from the output of which the signals are sent to the curtain control board with the curtain control circuit, amplifiers with a linear change in the transfer coefficient, to which through the signal separation element the alternating voltage components from the converter are supplied, to the other input of which the voltage Nia output from the conjugation circuit and the output levels of the signals which are input to an amplifier with selectable gain, filter bandwidth and formation of the final amplifier.

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