CN103760567A - Passive imaging system with distance measuring function and distance measuring method thereof - Google Patents

Abstract

The invention discloses a passive imaging system with a ranging function and a ranging method thereof. The system includes: a high-frequency low-energy pulse laser emitting device for emitting high-frequency low-energy laser pulses, and beam expansion and shaping to achieve far Distance; photodiode array detector imaging device, used to receive the laser spot and background image reflected back by the target, and obtain the distance value by adjusting the integration time; video amplification and analog-to-digital conversion device, used to convert the photodiode array detector The photo-generated charge of the imaging device is converted into a voltage, and the analog image is digitized through the analog-to-digital converter; the digital processing device for digital image processing and timing generation is used to preprocess and target the digital image input by the video amplification and analog-to-digital conversion device extract. The invention realizes the combination of high-performance passive imaging and ranging functions.

Description

A passive imaging system with ranging function and its ranging method

technical field

The invention belongs to the technical field of laser imaging and ranging, in particular to a passive imaging system with a ranging function and a ranging method thereof.

Background technique

The integration capacitor and transistor resources used for ranging can realize a very short integration time window (10ns-10μs), and realize the gating function to integrate the received signal.

The laser rangefinders currently on the market are all non-imaging rangefinders, which use a laser beam with a small divergence angle to irradiate the target to form a laser measurement point, and use a point detector to receive the reflected or scattered laser signal from the measurement point. Inversion obtains the target distance. Because the size of the laser spot formed when the laser is irradiated on the target is very small, it leads to the difficulty of homing, that is, it is difficult for the laser beam to aim at the target when measuring the distance of a long-distance target, especially a small target.

In order to solve this problem, the laser range finder is supplemented with a sighting telescope, and the observer can find the measured target through the telescope. However, the telescopic rangefinder can only be effectively homing under the condition of suitable ambient illumination, and cannot be effectively homing at night and other low-illuminance conditions, and when the ambient illumination is high or the laser wavelength is invisible to the human eye, It is difficult for the human eye to find the laser measurement point on the target. For this reason, the aiming telescope and the laser rangefinder are usually calibrated and calibrated, and the measurement point is selected by aiming at the cross reticle on the telescope, but this will cause the telescope rangefinder to Shocks are sensitive.

In addition, Leica Earth System Development Co., Ltd. invented a rangefinder with an aiming device (invention patent number ZL02814430.9). The range finder uses visible light beams to irradiate the target to form a measurement point on the target, and observe the measurement point with the help of the aiming device to ensure that the optical receiving system can effectively receive the signal from the target to achieve target distance measurement. However, when measuring the range of the target in a low-illuminance environment, the aiming device of the rangefinder still cannot be effectively homing.

Aiming at the problem of finding in low-light environment, Beihang University invented a hand-held day and night laser imaging rangefinder (invention patent application number: 201010293433.2), including laser imaging subsystem and laser ranging subsystem. Among them, the laser imaging The system realizes the effective detection of the target in the low-light environment, and the laser ranging subsystem realizes the target ranging. The laser imaging rangefinder mainly uses the laser imaging subsystem to replace the aiming telescope, and still uses the reticle to aim at the target. Therefore, it is essentially the same as the traditional telescope-type laser rangefinder, and it is still sensitive to impact, and the laser beam is difficult to detect. Form an effective measurement point for long-distance small targets.

To sum up, the divergence angle of the laser beam of the current laser range finder is very small, and the laser measurement point on the target is relatively small when measuring the distance. difficult question.

The present invention is mainly aimed at the aforesaid laser imaging subsystem and laser ranging subsystem, and the specific diagram is shown in accompanying drawing 2, to solve the main factors that affect the range of ranging in which laser ranging is based on the principle of time-of-flight (TOF) at present as follows:

1. The system has a large receiving field of view, which will introduce more background noise, resulting in a decrease in the signal-to-noise ratio (SNR), thereby affecting the measurement distance range;

2. The photomultiplier tube will also introduce large noise, which will affect the distance measurement;

3. In order to measure long-distance targets, high-energy and low-frequency pulsed lasers are used, which are bulky and costly;

4. If the same receiving optical system is used for ranging and passive imaging, the receiving area of the ranging system will be limited.

Therefore, there is an urgent need for an optoelectronic system with two functions of ranging and passive imaging, which can well solve the above-mentioned problems in both ranging and passive imaging, such as the narrowing of the ranging range, the reduction of the SNR, and the response Wait for a long time.

Contents of the invention

(1) Technical problems to be solved

In view of this, the main purpose of the present invention is to provide a passive imaging system with ranging function and its ranging method, so as to well solve the problem of ranging and passive imaging of existing laser imaging subsystems and laser ranging subsystems. There are two aspects of imaging.

(2) Technical solutions

In order to achieve the above object in one aspect, the present invention provides a passive imaging system with ranging function, the system includes a high-frequency low-energy pulse laser emitting device, a photodiode array detector imaging device, a video amplification and analog-to-digital conversion device And digital processing device for digital image processing and timing generation, including: high-frequency low-energy pulse laser emitting device for emitting high-frequency low-energy laser pulses, and beam expansion and shaping to achieve long-distance; photodiode array detector imaging device, It is used to receive the laser spot and background image reflected back by the target, and obtain the distance value by adjusting the integration time; the video amplification and analog-to-digital conversion device is used to convert the photogenerated charge of the photodiode array detector imaging device into a voltage, and The analog image is digitized through the analog-to-digital converter; the digital image processing and timing generation digital processing device is used for preprocessing and target extraction of the digital image input by the video amplification and analog-to-digital conversion device.

In the above scheme, the high-frequency low-energy pulsed laser emitting device includes a pulsed laser 104 and a laser emitting optical system 1041, wherein: the pulsed laser 104 is used to generate high-frequency and low-energy laser pulses; the laser emitting optical system 1041 is used to improve the alignment of the laser. Straightness for ideal long-distance measurement results.

In the above solution, the photodiode array detector imaging device includes a photodiode array detector 102 and an imaging optical system 101; wherein: the photodiode array detector 102 is used to convert weak light signals into electrical signals, and then obtain images and corresponding target The distance value of ; the imaging optical system 101 is used to receive weak light signals and focus them on the surface of the detector, increasing the effective receiving area of the detector.

In the above solution, the photodiode array detector 102 includes a row address selection circuit 1025, a column address selection circuit 1026, an address data multiplexer 1024, a readout control unit 1027, an APD diode unit 1021, a gate integrator 1022 and a Q/ V charge voltage conversion circuit 1023, wherein: the row address selection circuit 1025 is used to select the row number of the diode array detector, and the column address selection circuit 1026 is used to select the column number of the diode array detector, and the two are combined in the selected array detector A detector unit; address data multiplexer 1024 is used to realize the function of address bus and data bus in time division; readout control unit 1027 is used to read out the control circuit of array and subarray detector signals; APD diode unit 1021 It is used to convert weak light into an electrical signal; the gated integrator 1022 is used to adjust the integration time; the Q/V charge-to-voltage conversion circuit 1023 is used to convert the photogenerated charge of the diode into a voltage.

In the above solution, the video amplification and analog-to-digital conversion device 111 is used to realize video amplification and AD conversion for the video analog signal, and finally digitize the analog image, and output the obtained digital image to the digital processing device for digital image processing and timing generation 108.

In the above scheme, the digital processing device 108 for digital image processing and timing generation includes a spot detection processing unit 110 for conventional image processing, a distance monitoring unit 109 and a clock generator 103, wherein: the spot detection processing unit 110 is used to receive detection image, and compared with a given threshold to determine whether the target reflection signal exists; the distance monitoring unit 109 is used to judge the presence or absence of the target according to the acquired image and then control the clock generator 103 to generate the integration window offset signal of coarse positioning and fine positioning, including Offset signal 0ff or _offf ; clock generator 103, used to provide the control signal of the distance monitoring unit 109 and the control signal of the imaging unit, and adjust the gate integration time of the detector according to the presence or absence of the target.

In the above scheme, the control signal of the distance monitoring unit 109 provided by the clock generator 103 and the control signal of the imaging unit include: the start signal of the high-frequency low-energy pulse laser 104 emitting pulses, the connection between the photodiode 1021 and the integrator 1022 Whether there is a signal or not, wherein the photodiode 1021 and the integrator 1022 are connected with or without a signal for integration to generate a gating function.

In another aspect to achieve the above object, the present invention provides a ranging method based on the passive imaging system with a ranging function, the ranging method includes two steps of rough positioning and fine positioning, the rough positioning is first Post-precision positioning, specifically including:

First, in the coarse positioning stage, the light pulse reflected by the target is converted into the corresponding charge through the photodiode, and integrated by the integrator. window, where off<1/f and F<1/f; compare the integrated signal with the first predetermined threshold, as long as the integrated signal is lower than the threshold, the steps of integration and comparison are iteratively carried out, using the new offset value of the time window , its value is increased by F relative to the previous offset value off, once the integrated signal exceeds the predetermined threshold, the rough positioning distance value of the target is determined, corresponding to the time F and the offset value off _g ;

Second, in the fine positioning stage, the time value F is preset first, and the offset value off _f is equal to off _g ; the integral signal is compared with the second predetermined threshold, and as long as the integral signal is lower than the threshold, the steps of integration and comparison are repeated, using The new offset value of the time window, its value is increased by d relative to the previous offset value off _f , where d<F, and off _g <off _f <off _g +F; when the first iteration is less than the second threshold, Continue to iterate until it is greater than the second threshold; if the first iteration is greater than the second threshold, the iteration ends.

In the above solution, the predetermined time value F and the offset value off from the emission pulse to the start of integration are determined by the approximate distance value of the target, and the offset value increment d is determined by the positioning accuracy.

In the above solution, the rough positioning stage. Before comparing the integrated signal with the first predetermined threshold, the target return signal is integrated; according to the minimum signal estimated for the target and the number of integrations, the first threshold and the second threshold are preliminarily determined.

(3) Beneficial effects

It can be seen from the above technical solutions that, compared with the simple combination of the laser rangefinder and the imaging system, the present invention has the following beneficial effects:

1. The distance measurement is realized by adjusting the integration time through the gated integrator instead of TOF, so a single detector system (optical system and detector) can be used to realize the distance measurement and imaging functions.

2. Since the TOF laser ranging is omitted, the APD detector is not used, and the broadband amplifier system is avoided, the noise of the ranging channel is small;

3. The gated integrator function can effectively filter out the influence of atmospheric scattering, so that it can correct the inaccurate range measurement of the target due to strong atmospheric scattering;

4. Use the function of adjusting the gated integrator for distance measurement instead of TOF distance measurement, so low-energy high-frequency pulsed lasers can be used to avoid the use of high-cost, large-volume low-frequency high-energy lasers;

5. Use the same optical receiving system and detector to realize the combination of high-performance passive imaging and ranging functions.

Description of drawings

Fig. 1 is the schematic diagram of the passive imaging system with ranging function provided by the present invention;

Fig. 2 is the schematic diagram of the photoelectric system that the traditional laser rangefinder and the passive imaging system simply combine, it is the existing laser imaging ranging technology, and is used for the passive ranging function provided by the present invention shown in Fig. 1 Comparing with the imaging system, it is convenient to understand the improvements and advantages of the present invention;

Fig. 3 (a) is a schematic diagram of the time sequence mode of the rough positioning stage of the passive imaging system with ranging function provided by the present invention to realize the ranging of the target;

Fig. 3 (b) is a schematic diagram of the timing mode of the precise positioning stage of the passive imaging system with ranging function provided by the present invention to realize the ranging of the target;

Fig. 4 is a schematic diagram of the relationship curve between the maximum distance of the detection target and the frequency of laser emission by the passive imaging system with ranging function provided by the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Please refer to shown in Fig. 1, this passive imaging system with ranging function provided by the present invention includes high-frequency low-energy pulse laser emission device, photodiode array detector imaging device, video amplification and analog-to-digital conversion device and digital image Digital processing means for processing and timing generation, wherein:

High-frequency low-energy pulse laser emitting device, used to emit high-frequency low-energy laser pulses, and beam expansion and shaping to achieve long-distance;

The photodiode array detector imaging device is used to receive the laser spot and background image reflected back by the target, and obtain the distance value by adjusting the integration time;

The video amplification and analog-to-digital conversion device is used to convert the photogenerated charge of the photodiode array detector imaging device into a voltage, and digitize the analog image through the analog-to-digital converter;

The digital image processing and digital processing device for timing generation is used for preprocessing and target extraction of the digital image input by the video amplification and analog-to-digital conversion device.

Wherein, the high-frequency low-energy pulsed laser emitting device includes a pulsed laser 104 and a laser emitting optical system 1041, the pulsed laser 104 is used to generate high-frequency and low-energy laser pulses, and the laser emitting optical system 1041 is used to improve the collimation of the laser to obtain Ideal for long distance measurements.

The photodiode array detector imaging device includes a photodiode array detector 102 and an imaging optical system 101; wherein the photodiode array detector 102 is used to convert weak light signals into electrical signals, and then obtain images and distance values of corresponding targets, The imaging optical system 101 is used to receive weak light signals and focus them on the surface of the detector to increase the effective receiving area of the detector.

The photodiode array detector 102 includes a row address selection circuit 1025, a column address selection circuit 1026, an address data multiplexer 1024, a readout control unit 1027, an APD diode unit 1021, a gated integrator 1022, and a Q/V charge-voltage conversion Circuit 1023, wherein the row address selection circuit 1025 is used to select the number of rows of the diode array detector, and the column address selection circuit 1026 is used to select the number of columns of the diode array detector, and the two are combined to select a certain detector in the array detector Unit: address data multiplexer 1024 is used to realize the function of address bus and data bus in time division, readout control unit 1027 is used to read out the control circuit of array and subarray detector signal, APD diode unit 1021 is used for receiving weak light To convert it into an electrical signal, the gated integrator 1022 is used to adjust the integration time, and the Q/V charge-to-voltage conversion circuit 1023 is used to convert the photo-generated charge of the diode into a voltage.

The video amplification and analog-to-digital conversion device 111 is used to realize video amplification and AD conversion to the video analog signal, and finally digitize the analog image, and output the obtained digital image to the digital processing device 108 for digital image processing and timing generation;

The digital processing device 108 for digital image processing and timing generation includes a spot detection processing unit 110 for conventional image processing, a distance monitoring unit 109 and a clock generator 103, wherein the spot detection processing unit 110 is used to receive the detection image and communicate with the given image. Threshold comparison to determine whether the target reflection signal exists; the distance monitoring unit 109 is used to judge whether the target is present or not according to the acquired image, and then control the clock generator 103 to generate the integration window offset signal of coarse positioning and fine positioning, including offset signal off or off _f ; the clock generator 103 is used to provide the control signal of the distance monitoring unit 109 and the control signal of the imaging unit, and adjust the gate integration time of the detector according to the presence or absence of the target. These control signals are respectively: the start signal of the high-frequency low-energy pulse laser 104 emitting pulses, whether there is a signal connected between the photodiode 1021 and the integrator 1022 (the connection signal is used to realize integration and generate a gating function).

In this device, since the integration time of the detector is adjusted for ranging, imaging and ranging are the same part, so the laser ranging receiving part described in Fig. 2 includes a ranging detector 205, an amplifying circuit 2051 and a filtering circuit In 2052, the optical receiving part 206 becomes unnecessary. The distance calculation module is also replaced by the aforementioned rough positioning and fine positioning methods, and the signal integration and comparison operation methods can be implemented in the digital processing unit. The device adopts the same detection system, which can provide high sensitivity of the detection system by increasing the size of the receiving optical system.

In this device, the integrator 1022 of the photodiode array detector 102 is used for the gate control function, and only integrates the target but not the scene, and can be used to realize the ranging function. Therefore, the calculated distance is no longer determined by the time of flight (TOF), where the time of flight is determined by the time difference between the moment when the laser is emitted and the moment when the reflected signal from the target is received.

Fig. 3 shows the steps of the distance measuring method of the present invention, a schematic diagram (a) of the timing mode of the rough positioning stage for realizing ranging of the target, and a schematic diagram (b) of the timing mode of the fine positioning stage of realizing the ranging of the target.

First, the steps of the target rough positioning method are as follows:

For example, the pulse width of the pulsed laser determined by the system is 10 ns, and the repetition frequency f is less than a certain limited value (namely, the upper frequency limit), in order to avoid the overlapping of the transmitting pulse and the receiving pulse of the system. Wherein, the frequency upper limit is calculated according to the maximum measurement distance in FIG. 4 . It can be seen from Figure 4 that the measurement distance is 10km, and the corresponding upper limit of the repetition frequency is 20kHz. The time window of the known integration is F, and its frequency value is equal to the laser emission frequency, F<1/f.

In order to synchronize with the moment when the pulse reflected from the target reaches the detector, the integration window needs to be opened in advance, and then, when the readout circuit is used, the integration is started. The width F of the time window is determined by the distance value Dis of the corresponding target location. In addition, the distance value starts from the origin and is determined by the offset value from the emission pulse to the start of the integration time, off<1/f. Finally, the width F of the integration window and the offset value off correspond to the distance value Dis from the origin. For example, the integration window width is 13.4μs, corresponding to a distance range of 2km. The offset value is 20μs, which corresponds to a distance of 3km from the origin. Therefore, the distance range corresponding to the integration window is 3-5km. According to the return value of the target, it is determined whether it is within the distance or not. If the target falls within the distance range, for example 4km, the target return signal starts to integrate and is detected. That is to say, the target is roughly positioned at 3-5km, as shown in Figure 3(a), and the target return signal starts to integrate within the integration window. On the contrary, assuming that the target distance is 6km, the target return signal will not be detected.

If the target return signal is not detected, it means that the detection signal is less than a predetermined threshold. By adjusting the offset value of the integration window time, the charge signal converted by the photodiode is integrated and compared with the set threshold value, and this step is repeated until the integrated signal value exceeds the set threshold value, wherein the integration window needs to be offset by F( That is, the new off value is equal to the sum of the previous off value plus F), so that the corresponding distance value is 5km away from the origin O, that is, the distance range corresponding to the new integration window is 5-7km. To determine the continuity of this distance range with the next one, we make two consecutive integration windows overlap slightly. The offset value of the integration window is F-δF, and δF is 1% of the F value. Repeat the above process until the coarse positioning of the target is achieved.

Second, in the coarse positioning stage, the time window is composed of the 'coarse' window and the offset value off _g ; in the fine positioning stage, the time window is continuously offset by off _f on the basis of the 'coarse' window, where the new off _f value It is equal to the sum of the previous off _f value plus d. The integration window is equal to F or slightly smaller than F. On the one hand, the ranging algorithm can not integrate the non-target signals in the scene, and only obtain the distance value of the target; on the other hand, it optimizes the overall performance of the ranging system, including SNR. The algorithm locates the target, depending on the continuous offset value of the integration window. In practice, when the integral signal is greater than the predetermined threshold, the target return signal will only appear in several time windows, and when the delay d is greater than the pulse flight time, the target return signal will suddenly disappear, that is, the integration window time can only be in the 'coarse' window Medium offset, where off _g <off _f <off _g +F. The positioning accuracy is determined by the time offset value d of the integration window, and the distance value is obtained by increasing the integration window time offset value d or 1.5m/10ns. The time window F is 6.68μs, corresponding to a distance range of 1km, the offset value is 1.33μs, and the corresponding advance distance value is 200m. That is, 5 offset values are sufficient to cover a distance range of 1 km, and the ranging accuracy is 200 m. For example, the rough positioning results show that the target is within the range of 3-5km, the time window F is 6.68μs, the corresponding distance range is 1km, the offset value is 1.33μs, and the corresponding advance distance value is 200m, all of which can be determined. If the target distance is 3.5km, then the target return signal appears and is detected in the third time window, and disappears in the fourth time window. That is, the distance range of the precise measurement of the target is 3.4-3.6km.

In the present invention, the photodiode array detector 102 is composed of 256 rows×320 columns, and the material of the detector is consistent with the laser illumination wavelength. Among them, silicon is suitable for detecting lasers with a wavelength of 0.4 μm-1.1 μm; antimony chromium mercury CdHgTe is suitable for detecting lasers with a wavelength of 0.4 μm-1.5 μm; InGaAs is suitable for detecting lasers with a wavelength of 0.4 μm-2.5 μm. Moreover, the size of the integrator in each readout circuit of the detector array is appropriate to meet the limitation of passive imaging. In order to realize ranging, the integrator 1022, by occupying necessary transistor resources, realizes the opening of a very short (10ns-10μs) integration window period, and finally realizes the gating function, and only integrates the target reflected signal.

In the present invention, the control signal of the readout circuit of the photodiode array detector 102 is generated by the clock generator 103, and the precise control delay or offset value off or off _f is used to realize the integration window of the integrator of the target return signal Control; the gating function is realized by the presence or absence of signal connected between the photodiode 1021 and the integrator 1022, which is also provided by the clock generator 103; this enables the low-energy, high-frequency pulse laser 104 to meet the system requirements.

In the present invention, the size and position of the target imaging in the photodiode array detector 102 are random, and the detector of the sub-array where the target is located can be obtained by controlling the row selection circuit 1025 and the column selection circuit 1026 to select the address of the row and column. Moreover, it is possible to read only the region of interest by increasing the repetition rate of the laser very high (up to 20kHz). The entire observation field of view of the passive imaging detector is divided into several sub-fields of view, which is equivalent to several sub-detection units of the array detector. Under a given field of view, if a single field of view is small, the generated photon noise is negligible, so that very weak signals can be detected and the detection of very distant laser spots can be realized. The sub-array readout circuit can make the image with small size (tens of pixels) read out at a high frame rate (50μs-100μs). However, the size of the sub-array detector is usually larger than that of the traditional laser ranging detector, which greatly reduces the balance between the transmitting and receiving channels of the ranging.

To sum up, the size of the read sub-array is 32 columns × 10 rows, and the distance information is obtained in about a few ms. Thus spatially resizable subarrays provide the following advantages:

1. Reduce background photon noise and improve the sensitivity of spot detection and ranging;

2. Simplified the design of the receiving eyepiece;

3. The noise and circuit bandwidth of the corresponding circuit are reduced, and the gain sensitivity is improved.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. one kind has the passive imaging system of distance measurement function, it is characterized in that, this system comprises the digital processing unit that the low-yield pulse laser emitter of high frequency, photoelectron diode array detector imaging device, video amplifier and analog-digital commutator and Digital Image Processing and sequential occur, wherein:

The low-yield pulse laser emitter of high frequency, for launching the pulse of high frequency low-energy laser, and expands shaping to reach remote;

Photoelectron diode array detector imaging device, for receiving the laser facula and the background image that are reflected back by target, and obtains distance value integral time by adjusting;

Video amplifier and analog-digital commutator, for the photogenerated charge of photoelectron diode array detector imaging device is converted to voltage, and process analog to digital converter is by analog image digitizing;

The digital processing unit that Digital Image Processing and sequential occur, for carrying out pre-service and target extraction to the digital picture of video amplifier and analog-digital commutator input.

2. the passive imaging system with distance measurement function according to claim 1, is characterized in that, the low-yield pulse laser emitter of this high frequency comprises pulsed laser (104) and laser emission optical system (1041), wherein:

Pulsed laser (104) is for generation of the pulse of high frequency low-energy laser;

Laser emission optical system (1041) for the collimation of improving laser to obtain desirable telemeasurement effect.

3. the passive imaging system with distance measurement function according to claim 1, is characterized in that, this photoelectron diode array detector imaging device comprises photoelectron diode array detector (102) and imaging optical system (101); Wherein:

Photoelectron diode array detector (102) is for faint optical signal is converted to electric signal, and then obtains the distance value of image and respective objects;

Imaging optical system (101), for receiving faint optical signal and converging to detector surface, increases the capture area of detector.

4. the passive imaging system with distance measurement function according to claim 3, it is characterized in that, this photoelectron diode array detector (102) comprises row address selection circuit (1025), column address selection circuit (1026), address date multiplexer (1024), read-out control unit (1027), APD diode (1021), gated integrator (1022) and Q/V charge voltage change-over circuit (1023), wherein:

Row address selects circuit (1025) for selecting the line number of photodiode array detector, column address selects circuit (1026) for selecting the columns of photodiode array detector, and the two is in conjunction with certain detector cells in selected detector array;

Address date multiplexer (1024) is realized the function of address bus and data bus for timesharing;

Read-out control unit (1027) is for reading the control circuit of array and subarray detector signal;

APD diode (1021) transfers electric signal to for receiving faint light;

Gated integrator (1022) is for adjusting integral time;

Q/V charge voltage change-over circuit (1023) is for being converted to voltage by the photogenerated charge of diode.

5. the passive imaging system with distance measurement function according to claim 1, it is characterized in that, this video amplifier and analog-digital commutator (111) are for realizing video amplifier and AD conversion to video analog signal, finally by analog image digitizing, and the digital picture obtaining is exported to the digital processing unit (108) that Digital Image Processing and sequential occur.

6. the passive imaging system with distance measurement function according to claim 1, it is characterized in that, the digital processing unit (108) that this Digital Image Processing and sequential occur comprises for the laser spot detection processing unit (110) of normal image processing, apart from monitoring means (109) and clock generator (103), wherein:

Laser spot detection processing unit (110) is for receiving detection image, and with given threshold value comparison, to determine whether target echo exists;

Apart from monitoring means (109), be used for judging that according to obtaining image target has or not and then control the integration window shifted signal of clock generator (103) generation coarse positioning and fine positioning, comprises shifted signal off or offf;

Clock generator (103), is used to provide apart from the control signal of monitoring means (109) and the control signal of image-generating unit, and according to target, has or not to adjust the Gated integration time of detector.

7. the passive imaging system with distance measurement function according to claim 6, it is characterized in that, the control signal of the distance monitoring means (109) that this clock generator (103) provides and the control signal of image-generating unit comprise: the exomonental start signal of the low-energy pulsed laser of high frequency (104), photodiode (1021) and integrator (1022) be connected with no signal, wherein photodiode (1021) and integrator (1022) is connected with no signal for realizing integration, generation gate control function.

8. a distance-finding method for the passive imaging system with distance measurement function based on described in any one in claim 1 to 7, is characterized in that, this distance-finding method comprises coarse positioning and two steps of fine positioning, is fine positioning after first coarse positioning, specifically comprises:

One, the coarse positioning stage, the light pulse being reflected back by target is corresponding electric charge through photodiode converts, and by integrator integration, in schedule time value, be F, from transponder pulse to the off-set value off that starts integration, time window, wherein, off<1/f and F<1/f; By integrated signal and first predetermined threshold comparison, as long as integrated signal is lower than threshold value, the step iteration of integration, comparison is carried out, adopt the new off-set value of time window, the relatively previous off-set value off of its value increases F, once integrated signal exceedes predetermined threshold, the coarse positioning distance value of target is definite, and correspondence is off by time F and off-set value _g;

Its two, fine positioning stage, first Preset Time value F, off-set value off _fequal off _g; By integrated signal and second predetermined threshold comparison, need only integrated signal lower than threshold value, the step of integration, comparison repeats, and adopts the new off-set value of time window, and it is worth relatively previous off-set value off _fincrease d, wherein, d<F, and off _g<off _f<off _g+ F; When iteration is for the first time less than second threshold value, continue iteration, until be greater than second threshold value; If iteration is greater than second threshold value for the first time, iteration finishes.

9. distance-finding method according to claim 8, is characterized in that, described schedule time value F and being determined by the general distance value of target to starting the off-set value off of integration from transponder pulse, and off-set value recruitment d is determined by positioning precision.

10. distance-finding method according to claim 8, is characterized in that, the described coarse positioning stage.By integrated signal and first predetermined threshold relatively before, to target return signal integration; According to minimum signal and integral number of times that target is estimated, tentatively determine first threshold value and second threshold value.

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