WO2000002062A2

WO2000002062A2 - Method for detection of objects using optical and optoelectronic means

Info

Publication number: WO2000002062A2
Application number: PCT/RU1999/000214
Authority: WO
Inventors: Nikolai Nikolaevich Slipchenko; Sergei Anatolievich Mikhailenko; Alexandr Sergeevich Kazakov; Mikhail Iliich Krymsky; Viktor Alexeevich Podjuev
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-07-03
Filing date: 1999-06-29
Publication date: 2000-01-13
Anticipated expiration: 2001-01-03
Also published as: RU2133485C1; WO2000002062A9; EP1012626A2; WO2000002062A3

Abstract

Invention relates to the field of optical detection and ranging, strictly to types of detection and recognition of a type of object with using of TV-methods of signals' identification and can be used within creating of burglar alarm systems. The reached technical result is object detection within disturbing signals and signaling organization of their appearance in a mode, decreasing possibility of object misdetection, caused by human factor - operator's fatigue. Method is based on sounding of controlled space volume by scanning impulse laser emission, receipt of optical image signals from the ordered distance, transduction of the received image signals into videosignal, threshold selection for elimination of background image, as well as on the fact, that sounding of space value is carried out with frequency, equal to f1/n, and emissed impulses subsequence is coded by on-off keying with frequency ff/m, f1 and ff are line and frame frequencies accordingly of the used TV method of signals transduction, n and m - natural numbers, fulfilling the terms n≤f1/ff, 2≤m≤ff/2, reveal videosignals, correlated with a code of on-off keying of emissed impulse subsequence, and form alarm signal automatically, and after transduction of videosignals into optical image - brightness twinkle of TV screen is fixed out with the help of operator, with a frequency of on-off keying.

Description

METHOD FOR DETECTION OF OPTICAL AND OPTOELECTRONIC MEANS

BACKGROUND OF THE INVENTION

I. Field of invention

The invention relates to the field of optical detection and ranging, strictly to systems of optical search, detection and recognition of a type of the detected object using TV-methods of signals identification and it can be used for creation of burglar alarm systems, operating at the conditions of interferences, with ensuring

_* of signaling, which character considerably decreases probability of the fact, gears recorded, of object misdetection in a controlled zone, decreasing influence of human factor on the results of observation, designed for detection of the fact of unauthorized observation, making photos etc., including prevention of terrorists raids where optoelectronic devices and gears with optical elements are used.

II. Description of the prior art

The questions of prior art concerning signal detection by means of optical detection and ranging have been considered well in detail (Volohatuk V.A., Kotchetkov V.M., Krasovsky R.R. "Questions about optical detection and ranging". Edited by Krasovsky R.R. Moscow. Soviet Radio, 1971, pages 66-69, 100-102, 130, 148, 176-180). As a rule, an emitting device consists of emitter and output optical system. At the place of emitter, the optical quantum generator or another source of light is used. The output optical system can include optics, forming the required directional pattern and scanning device, providing needful field of view. Really, path of signal propagation contains a source of interferences, so their influence affects both direct and return signals, however predominate influence is their influence on the return signal.

The angle characteristics of emitter are chosen narrow enough for the most concentration of emitting energy in the ordered direction. Upon that, considerable part of calculation of light fields is definition of light diffusion from space-limited narrow-collimation source. Within usual conditions, object disperses the light signal diffusively, and that leads to re-emission of sounding signal in wide solid angle. Thus, calculating attenuation of light signal upon its movement from an object to optical radar's receiver, the task concerning a field of source, reflecting signal, should be solved.

The indicated technical task is analogous to the task settled in the applied invention, as far as the specificity of detected optical and optoelectronical objects is mirror (direct) character of reflection, upon which beam divergence of optical systems for detecting and ranging is equal before / after reflection.

"Metallic" lustre of clear (without oxides) surface of metals surface as well as bright glares upon light reflection from glass and water surfaces are explained by mirror reflection. In this case (for instance, Korostelev A.A. etc. "Technical basis of radio-location", edited by Dulevich V.E., 2 edition, Moscow: Soviet Radio, 1978, pages 503-509, 514-519), approximate evaluation of mirror reflection factor Ri can be carried out using Fresnel's formula. Upon normal fall of light flux on dielectric surface it comes from Fresnel's formula:

Ri = (n - l)²/ (n + l)²

n is refractive index of the surface material; for example, upon reflection of light flux from a glass surface, where n = 1,5 (that is typical enough for a variety of objects, detected in accordance with the applied method), value Ri = 0,04. Upon mirror dispertion the angle divergence of the reflected light flux is 10⁴-10⁵ as much, than upon diffusive dispertion, bearing in mind, that real objects, as a rule, are neither lambert diffusive reflectors, nor diffusers of mirror type, but their combination. The indicated circumstance, coming from the type of object, creates pre-condition for reliable extraction of signal over interference, however in this case, except necessity of account of non-stationary phenomena upon light propagation, a possibility of light interferences should be taken into consideration, which get into aperture of receiver and bring to naught advantages, that take place within operation with glaring sources of emission. Namely the indicated fact is a drawback, for elimination of which this invention is directed.

From patent sources a laser observation environmental system with discrete gating of distance, containing illumination pulse laser, gating detector of image and multicolour indication system, its each colour is connected with concrete distance site (GB 1262416, H4D, 02.02.72), is known.

The indicated technical solution, settling task of observation, does not afford however to truly perform at a condition of disturbing exposures, as it is not protected from natural or artificial interferences, this can be referred to its drawbacks.

It is known that another technical solution, namely patent FR # 1605187, published 25.05.73, where it was considered using of really sophisticated codes with subsequent correlation processing of received and reference signals for solution of anti-interference task, however this method does not use TV-method of transduction, which is taken as a base of the applied method, as far as affords to show current information about surroundings. Besides, a video signal, coming from sensor if it is necessary, can be recorded at a medium for subsequent viewing. The identification of signal in TV-system pursues several ends. One of them is to quantitatively redistribute information indexes of input image, such as definition, number of brightness gradations etc., so that to consult it in a best way with operator's vision analyser.

Another goal is to single out or to stress the features at the initial image, which are necessary for solution of a task of detection and/or recognition of objects. In this case the final solution can be taken either directly by operator with the help of picture monitor or by classifier, as distinguishing features of the investigated object are stored in its memory.

As the prior art (the closest analogue) of the applied invention, the passive-active method of observation was chosen, including observation within night time and poor weather conditions, described by Orlov V.A., Petrov B.I. in "Devices for observation at night and poor visibility". Moscow. Voennoje izdatelstvo, 1989, pages 116-118.

Method was described in the indicated source of information in accordance with it an object is illuminated by short laser impulses with a duration, less than a period of time of passage of illumination impulse towards an object and back, upon that distance gating and view depth receiving within receipt of reflected signal is stipulated, that is provided with the help of passive electrooptical observation device, opened at the moment when reflected from object signal reaches objective, and as a result parasitic exposure due to suspended in atmosphere particles of dust, moisture, smoke do not get into the device, increasing observation distance. However this method is not free of drawbacks, such as worsening of ration signal/interference upon inside lighting, because it does not contain any means, eliminating this influence, or enabling selection of signal type of interest. SUMMARY OF THE PRESENT INVENTION

For elimination of the indicated drawback a method for detection of optical and optoelectronic means is applied, based on sounding of controlled space volume by scanning pulse laser emission, receipt of optical signals in a spectrum range of the reflected laser emission from the ordered distance and surrounding site of space, determined by observation depth, transduction of received signals of image into videosignals, threshold selection of received video signals set for elimination of disturbing background image, where sounding of the controlled space volume is carried out with pulse repetition frequency of laser emission equal to fi/n, fi - line frequency of the used TV-method of signal transduction, n - natural number, fulfilling the term n < f / f_f, and f_f - frame frequency of the used TV-method of signal transduction, upon that emitting subsequence of laser impulses is coded by on-off keying with frequency f_f/m, m - natural number, fulfilling the term 2 < m < ft/2, reveal from a number of received videosignals, excessed threshold, videosignals, correlated with the code of on-off keying of pulses emissed subsequence, and if they are available, automatically form an alarm-signal, then after transduction of signals is carried out, correlated with the code of on-off keying of pulses emissed subsequence into optical image, fix (with the help of operator) fatigue twinkle of brightness of TV screen with a frequency of on-off keying.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features of the present invention will be described in greater detail with reference to an exemplary embodiment, which is intended to explain and not to limit the invention, and is illustrated in a drawing in which: FIGURE 1 shows a preferred embodiment in accordance with the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT

The indicated method can be implemented with the help of a device, presented at a structure scheme (FIGURE I) with a list of designations, as follows:

1 - object for detection;

2 - input objective;

3 - electrooptical transducer (EOT);

4 - reproduction objective;

5 - TV camera;

6 - picture monitor;

7 - videosignal processing unit;

8 - pulse bar unit;

9,11 high voltage impulse sources;

10 - synchronizer;

12 - laser;

13 - modulator;

14 - frame frequency divider;

15 - control console;

16 - automatic gain control scheme (AGC); 17 - secondary supply source.

Realization of the applied method is carried out as follows.

The controlled space volume, where presence of object for detection (1) is supposed, radiated by laser (12), i.e. by scanning impulse emission with repetition frequency fj/n and sequent on-off keying with frequency f_f/m carried out by modulator (13) and frame frequency divider (14) of TV camera (5). Laser emission (12), reflected from the object (1) and other objects in a controlled space volume, is received by objective (2), which forms image of projection of tested space volume at input photocathode of EOT (3). Image signals, reinforced by EOT (3), are imaged on photosensitive element of TV camera (5) through reproductive objective (4). Videosignals of the TV camera (5) output go to picture monitor (6), videosignal processing unit (7), synchronizer (10) and AGC scheme (16). Synchronizer (10) provides synchronous operation of high voltage impulse sources (9, 11), forming sync pulses, managing modulator (13), frame frequency divider (14), laser (12), pulse bar unit (8) and videosignal processing unit (7).

Reflected from the object, signal is reinforced in EOT (3) only within a period of time, determined by duration of bar pulses τ₃, and that corresponds with the depth of instant viewing site Δ R = C τ₃ / 2, C - velocity of light. Change of bar pulses delay with re _*gard to laser emission impulses define distance, where from signals, reflected from objects, are received. Changing mutual position of bar pulses and laser emission pulses using control console (15), sequent viewing of the depth of controlled space with discrete Δ R is provided. On-off keying, used with respect to sequence of emissed impulses with frequency ff/m, occurring to be a frequency with a range -3-5 Hz upon chosen values m, implemented with the help of signals, coming from frame frequency divider (14), enables using criterion of their correlation with emissed impulses upon processing in videosignal processing unit (7) for selection of the received signals reflected from object for detection, and as a result their image will twinkle at the screen of picture monitor (6) with indicated frequency, which being closest to the frequency of human brain α - rhythms causes fatigue influence, that affecting accordingly an observer-operator, automatically attracts his attention, not let him missing the fact of objective presence of object for detection. This parameter enables to provide selection of reflected signals at the background of outside exposures, for instance, such as car's head lights, illumination lamps in the appartments' windows etc., and videosignal processing unit (7) will produce alarm signal automatically. The scheme of automatic gain control (16), managing diaphragms of objectives (2) & (4) and EOT's reinforcement, provides support of signal at an optimum level at TV camera (5) input upon change of signal's level at a pupil of input objective (2). Upon tha, EOT (electro-optical transducers) of last generation are used, enabling to carry out all the indicated control.

Used correlation method for recognition of signals of concrete type, is implemented by saving of the code in videosignal processing unit (7), which determines operation of frame frequency divider (14), for a conformity with which reflected signal is checked up, entered the input of videosignal processing unit (7), exceeded threshold, determined for elimination of background level.

In the case, when value of correlation coefficient exceeds, determined according to tests results, the alarm signal automatically operates out and selected information signals, transduced into optical image, getting into picture monitor (6), enable to attract operator's attention, as far as screen, twinkling with a frequency of the code, used for a on-off keying, is a factor, affecting human physiology, that provides reduction of a possibility of the fact of missdetection.

Claims

WHAT IS CLAIMED IS:

Method for detection of optical and optoelectronic means, based on sounding of the controlled space value by scanning pulse laser emission, on receipt of image optical signals in spectrum range of reflected laser emission from the ordered distance and surrounding to this space site, determined by observation depth, on transduction of received image signals into videosignal, threshold selection of set of received videosignals for elimination of disturbing background's image, differing by the fact that sounding of the controlled space volume is carried out with repetition frequency of laser emission impulses, equal to fj/n, fi - line frequency of the used TV-method of signal transduction, n - natural number, fulfilling the term n < fi / f_f, and f_f - frame frequency of the used TV-method of signal transduction, upon that emissed subsequence of laser impulses is coded by on-off keying with frequency f_f/m, m - natural number, fulfilling the term 2 < m < f_f / 2, are revealed from the number of the received videosignals, exceeded threshold, videosignals, correlated with a code of on-off keying of impulse emissed subsequence, and automatically form alarm signal upon their presence, and after videosignals transduction, correlated with a code of on-off keying of impulse emission subsequence into optical image, fatigue twinkle of TV screen is fixed with the help of operator, with the frequency of on-off keying.