JPH01500230A - Object detection method and device using electro-optics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Object detection method and device using electro-optics This application is a continuation in part of No. 831,016, filed February 19, 1986. It is a wish.

Technical field The present invention relates generally to a system for detecting the presence of an object within an area under surveillance, and more particularly to a system for detecting the presence of an object within a monitored area. electro-optical means are used to detect the presence of objects, especially in automobiles and Relating to a detection system well suited for preventing collisions.

Background technology Various types of sensors used to detect the presence of objects within a monitored area or space A system of taps has been devised in the past. Many such systems rely on nearby objects. It is used to warn drivers of the presence of bodies and cars. used in cars These systems are sometimes referred to as collision avoidance systems.

Many types of different technologies have been employed in previous collision avoidance systems. Ru.

For example, one known type is based on ultrasound. high frequency sound waves is emitted into the monitored area, and the reflected sound having the frequency of the emitted sound wave is analyzed. to determine if an object is within the monitored area.

Ultrasonic type systems are slow in terms of response time.

Also, especially wind buffets and eddies, as well as interference noise that reduces system reliability. Depending on the source, it is exposed to a variety of different types of interference. In addition, the The ultrasonic transducer must be supported in the open air and therefore Exposure to dirt and moisture inside will gradually affect the proper operation of the system. .

Other types of known collision avoidance systems are radio frequency transmitters and receivers, or radars. We are hiring a driver. While the latter system is relatively superior in terms of performance, It is expensive and therefore not widely used in general passenger cars.

Optical systems are also known. This is the transmitted light that goes from the car to the object and back This is to measure the flight time of the aircraft. However, these systems are also expensive. requires sophisticated products and relatively complex circuits.

Thus, an inexpensive and relatively simple method for detecting the presence of an object within a monitored area, e.g. There has been a desire for a device that can be used in automobiles to avoid collisions.

Brief description of the drawing The drawings constitute a part of the specification and should be referred to together, and may be used in various ways. Symbols are employed to indicate the same thing in perspective.

FIG. 1 is a plan view of the main vehicle, which is the object detection device of the present invention. The driver is driving on a three-lane road and trying to pass a car in the adjacent lane. There is.

FIG. 2 is a schematic block diagram of an object detection device constituting a preferred embodiment of the present invention. .

Figure 3 shows the front view of the detection unit having the light emitting part and the light receiving part of the detection device of the present invention. It is a front view.

FIG. 4 is a diagram showing the relationship between the light emitting section and the light receiving section of the detection unit shown in FIG. 3.

FIG. 5 is a detailed diagram of the control section of FIG. 2.

Figure 6 shows one of the source drivers for the modulator in Figure 2 and its accompanying source driver. FIG. 2 is a detailed diagram of the optical device.

FIG. 7 is a diagram combining the block diagram and detailed diagram of the light receiving section of FIG. 2.

FIG. 8 is a detailed route diagram of the bandpass amplifier of FIG. 2.

Figure 9 is a block diagram and detailed diagram depicting the synchronization detector and threshold comparator in Figure 2. This is a diagram that combines the two.

FIG. 10 is a block diagram of another embodiment of the object detection device of the present invention.

FIG. 11 is a schematic diagram showing an improvement to the control section of FIG. 5.

FIG. 12 is a schematic diagram showing an improvement to the synchronization detection circuit of FIG. 9.

FIG. 13 is a diagram showing area detection in another embodiment of the present invention.

Example The present invention generally comprises an electro-optical system for detecting the presence of an object. , the device of the present invention relates to a device for detecting the presence of an object in an area under surveillance. Advantages include security monitoring (safety/security monitoring) and collision avoidance systems, etc. It is applied in various ways. However, for the sake of clarity, the detection device of the present invention It will be explained in detail in relation to collision avoidance systems for cars.

As shown in FIG. 1, the object detection device of the present invention detects an object within the monitored area, attached to the vehicle 10 to warn the driver of the vehicle 10 of the presence of the vehicle. It is.

In the example shown in FIG. It has a detection unit 18 attached to the rear corner. Or these The detection unit 18 is installed on the license plate bracket or rear window of the car 10. It is mounted inside the vehicle 10 in front of the vehicle. Each sensing unit 18 preferably is a fan of light energy in the infrared region with a wavelength of approximately 850 to 980 nanometers. A beam 12 is emitted. This beam 12 diverges at an angle of approximately 25 degrees; The core wire 14 extends parallel to the path of the vehicle 10 and past the detection unit 18. It is located approximately 45 degrees from axis 16.

The area under surveillance of the detection unit 18 is indicated by a dashed line 15. Therefore, under surveillance The area within the dashed line 15 indicates whether a rear view mirror is used or A “blind spot” that makes it difficult for drivers to see, requiring them to turn their head It can be seen from FIG. 1 that there is a region where this can occur.

The object detector of the present invention can be used as an automotive detector to monitor areas where there is a possibility of contact. The use of cognitive devices can assist drivers in changing lanes while driving in multiple lanes. This object detection device is particularly useful for Signals and/or audible signals may alert other vehicles to “possible contact.” When the computer intrudes into the area marked by broken line 15 under surveillance, which is considered to be an area with sexual activity. It is designed to give a warning. Ideally, both audible and visual alarms are included. It is emitted into the passenger compartment and alerts the driver to the presence of an object within the monitored area. audible The volume of the alarm should preferably be adjustable by the driver. . In the first mode, an audible and visual alarm is triggered when an object is detected in the monitored area. Both work together, but the driver can set the audible alarm to its lowest volume. and silence the audible alarm. In the second mode, this means that the driver It starts when I activate the turn signal, but there is an audible alarm. It operates at its maximum volume regardless of the volume setting level. and visible Alarms are also triggered when objects are detected. In this way, an alert is sent to the driver. given a certain amount of time, and a car in the lane next to the one the driver is attempting to enter is safe. Prevents drivers from changing lanes until they are separated by the same distance. driver's driving In addition to assisting the driver of the vehicle 10 with the object detection device of the present invention, When a nearby vehicle passes near the vehicle 10 or is in the process of issue an alarm.

Next, Figure 2 shows the basic components of the object detection device described above based on Figure 1. Take a look. The detection unit 18 is attached to each rear corner of the automobile 10, A center line extending approximately 45 degrees from the travel path of the vehicle 10 as shown in FIG. is positioned to monitor an area having some angle on either side of the area. Here the first 3 and 4, each sensing unit 18 is preferably supported by a common member. a suitable non-conductive material that prevents preemptive communication between the light emitting part 20 and the light receiving part 22. It has a housing 54 separated by a barrier 66 consisting of.

The light emitting section 20 and the light receiving section 22 are made of a material that is transparent to the wavelength of the light used. It is covered by outer shield 56. The outer shield 56 is shown in Figure 4. Includes two parts as shown or covers the entire exterior surface of the housing 54. It consists of a single unit.

The light emitting unit 20 includes an electro-optic infrared light emitter 58 (hereinafter referred to as a "light emitter") which will be detailed later. ).

The light emitters 58 are preferably arranged in three vertical and horizontal rows as shown in FIG. There is.

The light receiving section 22 of the detection unit 18 is a PIN photodiode or the like which will be described in detail later. A photosensitive semiconductor material 60 is provided. This photosensitive semiconductor material 60 has a predetermined shape, e.g. It is highly sensitive to light energy in the wavelength range of 750 to 1100 nanometers, The received light energy is the magnitude of the received light energy. It acts by converting it into an electrical signal that changes depending on the current. Outer shield 56 and The light passing through the filter 64 is directed to the photosensitive semiconductor material 60 by the aspheric optical lens 62. The light is focused on. Filter 64 substantially filters out light energy outside a preset wavelength. For example, filter 64 may be provided with a conventional light filter to attenuate the emitted light. 58 to provide maximum response at a wavelength that matches the wavelength of the emitted light energy. Sea urchins are chosen by sea urchins.

One feature of the invention is that the deposition of external objects on the outside of the outer shield 56 means for detecting the presence of Objects from outside are out The light energy attached to the surface of the tarshield 56 and detected by the light receiving section 22 moisture, ice, or other particles (for example) that reduce the amount of energy.

The above-mentioned sensing means is a dirty window detector 68, which is mounted on the housing 54 and It is configured so that the presence of deposits on the tarshield 56 can be detected optically. . Dirty window detector 68 will be described in detail later.

As shown in FIG. 2, the light emitting section 20 of the detection unit 18 is connected to the control section 26 and It is driven by a source driver 28 for the computer. The control unit 26 is configured in advance. It acts as a master tarlock that emits a tarlock signal at the selected frequency. Minimum, 50 Optimum results are obtained at a frequency of ~60 Hz, preferably 56 Hz. is known. The clock signal is then used for a modulator that drives the light emitting section 20. 0 emitter 58 used to modulate source driver 28. The constant wavelength optical energy is therefore modulated to the set frequency of the controller 26.

In this way, modulation to a certain specific frequency is essentially received by the light receiving section 22. Scenes caused by momentary light disturbances (flash) from sunlight or shadows in the illuminated background. Reduce the possibility of interference within the stem. The configured modulation frequency is also A signal fixed to the radiation energy that is recognized and processed by the optical section 22. Acts as a char.

The light reflected from the object 24 is received by the light receiving section 22. As mentioned above, A conventional filter 64 filters light energy outside a specific preset wavelength or wavelength range. It acts to attenuate the The light energy that has passed through the filter 64 is electrically The signal is converted into a signal and transmitted to the bandpass amplifier 30 via the line 100. van The toppass amplifier 30 is converted to the frequency of the control section 26 and is provided by the control section 26. to amplify signals with frequencies within a set range of clock frequencies. It acts like a sea urchin. Therefore, the bandpass amplifier 30 is controlled from the complex input signal. a first step of selecting input signal elements having a particular signature frequency of section 26; Acts as a one-step isolation measure.

The output of bandpass amplifier 30 is communicated through line 122 to sync detector 32. It will be done. This synchronization detector 32 transmits a timing reference signal transmitted on line 78 to the control section 2. Receive from 6. This timing reference signal is the source driver for the modulator. 28 on line 82.

The synchronization detector 32 converts the amplified signal transmitted from the line 122 into the line 78 tarok signal speed or frequency. Therefore, the same The period detector 32 constitutes a second stage of isolation means. More precisely, control A portion of the composite wave signal having the signature frequency of section 26 is utilized.

The output of the synchronization detector 32 has a magnitude corresponding to the emission received by the light receiving section 22. A set of signals proportional to the amount of light energy generated and emitted from the light section 20. Ru.

These output signals are transmitted to a threshold comparator 34, which compares the magnitude of the input signal. The corresponding threshold value is compared with the corresponding threshold value. The threshold value is adjusted by threshold value setting means 36.

When the magnitude of any one of the signals from the synchronization detector 32 exceeds the threshold, this occurs. The corresponding alarm signal is displayed through one or both of the two lines 136. The 0 indicating logic circuit 38, which is transmitted to the indicating logic circuit 38, responds to these latter signals. , one or more lights 40 and/or audible means 42. is activated, thereby informing the driver that the object 24 has been detected. . The threshold setting means 36 effectively adjust the sensitivity of the detection system and the detection unit 18. constitutes means for adjusting the range of distances that are effective for detecting the object 24. .

An optional overload detector 52 is augmented by a bandpass amplifier 30. If one of the two widened signals exceeds a preset value, that is, light reception Part 22 may be temporarily closed due to overload (for example, intense sunlight). ” is provided to detect a situation where the Overload like this The overload detector 52 displays one signal when the logic diagram FI? 1 38 and as a result an additional alarm alarm ( (not shown) is activated.

In order to detect the speed of a car that is passing next to it, A new detection unit 18 may be installed in the vehicle 10 at a different location.

Detection of multiple sets containing at least two consecutive or overlapping beams By employing the knowledge unit 18, the vehicle 10 can be brought close to nearby vehicles or objects. Approach speed detector to determine if you are following or moving away 50 makes it possible to create a pattern of reflected signals that is decoded. moreover , if two consecutive or overlapping beams are employed, the approach speed The detector 50 can be equipped with a complex algorithm such that the nearby car is the car 10. in the longitudinal direction (parallel to the vehicle 10) or in the radial or azimuthal direction (lane It is possible to detect if it is approaching from (change). The approach speed detector 50 is the synchronization detector 3 Detecting a steady increase in the approaching reflected signal driven by the output of 2. It works by hardware or software.

Approach speed detector 50 acts as a second threshold detector. That is, the synchronization detector 32 It is determined that the detected object has "approached" the set distance from the car 10 by comparing the signals from the vehicle 10. appropriate alarms (not shown) are activated by display logic 38.

Next, take a look at FIG. 5, which depicts details of the control section 26.

As described above, the control unit 26 generates a modulated clock signal and uses a preset frequency. Depending on the computer used, the light emitter 58 is 0N10FF, but it is 56kHz. A frequency of 2 provides optimal separation from background sunlight and light from other light sources. It turned out to be a sufficiently high frequency.

The control unit 26 is controlled by software or hardware as shown in FIG. is implemented to produce a 56 KHz square wave with stability preferably within ±0.2%.

The control unit 26 is operated by a suitable power source regulated by a voltage regulator 72. For example, a timer 74 such as an LH555CN micro unit is included.

The exact frequency of this timer 74 is adjusted using potentiometer 80.

The 112 KHz clock signal is output to flip-flop 76. Furi The flop 76 serves as a source driver for the sync detector 32 and the modulator, respectively. 28 (Figure 2) as a digital square wave of 56KH1 via lines 78 and 82. Generates a 50 percent duty cycle supplemental clock signal that is output. Acts as a divider.

One modulator source driver 28 and a set of accompanying source drivers 28 Optical device 58 is shown in FIG. The 56KH2 signal through line 82 is 84 to activate the base of NPN power transistor 86; Next, the NPN power transistor 88 is controlled. Source dry for modulator The output of each bar 28 is connected to three in series as a modulation current signal. The 0 emitter 58 that forms part of the emitter 20 is transmitted to the emitter 58 that is For example, it has several Siemens 10273 light emitting diodes, and these light emitting The diodes are placed close together and have a reference peak starting current of 100mA. The reference light emission at the center of the output beam 12 (FIG. 1) of the zero light emitting section 20 has a wavelength of 950. It is 2701-steradians in nanometers.

The emitted beam 12 has a nominal vertical dispersion of 15 degrees and a nominal horizontal dispersion of 25 degrees. The reference switching time of the zero emitter 58 is approximately 1 microsecond; The actual 0N10FF times are approximately 9 microseconds each.

As mentioned above, the light emitters 58 are arranged in three rows and columns, and each side of this arrangement The array of the light emitters 58, each side having a length of 1.5 inches, is arranged in the light receiving section 22 (Fig. 3). They may be spaced about 4 inches apart. Source drivers for the remaining five modulators The set of 28 and light emitter 58 is the same as the above circuit set explained in FIG. 6 and its details. are the same.

Next, take a look at FIG. 7, which depicts details of one light receiving section 22 of the detection unit 18.

The light receiving section 22 is a silicon PIN photo equipped with a Siemens 5FH205 device. It has a diode 23. The received light energy is the aspherical light beam mentioned above. The light is focused onto a Siemens 5FH205 device by a lens 62 (Figure 4). .

The filter 64 described above includes the photodiode 23 and has a wavelength of 800 nm. Eliminates non-nanometer radiation and provides peak response at a wavelength of 950 nanometers. It is made of infrared transparent plastic as shown.

The filter 64 is designed to effectively avoid flickering light from street lights such as mercury lamps. It also acts to reduce the sensitivity of the photodiode to sunlight. Photoda The output of diode 23 is connected to the inverting input of operational amplifier 90, which acts as a preamplifier. transmitted to the rollers.

Power is supplied to the operational amplifier 90 by the DC/DC converter 96, and the input power is Absorption and mitigation of electrical noise is achieved by regulator 98. operational amplifier The output of 90 is a DC coupled signal with a cutoff frequency of approximately 150 Hz. , and its size is equal to the light energy received by the photodiode 23. proportional to quantity. Resistor and capacitor of feedback circuit of operational amplifier 90 The inductor incorporated with the It can also reduce the effects of sunlight.

The output signal of operational amplifier 90 is routed via line 100 to a subsequent bandpass amplifier. It is transmitted to the width gauge 30. Details of this example are depicted in FIG. line 100 The upper input signal is connected to the non-inverting input side of the operational amplifier 104 via the capacitor 102. and a capacitor 110, and an adjustable bandpass coil 108 in parallel with the capacitor 110. and is sent to the EC network 106 consisting of.

The output of the operational amplifier 104 is passed through the capacitor 105 to the second operational amplifier 12. 0 non-inverting input side, a capacitor 116, and an adjustable to a second EC network 112 consisting of a bandpass coil 114. . Power to the regulated amplifier is provided by voltage regulator 118 [C Networks 106 and 112 are incorporated into operational amplifiers 104 and 120, respectively. and form two tuning stages. Each of them is used as a detector. Both have a bandwidth of approximately 1 Hz with zero phase at the center frequency for each stage. ) The total peak gain obtained by the zero stage is 500K. The 3db bandwidth is approximately 56 to 2000 Hz.

Next, take a look at FIG. 9, which shows details of the synchronization detector 32. Accompanied by detection unit 18 The input from bandpass amplifier 30 is coupled by capacitor 124, e.g. For example, analog multiplexer 1 with CD4052A microcircuit It is transmitted to the input of 26. Through line 78 to bin 10 of multiplexer 126 At 56, a Hz timing reference signal arrives. Multiplexer 126 Activated by the timing reference signal, the light emitter 58 coming through line 122 is used as a light source. The phase detector acts to isolate the signal from light reflected from the object 24 This signal, which acts as a detector, is amplified and averaged by an operational amplifier 128 to produce a signal of 0. It emits a DC signal with a response time of 0.5 seconds and an associated set of threshold comparators. - are transmitted to the data 34, respectively. One of the threshold comparators 34 is shown in detail. The target direction is depicted in the block diagram.

The inputs to multiplexer 126 via line 122 are each an operational amplifier. The output lines are switched to two sets of output lines connected to the inverting input terminal and the non-inverting input terminal of the converter 130. It will be done.

This switching is executed when the control section 26 is at a speed of 56KH2.

Since the non-inverting inputs of operational amplifier 130 are connected to a common circuit, the operational amplifier The output of 130 is a measurement of the detected light that is synchronized with the emitted light beam. Enter The incoming signal has a modulated frequency spectrum (e.g. wide frequency spectrum radiation) If it does not match, the average value summed to operational amplifier 130 will be zero. death However, if the incoming signal is detected by the radiation energy from the operational amplifier 130 to the inverting input of threshold comparator 34. Provides output. The threshold comparator 34 compares the value of the inverting input with the potentiometer 13. Compare the value of the non-inverting input from 4.

If higher than the threshold, a signal is sent to the display logic circuit via line 136. R38, which triggers one or more alarms.

Referring again to FIG. 2, the display logic circuit 38 has an alarm output light 40 and an audible alarm output. a turn signal sensor 44 employed for selectively activating the means 42; Receives a start signal from the accelerator sensor 46 or steering sensor 48 Ru. For example, any of the latter input signals indicates that the vehicle 10 has started an overtaking maneuver. It can be used to display. In that case, the presence of the object 24 within the monitored area As long as it is detected, for example, the audible arm 42 is activated.

The dirty window detector 68 described above is equivalent to the first detection system described above, but with additional features. It is equipped with a system with a small relative gain and a high threshold value.

To avoid interference between many vehicles, each vehicle is equipped with the object detection system of the present invention. key modulation technology will be used. This key modulation technique The control section 26 uses any means (e.g., computer software). The modulation frequency is specific to each vehicle. It changes depending on the “key” and is “random” for other car receivers. The receiver of each vehicle equipped with this detection system appears to be is equipped with a correlation detector that detects only reflected signals having a specific modulation frequency.

FIG. 10 shows another embodiment of the invention, in which the key modulation technique described above is achieved. Improvements to the circuit of Figure 2 are included. Therefore, sequence generator 1 40 is connected to the control section 26 and provides a characteristic "key" to a specific unit. output a series of modulation frequencies.

The control unit 26 has been improved to operate at a variable frequency under the control of the sequence generator 140. Provide a clock signal. The activation signal supplied on line 82.78 has one frequency has a frequency spectrum that can have either a number or multiple frequencies. are doing.

During operation, the sequence generator 140 presets the modulation frequency of the control unit 26. change at specified intervals. Sequence generator 140 is well known in the art. For example, it is a device that periodically commands a new modulation frequency to the control unit 26. A permanent storage device (not shown) is provided.

Each sensing unit is therefore provided with a specific frequency sequence in a fixed memory. to avoid interference with other systems in nearby vehicles. Alternatively each automatic The car also uses a known random sequence generator (e.g. multiple shift registers). (star and combinatorial logic circuit).

The activation signal is given a synchronous frequency (i.e. a frequency band with one or more frequencies). spectrum), the emitter is at a moderate level (e.g., half power level). It is desirable to have a medium level of luminescence.

This simplifies modulation at multiple frequencies.

The system improvement shown in Fig. 10 is achieved by the phase delay circuit 141 and the ratio circuit 142. The zero phase delay circuit B141 receives the square wave from line 78 and receives the timing reference signal. outputs a quadrature signal whose phase is shifted 90 degrees from the signal.

The output from the bandpass amplifier 30 is sensed synchronously in accordance with the phase-delayed signal described above. The output of the synchronous detector with zero phase lag improves the selectivity of the system. Synchronous detector with 0 phase lag which is zero under the normal luminous signal from the scene or system. The output from emitter 20 indicates that the detected light is not a reflection of light from emitter 20 but is (e.g. similar systems in other cars), or , the reflecting object is far enough away that the light emitter travels from the emitter to the object and back. Zero if it causes a significant delay due to the flight time of light with a path. If the quadrature (i.e. phase-lag) synchronous output exceeds the set value, the normal synchronous The output from the period detector is ignored. The ratio circuit 142 is Set the setpoint at a specific ratio of output. The output signal from the ratio circuit 142 is shown in the table below. It can be used to prevent object detection through explicit circuit logic, and it can also be used to The frequency sequence generated by the frequency generator 140 is changed to Used to avoid interference from the stem.

If the fundamental modulation frequency used is increased within the range of 1 to 10IIH2, You can also avoid objects that are farther away than the set distance. For example, 5 MHz Using the operating frequency, the light reflected from an object at 12.5 feet is delayed by 25 nanoseconds with a 45 degree phase shift.

In this case, the 90 degree phase shift detector is equal to that of a normal detector, this condition is Preventing responses to objects farther than 12.5 feet or other selected distance It can be used for. Furthermore, the output of the phase shift detector and the output of the synchronous detector are The ratio of can be used to find the distance to an object.

Next, looking at FIG. 11, we see that the exclusive OR gate for providing the phase delay circuit 141 is An improvement to the control section 26 is depicted having a gate 145 and an exclusive OR gate 145. The inputs are line 82 with a 56KIIZ base signal and a 112KHz tarokk signal. is connected to the output of a timer 74 having a signal. Therefore, the exclusive OR game The output of the gate 145 is a 56 KHz signal with a 90 degree phase delay.

The phase-delayed quadrature signal is then passed through a multiplexer as shown in Figure 12. A quadrature synchronous detector comprising a multiplexer 126 and an operational amplifier 128 is provided. The input to the quadrature detector, which is This is an input to the detector. The output of the quadrature synchronous detector is connected to the comparator via line 146. 148.

The output signal from a conventional synchronous detector passes through a potentiometer 147 to a comparator. 148. The signal on line 146 is passed through inverter 149. is inverted and fed to one input of another comparator 150.

The remaining input of comparator 150 is connected to the output of potentiometer 147. There is. The outputs of comparators 148 and 150 correspond to the respective inputs of NAND gates 150. Comparator 150.148 is on line 146 during operation. In a conventional analog system, the absolute value of the quadrature output signal is determined by potentiometer 147. The output of NAND gate 151 indicates whether the set ratio of the period detector output has been exceeded. The output controls a transfer gate 152 which is combined with the output from a conventional synchronous detector. . Therefore, when the set ratio is exceeded by the quadrature signal, the normal synchronization Output from the detector is blocked by closing transfer gate 152. NA The frequency from the Siegen generator 140 depends on the output from the NO gate 151. It is also desirable to vary the number sequence.

A further improvement to the invention is shown in FIG. One detector has one or more The upper light emitter is configured to receive radiation.

In the embodiment shown in FIG. emitting angularly spaced beams from a first location. -The set of detectors C and D is , in different parts of the car, with each channel receiving light from its respective area. The device is configured to receive light in a plurality of channels configured to receive light.

As shown in the figure, a plurality of spaced apart light emitters are provided in the light receiving area of the detector. beam exists. Therefore, detector C receives reflected light from areas indicated by AC and BC. be able to. Similarly, the detector receives light reflected from areas AD and BD. The beams from emitters A and B are multiplexed or modulated so that they cannot be detected. The detector can distinguish between the light from each beam. For example, from emitters A and B. The beams can be emitted sequentially to differentiate the beams.

Beams can be emitted simultaneously from emitters A, B at different frequency spectra. child To implement a system with separation of areas where the lights intersect, such as Requires multiple channels for a complete system.

Having described several embodiments of the invention, those skilled in the art will appreciate that Preferences selected to illustrate the invention without departing from the spirit and scope of its contribution to the art. It is understood that various modifications and additions may be made to the embodiments.

For example, emitter 58 may be pulse modulated at a preselected frequency. , the magnitude is sampled at the modulation frequency to determine whether the emitted pulse is present there. You can also decide. Accordingly, the protection hereby envisaged and conferred shall be upon the claimant. The scope of the invention should legitimately cover such matters and all things of the same nature. Conceivable.

FIG. 1 FIG, l○ Procedural amendment writing salmon) October 17, 1986 Yoshi, Commissioner of the Patent Office 1) Takeshi Moon 1. Indication of incident PCT/US871003252, title of invention Object detection device (Correction) 3. Person making the correction Relationship to the incident: Patent applicant Auto-Sense Limited 4. Agent Postal code 105 1-6-7 Atago, Minato-ku, Tokyo Atagoyama Attorney Building 5. Date of amendment order Self-initiated 6. Subject of correction Specification (column for title of invention) 7. Contents of correction international search report

Claims (13)

[Claims] (1) a light emitting means for emitting radiant energy within the area under surveillance; connected to the light emitting means to control the intensity of the radiant energy; control means for emitting the activation signal so as to have a frequency spectrum; Receives radiant energy from the monitored area and is proportional to the radiant energy detection means for emitting an electrical signal to connected to the detection means and the control means, and transmits the controlled frequency spectrum. synchronizing means for retrieving a first portion of said electrical signal, said synchronizing means having connected and for emitting an indication signal when the size of said first part exceeds a threshold value. threshold means and An object detection device for detecting the presence of an object within a monitored area. (2) Claim 1, wherein the controlled frequency spectrum changes over time. Apparatus described in section. (3) one in which the above-mentioned controlled frequency spectrum substantially changes with time; 2. A device according to claim 1, having only a frequency of . (4) In any of the above claims, wherein said controlled frequency spectrum has one or more frequencies. The device according to scope 1. (5) connected to said control means for commanding said frequency spectrum continuously; 3. Apparatus according to claim 2, further comprising key sequence generator means. (6) The key sequence generator means is configured to generate a sequence of commanded frequency spectra. 6. A device according to claim 5, further comprising a fixed storage device for subsequent reading. (7) The key sequence generator means randomly generates the frequency spectrum. Claim 5, further comprising a pseudo-random generator for changing the equipment. (8) connected to the control means and substantially phase-shifted by 90 degrees from the activation signal; delay means for emitting a quadrature signal; is connected to the detection means and the delay means, and has a substantially 90 degree phase shift from the activation signal. for retrieving a second portion of said electrical signal having a shifted frequency spectrum; quadrature means of; connected to said quadrature means and said threshold means, wherein the absolute value of said second portion is predetermined. and circuit means for interfering with the display signal when the set value is exceeded. 2. A device according to claim 1. (9) Claim 8, wherein the set value is the set ratio of the first part. equipment. (10) the light emitting means comprises a plurality of angularly spaced beams of the radiant energy; 2. A device according to claim 1, wherein the device is configured to emit. (11) Each of the plurality of beams has a different controlled frequency spectrum. 11. A device according to claim 10. (12) The method according to claim 10, wherein the plurality of beams are continuously emitted. Device. (13) The detection means detects whether each channel corresponds to each area within the area under monitoring. The above claim has a plurality of channels configured to receive radiant energy from The device according to item 10.