JP3240333B2 - Object detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detecting device,
In particular, the present invention relates to an object detection device that performs distance measurement using light.

[0002]

2. Description of the Related Art A distance measuring device is used for preventing collision between running objects such as unmanned vehicles running in a warehouse. Light is often used as a distance measuring medium in this distance measuring device. This distance measuring device is provided with a device that emits light from one moving body to the other moving body and a light receiving device, and a reflector that reflects light is provided on the other moving body, and is emitted from one moving body. The reflected light is reflected by the reflection plate of the other moving body, received by a light receiving device provided on one of the moving bodies, and the distance between the two moving bodies is measured by the intensity of the received light with respect to the emitted light.

[0003]

In the conventional apparatus as described above, since the distance is determined based on the intensity of the received light, the light intensity changes due to the influence of fog or floating dust. Could not measure the distance. Further, the amplifier for amplifying the received light has a drawback that the amplification factor changes depending on the temperature and accurate distance measurement cannot be performed. In addition, the configuration for covering the above-mentioned disadvantages is increased,
Due to the complicated configuration, there is also a disadvantage that the price of the entire apparatus increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the conventional apparatus, and has an object to simplify the structure and to accurately detect an object to be detected irrespective of a gas contamination state or an ambient temperature. It is an object of the present invention to provide an object detection device capable of measuring a distance and accurately detecting the object.

[0005]

The invention described in claim 1 of the present application is based on a comparison between light emitted from a luminous body and light radiated from the luminous body, reflected from the measured body, and returned. In an object detection device that detects a distance to, a reference signal generating unit that generates a signal serving as a reference for distance measurement,
A first light-emitting means disposed at a reference position for emitting light modulated by a signal generated from the reference signal generating means; and a light modulated for emitting a light modulated by a signal generated from the reference signal generating means. A second light emitting unit that emits light in the direction of the measured object and is disposed at a reference position; a switching unit that alternately switches and emits light from the first and second light emitting units; Light receiving means for directly receiving light emitted from the first light emitting means and receiving light returning from the object to be reflected by light emitted from the second light emitting means; and a phase of a signal generated from the reference signal generating means. And the phase difference between the light directly received and the light emitted from the first light emitting means is counted, and the phase of the signal generated from the reference signal generating means and the light emitted from the second light emitting means are measured. Reflected light reflected back to Counting means for counting the phase difference; a count value of the difference between the reference signal and the light emitted from the first light emitting means; and a reflection emitted from the reference signal and the second light emitting means and reflected from the object to be measured and returned. An object detecting device comprising: a calculating means for calculating a distance from the reference position to the object to be measured by comparing the counted value of the difference with light. According to a second aspect of the present invention, in addition to the first aspect, the two light-receiving signals received by the light-receiving means and the reference signal are up to a predetermined frequency by heterodyne detection having a local oscillator having the same phase. Provided is an object detection device characterized in that the count values are reduced and the count values are compared with each other. According to a third aspect of the present invention, in addition to the first aspect, a band-pass filter for passing only a reference signal component is provided in a circuit for obtaining a light receiving signal received by the light receiving means. An object detection device is provided.

[0006]

There is provided switching means for alternately switching the first and second light emitting means to emit light, and the phase of the signal generated by the reference signal generating means and the light emitted from the first light emitting means in the first fixed time. The phase difference between the light directly receiving the emitted light is counted, and in the next fixed time, the phase of the signal generated from the reference signal generating means and the light emitted from the second light emitting means are reflected on the object to be measured. The difference between the phases of the returning reflected light is counted, and the distance between the detected object and the object detection device is calculated by subtracting these two count values. It should be noted that a detection signal can be issued when the detected object approaches a predetermined distance. The above-described comparison of the count values may be performed after heterodyne detection of the fundamental wave and the signal received by the light receiving element is performed by a mixer having the same local oscillation frequency.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an object detection device according to the present invention. In FIG. 1, PD1 and PD2 are light emitting elements composed of LEDs. The light emitting element PD1 is a switching element T
Lights up when R1 is conducting, and light emitting element PD2 lights up when switching element TR2 is conducting. Reference numeral 1 denotes a reference oscillator which is connected to a crystal oscillator XTAL1.
A reference signal RF having a vibration frequency of Reference numeral 2 denotes a modulator, which is a light-emitting element PD1 or PD2 that is to emit light continuously
Is modulated by a high-frequency signal oscillated by the reference oscillator 1. P
R is a light receiving element. Reference numeral 3 denotes a convex lens for focusing light emitted from the light emitting element PD1 into a thin light beam, and reference numeral 4 denotes a convex lens for forming an image of light reflected from the detected object OB on the light receiving element PR. Light emitting elements PD1, P
D2 and the light receiving element PR are located at a close distance, and light emitted from the light emitting element PD1 is shielded so as not to directly enter the light receiving element PR, but light emitted from the light receiving element PD2 is directly transmitted to the light receiving element PR. It is configured to be incident. Switching elements TR1 and TR2 are turned on / off by switching signals L1 and L2 output from control circuit 5. The switching signals L1 and L2 are pulse signals that are 180 degrees out of phase. Therefore, the light emitting elements PD1 and PD2
Will operate alternately. Note that the switching signals L1, L
2 is lower than the frequency of the reference signal RF.

[0008] The light receiving element PR receives the reflected light reflected from the detected object OB and converts it into an electric signal. 6
Is an amplifier that amplifies the electric signal output from the light receiving element PR and outputs a received signal RS. Reference numeral 7 denotes a local oscillator which generates a local oscillation signal LF having a vibration frequency of the connected crystal resonator XTAL2. Each of 8 and 9 is a mixer, and the mixer 8 mixes the reference signal RF and the local oscillation signal LF to output an intermediate frequency signal IMS1. This intermediate frequency signal IMS1 is input to the waveform shaping circuit 11 through the low-pass filter 10. Further, the mixer 9 mixes the local oscillation signal LF and the reception signal RS to mix the intermediate frequency signal I
MS2 is output. This intermediate frequency signal IMS2 passes through the band pass filter 12 and is input to the waveform shaping circuit 13. In the waveform shaping circuits 11 and 13, the input signal is shaped into a clean pulse signal by shaping the waveform.
These pulse signals are input to the counter circuit 14, respectively. In the counter circuit 14, the intermediate frequency signal IMS1
And the phase of the IMS 2 is compared, the difference is counted, and sent to the next control circuit 5. The control circuit 5 has a microcomputer configuration including a CPU, a memory, and the like.
By calculating the distance between the light emitting element PD1 and the detected object OB,
The distance is output, but when the detected object OB and the object detection device according to the present invention are relatively moving, an output for detecting the detected object is generated when the distance between them is approached to a predetermined value. Various operations such as outputting a signal when the detected object is relatively within a predetermined range with the object detection device are performed. An operation plate 15 includes buttons for operating the object detection device according to the present invention, a display panel for displaying the distance between the device and the detected object, and the like. There is also provided a setting device for making settings such as issuing an output signal when the object OB approaches the position P1 or issuing a signal when the detected object OB exists between the position P2 and the position P3.

Next, the operation of the embodiment of the present invention will be described.
The reference signal RF oscillated from the reference oscillator 1 is heterodyne-detected by the mixer 8, converted into an intermediate frequency signal IMS 1, shaped by the waveform shaping circuit 11, and input to the counter circuit 14. As shown in FIG. 2, the timing of each rising of this signal is set to t0, and the counter is cleared to zero and counting starts at the same time. Switching signal L
When 2 is "1", the light emitting element PD2 is turned on and the light emitting element PD1 is turned off. The light from the light emitting element PD2 is directly received by the light receiving element PR and converted into an electric signal, then amplified by the amplifier 6 and input to the mixer 9, where it is heterodyne-detected and converted into the intermediate frequency signal IMS2, and the waveform shaping circuit 12
After the waveform is shaped by the counter circuit 1 as a direct wave
4 is input. Since this signal passes through the circuit from the light emitting element PD2 and the light receiving element PR to the counter circuit 14,
The counter circuit 1 is slightly delayed from the intermediate frequency signal IMS1.
Enter 4 In the counter circuit 14, the intermediate frequency signal I
The count is stopped by capturing the rising timing t1 of MS2, and the count number of (t1-t0) is set to the control circuit 5
Output to The control circuit 5 stores this count value as S1.

Thereafter, as shown in FIG. 2, the switching signal L2
Is switched to "0" and the switching signal L1 is switched to "1", the rising timing of the intermediate frequency signal IMS1 is set to t0, the counter is cleared to zero, and counting starts simultaneously. The switching signal L2 becomes "0" and the switching signal L1 becomes "0".
When switched to 1 ", the light emitting element PD1 is turned on and the light emitting element PD2 is turned off. Light emitted from the light emitting element PD1 is radiated in the direction of the detected object OB, reflected from this, and received by the light receiving element PR, After being converted into an electric signal, the signal is amplified by the amplifier 6 and input to the mixer 9 where it is heterodyne-detected and converted into the intermediate frequency signal IMS2. This signal is input to the light emitting element PD2,
Thereafter, the light is received by the light receiving element PR via the detected object OB, and passes through a circuit from the light receiving element PR to the counter circuit 14, so that the light is input to the counter circuit 14 later than the intermediate frequency signal IMS1. The counter circuit 14 stops counting by capturing the rising timing t2 of the intermediate frequency signal IMS2 and outputs the count number of (t2−t0) to the control circuit 5. The control circuit 5 calculates this count value as S2
To be stored. Thereafter, in the control circuit 5, (S2-S1)
Is calculated, and from this value, the light emitting element PD1 and the detected object O
The distance between B is calculated and output.

Note that, as shown in FIG.
Is set between the positions P2 and P3, the distance between the outputted light emitting element PD1 and the detected object OB is within a predetermined range or outside the range. The control device 5 also performs the calculation of whether or not.

In the above embodiment, both the reference signal and the signal received by the light receiving element are subjected to heterodyne detection. When the frequency of the reference signal is low, the reference signal and the received signal obtained from the light receiving element are directly shaped. Then, it may be input to the counter circuit. Further, the light source is not limited to the LED, and a laser light source can be used. If this is used, the distance measured can be extended as compared with the LED.

[0013]

As described above in detail, according to the present invention, since light is modulated by the reference signal, even if the light reflected from the detected object changes in intensity depending on the atmosphere,
These do not reduce the accuracy of distance measurement. In addition, since the reflected light and the direct light are processed in a time series by a single signal processing circuit, even if the amplification degree of the signal processing circuit changes due to the ambient temperature, a large error does not occur, and the configuration is also small. Since it is simpler than the conventional one, the cost can be kept low as compared with the conventional one. The timing of counting the difference between the phase of the signal generated from the reference signal generating means and the phase of the light directly receiving the emitted light emitted from the first light emitting means; The light emitted from the second light emitting means is reflected on the object to be measured, and the timing for counting the phase difference of the reflected light does not overlap, so that the light emitted from the first light emitting means and the light emitted from the second light emitting means does not overlap. There is also an effect that accurate distance measurement can be performed without causing interference.

In addition, in the case where a plurality of such object detecting devices are juxtaposed and juxtaposed, if the frequencies of the reference signals are mutually changed, they do not interfere with each other and no crosstalk occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an object detection device according to the present invention.

FIG. 2 is a time chart illustrating the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reference oscillator 2 ... Modulator 3 ... Convex lens 4 ... Convex lens 5 ... Control circuit 6 ... Amplifier 7 ... Local oscillator 8 ... Mixer 9 ... Mixing Instrument 10 Low pass filter 11 Waveform shaping circuit 12 Bandpass filter 13 Waveform shaping circuit 14 Counter circuit 15 Operation panel

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-304380 (JP, A) JP-A-3-189584 (JP, A) JP-A-61-218978 (JP, A) 106785 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01S ⁷ /48-7/50 G01S 17/00-17/88 G01C 3/02-3/08

Claims (3)

(57) [Claims] 1. An object detection apparatus for detecting a distance to a measured object by comparing light emitted from the illuminant with light emitted from the illuminated body and reflected and returned from the measured object. Reference signal generation means for generating a signal serving as a reference, first light emitting means for emitting light modulated by a signal generated from the reference signal generation means and disposed at a reference position, and from the reference signal generation means It emits light modulated by the generated signal and emits the emitted light in the direction of the object to be measured, and alternately switches between the first light emitting means and the second light emitting means disposed at the reference position. Switching means for emitting light; and light receiving means disposed at a reference position for directly receiving light emitted from the first light emitting means and receiving light returning from the object to be measured and emitted from the second light emitting means. Means and the reference signal The difference between the phase of the signal generated from the generating means and the phase of the light directly receiving the light emitted from the first light emitting means is counted, and the phase of the signal generated from the reference signal generating means and the second light emitting means are counted. Counting means for counting the phase difference of the reflected light in which light emitted from the light source is reflected by the object to be measured and returns, a count value of a difference between the reference signal and light emitted by the first light emitting means, and the reference signal And calculating means for calculating the distance from the reference position to the measured object by comparing the counted value of the difference between the reflected light emitted from the second light emitting means and the reflected light returning from the measured object. An object detection device that is a feature. 2. The method according to claim 1, wherein the two light receiving signals and the reference signal received by the light receiving means are reduced to a predetermined frequency by heterodyne detection having a local oscillator having the same phase, and the count values are compared with each other. The object detection device according to claim. 3. An object detection apparatus according to claim 1, wherein a band-pass filter for passing only a reference signal component is provided in a circuit for obtaining a light reception signal received by said light receiving means.