JP3217830B2 - 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 detection device for detecting whether or not an object exists in a predetermined detection area.
In particular, a semiconductor position detection element (Position
The present invention relates to an object detection device using Sensitive Detectors (hereinafter, referred to as PSD).

[0002]

2. Description of the Related Art Conventionally, an object detecting device using a PSD as a position detecting element has been known. The principle and configuration of object detection in the object detection device are described in, for example, JP-A-63-61112 and JP-A-62-204113, and a detailed description thereof will be omitted. ,
The outline is described below with reference to FIG.
The object detection device includes a light projecting unit 1, a light receiving unit 2, and a signal processing unit 3.

The light projecting section 1 includes a light emitting element 4 such as a light emitting diode (LED) and a lens 5 as an optical means for projecting a pulse light emitted by the light emitting element 4 to a predetermined detection area. I have.

The light receiving section 2 has a PSD as a position detecting element.
6 and a lens 7 which is an optical means for converging reflected light from the detection area direction on the PSD 6.
The light receiving unit 2 is triangulated with respect to the light projecting unit 1 and the detection area. Detected object 1 within detection area
In the case where the light source 8 does not exist, the pulsed light emitted from the light emitting part 1 emits the background light 1 such as a wall surface or a floor surface as shown by a solid line in the figure.
The reflected light is imaged by the lens 7 at the position P ₁ on the detection surface of the PSD 6. However, if the detected object 18 is present in the detection area, light reflected from the object to be detected object 18, as indicated by a broken line in the figure, the lens 7, the P ₁ on the detection surface of the PSD6 Different P ₂
The image is formed at the position.

[0005] The PSD 6 outputs two currents corresponding to the image forming position of the reflected light. These two output currents are subjected to the following processing in the signal processing section 3. First,
These two output currents are connected to a current / voltage conversion circuit (hereinafter, referred to as a current / voltage conversion circuit).
These are converted into voltages by the I / V conversion circuits 8 and 9 and input to the amplifiers 10 and 11, respectively. Outputs of the amplifiers 10 and 11 are input to AGC circuits 12 and 13, respectively. AGC circuits 12 and 13 include amplifiers 10 and 1
This is provided so as not to saturate one output signal. For example, it detects a peak level of an input signal and outputs a control signal corresponding to the peak level to the amplifiers 10 and 11. The gain of the amplifiers 10 and 11 is controlled by this control signal.

[0006] The outputs of the amplifiers 10 and 11 are also input to an arithmetic circuit 14 and subjected to predetermined arithmetic processing to generate a signal indicating the distance to the detected object (hereinafter, this signal is referred to as a distance signal). Is done. This distance signal is input to the comparison circuit 15 and compared with a preset threshold level.
The output circuit 16 performs a predetermined output process according to the output of the comparison circuit 15. For example, when the output of the comparison circuit 15 indicates the presence of the detected object, a signal indicating the presence of the detected object is provided. Is output.

[0007]

By the way, the distance from the light projecting unit 1 and the light receiving unit 2 to the background 17 changes according to the mounting position of the object detecting device. It needs to be changed according to the distance to the background 17. This is because the threshold level of the comparison circuit 15 does not deviate from the distance signal obtained when the detected object does not exist in the detection area, that is, the distance signal of the background 17.

For this purpose, in the conventional object detection device, the threshold level of the comparison circuit 15 is usually changed by a variable resistor or the like. However, this threshold level must be set manually. Therefore, it is very troublesome and troublesome to set the threshold level every time the device is attached, and an erroneous setting may cause a malfunction.

Although the signal processing unit 3 is provided with an AGC circuit to stabilize the signal, the range of the signal level which can be controlled by the AGC is naturally limited. When there is an object with a high level, the signal is saturated. On the other hand, in the case of an object having a very low reflectance, the output of the PSD 6 becomes very small, and the S / N ratio is extremely deteriorated. Further, since the AGC circuit controls the gain of the amplifier, it also amplifies the noise component. Therefore, it is difficult to greatly improve the S / N ratio.

The present invention solves the above-mentioned problem, and can easily and accurately set a threshold level of a comparison circuit, that is, a level corresponding to a distance serving as a reference for object detection. In addition, an object of the present invention is to provide an object detection device that does not saturate a signal and that can significantly improve the S / N ratio compared to the related art.

[0011]

According to an aspect of the present invention, there is provided an object detecting apparatus, comprising: a light projecting unit for projecting a light projecting beam toward a predetermined detection area; A semiconductor position detecting element for receiving the reflected light of the light beam projected from the section; a light receiving section triangulated with respect to the light projecting section and the detection area; and a semiconductor position detecting element output from the semiconductor position detecting element. Distance signal generating means for generating a signal indicating the distance to the object based on the two light receiving output signals; memory means; and a value stored in the memory means as a reference value. A comparison circuit for comparing an output signal of the means, an operation means, and a control means for, when the operation means is operated, writing an output signal of the distance signal generation means at that time to the memory means. And

According to a second aspect of the present invention, in the object detecting apparatus of the first aspect, a front surface of the semiconductor position detecting element of the light receiving section has an optical axis corresponding to a detection surface of the semiconductor position detecting element. An optical system shifted from the center position by a predetermined amount in the longitudinal direction of the detection surface is disposed.

According to a third aspect of the present invention, there is provided an object detecting device, comprising: a semiconductor position detecting element; first and second current / voltage converting means for converting first and second current outputs of the semiconductor position detecting element into voltages, respectively; First and second integrating means for integrating output signals of the first and second current / voltage converting means in synchronization with the light emitting timing of the light projector, and sampling / outputting the outputs of the first and second integrating means respectively. First and second sample / hold means for holding, and A / D conversion means for A / D converting output signals of the first and second sample / hold means and outputting data indicating a distance to an object;
Comparing means for comparing the output voltage of the first or second integrating means with a predetermined reference value, and controlling means, wherein the controlling means monitors the output level of the comparing means, and adjusts the output level of the comparing means. , If the output voltage of the first or second integrating means indicates that the output voltage is equal to or higher than the reference value,
And causing the second sample / hold circuit to perform a sample / hold operation, and after the hold operation of the first and second sample / hold circuits is completed, causing the A / D conversion means to perform the A / D conversion operation. It is characterized in that the second integration circuit is reset. An object detection device according to a fourth aspect is the object detection device according to the third aspect, wherein the comparing means has a hysteresis.

[0014]

According to the first aspect of the present invention, there is provided an object detecting apparatus including a memory unit, an operating unit, and a control unit.
The memory means stores a signal used as a reference value for object detection in the comparison circuit. Then, when the operating means is operated, the control means writes the output signal of the distance signal generating means at that time to the memory means. Therefore, since a signal corresponding to the distance to the background, which is a criterion for object detection, can be directly set as a reference value, not only can object detection be performed with high accuracy, but also its setting and change can be easily performed. Can be done.

[0015] The object detecting device according to the second aspect is the first aspect.
In addition to the configuration described above, an optical system is arranged on the front surface of the semiconductor position detecting element. The optical axis of this optical system is shifted from the center position of the detection surface of the semiconductor position detection element by a predetermined amount in the longitudinal direction of the detection surface. by this,
Since the reflected light from the object or the background is always received only in a predetermined direction from the center position of the detection surface of the semiconductor position detection element, a predetermined one of the two outputs of the semiconductor position detection element is output. It can always be larger than the other output, which not only makes signal processing easier,
Fine adjustment of the position of the optical system is not required, and the operation of position adjustment can be greatly simplified.

According to the third aspect of the present invention, the conventional AGC circuit is not provided. Instead, the first and second current outputs of the semiconductor position detecting element are converted into voltages. There are provided first and second integration means for integrating a signal in synchronization with the light emission timing of the light projector.
Therefore, even when the reflected light from the object or the background is very weak, the signal is integrated each time the light is projected, so that a signal with a good S / N ratio can be obtained.
In the AGC circuit, the signal may be saturated. However, the signal does not saturate by performing integration in synchronization with the light emission timing, and the signal indicating the distance to the object reliably and accurately. Can be obtained. Further, in the object detection device according to the third aspect, the output level of the comparison means is monitored, and the output level of the comparison means indicates that the output voltage of the first or second integration means is equal to or higher than the reference value. , The first and second sample / hold circuits are caused to perform a sample / hold operation, and after the hold operation of the first and second sample / hold circuits is completed, A
There is provided control means for causing the / D conversion means to perform an A / D conversion operation and resetting the first and second integration circuits. In addition, in the object detection device according to the fourth aspect, in addition to the configuration according to the third aspect, the comparison means has hysteresis, and the output voltage of the first or second integration circuit input to the comparison circuit fluctuates slightly. Even if it does, a stable output can be obtained.

[0017]

Embodiments will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of an embodiment of an object detection device according to the present invention. In FIG.
2 is a drive circuit, 23 is an LED, 24 is a lens, 31 is a light receiving unit, 32 is a lens, 33 is PSD, and 34 and 35 are I /
V conversion circuits, 36 and 37 are switches, 38 and 39 are integration circuits, 40 and 41 are switches, and 42 and 43 are samples /
Hold circuit (hereinafter referred to as S / H circuit), 44 is a comparison circuit, 45 is an A / D conversion circuit, 46 is an operation unit, 47 is a memory, 48 is a comparison circuit, 49 is an output circuit, and 50 and 51 are switches. Is shown.

In FIG. 1, a control means 20 manages the operation of each part of the object detecting device in a centralized manner and is composed of a microprocessor and its peripheral circuits. The light projecting unit 21 includes an LED 23 as a light emitting element, a drive circuit 22 for driving the LED 23, and a lens 24 for projecting pulse light emitted from the LED 23 in a direction of a predetermined detection area. The drive circuit 22 is formed of a constant current circuit, and operates only when the drive signal DR output from the control means 20 is at a predetermined level, for example, a high level as shown in FIG. 2A.

The light receiving section 31 is provided with a PSD 32 and a lens 32 for imaging reflected light from the detection area on the detection surface of the PSD 33.
In other words, the optical axis is shifted from the center position P of the detection surface of the PSD 33 by a predetermined offset amount D _{OF in} advance.
This is because the two output currents I ₁ and I ₂ of the PSD 33 must always satisfy the relationship of I ₁ ≧ I ₂ in the configuration of FIG. The center Q of the PSD 33 is shifted by D _OF from the center P of the detection surface of the PSD 33, so that the reflected light is always connected to one side of the center P of the detection surface of the PSD 33, and in the figure, only below the center P. Therefore, the above relationship is always satisfied.

The output currents I ₁ and I ₂ of the PSD 33 are converted into voltages by I / V conversion circuits 34 and 35, respectively. The switches 36 and 37 are closed in synchronization with the emission of the LED 23. That is, the circuit is closed when the drive signal DR is at a high level. As a result, only the reflected light is input to the integration circuits 38 and 39. Since the switches 40 and 41 of the integration circuits 38 and 39 are normally open, the input signals are sequentially integrated. As described above, the output voltage v ₁ of the integration circuit 38 is always equal to or higher than the output voltage v ₂ of the integration circuit 39. The output voltage v ₁ of the integration circuit 38 is input to the comparison circuit 44 and is compared with a predetermined reference voltage v ₀ .

The comparison circuit 44 compares v ₁ with the reference voltage v _0, and when v ₁ ≧ v ₀ , the low level, v ₁ <v
_When it is ₀ , it outputs a high level. However, the comparison circuit 44 is composed of a comparator circuit having hysteresis for stabilizing the operation. In the comparison circuit having no hysteresis, the threshold value V _TH1 when falling from the high level to the low level is the same as the threshold value V _TH2 when falling from the low level to the high level, but such a comparison circuit was used. In such a case, there are the following problems. That is, although the S / N ratio of the output voltage v ₁ of the integration circuit 38 is good due to the effect of signal integration, the output voltage v ₁ may fluctuate due to noise or other factors although the S / N ratio is good. If the voltage fluctuation occurs near the threshold value V _TH1 (= V _TH2 ) as shown in FIG. 3A, the output V _COM of the comparison circuit 44 becomes
As shown in (1), the high level and the low level are frequently repeated, and a stable output cannot be obtained.

On the other hand, in the comparison circuit having hysteresis, V _TH1 > V _TH2 is set so that even if the output voltage v ₁ slightly fluctuates as shown in FIG. _As long as ₁ does not fall below the threshold value V _TH2 , as shown in FIG. 3D, once the level becomes low, the state is maintained, so that a stable output can be obtained. In Comparative circuit 44 shown in FIG. 1, V _TH1
And V _TH2 , that is, the width of the hysteresis is R ₁ × V _B /
It is given by (R ₁ + R ₂ ).

As described above, since the signal based on the reflected light from the object is sequentially integrated in synchronization with the timing of the projection, the S / N is compared with the case where the conventional AGC circuit is used.
The ratio can be greatly improved. For example, when there is an object with a small reflectance in the distance, the reflected light becomes very weak, but the signal based on the reflected light is integrated every time the light is projected. / N
An output signal with a good ratio can be obtained.

The output signal V _COM of the comparison circuit 44 is sent to the control means 20. Control means 20 monitors the level of the signal V _COM, when a low level, as shown in FIG. 2, the sample / hold signal SH at a predetermined timing,
It outputs a signal AD for instructing the start of A / D conversion to the A / D conversion circuit 45, and outputs a reset signal RES following these signals.

That is, if the signal _VCOM goes low as shown in FIG. 2B when the integration is performed at a certain light emission timing, the control means 20 sends the sample / hold signal as shown in FIG. 2C. SH is converted to S / H circuits 42 and 4
3 to the switches 50 and 51. Switch 5
Since 0 and 51 are closed when the sample / hold signal SH is at a high level, the output voltages v ₁ and v ₂ of the integration circuits 38 and 39 are sampled and held during this period. That is, the S / H circuits 42 and 43 start the sampling operation at the rise of the sample / hold signal SH, and when the charge is accumulated in the capacitors C ₁ and C ₂ during the high level period and the sample / hold signal SH falls. Hold the accumulated charge.

The control means 20 includes an S / H circuit 42,
After the completion of the hold operation at 43, the reset signal RES shown in FIG.
2A, and outputs a signal AD indicating the start of A / D conversion shown in FIG. 2E to the A / D conversion circuit 45.
Output to The switches 40 and 41 are connected to the reset signal RES.
Is closed at the rising edge of the signal, so that the integration circuits 38, 3
9 is reset, so that the output signal V _COM
Is at a high level as shown in FIG. 2B. Also, S / H
The voltage held in the circuits 42 and 43 is applied to the A / D conversion circuit 45.
And digitized. At this time A / D conversion circuit _{45, V IN / (V REF (} +) -V REF (-)) the value of is to convert the digital value of a predetermined number of bits, V _{REF (-)}
Is grounded, the value of V _IN / V _{REF (+)} is digitized in the A / D conversion circuit 45 of FIG. It is clear that this value indicates the distance to the object (hereinafter, this data is referred to as distance data). Although the number of times of integration is different due to the difference in the reflectance of the object, it is apparent that the output of the A / D conversion circuit 45 is the same when the distance is the same.

If the output timing of the reset signal RES and the signal AD indicating the start of the A / D conversion is after the hold operation in the S / H circuits 42 and 43 has been established, the output order is the reset signal. Even if RES is first,
The signal AD may be the first signal or may be the same signal, but it is necessary that all the processing be completed within one cycle of the drive signal DR.

The control means 20 stores the distance data transferred from the A / D conversion circuit 45 into the memory immediately after the operation section 46 constituted by an appropriate switch such as a dip switch or a button switch is operated. When the operation unit 46 is not operated, the distance data is transferred to the comparison circuit 48. The comparison circuit 48 compares the distance data transferred from the control means 20 with the distance data written in the memory 47 and outputs a signal indicating the presence or absence of an object. Except that the operation is the same as that of the comparison circuit 15 of the conventional object detection device shown in FIG. The output circuit 49 is the same as the output circuit 16 shown in FIG.

Therefore, by operating the operation unit 46 after installing the object detecting device, it is possible to write distance data serving as a reference of the distance for object detection in the memory 47. When it is necessary to change the distance reference, for example, when the detection area is changed after the distance reference is once set, the operation unit 46 is operated again to store the new distance reference in the memory 47. Can be written to.

It goes without saying that such an object detecting device can be used for various purposes. However, a case where it is used as a vehicle interior sensor for detecting the presence or absence of a vehicle in a parking lot will be described as follows. is there.

Since the height of the ceiling of the vehicle compartment varies depending on the parking lot, it takes a very long time if the threshold level, which is the reference value of the distance, is manually set as in the prior art. However, according to the above configuration, simply by operating the operation unit 46 after installing the object detection device on the ceiling, the distance data to the floor, which is the background, can be easily and accurately determined as the memory 47. When a vehicle is present in the vehicle cabin, a signal indicating the presence of the vehicle can be output. Conversely, if the reference value is written to the memory 47 by operating the operation unit 46 when a vehicle is present, a signal indicating that fact can be output when the vehicle departs.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the memory 4
7, the comparison circuit 48 and the output circuit 49 are provided, but the reference value of the distance is written in the internal memory of the control means 20, and the operation of the comparison circuit 48 and the operation of the output circuit 49 are executed by the control means 20. It is clear to a person skilled in the art that this can be done.

Further, the integration after the sample / hold at the rising timing, the timing and the S / H circuit of the start of the A / D conversion of the sample / hold signal SH from the output V _COM of the comparison circuit 44 becomes low level Needless to say, the timing for resetting the circuit and the like can be appropriately set as needed.

Further, in the above embodiment, the operation section 46 is manually operated by the operator. However, it is also possible to automatically output a write instruction signal to the control means when the power is turned on. According to this, the reference value of the distance is automatically written into the memory when the power is turned on, so that the reference value of the distance can be set for many object detecting devices at once.

It is also possible to store two reference values having different values in the memory 47 and detect only an object having a size within a desired range or outside a desired range.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing timings of signals used in the configuration of FIG. 1;

FIG. 3 is a diagram for explaining hysteresis of a comparison circuit 44;

FIG. 4 is a diagram illustrating a conventional configuration example of an object detection device using a PSD.

[Explanation of symbols]

Reference numeral 20: control means, 21: light emitting unit, 22: drive circuit, 23
... LED, 24 ... Lens, 31 ... Light receiving part, 32 ... Lens, 33 ... PSD, 34,35 ... I / V conversion circuit, 3
6, 37 ... switch, 38, 39 ... integration circuit, 40, 4
1 switch, 42, 43 sample / hold circuit,
44: comparison circuit, 45: A / D conversion circuit, 46: operation unit, 47: memory, 48: comparison circuit, 49: output circuit,
50, 51 ... switches.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 3/06 G01B 11/00 G08B 13/181

Claims (4)

(57) [Claims] A light projecting section for projecting a light projecting beam toward a predetermined detection area; and a semiconductor position detecting element for receiving reflected light of the projecting beam projected from the light projecting section. A light receiving unit disposed triangularly with respect to the unit and the detection area, and a distance signal generating unit that generates a signal indicating a distance to an object based on two light receiving output signals output from the semiconductor position detecting element. A memory circuit, a comparison circuit that compares the reference value with an output signal of the distance signal generation unit using a value stored in the memory unit as a reference value, an operation unit, and the operation unit is operated. In such a case, the object detection device further comprises control means for writing the output signal of the distance signal generation means at that time to the memory means. 2. An optical system in which the optical axis is shifted by a predetermined amount in the longitudinal direction of the detection surface of the semiconductor position detection element from the center position of the detection surface of the semiconductor position detection element on the front surface of the semiconductor position detection element of the light receiving section. 2. The object detecting device according to claim 1, wherein the object is arranged. 3. A semiconductor position detecting element, first and second current / voltage converting means for converting first and second current outputs of the semiconductor position detecting element into voltages, respectively, and the first and second current / voltage. A first method of integrating the output signals of the conversion means in synchronization with the light emission timing of the light projector,
And second integration means, and outputs of the first and second integration means are sampled /
First and second sample / hold means for holding, A / D conversion means for A / D converting output signals of the first and second sample / hold means and outputting data indicating a distance to an object, Comparing means for comparing the output voltage of the first or second integrating means with a predetermined reference value; and control means. The control means monitors the output level of the comparing means. If the output voltage of the first or second integrating means is equal to or higher than the reference value, the first and second sample / hold circuits supply sample / hold signals.
A holding operation is performed, and after the holding operations of the first and second sample / hold circuits are completed, the A / D conversion unit is caused to perform the A / D conversion operation, and the first and second integration circuits are reset. Object detection device. 4. An object detecting apparatus according to claim 3, wherein said comparing means has a hysteresis.