JPH0830653B2 - Distance detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is directed to a semiconductor position detecting element (hereinafter referred to as PSD) that projects a light beam toward an object to be measured and detects a light receiving position of reflected light from the object to be measured.
(Hereinafter abbreviated as ") and the like, and relates to a distance detecting device that detects the distance to the object based on the measurement.

[Prior Art] Various distance detecting devices using PSD have been conventionally proposed, but the basic configuration thereof is as shown in FIGS. 8, 9, and 10. That is, in FIGS. 8 and 9, 1 is a light-emitting body that projects infrared light, 2 is a projection lens,
3 is a subject, 4 is a light receiving lens, and 5 is a PSD. The light-emitting body 1 is adapted to project pulsed light by an appropriate circuit system. The pulsed light is condensed by the light projecting lens 2 and irradiated on the subject 3, and the reflected light is imaged on the PSD 5 by the light receiving lens 4. When the image forming position is x from the optical axis y ₂ of the light receiving lens 4 and x, the distance e to the subject is e,
It is expressed by the base line length s and the distance f between the light receiving lens and the PSD, and x = s · f / e. As is well known, PSD5 divides the photocurrent by the inverse ratio of the distance from the position of incident light to the signal electrodes d ₁ and d ₂ at both ends, and outputs the signal currents I ₁ and I ₂ from the signal electrodes d ₁ and d _2. Then PSD5
When the center of the light receiving lens 4 and the optical axis y ₂ of the light receiving lens 4 are aligned, the ratio of the signal currents I ₁ and I ₂ at the incident light position of the distance x is PS
If the total length of D5 is t, then I ₁ : I ₂ = t / 2 + x: t / 2−x.

Therefore, the total current, that is, the difference output V of both signals normalized by the sum of both signal currents is as follows.

That is, it is proportional to the incident light position x with respect to the total length t of the PSD 5 and inversely proportional to the subject distance e. Therefore, the output V
The distance of the object can be detected by obtaining The relationship between the incident light position x and the output V is shown in FIG.

[Problems to be Solved by the Invention] In the above-described conventional example, since the reflected light is extremely small and a certain width is generated in the distance measurement data due to circuit noise or the like,
The output signal V tends to change largely with respect to the distance e. Here, FIG. 11 shows an example in which the amount of change in the output signal V with respect to the distance e is changed by changing the amount of movement of the reflected light with respect to the entire length of the PSD. The variation A of the output signal V caused by the circuit noise or the like is the same at the same distance 1 / e ₁ , but when converted into the variation B of the distance e, the movement amount x
It is understood that LA is smaller and the accuracy is better than LA when the amount of change in the output signal V with respect to the distance e is increased and is larger than S when the movement amount is decreased. However, if the amount of movement is increased, the reflected light will be PSD
There is a drawback in that the subject distance deviating from the distance, that is, the closest detectable distance becomes long. On the contrary, if the closest distance is set to be close, the movement amount must be reduced, and as described above, the distance measuring accuracy is deteriorated.

On the other hand, in order to eliminate the above-mentioned drawbacks, a method of disposing two light emitting light emitters with different base line lengths and selecting them according to the subject distance is also considered, but in this case, However, there is a drawback that the cost becomes higher and the space becomes larger accordingly.

The present invention is made in view of the above problems,
With only one light emitting unit, without degrading the ranging accuracy
An object of the present invention is to provide a distance detection device capable of further shortening the closest distance.

[Means and Actions for Solving Problems] A distance detecting device according to the first invention of the present application is a light emitting means and a lens for condensing irradiation light of the light emitting means and projecting a light beam toward an object. And a light-receiving lens arranged to be separated from the light-projecting lens by a base line length for collecting reflected light of the light flux from the object, and the reflection light collected by the light-receiving lens. An optical position detecting element having at least three or more electrodes for taking out output for receiving light and detecting the receiving position of the reflected light, and a pair of electrodes are selected from the plurality of electrodes. The distance detecting means is provided for determining the distance to the subject based on the selecting means and the ratio of the outputs from the pair of electrodes selected by the selecting means.

Further, a distance detecting device of a second invention of the present application, a light emitting means, a light projecting lens for condensing the irradiation light of the light emitting means and projecting a light flux toward an object, and the light projecting lens. Is arranged apart from the lens for the base line length, to receive the reflected light condensed by the light receiving lens for collecting the reflected light of the light flux from the object, An optical position detecting unit that has a plurality of position detecting functional units divided in the base line length direction to detect the light receiving position of the reflected light, and outputs a pair of signals from each position detecting functional unit; The switching means for causing the plurality of position detection function sections of the light position detecting means to function in a time division manner, and the object of the subject on the basis of the ratio of the pair of signals of the position detecting means functioning in a time division manner by the switching means. A distance detection means for determining the distance is also provided. It is.

[Embodiment] FIGS. 1 and 2 are views showing an embodiment of the present invention.
In the figure, the same parts as those of the prior art shown in FIGS. 8 and 9 are designated by the same reference numerals, and the details thereof will be omitted. First
In FIG. 2 and FIG. 2, in addition to the signal electrodes d ₁ and d ₂ provided at both ends, the PSD 50 is further provided with an intermediate electrode d ₃ therebetween. As shown in FIG. 1, when the optical axis y ₁ of the light receiving lens 4 is set at the center between the signal electrode d ₂ and the intermediate electrode d ₃ of the PSD 50 and d ₁ is set to the open state, I ₁ becomes zero. Then, the photocurrent is shunted to the electrodes d ₂ and d ₃ . At this time, if the output V is V ₂₃ = (I ₃ −I ₂ ) / (I ₃ + I ₂ ), the output V is at the position x until the incident light position x is t _1/2 as shown in FIG. 3H. proportionally, 1 to become the t _1/2 or more.
This is because output from all photocurrent intermediate electrode at t _1/2 or more.

Next, when the intermediate electrode is opened and the output V, that is, V ₁₂ = (I ₁ −I ₂ ) / (I ₁ + I ₂ ), is obtained based on the signal currents output from the signal electrodes d ₂ and d ₁ , It becomes as shown in FIG. Here, the dotted line is the case where the photocurrent due to the incident light is stable regardless of the distance. At this time, when the position of the incident light is the center of the electrodes d ₁ and d ₂ , that is, x ₁ , the output V is I ₁ = becomes zero since the I _2, X ₁ in the above I _1> I ₂ becomes indicates a positive value, a negative value is x ₁ below. However, in reality, the photocurrent changes with distance, becomes small at a long distance, and becomes zero at ∞. Therefore, the output V becomes zero in the vicinity of the position of the incident light near zero, and the shape becomes as shown by the solid line.

Therefore, by changing the combination of the electrodes to be used according to the subject distance, it is possible to bring the distance measuring range closer to each other without changing the distance measuring accuracy in the long distance direction.

FIG. 4 shows an embodiment of the distance detecting circuit using the PSD 50.

In the figure, the common electrode do of the PSD 50 is connected to the non-inverting input terminals of the first and second OP amplifiers 7 and 8 and the reference voltage Vr.
It is touched by ef. Further, the intermediate electrode d ₃ is connected to the inverting input terminal of the OP amplifier 7 via the analog switch 20. Further, the signal electrode d ₁ is OP via the analog switch 21.
The inverting input terminal of the amplifier 7 is in contact, and the signal electrode d ₂ is in contact with the inverting input terminal of the OP amplifier 8. Further, the OP amplifiers 7 and 8 are negatively fed back by resistors 9 and 10, respectively, to form a current / voltage conversion circuit. The filters 11 and 12 are connected to the output terminals of the OP amplifiers 7 and 8, respectively, and remove the variation of the photocurrent generated by the projection of the light emitter 1 from the photocurrent constantly generated by the background light or the like. It is designed to detect. The difference signal generation circuit 13 is connected to the filter 11 and the filter 12, and outputs the difference between the outputs of these two. The sum signal generation circuit 14 is connected to the filter 11 and the filter 12 and outputs the sum of the outputs of both. The distance signal output circuit 15 is connected to the sum signal generation circuit 14 and the difference signal generation circuit 13 and outputs a signal corresponding to the ratio of the difference output and the sum output, that is, the distance. The comparison circuit 16 receives the output of the distance signal output circuit 15 and the comparison voltage V ₂ and determines the magnitude relationship between both inputs to output. This comparison voltage V ₂ is a constant voltage that is determined by appropriately considering factors such as detection accuracy and the closest shooting distance. The transistor 18 is connected to the light emitter 1 and is connected to the control circuit 23.
The output from the device makes it pulse-like when the release button is pressed.
It is supposed to turn on. The analog switch 20 is inserted between the intermediate electrode d ₃ and the inverting input terminal of the OP amplifier 7,
It is connected to the control circuit 23 via the inverter 22. The analog switch 21 is inserted between the signal electrode d ₁ and the inverting input terminal of the OP amplifier 7 and connected to the control circuit 23. The analog switches 20 and 21 are turned on when receiving an H level signal.

 Next, the operation of the above embodiment will be described.

In the initial state, an L level signal is output from the control terminal 24 of the control circuit 23. At this time, analog switch 21
Is turned off and the analog switch 20 is turned on. Therefore, the intermediate electrode d ₃ of the PSD 50 is connected to the inverting terminal of the OP amplifier 7 forming the current-voltage conversion circuit, and the electrode d _{1 of} the PSD 50 is
Is open. Here, with the output of the control circuit 23, the transistor 18
When the light emitting element 1 is turned on in a pulsed manner, the photocurrent of the PSD 50 due to the reflected light from the subject is shunted to the intermediate electrode d ₃ and the signal electrode d ₂ according to the incident position and is output.
The shunted signal currents are current-voltage converted by the OP amplifiers 7 and 8, respectively, and separated from the photocurrents by the stationary light by the filters 11 and 12 and output. This filter 1
The outputs from 1 and 12 are difference signal output circuit 13 and sum signal output circuit 1
4 and the distance signal output circuit 15 calculate. Intermediate electrode d
₃ and the signal current output from the signal electrode d ₂
If I ₃ and I ₂ are given, the output V of the distance signal output circuit 15 becomes V ₂₃ = f ((I ₃ −I ₂ ) / (I ₃ + I ₂ )). Here, f is a coefficient related to current-voltage conversion. Therefore, the optical axis of the light receiving lens 4 and the position of the PSD 50 should be set to the first position.
When the relationship shown in the figure is set, the output shown in FIG. 3H is obtained, and the analog output inversely proportional to the subject distance is obtained.

On the other hand, when the output V from the distance signal output circuit 15 is larger than the comparison voltage V ₂ , the output of the comparator 16 becomes L,
The control circuit 23 sets the output of the control terminal 24 to H, and again the luminous body 1
Light in a pulsed manner. At this time, analog switch 20
Turns off, the analog switch 21 turns on, and the OP amplifier 7
The signal electrode d _{1 of the} PSD 50 is connected to the inverting terminal of the, and the intermediate electrode d ₃ is in an open state. Therefore, the photocurrent due to the reflected light is shunted to the signal electrodes d ₁ and d ₂ , and assuming that the respective signal currents are I ₁ and I ₂ , the signal output circuit 15 outputs V ₁₂ = An output of f ((I ₁ −I ₂ ) / (I ₁ + I ₂ )) is obtained. As a result, the output as shown in FIG. 3K is obtained.

Therefore, when the output of the distance signal output circuit 15 becomes lower than the comparison voltage V ₂ during the first distance measurement, that is, when the output of the comparator 16 becomes H, the first distance measurement result is used as it is. When the subject distance is V ₂ or more, that is, when the output of the comparator 16 is L, the second distance measurement result is appropriately converted and used as a distance signal, which is V ₂ or less. With such a subject distance, it is possible to bring the distance measuring range closer to the closest distance without deteriorating the distance measuring accuracy. In the second distance measurement, the amount of change in the output that is the distance signal with respect to the movement amount of the reflected light becomes smaller than that in the first distance measurement, and the accuracy deteriorates. Since the reflected light itself is large and the influence of circuit noise or the like is small, there is no particular problem.

FIG. 5 is a view showing another embodiment of the present invention. In the figure,
Signal electrodes d ₁ and d ₂ are provided at both ends of the PSD 51, and intermediate electrodes d ₃ and d ₄ are provided between the signal electrodes d ₁ and d ₂ . Here, the positions of the signal electrodes d ₁ and d ₂ and the intermediate electrodes d ₃ and d ₄ are set so that their centers are the same. If _one of the combinations of the signal electrodes d ₁ and d ₂ and the intermediate electrodes d ₃ and d ₄ is selected and the signal current is detected, the incident position of the reflected light is represented by the distance x from the center, as shown in FIG. You will get the output as shown. Here, P shows the case where the signal electrode d ₁ d ₂ is selected, and Q shows the case where the intermediate electrode d ₃ d ₄ is selected.

FIG. 7 is an example of a circuit using the PSD 51 described above, the same elements as those in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. The difference from the circuit shown in FIG. ₄ is that analog switches 41 and 42 for selecting the signal electrode d ₂ and the intermediate electrode d ₄ are added, and when the control terminal 24 of the control circuit 23 is H. Is the electrode d ₁ ,
Connect d ₂ to OP amps 7 and 8, and when L, connect electrodes d ₃ and d ₄
It is configured so that it is connected to the OP amplifiers 7 and 8.

Others are the same as those of the circuit of FIG. 4, so description thereof will be omitted.

EFFECTS OF THE INVENTION According to the present invention, the closest detectable distance can be shortened without degrading the ranging accuracy without providing two light emitters, that is, two light projecting portions.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a front view of the detecting element of the above embodiment, FIG. 3 is a diagram showing the output characteristics of the above embodiment, and FIG. 4 is of the above embodiment. A circuit diagram using a detecting element, FIG. 5 is a front view showing a detecting element of another embodiment of the present invention, FIG. 6 is a diagram showing output characteristics of the other embodiment, and FIG.
FIG. 8 is a circuit diagram using the detection element of the other embodiment described above, FIG. 8 is a plan view showing a conventional example, FIG. 9 is a plan view showing a detection element of the conventional example, and FIG. 10 shows output characteristics of the conventional example. FIG. 11 is a diagram showing the degree of variation in the output characteristics of the detection element. 50, 51 …… Semiconductor position detection elements d ₁ , d ₂ …… Signal electrodes d ₃ , d ₄ …… Intermediate electrodes

Claims (7)

[Claims] 1. A light emitting means, a lens for converging the irradiation light of the light emitting means, and projecting a light beam toward an object, and a lens arranged for a distance of a base line with respect to the light projecting lens. ,
A light-receiving lens for collecting the reflected light of the light flux from the object, and at least 3 for receiving the reflected light collected by the light-receiving lens and detecting the light receiving position of the reflected light. An optical position detecting element having a plurality of electrodes for extracting at least one output, a selecting means for selecting a pair of electrodes from the plurality of electrodes, and a pair of electrodes from the pair of electrodes selected by the selecting means. A distance detecting device that determines the distance of the subject based on an output ratio, and a distance detecting device. 2. The selection means includes a first area for detecting a light receiving position of the reflected light, and a first area for detecting a light receiving position of the reflected light in a wider area including the first area. 2. The distance detecting device according to claim 1, wherein the area 2 is switched by selecting the plurality of electrodes. 3. The distance detecting apparatus according to claim 2, wherein the selecting means first selects the second area. 4. A light emitting means, a light projecting lens for condensing light emitted from the light emitting means and projecting a light beam toward an object, and a light emitting lens separated from the light projecting lens by a base length. Placed
A light-receiving lens for collecting the reflected light of the light flux from the object, and the received light for the reflected light collected by the light-receiving lens, in order to detect the receiving position of the reflected light, An optical position detection unit having a plurality of position detection function units divided in the base line length direction, each pair of position detection function units outputting a pair of signals, and the plurality of position detection function units of the optical position detection unit. And a distance detecting means for determining the distance of the subject based on the ratio of the pair of signals of the position detecting means functioning in time division by the switching means. A distance detecting device characterized by: 5. The optical position detecting means comprises a position detecting function section having a wide rangeable area but relatively low range finding accuracy, and a position detecting function section having a narrow range finding area but relatively high range accuracy. The distance detection device according to claim 4, further comprising: 6. The distance detecting device according to claim 5, wherein the switching means first selects a position detecting function portion including a wide range. 7. The switching means determines whether or not to select another position detection function unit according to a distance measurement result based on any one of the plurality of position detection function units. The distance detection device according to claim 4.