JPS63167211A - Distance detecting device - Google Patents

Abstract

PURPOSE:To shorten the most approachable distance by only one light projection part without any deterioration in distance measurement accuracy by arranging at least one intermediate electrode between a couple of signal electrodes of a semiconductor position detecting element and switching the electrodes to be used according to an object distance. CONSTITUTION:The semiconductor position detecting element 50 is provided with at least one intermediate electrode d3 between signal electrodes d1 and d2 provided at both ends in addition to those electrodes d1 and d2. Then, a case wherein output currents from the couple of signal electrodes d1 and d2 are used for distance detection and a case wherein output currents from one of the couple of signal electrodes d1 and d2 and intermediate electrode or an output power source between the intermediate electrodes is used are switched according to the object distance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance detection device using a semiconductor position detection element (hereinafter abbreviated as PSD).

[Prior Art] Various distance detection devices using PSD have been proposed in the past, and their basic configurations are 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 light projecting lens, 3 is a subject, 4 is a light receiving lens, and 5 is a PSD.

The light emitter 1 is configured to project pulsed light using an appropriate circuit system. This pulsed light is focused by the light projecting lens 2 and irradiated onto the subject 3, and the light on the opposite side is imaged on the PAD 5 by the light receiving lens 4. The image formation position is expressed by the distance to the subject 01 the baseline length S1 the distance f between the light receiving lens and the PAD, where X is the distance from the optical axis y2 of the light receiving lens 4, and becomes x-s-f/e. As is well-known, the PAD5 divides the photocurrent with the opposite ratio of the distance from the position of the incident light to the signal electrodes d+ and dz at both ends, and outputs the signal currents II and 12 from the signal electrodes d1 and d2. Center and optical axis y2 of light receiving lens 4
When combined, the ratio of the signal current 11.12 at the incident light position of the above distance x is, when the total length of the PSD 5 is t, ! +: 12 =j/2+x:t/2-
It becomes X.

Therefore, the total current, that is, the difference output (2) between 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 of the PSD 5, and inversely proportional to the subject distance e.

Therefore, by obtaining the output V, the distance to the subject can be detected. 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 conventional example, since the reflected light is very small and a certain width occurs in the distance measurement data due to circuit noise, etc., there is a tendency for the change in the output signal ■ to be large with respect to the distance 1IIIe. It is in. Here, FIG. 11 shows an example in which the amount of change in the output signal (2) with respect to the distance e is varied 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 circuit noise etc. is the same at the same distance 1/e+, but this is the distance! Converting to the variation 8 of 1e, by increasing the movement amount X, the output signal for the distance e is
It can be seen that the distance error B is smaller in LA when the amount of change is made larger than in S when the amount of movement is made smaller, and the accuracy is better. However, when the amount of movement is increased, there is a drawback that the subject distance at which the reflected light deviates from the PSD, that is, the closest detectable distance becomes longer. On the other hand, if the closest distance is to be set close, the amount of movement must be made small, which has the disadvantage that the distance measurement accuracy deteriorates as described above.

On the other hand, in order to eliminate the above drawbacks, two light emitters for projecting light are installed! A method of arranging the wires with different lengths and having the wires selected depending on the distance to the subject has been considered, but this method has the drawbacks of increasing cost and increasing space.

The present invention has been made in view of the above problems, and includes:
With only one light emitting unit, distance measurement accuracy is not deteriorated.
An object of the present invention is to provide a distance detection device that can shorten the close distance.

[Means and effects for solving the problem] In a distance detection device using a PSD, at least one intermediate electrode is provided between a pair of signal electrodes provided on the PSD as an electrode for generating a current according to the distance of a subject. In the case where electrodes are provided and the output current from the pair of signal electrodes is used for distance detection depending on the subject distance, the output current from one signal electrode of the pair of signal electrodes and the intermediate electrode or the output current between the intermediate electrodes is used. It is designed to switch between using the output current.

[Embodiment] FIGS. 1 and 2 are diagrams showing an embodiment of the present invention. In the drawings, the same parts as those in the prior art shown in FIGS. 8 and 9 are given the same reference numerals, and details are omitted. Figure 1,
In FIG. 2, in addition to signal electrodes d, d2 provided at both ends of the PSD 50, an intermediate electrode d3 is further provided therebetween. As shown in FIG. 1, the signal i! of the PSD 50 receives the light and directs the optical axis V+ of the lens 4 to the signal i! If it is set at the center between the pole d2 and the intermediate electrode d3 and dl is in an open state, %II becomes zero and the photocurrent is shunted to the electrodes d2 and d3. At this time, if the output ■ is Vz3- (13-12)/(13+12), as shown in Figure 3H, the output V is proportional to the position X until the incident light position becomes. This is because (at 1/2 or more, all the photocurrent is output from the intermediate electrode).

Next, when the intermediate electrode is opened and the output ■, that is, VIZ = (1+ -12)/(II + I2), is calculated based on the signal currents output from the signal electrodes d2 and dl, it becomes as shown in the same figure. . Here, the dotted line indicates the case where the photocurrent due to the incident light exists stably regardless of the distance, but in this case, when the position of the incident light is at the center of the electrodes d and d2, that is, at X+, the output V becomes ll-I2 Therefore, it becomes zero, and when x1 or more, I+>I2, indicating a positive value, and below x1, a negative value. However, in reality the light
The flow changes depending on the distance, especially at long distances, it becomes small and becomes zero at a distance. Therefore, in the vicinity where the position of the incident light is close to zero, the output (2) becomes zero, resulting in a shape like a solid line.

Therefore, by changing the combination of electrodes used depending on the subject distance, it is possible to bring the distance measurement range closer to the object without deteriorating the distance measurement accuracy in the long distance direction.

FIG. 4 shows an embodiment of a distance detection circuit using the PSD 50 described above.

In the figure, the common electrode do- of the PSD 50 is connected to the first and second O
It is connected to the non-inverting input terminal of the P amplifier 7.8 and to the reference voltage y ref.

Further, the intermediate electrode d3 is connected to the O via the analog switch 20.
It is connected to the inverting input terminal of the P amplifier 7. Furthermore, the signal electrode d is connected to the OP amplifier 7 via the analog switch 21.
The signal electrode d2 is connected to the inverting input terminal of the OP amplifier 8.
is connected to the inverting input terminal of Further, each of the OP amplifiers 7.8 is subjected to negative feedback by a resistor 9.10, thereby forming a current/voltage conversion circuit. Filter 11.1
2 are connected to the output terminals of the OP amplifiers 7 and 8, respectively, so as to detect a change in the photocurrent generated by the emission of light from the light emitter 1 from the photocurrent constantly generated due to background light, etc. It has become.

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 generating circuit 14 is connected to the filter 11 and the filter 12 and outputs the sum of their outputs. 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 to 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 (2), determines the magnitude relationship between the forces of both persons, and outputs the result. This comparison voltage v2 is a constant voltage determined by appropriately considering factors such as detection accuracy and close shooting distance. The transistor 18 is connected to the light emitting body 1, and is turned on in a pulsed manner by an output from the control circuit 23 when the release button is pressed. The analog switch 2o is inserted between the intermediate electrode d3 and the inverting input terminal of the OP amplifier 7, and is connected to the control circuit 23 via the inverter 22. The analog switch 21 is inserted between the signal electrode dI and the inverting input terminal of the OP amplifier 7, and is connected to the control circuit 23.

Each of the analog switches 20 and 21 is turned on when receiving an H level signal.

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

In the initial state, the control terminal 24 of the control circuit 23 outputs an L level signal. At this time, the analog switch 21 is turned off, and the analog switch 20 is turned on. Therefore, the intermediate electrode d3 of the PSD 50 is connected to the inverting terminal of the OP amplifier 7 forming the current-voltage conversion circuit, and the electrode dl of the PSD 50 is in an oven state. Here, when the output of the control circuit 23 turns on the transistor 18 in conjunction with pressing the release button, etc., and lights up the light emitter 1 in a pulsed manner, the PS due to the reflected light from the subject
The photocurrent D50 is applied to the intermediate electrode d3 depending on its incident position.
and the signal electrode d2 and output. The shunted signal currents are each subjected to current-to-voltage conversion by an OP amplifier 7.8, separated from the photocurrent due to the stationary light by a filter 11.12, and output. This filter 11.
The output from 12 is calculated by a difference signal output circuit 13, a sum signal output circuit 14, and a distance signal output circuit 15. When the signal currents output from the intermediate electrode d3 and the signal electrode d2 are respectively l-112, the output ■ of the distance signal output circuit 15 is Vz3 = f((I co-12)/(1
3+12)). Here, f is a coefficient related to current-voltage conversion. Therefore, the optical axis of the light receiving lens 4 and P
If the position of the SD 50 is set in the relationship shown in FIG. 1, the output shown in the third example can be obtained, and an analog output that is inversely proportional to the subject distance can be obtained.

On the other hand, when the output ■ from the distance signal output circuit 15 is higher than the comparison voltage v2, the output of the comparator 16 becomes low, and the control circuit 23 sets the output of the control terminal 24 to H to pulse the light emitter 1 again. Turn it on. At this time, the analog switch 20 is turned off, and the analog switch 21 is turned off.
Then, the signal electrode d1 of the PSD 50 is connected to the inverting terminal of the OP amplifier 7, and the intermediate electrode d3 is in an oven state. Therefore, the photocurrent due to reflected light is generated by the signal electrodes d1 and d2.
Assuming that the respective signal currents are II and 12, the signal output circuit 15 obtains an output of Vrz-f ((II 12>/CII+12)) in the same way as in the distance measuring operation. As a result, an output as shown in FIG. 3K is obtained.

Therefore, when the object distance is such that the output of the distance signal output circuit 15 becomes lower than the comparison voltage v2 during the first distance measurement, that is, when the output of the comparator 16 becomes H, the first distance measurement result is used as is for the object. Used as a distance signal,■
When the object distance is 2 or more, that is, the output of the comparator 16 is L, the second distance measurement result is appropriately converted and used as a distance signal.■ Until the object distance is 2 or less, Without degrading distance measurement accuracy,
The distance measurement range can be brought closer. In addition, during the second distance measurement, the amount of change in the output that becomes the distance signal with respect to the amount of movement of the reflected light is smaller than the first distance measurement, and the accuracy tends to deteriorate, but at short distances Since the reflected light itself is large and the influence of circuit noise etc. is small, this does not pose a particular problem.

FIG. 5 is a diagram showing another embodiment of the present invention.

In the figure, signal electrodes d, d2 are provided at both ends of the PSD 51, and an intermediate electrode d is provided between the signal electrodes d+ and d2.
3. d is provided.

Here, the positions of the signal electrodes d1 and d2 and the intermediate electrodes d3 and d4 are set so that their respective centers are the same. The signal electrodes d1 and d2, the intermediate electrodes d3 and 64
If one of the combinations is selected and the signal current is detected, an output as shown in FIG. 6 can be obtained by expressing the incident position of the reflected light as the distance x from the center. Here, P is the signal electrode d
When +dz is selected, Q indicates the case where intermediate electrodes d3d4 are selected.

FIG. 7 shows an example of a circuit using the above-mentioned PSD 51, and the same elements as in FIG. 4 are denoted by the same reference numerals, and the explanation thereof will be omitted. The difference from the circuit shown in FIG. 4 above is that the signal is 1! Analog switches 41 and 42 for selecting ff1dz and intermediate electrode d4 are added, and the control terminal 24 of the control circuit 23
When is H, the electrodes d+ and d2 are connected to the OP amplifier 7.8, and when is L, the electrodes d3 and d4 are connected to the op amplifier 7.8.

The rest of the circuit is the same as the circuit shown in FIG. 4, so a description thereof will be omitted.

[Effects of the Invention] According to the present invention, the closest detectable distance can be shortened without deteriorating the distance measurement accuracy without providing two light emitters, that is, light projectors.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an embodiment of the present invention, Fig. 2 is a front view of the detection element of the above embodiment, Fig. 3 is a diagram showing the output characteristics of the above embodiment, and Fig. 4 is a diagram of the above embodiment. A circuit diagram using a detection element, FIG. 5 is a front view showing a detection element of another embodiment of the present invention, FIG. 6 is a diagram showing output characteristics of the other embodiment described above, and FIG.
The figure is a circuit diagram using the detection element of the other embodiment mentioned above, Figure 8 is a plan view showing the conventional example, Figure 9 is a plan view showing the detection element of the conventional example, and Figure 10 shows the output characteristics of the conventional example. Figure shown, 1st
FIG. 1 is a diagram showing the degree of variation in the output characteristics of the detection elements.

Claims (1)

[Claims] A distance detection device using a semiconductor position detection element having a pair of signal electrodes for generating a current according to the distance of an object, wherein at least one intermediate electrode is provided between the pair of signal electrodes. Depending on the subject distance, the output current from the pair of signal electrodes is used for distance detection, the output current from one signal electrode of the pair of signal electrodes and the intermediate electrode, or the output current between the intermediate electrodes. A distance detection device characterized by switching between using the output current for distance detection.