JPS62289714A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To remove the influence of ordinary light with simple constitution by connecting an LC parallel resonance circuit as a substitute for a feedback resistance and converting the output photocurrent of a semiconductor position detecting element into a voltage. CONSTITUTION:Two kinds of photocurrents outputted by a PSD5 which receives reflected light from an object 3 through intermittent light projecting operation are converted into voltages by operational amplifier parts 8 and 9 consisting of operational amplifiers 8a and 9a to which LC parallel resonance circuits 8b and 9b having points of resonance with the projection operation are connected as a substitute for feedback resistances. The photocurrents based on the ordinary light have only voltage drops due to only the DC resistance component of L, so the saturation of the operational amplifier parts need not be considered and only the signal photocurrents are converted into the voltages with high impedance.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a distance measuring device used in an autofocus device of a photographic camera and the like.

Conventional technology In recent years, active methods have become mainstream in distance measuring devices, and most of them are based on triangulation, which enables distance measurement without any moving parts and relatively simple signal processing. The number of distance measuring devices using a semiconductor device detection element (hereinafter referred to as PSD) on the light receiving side is increasing.

Here, the distance measuring principle of a distance measuring device using a PSD will be briefly explained with reference to the entire schematic configuration diagram shown in FIG.

In FIG. 5, the light emitted from the light emitting source 1 through the emitting side lens 2 is reflected by the subject 3, and is transmitted through the light receiving side lens 4 to an effective light receiving surface arranged at the focal plane of this lens 4. Assume that the light is incident at a position X that is X away from the center 0 of the PSD 5 with a length of 1.

If the resistance between terminals A and B is Rp, the photocurrent generated by the incident light is the distance X from the center 0 to the incident position
The current is shunted in inverse proportion to the dividing resistance of RP corresponding to .

Therefore, if the resistance from the terminal to the incident position X is Rm, and the resistance from the terminal B to the incident position X is RB, then
The current output from the terminals of the husband and B is M, I
8. Also, if M+IB=IO, then That is, it is expressed by an expression including the distance RX from the center 0 to the incident position X.

Here, in order to eliminate the influence of the amount of incident light, if we perform the calculation of M/ to eliminate the term 〇, we obtain an expression that depends only on the distance X indicating the incident position X.

Furthermore, if information on the distance X from the center O to the incident position It will be easily obtained.

Furthermore, it goes without saying that logarithmic compression and differential amplification processing are generally performed on actual circuits in lieu of the above-mentioned calculations.

On the other hand, in the above-mentioned distance measuring device, if steady light other than the reflected light from the subject 3 enters a position other than the above-mentioned incident position X, the current em output from terminals A and B changes. This causes a problem in that the apparent previous incident position X moves, making it impossible to perform accurate distance measuring operations.

For this reason, conventional devices employ the following method of removing the influence of stationary light.

One method is disclosed in Japanese Patent Application Laid-Open No. 59-64806, etc., in which an operational amplifier performs current-to-voltage conversion, including the photocurrent caused by standing light. This method removes the voltage caused by current.

The other method is disclosed in Japanese Patent Application Laid-open No. 60-100009, etc., in which the steady light state before light emission is stored in a holding capacitor, and the steady light state corresponding to the stored content is based on the method. This is a method in which the photocurrent is passed outside the logarithmic compression circuit, and only the signal photocurrent based on reflected light is guided to the logarithmic compression circuit.

Problems to be Solved by the Invention The above-mentioned two methods are representative methods for eliminating the influence of stationary light in distance measuring equipment using PSD.
The former method is processed after current-voltage conversion, so
Considering saturation due to stationary light, only a few hundred ohms of resistance can be used as the return resistance of the operational amplifier, and the amplification factor of the next stage and subsequent stages must be increased, which increases the number of amplifiers.
(It still has the problem of being disadvantageous in terms of N ratio.

Furthermore, the latter method requires two capacitors with low leakage current and a certain large capacity as holding capacitors, which is disadvantageous in terms of device size and cost.

The present invention has been made in consideration of the above points, and it is an object of the present invention to provide a distance measuring device using a PSD that has a simple configuration and can eliminate the influence of stationary light.

Means for Solving the Problems The distance measuring device according to the present invention has a light projecting section that performs an intermittent light projecting operation, and an L having a co-transport point that can resonate with the intermittent light projecting operation.
A C parallel resonant circuit is connected in place of the feedback resistor, and includes an operational amplifier section that converts the photocurrent output from the PSD into a current-to-voltage.

Operation Since the distance measuring device according to the present invention is configured as described above, there is no need to consider the saturation of the operational amplifier section because the photocurrent caused by the steady light only causes a voltage drop due to the DC resistance component of L. Only the signal photocurrent will be converted into voltage with high impedance.

Embodiment FIG. 1 is a schematic electrical circuit diagram of an embodiment of a distance measuring device according to the present invention, and the same reference numerals as in FIG. 5 indicate the same functional members.

In the figure, numeral 6 indicates a light projecting section comprising a light projecting source 1 and a driving means 7 for causing the light projecting source 1 to perform a light projecting operation at, for example, a predetermined frequency.

8 and 9 are operational amplifiers that convert the photocurrents Im and IB output from both terminals A and B of the PSD into voltages, and are connected to the operational amplifiers Ba and ga, respectively, in place of the feedback resistor.
It is composed of C parallel co-stimulating circuits ab and 9b.

Reference numeral 10.11 indicates an amplification section, 12.13 a logarithmic compression section, 14 a peak hold section, and 15 a differential amplification section, all of which have well-known configurations.

In addition, the resonance points of the above-mentioned LC parallel resonance circuits ab and 9b are as follows:
Needless to say, the setting is made to match the light projection operation of the light projection section. That is, when the drive circuit 7 is set so that the light projecting section 60 performs the light projecting operation at a predetermined frequency F, the resonant frequency of the LC parallel resonant circuits 8b and 9b is set to the above frequency F, Further, when the light projection operation is set to be performed while varying the light projection frequency within a predetermined frequency band, the setting is made so that it can resonate with any frequency included within the above band.

Hereinafter, the operation of one embodiment of the distance measuring device according to the present invention shown in FIG. 1 will be explained with reference to the waveform diagram for explaining the operation shown in FIG.

By operating the driving means 7 of the light projecting unit 6, light as shown in FIG. Suppose that it is injected through 2.

The above-mentioned light is reflected by the subject 3 and enters the appropriate position on the PSDS via the light-receiving lens 4, so that the psns is connected to both terminals A of the PSDS as described above.

From B, a photocurrent M is outputted according to the above-mentioned appropriate incident position.

The photocurrent M output from the PSD 5 is supplied to operational amplifiers 8a and 9& of operational amplifiers 8 and 9, respectively, for voltage conversion.

As mentioned earlier, the operational amplifiers 8a and 9& have a resonance point caused by the intermittent light projection operation of the light projection section 6, that is, in this case, the L and GO values are set so that they can resonate with the frequency F. An LC parallel resonant circuit sb, 9b, which is set appropriately, is connected instead of the feedback resistor.

Therefore, even if the photocurrents M and IB include photocurrents due to steady light, they will not be greatly amplified, that is, only the voltage drop will occur due to the DC resistance component of L, and intermittent light emission due to intermittent light emission will occur. Only the signal photocurrent based on reflected light is converted into voltage at high impedance.

Therefore, there is no risk that the operational amplifiers ab and 9b will be saturated by the photocurrent based on the steady light, and unlike the conventional method, the amplification degree of the next stage amplification section is not increased more than necessary.
The desired amplification degree is determined by the operational amplifier 8b.

This can be set in 9b.

The signal optical voltage obtained by voltage conversion of the signal optical current in the operational amplifier section 8.9 is then amplified by the amplifier section 10.11, and then supplied to the logarithmic compression section 12.13, where the logarithmic compression is performed. Section 12.13 is shown in FIG. 2(b).

A logarithmically compressed output as shown in <c) is output, and the peak value of each of these outputs is held in the peak hold section 14, and the peak value is supplied to the next stage differential amplification section 15.

In addition, VA and VB shown in Fig. 2 (b) and (C) are as follows.
The voltages obtained by amplifying the signal optical voltage supplied via the operational amplification section 8.9 by the amplification sections 10.11, that is, the amplification sections 10.1
1 indicates the amplified signal optical voltage outputted respectively.

The differential amplification section 15 differentially amplifies the outputs supplied from the logarithmic compression section 12.13 via the peak hold section 14, respectively, and outputs the output voltage Vo k output terminal 15 & as shown in FIG. 2(d). It will be output from.

Incidentally, this voltage vO is determined by the electron charge, q1, Boltzmann's constant, and 1, absolute temperature, T1, as mentioned earlier, in the amplifying section 10.
Letting VA and vB be the amplified signal optical voltages outputted by No. 11, respectively, it can be expressed as follows. Of course, this output voltage vQ is equal to the signal optical current M + Since it is based on "B" and has been divided, it can be used as distance information to object 3.

The embodiment shown in FIG. 1 has been described above, but when considering the actual use of such an embodiment, it is necessary to pay great attention to variations in the characteristics of the parts used.

For example, the resonant impedance Z9 of each of the LC parallel resonant circuits 3b and 9b. If Z differs due to variations in components, the output voltage vO obtained at the final stage will be exactly equal to the photocurrent 1. , IB operation, i.e. I A/
In the end, we would not be able to respond to Engineering 8.
There is a risk of performing an erroneous ff1ll distance operation, and therefore great care must be taken in component management and compensation.

FIG. 3 is a schematic electrical circuit diagram showing an embodiment of a distance measuring device according to the present invention, taking into consideration the variation in characteristics of eaves parts as described above, and in the figure, the same reference numerals as in FIG. 1 are used. 9 are the same
Functional parts are shown.

Reference numeral 16 designates a first analog switch whose state is switched by an electrical control signal, and as is clear from FIG. .21°22, and is provided between both terminals of the PSD 5, B, and the reference voltage generation section 23 and the operational amplifier section 24 that converts the supplied current into voltage.
The electrical contact piece 17, 1B and the electrical contact 19.20, 2
The electrical connection state between the above-mentioned parts is changed by the 1°22 connection.

Note that the operational amplifier section 24 is the operational amplifier section 8, 9 shown in FIG.
A configuration similar to that of the operational amplifier 24? L and an LC parallel resonant circuit 24b connected in place of the feedback resistor,
Its operation is similar to that of the operational amplifier section 8.9.

25 and 26 indicate the amplification section and the logarithmic compression section, respectively, and the first
Amplification section 10.11 and logarithmic compression section 12.1 shown in the figure
It has the same configuration as No. 3 and performs the same operation.

27 and 28 are the first . 29 indicates the second peak hold section, and 29 indicates the first peak hold section. This differential amplification section performs differential amplification of the holding outputs supplied from the second peak hold sections 27 and 28, and outputs the blade voltage vO1k from its output terminal 29&.

3o consists of an electrical contact piece 31 and two electrical contacts 32 and 33, and as is clear from FIG.
and 1st. A second analog switch is provided between the second peak hold section 27 and the second peak hold section 27 and 28, and switches the electrical connection state between the above-mentioned sections in conjunction with the switching operation of the first analog switch 15 described above. There is.

34 is a light projecting source 1 similar to the driving means explained in FIG.
The driving means is shown for controlling the light projection operation from 1 to 3 and the intermittent light projection operation, and for performing the light projection operation twice in one distance measuring operation.

Hereinafter, the operation of the embodiment shown in FIG. 3, which has the groove bottom as described above, will be explained with reference to the waveform chart for explaining the operation shown in FIG.

Now, number one. It is assumed that the respective electrical contacts 17, 18 and 31 of the second analog switches 16, 30 are connected to the electrical contacts 19, 21 and 32, respectively, as shown in solid lines in FIG.

When the driving means 34 operates in the above state and the first light is emitted from the light source 1 toward the subject 3 as shown in FIG. 4 (2L), it is reflected by the subject 3. The reflected light enters an appropriate position on P3D5 via the light-receiving lens 4.

One end of the PSD 5 is connected to the operational amplifier 24& of the operational amplifier section 24 through the first analog switch 15, and the other end B is connected to the reference voltage generating section 1 through the first analog switch 16.
Therefore, the photocurrent M+"atl" corresponding to the incident position of the reflected light is output from both terminals A and B, and the photocurrent Only M is supplied to the operational amplifier section 24.

The photocurrent M is subjected to current-voltage conversion in the operational amplifier 24 as in the previous embodiment, and is supplied to the amplifier 25 as a signal optical voltage.
The signal is amplified and further supplied to the logarithmic compression section 26.

The logarithmic compression section 26 logarithmically compresses the signal optical voltage supplied via the amplification section 25, and its output terminal 26? A logarithmically compressed output based on the photocurrent M as shown in FIG. 4(C) is output to L.

This logarithm compression output is supplied to the first peak hold section 2 through the second analog switch 3o, and this
The peak hold unit 27 holds the peak value of the logarithmically compressed output as shown in FIG. 4 (6), and outputs the output terminal 27?
The signal is output from L to the differential amplification section 29 at the next stage.

When the peak value of the logarithm compression output is finished being held by the first peak hold section 2, the first and second analog switches 16. That is, each electrical contact piece 17, 1B and 31 is controlled to be connected to an electrical contact 20.22 and 32. Although such control operations will not be described in detail, for example,
It goes without saying that the detection means for detecting the operation of the drive means detects the end of the light projecting operation, and the detection is carried out based on the detection output.

Next, in this state, a second light projection operation as shown in FIG. 4(b) is performed by the operation of the driving means 34.

Therefore, as in the case described above, the reflected light from the subject 3 is P
The light is incident on an appropriate position on the SDS, and the PSD 5 outputs a photocurrent M according to the incident position.

However, in this case, since the state of the first analog switch 16 is switched as shown by the broken line, only the photocurrent IB is supplied to the operational amplifier section 24, and the current -
The voltage will be converted.

The signal photovoltage obtained by current-to-voltage conversion of the photocurrent is amplified by the amplifier 25 and supplied to the logarithmic compression section 2e, as in the previous case, and the logarithmic compression section 26 has its output terminal 26'. From a-, the photocurrent IB as shown in Fig. 4(d)
It will output logarithmic compression output based on .

As shown in the temporary set in FIG. FIG. 4 (f'lK As shown above, the photocurrent 1
．． It holds the peak value of the logarithmic compression output based on the output terminal 28? The signal is output from L to the differential amplification section 29 at the next stage.

As a result, the differential amplifying section 29 performs the first and second light emitting operations based on the photocurrents Em and IB by performing the light projection operation twice as described above, although not simultaneously like the differential amplifying section 15 of the previous embodiment. The second peak hold unit receives the output signal of the second peak hold unit 2 and 28 and differentially amplifies both signals 9, from the start of the second light projection operation. Output terminal 2
The output voltage VOj will be output to 92L.

It goes without saying in detail that this output voltage "01" is equivalent to the output voltage vo output from the differential amplifier section 14 described in the previous embodiment, and therefore the voltage VO1 can be used as distance information to the subject 3. Needless to say.

Effects of the Invention As described above, the distance measuring device according to the present invention detects PSD by receiving reflected light from a subject through intermittent light projection operation.
The two types of photocurrents output by the LC parallel resonant circuit each having a resonance point capable of resonating with the above-mentioned light projecting operation are converted into current-to-voltage by an operational amplifier section consisting of an operational amplifier connected instead of a feedback resistor. , it is possible to amplify only the photocurrent caused by the signal light without considering the saturation of the operational amplifier due to the steady light, and the structure is simple, and the amplification factor of the next stage can be set to an appropriate value. Therefore, the number of amplifiers, S/ This has an advantageous effect in terms of N ratio.

Further, in the distance measuring device according to the present invention, an LC parallel resonant circuit is connected to the two types of photocurrents outputted by the PSD described above through two light projection operations in place of the feedback resistor via the first analog switch. The output of the operational amplifier section is supplied to one operational amplifier section consisting of an arithmetic amplifier, and the output of this operational amplifier section is supplied to one amplifier section, a logarithmic compression section, and a second analog switch that is switched in conjunction with the first analog switch. 1.Sequentially via analog switch. This first peak hold section is guided to the second peak hold section. Since each output of the second peak hold section is differentially amplified by the differential amplification section, the two types of photocurrents output by the PSD are the first and second peak hold sections. All parts other than the second peak hold section can be processed using commonly used parts, which simplifies the configuration and eliminates any negative effects caused by variations in characteristics between the parts used.In other words, there is no need to compensate for the above-mentioned variations. Has good effect.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic electrical circuit diagram showing one embodiment of the distance measuring device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 1, and FIG. The figure is a schematic electrical circuit diagram showing another embodiment of the distance measuring device according to the present invention, and FIG. 4 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 3. 1...Light source, 2・・・・・・
・Emission side lens, 3...Subject, 4...
・Lens on the light receiving side, 5... Semiconductor device detection element (
PSD), 6... Light projecting section, 7... Drive means, 8, 9.23... Operational amplifier section, 8a
, 9a. 242L...Operation amplifier, 8b, 9b, 24
b...L'C parallel resonant circuit, 10, 11.25
...... Amplification section, 12.13.26... Logarithmic compression section, 14.2 completed. 28...Peak hold section, 16.29...
...Differential amplification section, 16.30...Analog switch, 17°18.31...Electrical contact piece, 1
9, 20, 21° 22, 32, 33... Electrical contact, 23... Reference upper pressure generating section, 34...
..., driving means. Name of agent: Patent attorney Toshio Nakao and 1 other person
2 Figure 4

Claims (3)

[Claims] (1) Using a semiconductor device detection element that outputs two types of photocurrent depending on the light receiving position by receiving reflected light from the subject due to the light emitting operation of the light projecting unit, and converting the photocurrent into voltage. In the distance measuring device that obtains distance information to the subject by performing appropriate electrical processing with the light emitting device, a driving means provided in the light projecting section makes the light projecting operation an intermittent light projecting operation; The LC parallel resonant circuit having a resonance point capable of resonating with the frequency of operation is provided with an operational amplifier section which is comprised of an operational amplifier connected in place of the feedback resistor and converts each of the two types of photocurrents inputted into voltages. A distance measuring device featuring: (2) A light projecting unit including a driving means that performs two intermittent light projecting operations in which the light projecting source emits light toward the subject, and which receives reflected light from the subject and responds to the light receiving position. a semiconductor device detection element that outputs two types of photocurrent; and an LC that has a resonance point that can resonate with the frequency of the intermittent light projection operation.
A parallel resonant circuit is provided between an operational amplifier consisting of an operational amplifier connected in place of a feedback resistor, the semiconductor device detection element and the operational amplifier, and controls the electrical connection state between the two. a first analog switch that sequentially supplies a seed photocurrent to the operational amplifier section in response to the two intermittent light projection operations; an amplifier section that amplifies the output of the operational amplifier section; and an output of the amplifier section. a logarithmic compression unit that logarithmically compresses the input signal, first and second peak hold units that hold and output the peak value of the supplied input signal, and the logarithmic compression unit and the first and second peak hold units; The logarithmic compression section sequentially outputs an output based on each of the two types of photocurrents by controlling the electrical connection state between the two in conjunction with the operation of the first analog switch. a second analog switch that supplies the first and second peak hold sections separately; and a second analog switch that receives the outputs of the first and second peak hold sections and differentially amplifies both outputs to correspond to the distance to the subject; and a differential amplification section that outputs distance information. (3) The first analog switch sequentially connects one end of the semiconductor device detection element to the operational amplifier section, and connects the other end not connected to the operational amplifier section to a predetermined potential point. The distance measuring device described in .