JPS61104217A - Distance detecting apparatus - Google Patents

Abstract

PURPOSE:To obtain high distance detecting capacity with a simple circuit construction, by scanning with a light-shielding member over an incident surface of a pair of light-receiving elements connected in such a way that photoelectric outputs balance each other and detecting a time point where output polarities of the pair change. CONSTITUTION:A ray of light of a luminous element 2 is concentrated into a beam-shape by an irradiating lens 3 and irradiated onto an object 1. A reflected ray 5 from the object 1 is collected with a light-receiving lens 6 and generates a light spot 15 on light-receiving element pair 71, 72 after passing through a light-transmitting slit of a light-shielding member 8. The pair 71, 72 are connected in such a way that these outputs balance each other. The light-transmitting slit is accompanied with a deviation of position in each longitudinal direction of the basic line and consequently, a portion differentiated by spot image intensity distribution is irradiated. There, by scanning the light- shielding member 8 and detecting the time point where the output polarities of element pair 71, 72, a distance up to the object 1 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a distance detection device using a light beam projection method applying the principle of triangulation. li
The present invention relates to a distance detection device that measures the distance to a subject by detecting a change in p.

(Prior art) As shown in FIG. 5 (AJK), a light beam 4 is projected onto a subject 1 from a light emitting element 2 through a light projecting lens 3, and reflected light 5 from the subject 1 is transmitted through a light receiving lens 6. There are two technical problems that must be solved in a conventional distance measuring device that utilizes the principle of triangular distance measurement in which light is received by a light receiving means including a light receiving element 7 that is separated from the light projecting means by a long baseline distance.

That is, problem 1. The intensity of the signal light incident on the light receiving element due to the reflected light from the subject is shown in Figure 5 (B).
Since the distance from the camera to the subject is inversely proportional to the square of the distance d, considering the variation in subject reflectance, the variation in luminous ability, and the ability to detect the tail part of the spot intensity distribution, the distance measurement range is short distance 0.8 m ~ 10 even if the distance is 8m
As a result, the detection circuit is required to have a very wide dynamic range.

This is an extremely disadvantageous condition for a distance measuring device that requires an operation to detect the amount of incident light in an analog manner.

Problem 29 As is well known, one fatal problem is the problem of background light. The light intensity of the signal incident on the light receiving element due to the reflected light from the subject is 1/~'/10. . . .

It is a value of degree. Therefore, i,oo.

Extracting the photocurrent caused by a minute amount of reflected light from such background light and amplifying it above the noise level of the signal processing circuit that follows the detection circuit is a process that requires the brightness of nine candles with the sun behind them. This is an extremely disadvantageous condition for distance measuring devices that require analog detection of the incident light needle.

In this way, the general Kffi light is subjected to analog detection processing.
Distance measuring devices that require operations such as
The complexity and sophistication of its circuit configuration places an extremely large burden on it compared to VC.

Next 1 The present invention FC Closest known prior art C% 1985
-62512, JP-A-57-48705.

JP-A-58-120110 1% JP-A-58-105
41() and Utility Model Application Laid-open No. 58-81507), the principle of distance measurement will be summarized and briefly explained.

These devices have a single light receiving element 7 as shown in FIG.
A light shielding member 8 is disposed movably in the baseline length direction on the incident surface of the object 1, and distance measurement is performed by utilizing the change in photoelectric output by operating this light shielding member 8 in a certain correlation with the distance to the subject 1. It is something to do.

Figure 7 shows an example of the detection circuit of the above distance measuring device.
81 indicates the signal waveform. In order to remove background light, the projected irradiation beam 4 (see FIG. 7 (Bl)) performs modulated light projection, and the photocurrent output from the light receiving element 7 of the photoelectric converter due to the reflected light 5 from the subject 1 is as follows. It is amplified by the operational amplifier A, and is input to the bypass filter circuit 10 via the coupling capacitor 9, and its output (see Figure 7 (see ■ in Bl) is transmitted to the next stage peak hold smoothing circuit 11. The circuit 11 is for obtaining the output of the spot intensity waveform (see Figure 7 (■ in Bl)), and the peak position is detected by the peak position detection circuit 12 in the next stage.
By knowing the position k, the distance to the subject 1 is detected.

In such a conventional device, (al
Since a single light-receiving element is used, measures to remove background light have been taken by electrical circuit means.

Currently known technical means for removing background light include:
There are two methods: one is an AC coupling method, and the other is a method in which the difference between the background light level and the background light level plus the signal light level is obtained by using the response delay of the circuit. However, in the latter method, background light must be removed for each minute movement of the light shielding member, and the circuit scale increases accordingly. For this reason, this method cannot be said to be appropriate. In addition, the former method simplifies the circuit configuration because there is no need to provide a background light removal circuit, but since the first stage signal detection circuit is directly affected by the background light, there is a risk that the detector will become saturated and the amplification It is not possible to increase the ratio. Furthermore, since it is connected to the next stage by 1 capacitor coupling, k
”/N ratio becomes extremely poor.

(bJ The spot intensity distribution generally has a certain spread, so if a comparator is used as a means to know the spot position, a distance measurement error will occur depending on the judgment level of the comparator as shown in Fig. 8. These are diagrams for explaining problems in detecting changes in photoelectric output in this conventional method. FIG. 8 is a front view of the slit 8 moving forward in the base line length direction. The spot image intensity distribution obtained by receiving light through the slit 8 by the light receiving element 7 is shown in FIG.
J13, which is a curve that is wider than the spot light intensity distribution. Now, if the peak position is detected with the determination level uncertainty width constant, the comparator determination level (2) in FIG. 8(C) will be k, and a distance measurement error 14 will occur. This comparator judgment level is determined by the distance measurement range, and if you want to measure distances up to m, you will have to lower the judgment level to 5 as shown in the comparator judgment level (1) k. . When the distance measurement range is expanded in this way, the distance measurement error 14 increases, and if the comparator determination level is increased in an attempt to eliminate this distance measurement error, long distance measurement becomes impossible.

In order to reduce this distance measurement error 14, the spot light intensity distribution must be made as sharp as possible, but this requires both the light emitting optical system and the light receiving optical system to become more precise and sophisticated. It is not suitable for use in compact cameras and the like. Also, there are limits. Therefore, in this method, a peak position detection circuit is essential, and a highly accurate spot light intensity distribution signal must be supplied to the peak position detection circuit in order to detect the peak position. This is an analog detection operation itself, and cannot avoid the difficulties pointed out in Problems 1 and 2 above.

(C1 In this method, a part of the signal light spot is received by a light shielding member. Therefore, the photoelectric output of the light receiving element of the photoelectric converter is smaller than that of other methods, and an appropriate 87. This is disadvantageous in terms of increasing the amount of light received.If the slit width of the light shielding member is increased to increase the amount of light received,
As shown in FIG. 8(C), the Q value of the detected spot light intensity distribution is small, that is, it lacks sharpness. This causes an error in detecting the peak position, resulting in a decrease in distance measurement resolution. Generally, the smaller the width of one slit, the better, and this direction is the opposite direction from the point of view of improving the lead-through ratio.

Although some of the drawbacks of this type of conventional apparatus and method have been listed above, it has been difficult to improve accuracy while avoiding high-grade technology.

(Objective) In view of the above points, an object of the present invention is to overcome the above-mentioned conventional drawbacks with a relatively low-precision optical system and a simple circuit configuration, and to
There is a method to obtain a distance detection device that can obtain distance detection capability with higher accuracy.

(overview)
In order to achieve the above object, the present invention projects light toward a subject and receives reflected light from the subject with a pair of photoelectric conversion light receiving elements connected so that the photoelectric outputs are mutually exclusive. The output polarity of the light receiving element pair is detected by a detection circuit, and the light shielding member scans the incident surface of the light receiving element pair, thereby detecting the point in time when the output polarity of the detection circuit changes, and measuring distance. It is configured to do the following.

(Example) Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a diagram showing the overall configuration when the distance detection device according to the present invention is applied to a still camera, and FIG.
- FIG. 2(C) is a diagram showing the shapes of the light-receiving element pair 72, the light-shielding member 8, and the light-receiving lens 6 of the above device. In the description of this embodiment, the same members as those in the above-mentioned prior art are given the same reference numerals, and detailed explanation thereof will be omitted.

The distance m detection device of the present invention has a pair of light receiving elements 7. ．． 7
2, a light-receiving lens 6 and the light-receiving element pair 7
．． , 72, a light shielding member 8 is disposed between them.

This light shielding member 8 is connected to the light receiving element pair 7. .

720 plane along the base line length direction. FIG. 2(B) shows each side of the shape of this light shielding member 8, and a pair of light receiving elements 74 forming a pair of light receiving elements 7.
, 7 □, the light-transmitting portion or the light-shielding portion is configured as 5 to cause lateral displacement.

That is, the light shielding member 8 of the first example. The light shielding member 82 of the second example has a slit that is shifted in a stepwise manner, and the light shielding member 83 of the third example has a slit that is shifted in a stepwise manner. The light-shielding member 84 of the fourth example has a light-shielding part that is laterally shifted obliquely, contrary to the light-shielding member 82 described above. There may be.

FIG. 2(C) shows an example in which a cylindrical lens 6 is used as the light-receiving lens 6, and an ideal light-receiving optical system configured so that the intensity distribution of the background light incident on the light-receiving element 71゜7□ is equal. It shows. It goes without saying that an ordinary spherical optical system as shown in FIG. 2 may be used as long as a certain degree of error is allowed. In any case, it is necessary to construct the photocurrent generated by the spot reflected light 15 by the light receiving lens so that it is partially absorbed by the light receiving elements 71 and 72. This may also be done electrically with an electrical circuit.

The third position and FIG. 4 (4) each show an example of the electric circuit of the distance detecting device of the present invention. In the third position, the light receiving elements 71 and 72 are constituted by a pair of light receiving elements, such as 5PD (silicon photodiode), whose outputs are connected to each other so that their outputs compete with each other. Connected to each input terminal of the inverter. This operational amplifier 21K causes the light receiving element pair 7 to
The short circuit current of 1 m72 is amplified and input to the comparator 22.

In this embodiment, the influence of background light can be almost eliminated by connecting the pair of light receiving elements 74 and 72 to 5 so that they are mutually antagonistic. Light receiving element pair 7. ,
In addition to directly connecting the operational amplifier 21m as described above, the light receiving elements 72 may be connected in such a way that the outputs of each independent light receiving element are input so as to compete with each other in one electric circuit. In FIG. 1, IR, which is a light emitting element 2,
The light from the LED is focused into a beam by a projection lens B, and is projected onto the subject 1 as a projection beam 4. The reflected light 5 from the subject 1 is focused by the light receiving lens 6, and a spot light 15 is generated on the light receiving element pair 7,172.

This spot light 15 is divided almost equally and received by a pair of light receiving elements 7..72 as shown in FIG. Therefore, the positions generated on the light-receiving element pair 71 + 72 are laterally shifted in the base line length direction by the light-shielding member 8 and are different.Therefore, the moving light-shielding member 8 and the light-receiving element pair 71.72K! The peak position of the spot is detected by a method described later, and the corresponding distance is detected.

Light shielding member 8 in FIG. 2(B). We will explain the case using . The spot reflected light 15 is the light of the light shielding member 8I.
is imaged onto a pair of light receiving elements 71.7□ through a transmission slit. This light shielding member 8. Since the light transmitting slits are shifted in the base line length direction, the light receiving element 71
．． Portions with different spot image intensity distributions are incident on 72. Therefore, the output of the output of the light-receiving element pair 7, 172 at the mouth point in the circuit of the third position is the output of the light shielding member 8m as shown by the dotted line at the mouth shown in the time chart of FIG. With the scanning, the reference voltage Vref is used as a reference,
The signal waveform changes from positive polarity to negative polarity. The point where the polarity changes from positive to negative is the peak position of the spot light intensity distribution. The signal waveform shown by the solid line is a waveform saturated by the amplifier 21, but there is no problem with K detecting the point. As described above, according to the method of the embodiment of the present invention, it is possible to construct an amplifier circuit that does not necessarily take into account the dynamic range of the incident signal, and it is possible to obtain a desired to-N ratio.

In Figure 3 (B), point! , is detected as the point at which the comparator 22 changes from high level H to low level L. This is shown in Figure 3 (B
This is the waveform of l's mouth.

Next, to explain the 1 focusing operation in terms of time sequence using FIG. is generated, the transistor Tr2 is turned on, the magnet Mgi is turned on, and the second check 25 is locked to the magnet Mg1. Next, the light shielding member 81 starts scanning from the close position to the ■ position, and at the same time, the photographing lens 26 starts rotating from the close position to the flash position. At the point 2p where the output polarity of the light receiving element pair 71 and 72 changes due to the scanning of the light shielding member 8I, the comparator 22 is reversed from high level H to low level L, the magnet Mgl is turned off through the AND gate, and the ratchet 25 is disconnected from the magnet Mg1. The lock is released, the ratchet 25 stops the rotation of the photographic lens 26, and the focusing operation is completed.

Next, a second embodiment of the present invention will be described based on FIG. In this example, the AC coupling method is used to prevent erroneous distance measurements that may occur when the background light receiving surface distribution has a very high contrast. Now, when the switch SW1 is opened in response to a release (not shown), the gate 27 is opened and the light emitting element 2, which is an IRLED, emits pulsed light in synchronization with the pulse output at point 1p. Light receiving element pair 7. ,7
2 outputs a polarity output corresponding to the scanning position of the light shielding member 8I in synchronization with the pulsed light emission. An amplifier system composed of operational amplifiers 31 and 32 generates an AC amplifier 33 in the next stage.
87. It is amplified so that the ratio can be obtained. At the output point of the next stage AC amplifier 33
An AC waveform as shown in the time chart of FIG. 4 (Bl) is obtained. When this waveform is shaped by the comparator 34, a pulse waveform as shown in FIG. 4 (B) is obtained. When the gate 35 calculates the AND with the pulse (a) having twice the frequency of the emission pulse, the fourth (2)
A pulse waveform from the point in time when the output polarity of the light receiving element pair 71, 72 changes as shown in l1mK in (B) is obtained. With this waveform, R, -87! The J tube 70 tube circuit 36 is set. As a result, Magnet) MJ? 1 is turned off, a ratchet (not shown) locks the photographing lens, and the position of the photographing lens is adjusted to the in-focus point. Through the above sequence, the light receiving element pair 7. , 72
The magnet Mg1 can be turned off at the point when the output polarity of the magnet changes.

With the above configuration, it is possible to perform accurate distance measurement without error under any subject conditions.

(Effects of the Invention) As described above, the distance detection device of the present invention has the above-mentioned problem 1 in an active light-shielding member scanning type distance detection device.
. Things that could only be removed with technology using large-scale circuit configurations,
This can be done with a very simple configuration of the light receiving optical system and circuit configuration. In addition, there is no risk that the first stage photocurrent detector will be saturated by background light, and by capacitor coupling it is possible to obtain a desired ratio sufficient to transmit to the next stage.

(11) Since the distance measurement method is based on changes in the output polarity of the light receiving element pair, there is no need to obtain the spot light intensity distribution as in the prior art. That is, since there is no need to extract and process the signal output as an analog value, there is no need to consider the dynamic range at all. This facilitates digitization of the circuit. Furthermore, the load on the light receiving optical system is reduced. This is because the focus detection accuracy can be obtained as in the conventional method without forming a sharp spot light image. Moreover, the peak position detection circuit, which is an essential signal processing circuit in the prior art, is no longer required, and therefore the signal processing circuit can be significantly simplified.

(ili) The output polarity of the light-receiving element pair is not affected by the slit width of the light-shielding plate, so the amount of incident reflected light can be maximized, and the ratio can be improved.

As described above, this method provides significant advantages and flexibility compared to conventional systems. Furthermore, the light receiving element can be an element such as a photodiode, and the cost is low. Furthermore, since there is no movable mirror for scanning, the conventional advantage of not requiring difficult adjustment is not lost in any way. Further, in the above embodiments, the case where the device of the present invention is applied to a still camera has been described, but it goes without saying that the device can be used not only for still cameras but also as a distance detecting device in various fields.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram when the distance detection device of the present invention is applied to a still camera, Figure 2 (A) is a perspective view of the light receiving optical system in Figure 1, and Figure 2 (B) is , a front view showing a modified example of the light shielding member, FIG. 2(C) is a perspective view of a modified example of the light receiving optical system of FIG. 2(A), and FIGS. Electric circuit diagram and timing chart of a distance detection device showing an example of the fourth embodiment.
Figures (A) and (B) are an electric circuit diagram and a timing chart of a distance detection device showing another embodiment of the present invention, and Figures (A) and (B) are diagrams showing a conventional triangulation principle and a timing chart. Fig. 6 is a diagram of the groove bottom of a conventional gobo plate scanning type distance measuring device; Fig. 7 is a diagram showing the relationship between object distance and incident light intensity; (A) and (B) are electric circuit diagrams and signal waveform diagrams of a conventional distance detection device. Figures 8 (A), (B), and (C) are graphs showing changes in photoelectric output using the conventional method. FIG. 3 is a diagram for explaining problems that occur when 1... Class photographic object 2... Light emitting element 3... Light emitting lens 77... Light receiving element pair 8... ...... Light shielding member 22, 34... Comparator (detection circuit) horse 2
Ward (A) (B) (C) 84＾1 --1111--Shuichi-M'l;I4to] 1 giant day-41
Atsushi 6th Ward

Claims (1)

[Scope of Claims] A light projecting means consisting of a light emitting element and a light projecting lens, and a pair of light projecting means provided adjacent to each other in the direction perpendicular to the base line length so as to receive the light reflected from the subject by the light projecting means. a light-receiving element, a light-shielding member that moves in front of the pair of light-receiving elements in the baseline length direction, and in which a light-transmitting part or a light-shielding part corresponding to the two light-receiving elements is shifted in the base-line length direction; A distance detection device comprising: a detection circuit that detects a change in a difference in photoelectric output from a light receiving element;