JPS61107111A - Range finder - Google Patents

Abstract

PURPOSE:To attain to magnify a measurable range having reliability, by obtaining a range signal on the basis of the light receiving quantity of a light receiving element for watching a remote side higher than a predetermined level when the light receiving quantity of a light receiving element for watching a near side is lower than the predetermined level. CONSTITUTION:A zone judge circuit 19 operates the range finding zone corresponding to the magnitude of the output ratio of light receiving elements 2a, 2b, which respectively watch a remote side and a near side, being the output 64 of a differential amplifying circuit 15 on the basis of the outputs 57, 58 of indefinite remote level judge circuits 16, 17 when each of both light receiving quantities of said elements 21, 2b is larger than an indefinite level. When the light receiving quantity of the element 2a is equal to or less than the indefinite remote level and that of the element 2b is equal to or more than said indefinite remote level while the output of the circuit 16 is 0 and that of the circuit 17 is 1, the circuit 19 outputs a signal showing that a subject is present in the near side zone adjacent to an indefinite remote zone. When each of both light receiving quantities of the elements 2a, 2b is lower than the indefinite remote level, the circuit 19 outputs a signal showing that the subject is present in the indefinite remote zone.

Description

[Detailed description of the invention] [Industrial application field 1 The present invention relates to a distance measuring device using a triangular distance measuring method.

[Prior art and its problems 1 Triangulation distance measurement method with an infrared light emitting element and two light receiving elements 1
In this case, the amount of light reflected from the subject on the infrared light emitting element and entering the two light receiving elements is measured, and the ratio is calculated to determine in which distance zone the subject is located (hereinafter simply referred to as subject distance). I had decided. However, since noise components are present in the photometry device that measures the amount of light entering the light-receiving element, it is not possible to perform photometry with a good S/H for light below a certain value. Like this S/
If the ratio is calculated using a bad photometric amount of N, the variation in the photometric result will be the sum of the photometric variation in the light amount of each light receiving element, resulting in a large error. Therefore, in this conventional system, the light intensity of either photodetector is at a certain level that can be photometered (this level is called the infinity level).
If the subject does not reach , it is determined that the subject is sufficiently far away and is within the farthest zone. If the measurable distance is defined as the distance to a subject with an amount of reflected light exceeding this infinity level, the higher the infinity level is, the closer the measurable distance is, and the further the infinity level is lowered, the farther the measurable distance is. However, at the same time as lowering the infinity level, the S
/ As H deteriorates, the distance measurement error increases. If a lens with a long focus tolerance or a bright F-number is used as a photographic lens, it is necessary to extend the measurable distance to the far side without lowering the infinity level due to the depth of field. Due to the problem of H, it was not possible to expand the measurable distance by simply taking the ratio of both receiving elements, such as the conventional triangulation method.

[Objective of the Invention 1 The object of the present invention is to provide a ranging circuit that can expand the ranging zone on the infinity side using a triangular ranging method and without impairing the S/N ratio. It is something.

[Configuration 1 of the Invention The distance measuring circuit of the present invention is a distance measuring device equipped with a light emitting means and two light receiving elements gazing toward the near side and the far side. A circuit that determines whether the amount of light reflected from the subject is at a certain level, a circuit that calculates the ratio of the amount of light reflected from the subject to the light-emitting element that enters the two light-receiving elements, and a circuit that calculates the ratio of the amount of light reflected from the subject to the light-emitting element that enters the two light-receiving elements. When the amount of light received by the element is higher than the predetermined level I) and the amount of light received by the light receiving element gazing toward the near side is lower than the predetermined level,
The present invention is characterized by comprising means for obtaining a signal representing a distance based on the amount of light received by a light receiving element gazing toward a far side.

With this configuration, 1) An infinity level is set for each of the two light-receiving elements on the far side and the near side, and when a light amount exceeding the infinity level is incident on both light-receiving elements, the subject is photographed according to the incident light amount ratio Decide on the zone. Next, if the light-receiving element looking toward the near side does not have an amount of incident light exceeding the infinity level, and the light-receiving element looking toward the far side has an amount of incident light exceeding the infinity level, then the farthest zone 1
This zone is determined to be the closest zone. Next, if there is no amount of light received by both of the two light receiving elements that exceeds the infinity level, the zone is determined to be the farthest zone.

In this way, it is possible to perform reliable distance measurement with a sufficient S/N ratio and to expand the measurable distance without changing the conventional configuration.

[Example 1 The present invention will be described below with reference to one embodiment.

First, the triangulation method will be explained. In FIG. 2, light emitted from the distance measuring light emitting element 1 is projected onto a subject 6 through a projection lens. Next, the light reflected on the subject 6 is collected by a light-receiving lens 4, passes through a filter 5 for cutting harmful light, and is received on two light-receiving elements 2a and 2b arranged adjacent to each other. Ru. Figure 3 shows the light receiving element 2.
2a and 2b show images of the light emitting element 1 on top. Third
The figure shows reflected light from distance R2. in this case,
The same amount of light enters the light receiving elements 2a and 2b.

The reflected light from the distance R1, which is closer than R2, enters the light receiving element 62b in a larger amount than the light receiving element 2a, and the reflected light from the distance R1, which is closer than R2, enters the light receiving element 62b.
A larger amount of reflected light from the light receiving element 2a enters the light receiving element 2b than from the light receiving element 2b. FIGS. 4 and 5 show the relationship between the amounts of light entering the light receiving elements 2a and 2b. As can be seen from FIGS. 4 and 5, the output distance R2 of the light receiving elements 2a and 2b
At a distance closer than R2, the output p2b of the light receiving element 2b>the output P2a of the light receiving element 2a, and the output ratio P
za/P 2b becomes smaller as the subject gets closer than distance R2, and conversely, at a distance farther than R2,
P, b<Paa, and the ratio P=a/P2b increases as the distance increases from R2. Therefore, the light receiving element 2a
By detecting the output ratio P+a/P2b of P2b and P2b, the distance Rx of the subject 6 can be determined.

FIG. 6 shows the output ratio of the light receiving elements 2a and 2b. In this way, the output ratio of the light receiving elements 2a and 2b is P 2a/
P zb monotonically increases depending on the distance. Therefore, it is determined by the camera lens. The subject distance is divided into zones by zone division considered from the depth of field, and the output ratio of the light receiving elements 2a and 2b corresponding to the distance of the dividing point and the ratio of the light receiving elements 2a and 2b obtained by actual distance measurement are calculated. By comparing the values, the object distance can be obtained as a zone output.

In this invention, the light receiving element 2a gazing toward the far side
When the output of the photodetector 2b looking toward the near side is smaller than the infinity level, P2a/P=b is determined by only the photometric output of the photodetector 2a.
Measure distances in zones that cannot be determined by the ratio of

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
is a quick charging circuit section that stabilizes the power supply voltage of the photometric circuit system, and its operation will be described later.

The light receiving elements 2a and 2b in the triangular distance measurement described above are connected to the first and second photometric circuits 1.3 and 14, respectively, and the output terminals of the first photometric circuit 13 are P, a/P2.
The output terminal of the second optical circuit 14 is connected to the difference amplifier circuit 15 that calculates b and the first infinity level determination circuit 16, and the output terminal of the second optical circuit 14 is connected to the difference amplifier circuit 15 and the second infinity level determination circuit 1? connected to.

Difference amplifier circuit 15. 1st infinity level judgment circuit 16° 2nd
The output of the infinite level determination circuit 17 is sent to the zone determination circuit 19.
It is connected to the. The zone determination circuit 19 uses the outputs 57 and 58 of the first and second infinity level determination circuits 16 and 17 to determine whether the difference amplification circuit 15 outputs a signal when the amount of light received by each of the light receiving elements 2a and 2b is greater than the infinity level. A distance measurement zone is calculated according to the output 64, that is, the magnitude of Pa/Pb.

Further, when the amount of light received by the light receiving element 2a is below the infinity level and the amount of light received by the light receiving element 2b is above the infinity level, that is, the output of the @1 infinity level determination circuit 16 is "O",
If the output of the second infinity level determination circuit 17 is "1", the object 6 is in the adjacent near zone (outside the infinity zone).
The zone determination circuit 19 outputs a signal indicating the presence of the zone. When the amount of light received by both light receiving elements 2a+2b is lower than the infinity level, that is, when the outputs of both infinity level determination circuits 16 and 17 are both "0", the zone determination circuit 19 determines that the subject is at infinity. Outputs a signal indicating that it is in the far zone.

The operation of the above circuit and the circuit configuration of the pond will be explained below.

In FIG. 1, in conjunction with pressing the shutter button of the camera, the first quick charging circuit 11 that rapidly charges the capacitor 102 of the stabilized power supply 10 is activated, and a stabilized voltage Veal rises. Timer 2 with switch 5 ION
5 starts and after time t+M has passed since the switch 5ION, the quick charge OK signal 1 from the timer 25 becomes 'H', the second quick charge circuit 12 is activated, and the first photometering circuit is activated.
Rapidly stabilize the second photometric circuit. This continues until time L2, and after t2 has passed, the quick charge OK signal 51 becomes 'L' and the second quick charge circuit 12 is turned off. The enable signal 52 is applied to the light emission control circuit 26, the light emission pulse signal 53 is applied, and the light emitting element 1 is lit in pulses.This light pulse is projected onto the subject 6, and the reflected light from the subject 6 is transmitted to the light receiving element 2a. , 2b. Then,
The light receiving elements 2b and 2a output photocurrent according to the amount of received light.
It is input to the photometric circuit 13 and the second photometric circuit 14. Each of the photometric circuits 13 and 14 outputs a logarithmically compressed value of the photocurrent input from the light receiving elements 2b and 2a.

The output 61 of the first photometric circuit 13 and the output 62 of the second photometric circuit 14 are input to the difference amplifier circuit 15, and Ikekata is subtracted from one of them. This means that the difference in the logarithmically compressed outputs, that is, the ratio P2a/P2b of the outputs of the light receiving elements 2b and 2a, is calculated. Therefore, the output 64 of the difference amplifier circuit 15 is an output corresponding to the ratio of the light receiving element outputs shown in FIG.

The output 61 of the first photometric circuit 13 and the output 62 of the second photometric circuit 14 are input to the first infinity level determination circuit 16 and the second infinity level determination circuit 17, respectively.
Output s7 indicating whether 1.62 exceeds the infinity level
, 58 are input to the zone determination circuit 19. *In addition, the output 62 of the second photometric circuit 14 is input to the pulsating current circuit 18, and is also used for light emission control under pulsating light illumination such as a fluorescent lamp.

The zone determination circuit 19 includes the output 64 of the difference amplifier circuit 15,
In other words, the output ratio of the light receiving elements 2b and 2a and the outputs 57.58 of the first infinity level determination circuit 16 and the second infinity level determination circuit 17, that is, whether or not the amount of light exceeding a certain level is incident on the light receiving element. A signal indicating that is being input. Therefore, the zone determination circuit 19 first determines the output 57 of the first infinity level determination circuit 16 and the @2 infinity level determination circuit 17.
The output of ゜58 is determined. Then, both light receiving elements 2
If there is no light amount input exceeding the infinity level in a and 2b, it is determined that the infinity zone (Vll! zone) is present.

Next, the output of the second infinity level determination circuit 17 is determined to exceed the infinity level, while the output of the first infinity level determination circuit 16 is determined not to exceed the infinity level. When the judgment is made, perform the judgment of the V[I zone. Finally, only when it is determined that the outputs of both infinity level determination circuits exceed the infinity level, it is determined in which zone of ■ to ν1 the subject 6 is located according to the magnitude of the output 63 of the difference amplifier circuit 15. Ru.

This determination is performed by the zone memory circuit 2 under timing control by the ranging memory signal 54 synchronized with the light emission pulse 53.
1 is stored. The memorized zone signal 60 is sent to the decoder 22 and the first . Second. It is decoded into a tjIJ3 zone signal 65.66.67 and a fourth zone signal for stopping the camera lens in a predetermined position.

On the other hand, after the distance measurement is completed, the photographing lens (not shown) of the camera starts moving by further pressing the shutter button of the camera, and as it moves, a lens position signal 56 indicating the lens position is input to the lens position input circuit 20. be done. This output 63 and the fourth zone signal 68 are compared by the lens stop circuit 23, and when they match, the lens magnet 7 is turned off to stop the photographing lens.

In the above system, the infinity zone (Vlll zone) and the Vlll zone one zone before infinity are determined by determining whether or not there is a scene at a certain level or higher in the light receiving element 2a. Therefore, if the infinite level is set uniformly, the switching distance between the Vlll zone and the Vlll zone will change depending on variations in the luminance of the light emitting element, the sensitivity of the light receiving element, the reflectance of the subject, etc. Therefore, for a subject with a certain standard reflectance, the appropriate Vllll zone and V
Is it necessary to adjust this infinity level so that it switches at the switching point of the ll zone? Also, for example,
When Vcc changes from 2.0V to 3.3V, the brightness of the light emitting element increases by about 1.5 times. Therefore, it is necessary to change the infinity level depending on Vcc. For this purpose, the bias circuit 28 detects changes in voltage Vcc and controls the infinity determination level in response to this change in Vcc.

Details of the bias circuit 28 will be explained with reference to FIG.

Consider a time when an appropriate charge is accumulated in the capacitor 142 by the quick charging circuit 12 and the photometric output 61 is equal to the reference voltage V ref, that is, when the first photometric circuit 13 is in a stable state.

Let's use concrete numbers to make it easier to understand.

Assuming constant current source I = 10 μA and constant current source l2 = 2 μA, in order for the output 61 of the first photometric circuit to be the reference voltage Vref, the transistor 142 (1') - ry99 - current =: the collector of the transistor 141. Current = 1 μA. At this time, transistor 139, transistor 146
．． ) The collector current of each transistor 131 is 1μ.
It becomes A. Therefore, transistor 130. ) The collector current of the lunge converter 126 is 1 μA, and if the area ratio of the transistor 126 and the transistor 143 is 1 = lO, the collector current of the transistor 143 = 10 μA.
Therefore, constant current source 1. balance with the current. The first photometric circuit 13 is thus in a stable state, and at this time,
The transistor 13 is connected to the transistor 124 and the resistor 125.
Ignoring the base current of 0, the bias current 123 flows when the subject 6 is in the dark, and when the subject is illuminated with light that does not change over time (abbreviated as constant light) such as sunlight. The sum of the output current of the light receiving element 2b and the bias current of the constant voltage m source 123 flows into the transistor 124. In other words, the transistor 124 is a bypass circuit for constant light.

For example, suppose that the brightness on the subject becomes brighter from a stable state, such as when pointing the camera at a wall that is dimly lit by constant light. At this time, the base of the transistor 124 is connected to the capacitor 13.
The collector current of the transistor 124 does not flow more than the current flowing in a stable state. Therefore, the increase iL in the photocurrent of the light receiving element 2b due to the brightness becomes the base current of the transistor 130. Therefore transistor 130
The collector current increases by hFE times iL, and is further amplified by the area ratio of transistors 126 and 143 of 1:10 to become the collector current of transistor 143. This current flows into logarithmic compression diodes 144 and 145, increasing the photometric output. Then, transistors 142 and 141
The balance of the transistors 140 and 139.14 is lost, and the collector current of the transistor 141 decreases.
6 collector current decreases, transistor 131
collector current decreases.

Therefore, the collector current of transistor 130 becomes a current that charges capacitor 132, and capacitor 13
2, that is, the base potential of the transistor 124 increases.

Therefore, the collector current of the transistor 124 increases, and works to bypass the increased photocurrent iL caused by the brightness of the object. Then, the collector current of the transistor 130 decreases, and the photometric circuit returns to its normal state. In other words, transistor 130→14
3→142→141→140→139→146→131
constitutes a negative feedback circuit. Without the capacitor 132, the feedback would be instantaneous, and the larger the capacitor 132, the longer the feedback would take.

During distance measurement, the light emitting element 1 is lit in pulses, and the increase ΔiL in the photocurrent of the light receiving element due to the reflected light from the subject is multiplied by hFE in the transistor 130, and
The width is further increased by an area ratio of 26 and 143. The current flowing through the logarithmic compression diodes 144 and 145 in a stable state is ID
Then, the increase in photometric output due to ΔiL is 2 X E-
T-7i n(10x hFExΔiL/iD>) Since distance measurement is performed in a pulsed manner, the potential of the capacitor 132 hardly increases during the pulse,
Therefore, rather than saying that there is no negative feedback, the capacitance of the capacitor 132 is designed so that negative feedback is strong enough for steady light, and negative feedback is strong enough for side control pulse time. The capacity can be determined in such a way that there is no such thing. The same applies to the second photometric circuit 14.

In the above circuit, the bias circuit 28 that controls the infinite distance determination level with respect to changes in Vcc will be explained. It is created by flowing current I4.

Now, Vccl and transistors 118, 115. created by this bias circuit. The voltage between the bases of IIL 106 is
It is constant regardless of Vcc. Therefore, variable resistor 10
If 9 is made large, the voltage applied to the variable resistor becomes large, and conversely, the voltage between the base and emitter of the transistor 110 decreases, and I becomes small. Conversely, if the variable resistor 109 is made smaller, the voltage between the base and emitter of the transistor 110 increases, and the current I becomes larger. By changing the variable resistor 109 in this manner, .circlein. can be arbitrarily changed, and this .circlein. has no Vcc dependence. On the contrary, 1. is a current that has Vcc dependence.

Now, when we calculate the current flowing through the diode 114 and the resistor 147, we find that Vccl is 2. When OV, diode 11
The voltage applied to 4 is 0.6V, and the resistance value of resistor 147 is Rv.
Then, if the zero-order Vce1 changes to 3.3■, which becomes 1.4/Rv (A), the voltage applied to the diode hardly increases, so it becomes 2.7/Rv (A),
A current that is dependent on the power supply voltage flows. Vcc is 2.0■
When the voltage changes from to 3.3V, the current flowing through this diode 114 and resistor 147 is (2,7-1,4)/Rv<A)
only changes.

Since the transistor 113 and the guide l'114 are a mirror circuit, this diode 114 and the resistor 147
The current flowing in is equal. (2) The amount of increase due to the power supply voltage is determined by determining the resistor 147.

Therefore, at the infinite level, the resistance value of the resistor 111 is R
Assuming ω, when Vcc changes from 2.0■ to 3.3■, the infinity level increases by 1.3/RvXR■. The i2 resistances 147 and 111 are determined so that this increase corresponds to the increase in the amount of light emitted by the light emitting element due to the change in Vcc.

Although the above embodiment detects the distance in zones, the present invention is not limited to this, and the distance may be detected in an analog manner. Therefore, the distance range (distance zone V
(corresponding to II), the analog distance may be detected only by the output of the light receiving element 2a.

Further, in the above embodiment, the same infinity level was set for both the light receiving elements 2a and 2b, but 7'L:
However, different levels may be set.

Furthermore, in the above embodiment, the case where the output of the far side light receiving element is above the infinity level and the output of the near side light receiving element is below the infinity level is treated as the zone one zone before the infinity zone. , the output of the light-receiving element on the far side of this zone is 2
Depending on the situation, the zone may be divided into two or more zones.

[Effect of the Invention 1 As described above, according to the present invention, when the output of any of the light receiving elements is lower than the infinity level shown in FIG. 5, the infinity zone is determined. Therefore, one distance zone can be newly established on the long distance side, and the measurable distance can be expanded. For example, when there is a distance measurement target at distance R4 shown in FIG. 5, in the conventional example it is determined to be in the infinity zone, but according to the present invention, as shown in FIG. This can also be detected as the previous zone (Vll). Furthermore, since there is no need to lower the infinity level in order to extend the measurable distance, the S/N ratio does not deteriorate. Conversely, it is possible to improve the distance measurement accuracy by increasing the number of distance zones without increasing the measurable distance, which is effective for cameras that use lenses with a shallow depth of field, such as telephoto lenses or bright lenses. be.

Also, at long distances, the amount of light incident on the light receiving element tends to be small and the S/N ratio tends to deteriorate, so rather than measuring distance using the output ratio of two light receiving elements, it is better to It is better to perform distance measurement only based on the output level of the other light receiving element after the light receiving element has decreased in accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a simple embodiment of the present invention, FIG. 2 is a diagram showing an example of a triangular distance measuring method, FIGS. 3 to 7 are illustrations for explaining the operation of the distance measuring method shown in FIG. FIG. 8 is a detailed circuit diagram of the bias circuit. 1... Light emitting means, 2a... Light receiving element 2 looking at the far side
b... Light-receiving element looking toward the near side, 13.14.1'5... Calculating means, 16... Second determining means, 17... First determining means, 1
9...Detection means.

Claims (3)

[Claims] (1) A light-emitting device, a light-receiving element gazing at the near side, and a light-receiving element gazing at the far side, which are arranged adjacent to each other so as to receive the reflected light emitted from the light-emitting means and reflected by the object to be measured. A distance measuring device comprising: a first determining means for determining whether the output of the light receiving element facing toward the far side is above or below a predetermined first level; a second determination means for determining whether the output of the facing light-receiving element is above or below a second predetermined level; a calculation means for calculating the output ratio of both the light-receiving elements; is determined to be below the first and second predetermined levels, respectively, it is determined that the distance is infinite, and if the output of the light receiving element gazing toward the far side is above the first predetermined level, If it is determined that the output is below the second predetermined level, the distance is detected based only on the output of the light receiving element looking toward the far side, and the outputs of both light receiving elements are respectively above the first and second predetermined levels. 1. A distance measuring device comprising: a detecting means for detecting a distance according to a calculation result of the calculating means when it is determined that the distance measuring apparatus is (2) The detection means detects the distance to the distance measurement target as a distance zone, and when it is determined that the outputs of both light receiving elements are below the first and second predetermined levels, the distance to infinity is detected. zone, and if it is determined that the output of the light-receiving element looking toward the far side is above the first predetermined level and the output of the light-receiving element looking towards the near side is below the second predetermined level, the light-receiving element looks into the infinity zone. Detecting the farthest adjacent zone, and detecting the distance zone according to the calculation result of the calculation means when it is determined that the outputs of both light receiving elements are respectively equal to or higher than first and second predetermined levels. A distance measuring device according to claim 1, characterized in that: (3) The distance measuring device according to claim 1 or 2, further comprising level adjustment means for adjusting the first and second predetermined levels according to the power supply voltage.