JPH01206282A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To automatically alter the light emitting current of a light source according to the condition of an object, by supplying the output of a light detection means with respect to a setting means for setting the min. value capable of being processed by a distance operation means to a drive means for controlling the intensity of the light source. CONSTITUTION:The pulse P1 from a pulse generating circuit 26 is supplied to a drive circuit 24 and a light source 10 emits light on the basis of the magnitude of a current I0. In a moment when the pulse P1 rises, reflected light does not yet reach a photodetector 18 and voltage V3 is low and the voltage V0 from a setting circuit 23 for setting the min. value of all of output currents from the photodetector 18 capable of being processed by a distance operation circuit 28 is larger than the voltage V3. Therefore, the voltage V4 from a control means 22 is highest and the intensity of the light from the light source 10 becomes max. When the reflected light is inputted to the photodetector 18, the voltage V3 becomes high and exceeds the set voltage V0 to become high to a large extent while the voltage V4 from the control means 22 is suddenly dropped and the intensity of the light from the light source 10 is also suddenly dropped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance measuring device used in a camera or the like to measure the distance to a subject when photographing.

[Prior Art] As an active type distance measuring device, one shown in FIG. 5 has been proposed.

light source! 0 (infrared light emitting light source, etc.) is transmitted through lens system I2.
The reflected light passes through the lens system 16 and is projected onto the light receiving element 18 as a light spot.

This light receiving element 18 has a position of 5
ve detector is a position detector, and depending on the position of the light spot, the current obtained from electrode 18a and electrode +8b! , and I are different in magnitude, and I+/I
The angle θ of the reflected light 10b with respect to the projected light 10a is determined from t, and the distance to the subject 14 is measured.

At this time, if the light spot obtained on the light receiving element 18 is weak, the distance calculation circuit cannot perform processing due to noise, so the current II and ! , must be large enough to be computationally processable. Therefore, in consideration of the worst conditions during distance measurement (the subject 14 is far away and the light reflectance is low), a large current is always supplied to the light source 10 during measurement, causing it to emit strong light. There is.

[Problem to be solved by the invention 1 However, for distance measurement, it is sufficient to obtain the ratio of the currents ■1 and I, and their absolute values are irrelevant.
It is wasteful to emit strong light when the number 4 is close and the light reflectance is high, and it wastes power.Especially when performing multiple measurements with a battery-powered device, it is wasteful to emit strong light. There was a problem that the number of measurements decreased due to increased wear and tear.

In addition, if the light source IO is emitted strongly all the time, the light source IO tends to deteriorate, and a large current flows in a pulsed manner, which tends to generate noise, which has a negative impact on the surrounding circuits.The purpose of the present invention is to solve the above problems. In view of the above, it is an object of the present invention to provide a distance measuring device that can automatically change the light emitting current of the light source lO depending on the conditions of the subject i4.

[Means for solving the problem] In order to achieve this object, the present invention includes a light receiving means for detecting the light receiving position of a light spot, and a distance to a target object is measured using the output of the light receiving means. a setting means for presetting a minimum value from the light receiving means that can be processed by the distance calculating means; and a driving means for controlling the intensity of the beam of light irradiating the target object. , and control means for supplying the output of the light receiving means to the setting means to the drive means by being supplied with respective outputs of the light receiving means and the setting means.

[Embodiments] (1) First Embodiment FIG. 1 shows a diagram to which the present invention is applied! A block diagram of main parts of the embodiment is shown.

Current from light receiving element 18! , and ■ are supplied to the current-to-voltage converter 420 & and the current-to-voltage converter 20b that constitute a part of the addition calculation means 20, and the outputs (voltages) vl and V from these are supplied to the other parts of the addition calculation means 20. V r + V * = V r + V * =
Vs is calculated.

A voltage V is applied to the control means 22, to which a setting value converted into a voltage v0 is applied from a setting circuit 23. In this example, the control means 22 is a differential amplifier.

Control means 22 obtained based on the difference between the voltages o and V
A voltage v4 from is applied to the drive circuit 24.

Although not shown, a pulse P+ is obtained from the timing pulse generation circuit 26 in response to a signal from a release shutter button or the like (such as turning on a switch by a button), and this is supplied to the drive circuit 24.

As a result, the voltage V4 or the current converted from the voltage v4■
. is the light source! 0, and the light source IO emits light with an intensity corresponding to the size.

Furthermore, a pulse P is output from the timing pulse generation circuit 26.
, P2 is obtained later, and this is supplied to the distance calculation circuit 28, and at this point, ■1 and V.

A distance calculation is performed based on this and is output to the terminal 30.

Next, the operation will be explained using FIG. 2. Note that the setting circuit (23) sets the minimum value of the total output current 11 +I t from the light receiving element 18 that can be processed by the distance calculation circuit 28. Further, the upper limit of the output current of the drive circuit 24 is a value that clears the above-described worst condition.

Switches such as the shirt button are turned on at time 1+ (p to the same figure)
o), the pulse P1 (B in the figure) is obtained from the timing pulse generation circuit 26 after a certain period of time. The time points of the leading and trailing edges of this pulse P, are t! and t4, and the period is TI. The pulse Pt is supplied to the drive circuit 24, so that the light source 10 receives a current! . emits light based on the size of the

This light becomes reflected light from the subject 14 and enters the light receiving element 18, but at the instant of the rise of the pulse P, the reflected light has not yet reached the light receiving element 18, and therefore the voltage V is extremely small or O , and the voltage from the setting circuit 23 is ■. is higher.

Therefore, the voltage v4 from the control means 22 is at this time t,
In other words, the current Io (C in the figure) is the highest, and the intensity of the light from the light source IO is maximum at this point.

When the reflected light enters the light receiving element 18, the voltage V increases. When the reflectance is good, the voltage V, as shown in the same figure, becomes significantly higher than the set voltage v0 (indicated as vSl in the second figure), and therefore the voltage v from the control means 22 increases.
4 suddenly decreases (the current 1o also decreases rapidly), and this causes the light source! The intensity of light at zero also drops rapidly.

In this way, the incidence of the reflected light on the light-receiving element 18 is rapidly attenuated, and the voltage V is rapidly reduced, and after the point in time when it corresponds to the set value v0 from the setting circuit 23, the intensity of the light becomes constant. becomes stable. Light emission is stopped at time t4.

Also, the time t3 to ts (Tt
) between the timing pulse generation circuit 2 and
6, a pulse P is obtained from the distance calculation circuit 2.
8, distance calculation processing is performed and the measured value is output to the terminal 30. The greater the change in current, the greater the noise. Since the noise generated at t4 during distance calculation processing is reduced compared to the conventional method, erroneous calculations due to noise can be reduced and accurate measured values can be obtained.

Next, when the shirt button is pressed again at time t6, time t7
A pulse Pt is obtained between ~ts ('t'+), and the current I0 is supplied to the light source 10 to emit light as in the previous time. Time t
The magnitude of the current I0 at point 7 is the same as at time jt. If the reflectance of the subject 14 is poor and the reflected light incident on the light receiving element 18 is weaker than the previous time, the initial value of the voltage V will be lower than that at time t (shown as v3! in the second diagram). , hence the current! . is gradually attenuated compared to the previous time.

However, since the reflected light is weak, the voltage v3 becomes stable corresponding to vo at the time when the current does not attenuate to the previous current value. Last steady state current! . The value of I. Let's call it I and use it this time! .

, then I al< I. , and the light becomes stable with relatively stronger light than the previous time.

In either case, the current ■. is attenuated according to the intensity of reflected light, which helps reduce power consumption compared to conventional methods. Second
Energy is saved in the dotted hatched area in Figure C.

(2) Second Embodiment FIG. 3 shows a block diagram of the main parts of the second embodiment. In this example, except for the control means 22, the other configurations are the same as in the case of FIG. Therefore, the control means 22 of this example will be explained, and the same reference numerals will be given to the other parts corresponding to those in FIG. 1, and the explanation will be omitted.

The control means 22 of this example is composed of (a division circuit 22a), (a multiplication circuit 22b), and (a storage circuit 22c).

The voltage v0 from the setting circuit 23 and the voltage V from the addition circuit 20c are input to the division circuit 22a, and V o/v ,
is calculated and the value Q1 is obtained.

This value Q, is input manually to the multiplication circuit 22b, and Q, which will be described later, is
(QIXQI) to obtain the output Q.

This is manually input and stored in the storage circuit 22c, and this stored value becomes Q and is input to the multiplier circuit 22b and also to the drive circuit 24.

Further, when the reset signal Pr obtained from the timing pulse generation circuit 26 is input to the storage circuit 22c, it is reset to the initial value.

The operation of the second embodiment will be explained using the timing chart of FIG. Note that parts corresponding to those in FIG. 2 are given the same reference numerals.

When the switch is turned on at time t (to the same figure), the timing pulse generation circuit 2 at the trailing edge of pulse P0 (time 11)
6, a reset pulse Pr (B in the same figure) is obtained, the memory circuit 22c is reset, and its Q3 is initialized. This initial value is selected to be a large value in consideration of the above-mentioned worst condition. FIG. 4C shows the value of Q3.

At the trailing edge of the reset pulse Pr (time t3), the timing pulse generation circuit 26 generates a pulse P, as shown in the figure.
is obtained and input to the drive circuit 24. This causes a large current I0 to flow from the drive circuit 24 to the light source, as shown in FIG. 4E! 0, and the light source 10 emits strong light. Time t, ~t, is a light emission period TI,
In this example, the current during this period of T1! . The value of is constant, and the light source 10 emits light of the same intensity during the T8 period.

In the T8 period, the voltage is further increased to V in the division circuit 22a. /V is calculated. At this time, the voltage v3 (FIG. 4F) is V.

>>V, and Q obtained from the division circuit 22a
, is less than 1. As a result, the value of the multiplication operation (QIXQ+=Q,) in the multiplication circuit 22b also becomes relatively small (Q becomes smaller).

Pulse P from the timing pulse generation circuit 26.

(FIG. 4G), the value of Q is stored in the storage circuit 22C and becomes Q. That is, Q, which was a large value at the reset time (time ta), is rewritten to a smaller value. At the same time, the distance calculation circuit 28 calculates the distance from V 2 and /V 2 (FIG. 4H).

T is the calculation period. The above is considered to be the first light emission.

At time t7, a pulse P is obtained from the timing pulse generation circuit 26 again, and the value of Q3 stored in the storage circuit 22c in the first light emission (V compared to the previous time).

/VS. ■ the magnitude of the current based on (times). light source 10
emits light (the amount of light emitted is proportional to ■., so it is twice ■./Vt. compared to the previous time). This luminescence is TI (at the time of ~
ts) continues with a constant strength, but compared to the previous time vo/
vz. It becomes twice as weak. Therefore, the reflected light is also Vo/V3o
It becomes twice as weak. Time point L7-t in FIG.

Between, the voltage V 31 (V 31 - V
1oXVO/V3°=V0) corresponds to the set value v0. Then, in the division circuit 22a, V
0/V31=Q l is calculated, this time it becomes Q, -1, and the multiplier circuit 22b calculates Q IX Q s = Q t
is calculated, and this time, Q ,=Q , and therefore, the memory contents of the memory circuit 22c are rewritten at time t, but this time they are the same as those after the first light emission. The above is considered as the second light emission.

Furthermore, a pulse P is obtained from the timing pulse generation circuit 26 at time tll, and a light emission operation is performed in the same manner as described above. In this time (third time) as well, since Q at the time of the second light emission is stored in the memory circuit 22c, a relatively weak light emission is performed as shown in the period from time tll to t+3 in FIG. 4E. Ru.

And if the reflected light is too weak in this third light emission, V 3
．． < V, then the value of Q (vo/v s*)
becomes larger than 1, so 03 in the memory circuit 22c that was stored at the time of the third light emission is rewritten to a larger value, and the next time the light is emitted, an appropriate intensity is set based on this corrected value. Luminescence is obtained.

In this second embodiment, the intensity of the next light emission is controlled based on the state of the previous reflected light, and the intensity of the next light emission is controlled several times or once.
When measuring distance using the average value of several measurements,
The second and subsequent light emissions can be controlled to an appropriate intensity, thus avoiding wasteful and large energy consumption.

[Effects of the Invention] According to the distance measuring device of the present invention, depending on the intensity of reflected light,
A control circuit is provided to control the intensity of light emitted from the light source, so when measuring distance by illuminating a subject with good reflectance,
It does not consume unnecessary light emitting current, and has the excellent effect of avoiding unnecessary battery consumption, especially when distance measurement is performed multiple times using batteries, and allowing multiple distance measurement operations to be performed. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the first embodiment of the distance measuring device of the present invention, FIG. 2 is a time chart explaining its operation, FIG. 3 is a block diagram showing the second embodiment, and FIG. 5 is a time chart explaining its operation, and FIG. 5 is a basic explanatory diagram of the distance measuring device. IO: Light source I8: Light receiving element 22: Control means 23: Setting circuit 24 Nidrive circuit 26: Timing pulse generation circuit 28: Distance calculation circuit

Claims (1)

[Scope of Claims] A distance measuring device comprising a light receiving means for detecting a light receiving position of a light spot, and a distance calculating means for measuring a distance to a target using an output of the light receiving means, the distance calculating means a setting means for presetting the minimum value of the total output from the light receiving means that can be processed by the light receiving means; a driving means for controlling the intensity of the light source that illuminates the target object; A distance measuring device comprising: a control means for supplying the output of the light receiving means to the setting means to the driving means.