JP3174941B2 - Camera ranging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device such as a camera.

[0002]

2. Description of the Related Art Conventionally, various distance measuring devices of a light emitting / receiving type using an integrating circuit have been proposed. These devices operate a light emitting circuit and emit light until the integrated voltage exceeds a predetermined voltage. The distance to the subject was calculated by measuring the number of times or the time.

[0003]

However, in the distance measuring device as described above, the time until the integrated voltage exceeds a predetermined voltage cannot be predicted. Therefore, when the subject is very far or the reflected light from the subject is very small. When the distance is small, the distance measurement takes too much time, so that a shutter chance is missed, and it is very disadvantageous when shooting a moving subject or in continuous shooting.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a light projecting means for irradiating a subject with pulsed light, and a semiconductor for receiving light reflected by the subject when the light emitted from the light projecting means is reflected by the subject. A position detection element , a current-voltage conversion circuit that converts an output current of the semiconductor position detection element into a voltage, an amplification circuit that amplifies an output signal of the current-voltage conversion circuit, and an integration circuit that integrates an output signal of the amplification circuit. A counting means for counting the number of light projections of the light receiving means, and the light emitting means when the output voltage of the integration circuit exceeds a first predetermined voltage or the output value of the counting means exceeds a predetermined value. The light operation is completed, and the output value of the counting
When the light emitting operation is terminated by exceeding a predetermined value,
The output voltage of the integrating circuit at that time is equal to a second predetermined voltage.
Operating means for obtaining a distance signal that varies according to the calculated value of the ratio of the output voltage of the integration circuit to the first predetermined voltage at that time and the output value of the counting means when the pressure has reached Have.

[0005]

The detection of the integrated voltage and the counting of the number of times of light emission are simultaneously performed during the light emission to the subject, and when any one of the conditions is satisfied, the distance measurement is terminated, and the output value of the counting means becomes equal to the predetermined value.
When the light emission operation is terminated by exceeding the value of
The output voltage of the integrator at has reached the second predetermined voltage.
In this case, a distance signal that fluctuates according to the calculated value of the ratio of the integrated voltage to the first predetermined voltage and the count number obtained at that time is obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described with reference to FIG. The light emitting circuit 10 is a near-infrared light emitting element (hereinafter referred to as IRED) 1
4 is a driving circuit for driving the transistor 1
1, the resistors 12, 13 and the IRED 14. When a light emission signal is output from the arithmetic circuit 80 (hereinafter, referred to as CPU), the IRED 14 emits light. The emitted light passes through the light projecting lens 1 and is partially reflected by a subject (not shown). A part of the reflected light passes through the light receiving lens 2 and the PSD 3
Incident on. Actually, the IRED 14 is pulse-driven.

The first current-voltage conversion circuit 20 and the second current-voltage conversion circuit 30 are provided with a semiconductor position detecting element 3 (hereinafter referred to as PSD).
To form one light receiving circuit. P
When an optical signal is incident on SD3, PSD3 outputs a current corresponding to the intensity and incident position to current / voltage conversion circuits 20, 30. The first current-voltage conversion circuit 20 is a circuit composed of an amplifier 21 and a feedback resistor 22, and outputs a voltage proportional to the input current. The second current-to-voltage conversion circuit 30 includes an amplifier 31 and a feedback resistor 32. The second current-to-voltage conversion circuit 30 has the same configuration as the current-to-voltage conversion circuit 20, and outputs a voltage proportional to the signal current. The switch 4 outputs one of the outputs of the current-voltage conversion circuits 20 and 30 to the amplification circuit 40. The switch 4 is controlled by the CPU 80, and is turned on to the first current-voltage conversion circuit 20 side for distance measurement on the long distance side, and to the second current-voltage conversion circuit 30 side for distance measurement on the short distance side. I do.

A first amplifier circuit 40 and a second amplifier circuit 50
Is an amplifier circuit capable of switching gain. Since these amplifier circuits have the same configuration, the first amplifier circuit 40 will be described as an example. The capacitor 5 is connected before the amplifier circuit 40, and the direct current component of the input signal is cut here. The amplifier circuit 40 includes an amplifier 41, three feedback resistors, and switches 46 and 47 for turning on or off the resistors.
And a circuit for amplifying the input signal with a certain gain. The switches 46 and 47 are connected to the CPU 80
Is controlled by The switch 46 includes a feedback resistor 45,
The switch 47 short-circuits or releases the feedback resistor 44 and the feedback resistor 45, respectively, so that the gain of the amplifier 41 changes stepwise according to the state of these switches. Therefore, the conversion from the signal current to the voltage is also performed according to the changed gain, and is output to the subsequent circuit. The second amplifier circuit 50 operates in exactly the same way, and the CPU 80 operates the switches 56 and 57 to set an appropriate gain, and the signal output from the amplifier circuit 40 is amplified accordingly. The output signal of the amplifier circuit 50 is output to the integration circuit 60 via the switch 7.

The integrating circuit 60 includes an amplifier 61 and an input resistor 6
2, integrating capacitor 63, switch 64, voltage follower 6
5 is a circuit for integrating an input signal.
When the switch 64 is turned on, the charge of the integrating capacitor 63 is discharged. Integration voltage Vi between terminals of integration capacitor 63
Is output to the ADC 70 via the voltage follower 65. A
The DC 70 converts the integrated voltage Vi into a digital value and
Output to 80.

A readable and writable volatile memory 81 (hereinafter referred to as a RAM) is used for calculation of the CPU 80 and a temporary storage of count values and flags, and a readable non-volatile memory 82 (hereinafter referred to as a ROM). , CP
Used to store U80 programs and data.

Next, the operation of the circuit according to the embodiment of the present invention will be described. When entering this distance measurement routine, first, the power supplies of all the circuits in FIG. 1 are turned on. Next, the contents of the RAM 81 are cleared, and optimal gains of the amplifier circuits 40 and 50 are determined. If it is determined that the subject is very close or the reflected light from the subject is very large during the operation of determining the gain, the closest flag Fn in the RAM 81 is set. Without performing this, it is determined that the distance is closest, and the value X is set to 1. Then, the distance is measured by the first current-voltage conversion circuit 20, and the value Xf given by the following equation (1) is calculated by R
Store it in the appropriate address of AM81.

Xf = Nf · V3 / Vi (1) Then, the distance is measured by the second current-voltage conversion circuit 30 and the value Xn given by the following equation (2) is stored in an appropriate address of the RAM 81.

Xn = Nn · V3 / Vi (2) When it is determined that the subject is very far or the reflected light from the subject is very small during the execution of the first and second distance measurement. Since the infinity flag Ff in the RAM 81 is set, in this case, it is determined to be infinity, and the value X is set to 0.5. When the distance measuring operation is completed, the infinity flag and the close distance flag Fn are set if the infinity flag Ff is set.
Is set, RAM is set if none is set
Using the number of times Nf and Nn stored in 81, a value X given by the following equation (3) is calculated.

X = Xf / (Xf + Xn) (3) When the value X is determined, the ROM 8 uniquely determined by the value X is determined.
With reference to the address 2 (FIG. 6), the distance to the subject is obtained. Finally, after controlling the motor 83 to drive the lens barrel 84 to the in-focus position, the power supply of the distance measuring circuit is turned off, and the routine exits.

Next, the operation of determining the gain of the first amplifier circuit 40 and the second amplifier circuit 50 will be described in detail with reference to FIG. First, the CPU 80 turns the switch 4 on to the current-voltage conversion circuit 20 side. Then, the switch 64 is turned on to discharge the electric charge accumulated in the integration capacitor 63 (FIG. 2A). After sufficiently discharging the electric charge, the switch 64 is turned off (FIG. 2B), and the clear signal CR is generated and the number Nf of times is increased.
Is cleared to 0 (c in FIG. 2). Then, the CPU 80 operates the light emitting circuit 10 to generate the light emitting signal EM and
D14 is driven to start light emission (d in FIG. 2). In order to secure the rise time of each amplifier at the start of light emission and reduce the influence of power supply fluctuation, the switch 7 is turned on after the time T1 has elapsed after light emission, and integration is performed only during the time T2 (FIG. 2). e). When it is over, stop the light emission and switch 7
Is turned off (f in FIG. 2), and waits for a time T3, generates a count-up signal CU and adds 1 to the number Nf (g in FIG. 2).

The above operation is performed a predetermined number of times N
g (for example, 10 times), the voltage between the terminals of the integration capacitor 63, that is, the integration voltage Vi is changed to the ADC 70.
The ADC 70 converts the result into a digital signal and outputs it to the CPU 80. The CPU 80 includes the ADC 7
If the output of 0 is higher than the voltage V1 (h in FIG. 2), the switch 46 is turned on (i in FIG. 2). If the output is equal to or lower than the voltage V1, it is considered that the optimum gain has been reached. Similarly,
The integration operation and the comparison operation are repeated. If the output of the ADC 70 is higher than the voltage V1, the switches 56, 47, and 57 are turned on in this order. If the voltage is still higher than the voltage V1 even if all the switches are turned on, the close flag Fn is set. Thus, the gain of the entire amplifier circuit is determined. FIG. 3 shows a case where an optimum gain is obtained in the fourth gain determination operation, that is, in a state where the switches 46, 56, and 47 are turned on.

Next, the distance measurement by the first current / voltage conversion circuit 20 will be described in detail with reference to FIG. First, the switch 4 is turned on to the current-voltage conversion circuit 20 side (a in FIG. 4).
Next, the switch 64 is turned on to discharge the electric charge accumulated in the integration capacitor 63, and then the switch 64 is turned off (b in FIG. 4). Thus, the potential difference between both ends of the integration capacitor 63 becomes zero. Then, the clear signal CR is generated and the number of times N
Clear f to 0 (c in FIG. 4). Then, the CPU 80 operates the light emitting circuit 10 to generate a light emitting signal EM and
The ED 14 is driven to start light emission (d in FIG. 4). In order to secure the rise time of each amplifier at the start of light emission and reduce the influence of power supply fluctuation, the integration circuit is operated only for the time T2 after the time T1 has elapsed after the light emission (e in FIG. 4). After that, the light emission / integration is stopped (f in FIG. 4), and the apparatus stands by for a time T3, generates a count-up signal CU, and adds 1 to the number Nf (g in FIG. 4). Subsequently, the number of times Nf
Does not reach the number of times Nfm (for example, 300 times) and the integrated voltage Vi does not reach the voltage V3, the CPU 80 adds the number of times Nf while repeating the above operations of FIGS. If the integrated voltage Vi does not reach the voltage V2 even after the number of times Nfm has been reached, the RAM 81
Set the middle infinity flag Ff, and if it has reached the value Xf
Is calculated and the processing ends. Even if the number Nf has not reached the number Nfm, if the integrated voltage Vi has reached the voltage V3 (h in FIG. 4), the value Xf is calculated again and the processing is terminated.

Similarly, the second current-voltage conversion circuit 30 measures the distance. First, the switch 4 is connected to the current / voltage conversion circuit 30.
Is turned on (i in FIG. 4). Next, the switch 64 is turned on (j in FIG. 4) to discharge the electric charge accumulated in the integration capacitor 63, and then the switch 64 is turned off (k in FIG. 4). Then, a clear signal CR is generated to clear the number Nn to 0 (l in FIG. 4). Subsequently, the number of times Nn is added while repeating the light projection (m in FIG. 4), and the number of times Nn reaches the number of times Nnm (for example, 700 times) or the integration voltage Vi.
Until the voltage reaches the voltage V3, and as a result, the value Xn
Or set the infinity flag Ff and terminate.

FIG. 5 shows the movement of the main part during a series of operations from the start of the gain determination operation of the amplifier circuits 40 and 50 described above to the end of the distance measurement by the second current-voltage conversion circuit.
The timing chart is shown in FIG.

The above is the operation of the circuit in this embodiment. FIG. 7 to FIG.
It will be like 0. First, the main routine will be described with reference to FIG. When entering the distance measuring routine, the CPU 80 turns on the power of the entire distance measuring circuit (# 001) and sets each switch (# 002). Next, the contents of the RAM 81 are cleared (# 003). Then, the amplification circuit 40 and the amplification circuit 5
A gain of 0 is determined (# 004), the state of the close flag Fn is confirmed (# 005), and if the close flag Fn is set, the value X is set to 1 (corresponding to the closest).
(# 006) Jump to # 013. If one has yet to be set close flag Fn, and the distance measurement in the first current-voltage conversion circuit 20 (# 00 7), then infinity flag F
The state of f is confirmed (# 008), and if set, the value X is set to 0.5 (corresponding to infinity) (# 00).
9) Jump to # 013. Subsequently, the distance is measured by the second current-voltage conversion circuit 30 (# 010), the state of the infinity flag Ff is confirmed (# 011), and if it is set, the value X is set to 0.5 (corresponding to infinity). (# 0)
09), jump to # 013.

A value X is calculated from the values Xf and Xn obtained by the operations of the subroutines # 007 and # 010 (# 01
2). As a result, the ROM 82 uniquely determined by the value X
Find the distance to the subject by referring to the address of (#
013). After the motor 83 is controlled to drive the lens barrel 84 to the in-focus position (# 014), the power of the distance measuring circuit is finally turned off (# 015), and the process exits from this routine.

Next, the operation in each subroutine will be described. First, the amplification circuit (amplification circuit 40, amplification circuit 5
The subroutine of 0) gain determination will be described with reference to FIG. When the CPU 80 enters the subroutine for determining the gain of the subsequent amplification circuit, the CPU 80 switches the switch 4 to the current-voltage conversion circuit 20.
Side (# 101), and clears the number Ns to 0 (# 101).
102), the switch 64 is turned on to discharge the electric charge accumulated in the integration capacitor 63, and then the switch 64 is turned off (# 103). The clear signal CR is generated to clear the number Ne to 0 (# 104).

Subsequently, the CPU 80 generates a light emitting signal EM, operates the light emitting circuit 10 and starts emitting light (# 105).
When the operation waits for the time T1 (# 106), the switch 7 is turned on, and the operation waits for the time T2 while performing the integration operation (# 107). During this time, charge is stored in the integration capacitor 63 (# 108). Then, the operation of the light emitting circuit 10 is stopped to end the light emitting operation, the switch 7 is turned off and the integrating operation is finished (# 109), a count-up signal CU is generated and 1 is added to the number Ne (# 110). . If the number Ne is less than the predetermined number Ng, the process jumps to # 105 (# 111). CP when the number Nf reaches the number Ng
U80 turns off the switch 7 and reads the integrated voltage Vi through the ADC 70 (# 112). The CPU 80 compares the integrated voltage Vi with the voltage V1 (# 113), and returns to the main routine if the voltage is equal to or lower than the voltage V1.

When the integral voltage Vi is higher than the voltage V1, if the number Ns is 0 (# 114), the switch 46 is turned on (# 115). If the number Ns is 1 (# 116), the switch 56 is turned on (# 117). ), If the number Ns is 2 (# 11
8), the switch 47 is turned on (# 119), and if the number Ns is 3 (# 120), the switch 57 is turned on (# 121), and 1 is added to the number Ns (# 122), and # 10
Return to 3 . If the number Ns is not any one of 0 to 3, the close flag Fn is set (# 12 3 ), the process exits this subroutine, and returns to the main routine.

Next, a subroutine for calculating the value Xf by the first current / voltage conversion circuit 20 will be described with reference to FIG. When the subroutine of the distance measurement by the current / voltage conversion circuit 20 is started, the switch 4 is turned on to the first current / voltage conversion circuit 20 side (# 201), the clear signal CR is generated and the number of times N is increased.
f is cleared to 0 (# 202), the switch 64 is turned on to discharge the electric charge accumulated in the integration capacitor 63, and then the switch 64 is turned off (# 203).

Subsequently, the CPU 80 outputs the light emitting signal EM, operates the light emitting circuit 10 and starts emitting light (# 204).
When waiting for the time T1 (# 205), the switch 7 is turned on to perform the integration operation (# 206), and then waits for the time T2 (# 207). During this time, charge is stored in the integration capacitor 63. Then, the operation of the light emitting circuit 10 is stopped to end the light emitting operation, the switch 7 is turned off and the integrating operation is ended (# 208), and a count-up signal CU is generated and 1 is added to the number of times Nf (# 209). . Here, the number of times Nf is N
fm (# 210). If the number Nf is greater than Nfm, the integrated voltage Vi is compared with V2 (# 211). If the integrated voltage Vi is smaller than V2, the infinity flag Ff is set (# 212). Value Xf if equal to or greater than Vi
Is calculated (# 213), and the process returns to the main routine. Number N
If f is smaller than Nfm, the CPU 80 sets the integrated voltages Vi and V
3 and compares the (# 214), the integration voltage Vi is jump to # 20 4 If V3 less, greater than the voltage V 3 calculates a value Xf (# 213), the flow returns to the main routine.

Next, a subroutine for calculating the value Xn by the second current / voltage conversion circuit 30 will be described with reference to FIG. When a subroutine for distance measurement by the current-voltage conversion circuit 30 is entered, the switch 4 is turned on to the second current-voltage conversion circuit 30 (# 301), a clear signal CR is generated, and the number Nn is cleared to 0 (##). 302), the switch 64 is turned on to discharge the electric charge accumulated in the integration capacitor 63, and then the switch 64 is turned off (# 303).

Subsequently, the CPU 80 outputs a light emitting signal EM, operates the light emitting circuit 10 and starts emitting light (# 304).
After waiting for the time T1 (# 305), the switch 7 is turned on to perform the integration operation (# 306), and then waits for the time T2 (# 307). During this time, charge is stored in the integration capacitor 63. Then, the operation of the light projecting circuit 10 is stopped to end the light projecting operation, the switch 7 is turned off, the integration operation is finished (# 308), the count-up signal CU is generated, and 1 is added to the number Nn (# 309). . Here, the number Nn is N
nm (# 310). If the number Nn is greater than Nnm, the integrated voltage Vi is compared with V2 (# 311). If the integrated voltage Vi is smaller than V2, the infinity flag Ff is set (# 312). Value Xn if equal to or greater than V2
Is calculated (# 313), and the process returns to the main routine. Number N
If n is not larger than Nnm, the CPU 80 sets the integrated voltage V
i is compared with V3 (# 314), and the integrated voltage Vi is V3
It jumps to # 30 4 equal to or less than, greater than V3 to calculate the value Xn (# 313), the flow returns to the main routine. With the above operation, the distance to the subject is measured.

In the above embodiment, the number of times Nfm and Nnm and the voltage V3 are fixed.
By setting a small value or setting the voltage V3 to a low value, a faster distance measurement can be performed, so that the time from when the release switch is turned on to when the shooting is performed is shortened, and the speed of the continuous shooting can be increased. Integral power to end ranging
The pressure can be changed, so it is higher for normal shooting
In the case of continuous shooting, set the
More appropriate shooting can be performed according to the situation.

[0030]

According to the camera distance measuring apparatus of the present invention, the integration
If the output voltage of the circuit exceeds a first predetermined voltage and
Light emission operation when the output value of the counting means exceeds a predetermined value.
Is completed, and the output value of the counting means exceeds a predetermined value.
When the light emission operation is completed with
When the output voltage has reached the second predetermined voltage,
And the ratio of the output voltage of the integrating circuit to the predetermined voltage at
Distance signal that fluctuates according to the output value of the
Since obtaining, possible to prevent the distance measurement time is longer than necessary
Can be. Therefore, the entire distance measurement time can be shortened, which is advantageous for a photo opportunity.

Further, the output voltage of the integrating circuit is a predetermined voltage.
Exceeding or the output value of the counting means exceeds a predetermined value
The light emission operation is terminated when the
Of the output voltage of the integrating circuit to the output of the counting means
Obtain a distance signal that fluctuates according to the calculated value.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an operation diagram illustrating an integration operation according to the embodiment of the present invention.

FIG. 3 is an operation diagram illustrating a series of operations when determining a gain according to the embodiment of the present invention.

FIG. 4 is an operation diagram illustrating a method of calculating the number of times Nf and Nn according to the embodiment of the present invention.

FIG. 5 is an operation diagram illustrating a series of operations at the time of distance measurement according to the embodiment of the present invention.

FIG. 6 is a ROM for calculating a distance from a value X according to the embodiment of the present invention;
82 is a table.

FIG. 7 is a flowchart showing the operation of the embodiment of the present invention.

8 is a flowchart showing a subroutine of a part for determining a gain of the amplifier circuit 40 and the amplifier circuit 50 in the flowchart of FIG. 7;

9 is a flowchart showing a subroutine of a distance measurement part by the first current / voltage conversion circuit 20 in the flowchart of FIG. 7;

FIG. 10 is a flowchart showing a subroutine of a distance measurement part by the second current / voltage conversion circuit 30 in the flowchart of FIG. 7;

[Explanation of symbols]

 Reference Signs List 3 PSD 10 Floodlight circuit 14 IRED 20, 30 Current / voltage conversion circuit 40, 50 Amplification circuit 60 Integration circuit 80 Operation circuit (CPU)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-908 (JP, A) JP-A-4-353713 (JP, A) JP-A-61-289313 (JP, A) JP-A-59-1985 201007 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B ^7/ 28-7/40 G03B 3/00-3/12

Claims (1)

(57) [Claims] 1. A light projecting means for irradiating a subject with pulsed light, and a light emitted from the light projecting means reflected by the subject is received.
A semiconductor position detection element ; a current-voltage conversion circuit that converts an output current of the semiconductor position detection element into a voltage; an amplification circuit that amplifies an output signal of the current-voltage conversion circuit; and an integration that integrates an output signal of the amplification circuit. A circuit; a counting means for counting the number of light projections of the light receiving means; and if the output voltage of the integration circuit exceeds a first predetermined voltage or the output value of the counting means exceeds a predetermined value, Ends the light emission operation and outputs the output of the counting means.
When the value exceeds the predetermined value, the light emitting operation ends.
The output voltage of the integrating circuit at that time
A distance which varies according to a calculated value of a ratio of an output voltage of the integration circuit to the first predetermined voltage at the time when the voltage has reached a predetermined voltage and an output value of the counting means. A distance measuring device for a camera, comprising: arithmetic means for obtaining a signal.