JPS62156631A - Auto-fucusing device for camera - Google Patents

Abstract

PURPOSE:To control the light emission in a wide range with good responsiveness by simple constitution, by controlling the light emission of a light emission body with the quantity of light proportional to the charging voltage of a capacitor controlled with a switch. CONSTITUTION:When a switch SW3 is turned off and a switch SW2 is turned on, the electric charge from a power source VCC charges a capacitor C through a resistance R11 and the witch SW2. When the switch SW2 is turned off and the switch SW3 is turned on, the electric charge of the capacitor C is discharged through a resistance R12. An operational amplifier U10, resistances R14 and R15, and transistors Q1 and Q2 constitute a constant current circuit; and when the switch SW1 is turned on, the voltage charged in the capacitor C is applied to this constant current circuit, and an infrared LED 1 is lit by the output current. Its light is projected to an object, and the reflected light is detected and is subjected to the operation processing, and the focus of a lens system is controlled automatically in accordance with the result.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic focus adjustment device for cameras, and more particularly, to an automatic focus adjustment device for cameras that controls the luminescent mold of a light emitter in proportion to the charging voltage of a capacitor. The present invention relates to an automatic focus adjustment device.

(Prior Art) In recent years, autofocus cameras and autofocus video cameras have been developed, making it much easier to create spiral shapes.
Bokeh image detection method that detects the sharpness of the subject image, left and right 2
A double image coincidence detection method that detects the shape of two objects to be measured, or an upper and lower image coincidence detection method, uses the reflected light of the light beam emitted toward the object to be measured, and calculates the angle of the triangle from the baseline length and viewing angle.
Various methods are known, such as the ray distance method, which calculates distance using formulas.

FIG. 6 shows the principle of distance measurement using the ray distance method, in which a narrow beam of infrared rays is projected onto a subject 3 through a projection lens 2 from an infrared light emitting diode 1 driven by a pulse modulation method. The infrared beam reflected from the object 3 passes through the light receiving lens 4 and is received by the optical position detector 5 as a spot light.

As shown in FIG. 7(a), the optical position detector 5 is a photodiode which is connected to two electrodes P+ and P2 at 1a and has photoelectric ratio output terminals 5a and 5b and a common terminal (~terminal 5C). The deviation d of the infrared spot light from the position center P on the optical position detector 5 is the distance from the light emitting lens 2 to the subject 3, and the focal length of the light receiving lens 4 is "," .4 distance between optical axes (called baseline length)
If S is (1=SX(f,/L)
...(1), and it can be seen that the imaging position of the infrared spot light changes depending on the distance to the subject 3. on the other hand,
The magnitude of the photocurrent II, +2 output from the output terminals 5a, 5b of the optical position detector 5 changes depending on the position of the infrared spot light (τ), and is expressed by the following relational expression.

Here, C is the effective length of light receiving by the optical position detector 5.

It”-(C/2)-d=(c/2>-(
f S/L)...(2) 12 K <,C,'2>+d = (C/2)+ (
f S/L)...(3) ,', 11/12 = ((c/2>+(f S/L))
/((c/2) −(f S/L))=((c
L/2>+f S)/((c L/2)-f S)...(4) This relationship is illustrated in Figure 7 (b), r 2
It can be seen that /I + is approximately proportional to 1/L.

As can be seen from the above formula, I2/■l is determined only by the base line length S, the focal length r of the light receiving lens 4, and the light receiving surface length C of the optical position detector 5, so it is determined by the difference in reflectance of the subject and the infrared light emitting diode. [1] Spots due to deterioration over time, etc.] - Distance measurement becomes possible regardless of the strength of light. Furthermore, as can be seen from FIG. 7(b), the smaller the distance to the subject, the greater the output value and the greater the change, allowing for highly accurate distance measurement.

(Problem to be solved by the invention) In this way, the optical distance measuring method performs distance measuring purely electrically and does not require any mechanical mechanism or operation, making it compact and highly reliable. However, in a ranging system as shown in Fig. 6,
When the light component of the infrared light emitting diode 1 is held constant, the received light ff1Q of the optical position detector 5 is expressed by the following equation.

Q(γ/L2) Here, γ is the reflectance of the subject (5 to 100%). Now, even if the distance to the subject 1) nL is 1 to 10 m, the received light fiQ is 1/103, which is a very wide range. Because it changes over the range, the front-stage amplification of the optical position detector 5 should not be logarithmically compressed (
You have to pull it.

Therefore, the distance measurement output becomes /Nlz/It, which is not simply proportional to 1/L. Therefore, in order to move the photographing lens continuously like in a video camera, the amount of extension is calculated from the distance measurement output. 41 is required, and there is a conversion circuit for that! There is a problem that it becomes cluttered.

Furthermore, since the amount of light emitted from the infrared light emitting diode is constant, there is also the problem that a constant amount of power is always consumed.

Therefore, the applicant would like to propose an automatic focus adjustment device as shown in FIG. 8 (Japanese Patent Application No. 60-66537). This device consists of a ranging system A and a lens control system B J')11 as shown in the figure.
It is composed of The operation of this device will be explained below.

The infrared light emitting diode 1 is driven by a light emission control circuit 10 to emit light. This emitted light is focused by the projection lens 2 and then irradiated onto the subject 3. After the reflected light from the subject 3 is focused by the light receiving lens 4, it is transmitted to the optical position detector 5.
Tie a spot light on top. The optical position detector 5 outputs currents 1t and 12 that contradict each other depending on the position of the spot light.

These currents 11. T2 enters the light receiving circuit 6.7 and is converted into corresponding voltage signals Vl and V2. The voltage signals V+ and V2 enter a subtraction circuit 8 and an addition circuit 9. The subtraction circuit 8 outputs a ranging signal (VI V2), and the addition circuit 9 outputs a signal (V1+V2) corresponding to the amount of received light.

Here, the output of the subtraction circuit 8 enters the subtraction circuit 11 of the lens control system B, and is compared with the lens extension signal Y from the position sensor 16 that detects the lens position. Subtraction circuit 1
1 is the ranging signal (VI V2) and lens extension ff1
The difference from Y is output and applied to the window comparator 12.

First, the focusing operation of lens control system B will be explained. The window comparator 12 determines whether the deviation output of the aperture reduction circuit 11 is within an allowable range, and outputs a binary signal according to the determination result.

The motor drive circuit 13 receives the binary signal from the window comparator 12 and outputs a motor drive signal. The motor 14 rotates in a predetermined direction in response to this motor drive signal, and moves the focusing lens 15 in the direction of the arrow in the figure. When the focusing lens 15 moves, the position sensor 16 moves the lens ff in conjunction with the lens.
Change 1Y. The changed Y enters the subtraction circuit 11 again, and the above-described focusing operation is repeated. Ultimately, the focusing operation ends when the output (deviation) of the subtraction circuit 11 falls within a predetermined tolerance range.

Next, the Hokukyun control will be explained. The light emission control circuit 10 controls the amount of light emission. As shown in FIG. 9, the light emission control circuit 10 includes a reduction circuit 10a, an integrator 10b, and a pulse modulation circuit 10c. Output of adder circuit 9 (
■1 +V2) is compared with the reference light quantity vO in the subtraction circuit 10a, and the subtraction circuit 10a outputs the difference @v' between the received light quantity (VI+V2) and the reference light quantity ■0.This difference signal V
r is integrated by the subsequent integrator 10b. The output vg of the integrator 10b enters the pulse modulation circuit 10c, and the pulse modulation circuit 10c performs pulse modulation according to the input signal Vg,
The infrared light emitting diode 1 is driven.

The change in the amount of received light results in a change in the (V, +V2) signal, which enters the light emission control circuit 10 again, and the above-described light emission control operation is repeated. Finally, (V1+V2) and V
It becomes stable when o becomes equal.

FIG. 10 is an electric circuit diagram showing a specific example of the configuration of the light emission control circuit 10. The reference light amount 0 is created by dividing the (V+ ↓V2) signal and the voltage VCC using the voltage dividing resistor 20.
The integrator 21 integrates the difference between the two.

This integral output v9 is passed through an externally controlled on/off switch 22 to an amplifier circuit 23 consisting of an operational amplifier U.
The positive input of is marked +Jn. The output of the amplifier circuit 23 is connected to a current boost circuit 24 consisting of Darling-connected transistors, and the infrared light emitting diode 1 is driven by the current boost circuit 24.

Resistor R connected between the positive input terminal of operational amplifier U and ground
2 is for making the input Ov when the switch 22 is off, and the diode D connected between the output of the operational amplifier U and the ground is for clamping the output so that it does not become negative.

Also, a resistor R connected between the current boost circuit 24 and ground
3 is a voltage-current conversion resistor. The potential at the connection point between the resistor R3 and the current boost circuit 24 is fed back to the negative input terminal of the operational amplifier U, and the operational amplifier U, the current boost circuit 24, and the resistor R3 constitute a constant current circuit.

Assuming that the voltage applied to the positive input of the operational amplifier U is Vs, and that R3 is used as it is as the resistance value of the voltage-current conversion resistor R3, the current 2 of the constant current circuit is expressed as 1=Vs/R3-(5). This current I flows through the infrared light emitting diode 1, which emits light. Here, when the switch 22 is turned on and off by external control, a current I flows intermittently through the infrared light emitting diode 1, causing pulsed light emission. It can be seen from the above equation that the light emission can be varied by changing VS.

As mentioned above, the light emission control circuit shown in FIG.
+V2> is compared with the voltage division level 0 of the voltage division resistor 20, and the difference is integrated by the integration 'A21, and the output voltage v9 is taken as the brightness level of the next light emission. However, (v
The signal I+V2) must be a trapezoidal or triangular waveform, while its integral output V9 must be a DC waveform. Therefore, in order for 7g to become a constant voltage, its level must not fluctuate. Therefore, the integration time constant CIR of the integrator 21
It is necessary to make the time constant of I sufficiently large.

However, when the time constant @CtR+ becomes large, the response of light amount control becomes slow. Furthermore, digital control using a microcomputer is difficult.

The present invention has been made in view of these points, and
The purpose is to realize an automatic focus adjustment device for a camera that can perform light emission control over a wide range and with good responsiveness using a simple circuit.

(Means for Solving the Problems) The present invention, which solves the problems described above, illuminates a subject with a light emitter, receives and detects the reflected light, and performs predetermined arithmetic processing to automatically focus the lens system. The automatic focus adjustment device for a camera to be adjusted is equipped with a light emission control circuit that controls charging and discharging of a capacitor using a switch, and controls the light emission of the light emitter with light proportional to the charging voltage of the capacitor. This is a characteristic feature.

(Function) The present invention utilizes charging and discharging of a capacitor to vary the voltage and control light emission.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. Components that are the same as those in FIG. 8 are designated by the same numbers. 3
1 is a Δ,/[) converter that converts the output v1°Vl of the light receiving circuit 6.7, the output of the light emission control circuit, and the lens detection amount signal of the position sensor 16 into digital data, respectively; 32 is the A/D converter 31; It is a microcomputer that receives output data, performs various arithmetic processing, and outputs a light emission amount control signal to the light emission control circuit 10 and a lens control signal to the motor drive circuit 13. The operation of the device configured as described above will be explained as follows.

The light receiving signal V+ converted into current and voltage by the light receiving circuit 6.7,
Vl is converted into digital data by the A/D converter 31 and sent to the microcomputer 32. The microcomputer 32 converts Vl and V into digital values.
For example, (VI − Vl ), (Vl +
V2) is calculated.

First, the focusing operation of the device (not shown) will be explained. The lens extension ffi signal detected by the position sensor 16 is
After being converted into digital data by the A/D converter 31, it is sent to the microcomputer 32. The microcomputer 32 sends a lens control signal to the motor drive circuit 13 so that the flea's (VI Vz) e distance measurement signal Toshi, Ko (7) (Vi Vl) and the lens extension group signal of the position sensor 16 are equal. give. As a result, the motor drive circuit 13 drives the motor 14 to move the focusing lens 15 in the direction of the arrow in the figure. When the focusing lens 15 moves, the position sensor 16
changes the position signal (lens extension signal). The changed lens extension amount signal enters the A/D converter 31 again and is converted into digital data, after which it is compared with (VI Vl) by the subsequent microcomputer 32. This sequence is repeated to obtain R reduction (VI
When the lens extension amount signal (Vl) and the lens extension amount signal match, a focused state is reached.

Next, the light emission control circuit will be explained. As described above, the microcomputer 32 calculates (V, +V2), and this (Vl +V2) corresponds to the amount of spot light received by the optical position detector 5. Therefore, this (V
The amount of received light can be determined from 1+V2). The microcomputer 32 compares this (Vl +V2) with the reference light ffiVo, and sends a light emission control signal according to the comparison result to the light emission control circuit 1°. The light emission control circuit 10 drives the infrared light emitting diode 1 according to an input control signal.

FIG. 2 is an electrical circuit diagram showing a specific example of the configuration of the light emission control circuit 10. In the figure, the power supply voltage VcC is the resistance R++
is connected to R++, and the other end of R++ is an on/off switch SW
2, and the other end of S W 2 is an on/off switch S
The other end of S W 3 is connected to resistor R12, and the other end of R12 is grounded. An on/off switch S W l is connected between the ten terminal of the operational amplifier U + o and the connection point of S W 2 and SW3. A charging/discharging capacitor C is connected between one end of the switch S W r and the ground.
is connected between the other end of switch SW1 and ground.
A grounding resistor R13 is connected to hold the positive input of the operational amplifier U+o at O■ when the output voltage 1 is off. These switches SW 1 to SW 3 are turned on and off by control signals from the microcomputer 32 described above.

The output of the operational amplifier U+o is connected to the transistor Q1. It is connected to a Darlington connected transistor circuit for current booths 1 to Q2. A current-voltage conversion resistor RI5 is connected between the emitter of the output stage transistor Q2 and ground. and,
The potential at the connection point between the emitter of Q2 and R15 is fed back to the output of the operational amplifier U+o. The collectors of the commonly connected transistors Q1 and Q2 are connected to the cathode of the infrared light emitting diode 1, and the anode of the infrared light emitting diode 1 is connected to the power supply voltage Vcc.

The operation of the circuit configured as described above will be explained as follows.

When charging the capacitor C, the switch S W B is turned off and the switch S W Z is turned on. As a result,
Charge from the power supply flows into the capacitor C via the route of the resistor R++→S W z and is charged. When discharging the capacitor C, turn off the switch SW2 and turn off the switch S.
Turn on W3. As a result, the charge stored in the capacitor C is discharged through the resistor R12.

On the other hand, the circuit composed of the operational amplifier UIO, the resistors Rt+, R15, and the transistor circuit has a constant current circuit, and when the switch SWI is turned on, the voltage charged in the capacitor C is applied to this constant current circuit. Now, the voltage of capacitor CIG is Vs.

Let RIs be the resistance value of constant voltage resistor R+s. The output current I of this constant current circuit is given by the following equation similarly to equation (5).

I = V s 7' RIs −
(6) A constant current I expressed by the above equation flows through the infrared light emitting diode 1 and lights the infrared light emitting diode 1.

In this way, by changing the charging voltage Vs of the capacitor C, the lightning (h) value flowing through the infrared light emitting diode 1 can be changed, and the amount of light emitted can be controlled. Note that the charging voltage Vsf of the capacitor C is input to the A/D converter 31, and after being converted into digital data, it is provided to the microcomputer 32. The microcomputer 32 is.

It is determined whether this charging voltage is within the operating range of the operational amplifier U1o, and depending on the determination result, Vs is within the operational range of the operational amplifier U1o.
A constraint is applied to keep the tO within the operating range (details will be described later).

On the other hand, when the switch S W 1 is turned off, the ten inputs of the A amplifier U IQ become 0 potential, Vs=O, and therefore (
According to equation 6), the current ■ becomes O, and the infrared light emitting diode 1 no longer lights up. Here, when the switch S W 1 is turned on and off with the capacitor C charged, the infrared light emitting diode 1 can be lit in pulses. That is,
The number of light emitting pulses can be controlled. FIG. 3 is a diagram showing the state of pulse lighting of the infrared light emitting diode 1. (
A) shows the case where the number of pulses is 4, and (B) shows the case where the number of pulses is 16. The king is the sampling period.

Even if the brightness level is maximum, if the amount of received light is insufficient, the number of light emission pulses is increased as shown in (b). This allows stable light emission control.

The microcomputer 32 sends a control signal to the light emission control circuit 10 configured as described above to control the amount of light emission and the number of light emission pulses. In other words, when <v1+v2)<0, it indicates that the amount of light received is insufficient, so switch SW
2 is turned on for a certain period of time, and the capacitor C is charged W? Increase the pressure and increase the brightness of the next light emission. On the contrary, (Vl +V2
)>VO indicates that the amount of light received is too large, so the switch SW3 is turned on for a certain period of time to lower the charging voltage of the capacitor C and lower the brightness of the next light emission.

Next, control of the number of light emission pulses will be explained. Capacitor C
The A/D converter 31 converts the charging voltage into a digital value and inputs it into the microcomputer 32. As shown in FIG. 4, the microcomputer 32 determines whether this voltage value is within the operating range of the operational amplifier U+o, and if it exceeds the lower limit of the operating range, reduces the number of pulses.
If the upper limit is exceeded, increase the number of pulses. If it is within the operating range, do not change the pulse. FIG. 4 is a flowchart showing the sequence of this light emission amount control.

FIG. 5 is a block diagram showing another embodiment of the present invention. The device shown in the figure uses a comparator instead of the A/D converter 31 in FIG. 1 to convert the signal into a binary signal of 0.degree. In the figure, 41 HaV+, V2
A subtraction circuit 42 receives Vl and V2 and calculates (Vl+V2). The output of the reduction i circuit 42 is connected to the first comparator/
The output of the adder circuit 42 enters the second comparator 44 and is compared with the reference light aVo. The capacitor charging voltage S in the light emission control circuit 10 enters a third comparator 45 and is compared with a reference value (having two values for an upper limit and a lower limit). The outputs of these comparators 43 to 45 are input to the microcomputer 32. Since the subsequent operation is the same as that shown in FIG. 1, the explanation will be omitted.

In the above description, an example is given in which an infrared light emitting diode is used as the light emitter for l13, but any light emitter may be used as long as it is capable of high-speed on/off operation. Further, the light emission control does not necessarily need to be performed by a microcomputer, and may be performed by hard logic having equivalent functions.

(Effects of the Invention) As described above in detail, according to the present invention, the charging and discharging of a capacitor is controlled, and the charging voltage is used to control the light emission of an infrared light emitting diode, thereby making it possible to operate a microwave oven with a simple configuration. Accordingly, it is possible to realize an automatic focus adjustment device for a camera that can perform light emission control over a wide range and with good responsiveness.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention, and FIG.
The figure is an electric circuit diagram showing a specific configuration example of the light emission control circuit, FIG. 3 is a diagram showing the pulse lighting state of the infrared light emitting diode, and FIG. 4 is a flowchart showing the light emission control sequence.
FIG. 5 is a configuration block diagram showing an embodiment of the present invention, FIG. 6 is a diagram for explaining the principle of the conventional distance measuring method, and FIG.
A) is a diagram showing an example of the external configuration of an optical position detector, FIG. 7 (B) is a diagram showing its output characteristics, FIG. 8 is a diagram showing an example of an automatic focus adjustment device, and FIG. 9 is a diagram showing light emission control. FIG. 10 is an electric circuit diagram showing a specific example of the structure of the light emission control circuit. 1... Infrared light emitting diode 2... Light emitting lens 3... Subject 4... Light receiving lens 5... Optical position detector 6.7... Light receiving circuit 8, 41... Subtraction circuit 9.42... Addition circuit 10... Light emission control circuit 11... Subtraction circuit 12... Window comparator 13... Motor drive circuit 14... Motor 15...
-Focusing lens 16...Position sensor 20...Voltage dividing resistor 21.
10b...Integrator 22...Switch 23...Amplification immediate circuit 24...Current boost circuit 31...Δ/D converter 32...Microcomputer 43-45...Comparator 10a...Subtraction Device 10C... Pulse modulation circuit R1-R3, R+ +~R+5... Resistor S W l~
S W 3... Switch C, Cl... Capacitor U, Ulo... Operational amplifier D... Guio 1~2 Figure 3

Claims (1)

[Claims] A switch is used to control the charging and discharging of a capacitor in an automatic camera focus adjustment device that illuminates a subject with a light emitter, receives and detects the reflected light, and performs predetermined calculation processing to automatically adjust the focus of the lens system. An automatic focus adjustment device for a camera, comprising: a light emission control circuit that controls light emission of the light emitter with a light amount proportional to the charging voltage of the capacitor.