JPS59193308A - Distance detection system using differential type sensor - Google Patents

Abstract

PURPOSE:To obtain a focus detection signal with an improved S/N ratio by a simple circuitry by connecting a differential type photoelectromotive type optoelectric conversion element in opposite polarity between input terminals of an arithmetic amplifier to obtain a differential output signal employing one arithmetic amplifier only. CONSTITUTION:Differential type photoelectromotive type optoelectric conversion elements DS1 and DS2 are connected to the input of an arithmetic amplifier OP30 in opposite polarity to amplify the output signal of difference. The output of the OP30 is integrated with a synchronous integration circuit SI3 synchronizing the projection to drive a photographic lens in the direction of focusing through a control circuit CKT. The output difference between the elements DS1 and DS2 is small with the projection spot located near the focusing, the output of the synchronous integration circuit SI3 is limited between reference voltages determined by resistances R33-R35 so that outputs of comparators CP30 and CP31 are both at a high level to invert the output of an AND gate AN1 to a high level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of projecting light onto a subject and detecting distance based on reflected light.

Conventional light is projected onto the subject, the reflected light is detected by two photoelectric conversion elements, each of the detection outputs is AC amplified, and integrated in synchronization with the light emission, and the distance to the subject is detected based on each integration result. A method to do this is known.

This known method requires a complex circuit and is expensive.

The present invention provides a method for solving these problems, in which differential photovoltaic photoelectric conversion elements are connected in series or parallel with opposite polarity between the input terminals of an operational amplifier, and a feedback path is connected between the input terminals of an operational amplifier. T, which is a network consisting of resistors and capacitors,
The present invention proposes a method in which a differential output signal is obtained using a single operational amplifier by arranging a type low-pass filter. The present invention also presents a means for determining whether or not a subject is within a distance detectable range by disposing the differential photoelectric conversion element as the switching means and controlling it at a predetermined cycle only when the output difference of the differential photoelectric conversion element is small. It is something.

The present invention will be specifically described below with reference to the drawings. FIG. 1 is a diagram showing the principle of distance detection in which light is projected onto a subject and reflected light is received by a differential sensor.

LE is a light emitting light source for projecting light, and LNl is a projecting lens, which projects a spot onto the objects OBI and OB2. A reflected light spot from the subject passes through the light receiving lens LN2 to the differential sensor DS1. Images are formed on spl and sp2 on DS2.

When a photographing lens (not shown) is at the focusing position, the reflected light spot is located at the center SP1 of the differential sensors DSI and DS2. Also, when the subject is within the distance detection range, the reflected light spot is a differential type sensor? It is configured to be located on DS 1 and DS2.

Figure 2 shows a distance detection circuit using a conventional differential sensor.The outputs of the differential sensors DS1 and DS2 are operationally amplified by 50
P10,0P20, resistance RIO-R12゜R20~R2
2. AC amplification is carried out through an AC amplifier circuit consisting of capacitors t010 and 020, and a synchronous integration circuit s'r1 is generated in synchronization with the light emission of the light emitting element LE, which is controlled to emit light by the transistor Tri, which is controlled on and off by the oscillation of the oscillator O8C.
, 0PiQ in sr2.

The output of 0P20 is synchronously integrated.

Synchronous integration circuit S11. The output of SI2 is compared by comparison circuit CP1, and based on the comparison result, the photographing lens is driven in the focusing direction via control circuit GKT.

In this case, two AC amplifier circuits and a synchronous integration circuit are required, and the disadvantage is that the circuit is not complicated, and it is difficult to match the characteristics of the amplifier circuits, requiring various adjustments.

This application presents a method to overcome these shortcomings.

Figure 6 shows a distance detection circuit using a differential type sensor according to the present invention, and Figure 4 is a timing chart of the main parts of Figure 6. Differential photovoltaic photoelectric conversion element DS1. DS2 is connected with the opposite polarity to the operational amplifier 0P300A, and the differential output signal is AC amplified via a feedback circuit consisting of resistors R30 to R32 and capacitor 030. The output of 0P60 is integrated in synchronous integration circuit SI3 in synchronization with light projection.

When the projected light spot is near the focus and the output difference between DSI and DS2 is small, the output of the synchronous integration circuit SI3 is also small, and the output of the comparators CP3D and CP31 falls between the reference voltages determined by the resistors R33-R35. Both become high level, and the output of AN1 (and goo) is also inverted to high level.

At this time, even if the subject is very far away and the reflected light from the projected light spot from the subject is weak, the difference in the outputs of DS1 and DS2 will be small in the AC amplifier circuit configured according to the present invention, and there is a possibility that the in-focus state will be misjudged. There is.

In the present invention, the DS1DS is
Only when the output difference between 2 and 0P30 is small, one photoelectric conversion element is separated from the circuit, only the output from the other photoelectric conversion element is discriminated by the level discrimination circuit, and the output from only the other photoelectric conversion element is determined. OD is a frequency divider that divides the output of the oscillator O3G. , the frequency-divided pulses are supplied to CP as count pulses of counter CNT. When the counter CNT fully counts, a carry is generated from the OR terminal. When this carry signal and the output of AND gate ANi are both at high level, the output of AND gate AN2 is inverted to high level, so one shot) O
N generates a one-shot pulse in synchronization with the rising pulse. While this one-shot pulse is at a high level, the analog signal AG1 is turned off via the inverter IN1, so that only the optical signal generated from the photoelectric conversion element DS2 is AC amplified.

When the subject is far away and the reflected light spot of the projected light is weak, the output signal of DS2 is also small, so the source power of op30 is small, and the comparator 0P30. CF3I becomes high level due to light and AND gate AN1. The transistor Tr2 is turned on via AN3 while the one-shot ON is at a high level, and the warning display element LD emits light to display a warning to the photographer.

Furthermore, Fig. 5 is an example of the connection of the photoelectric conversion element shown in Fig. 6, and Fig. 6 is another example of the feedback circuit shown in Fig. 6, and the operation and effect are almost the same as in Fig. 3. If the present invention is used as shown in 0 or more, good S/S/
There is a remarkable feature that N focus detection signals can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of the distance and attitude detection method of the present invention. Figure 2 is a conventional circuit diagram. FIG. 6 is a circuit diagram of an embodiment of the present invention. FIG. 4 is an output waveform diagram in an embodiment of the present invention. 5 and 6 are circuit diagrams of other embodiments of the present invention. DSl/DS2... Differential photovoltaic photoelectric conversion element 0P60... Operational amplifier CF2O, CF3I... Comparator

Claims (1)

[Claims] (1) Differential photovoltaic photoelectric conversion elements are connected in series or parallel with opposite polarity between the input terminals of an operational amplifier, and the return path of the operational amplifier is composed of a resistor and a capacitor. Distance detection method using a differential sensor characterized by disposing a filter network 0 ■ A switching means is disposed in series or parallel with the differential photovoltaic photoelectric conversion element, and a predetermined period is set. A distance detection method using a differential sensor according to claim 1, wherein the switching means is controlled by: (6) Claim 0, characterized by comprising means for determining whether or not the subject is within a distance detectable range based on the output of the switching means controlled at the added period. Distance detection method using the differential type sensor described. (4) When the subject is not within the distance detectable range, the warning display means is driven.
Distance detection method using a differential sensor described in section 6). (5) Distance by the differential type sensor according to claim (1), characterized in that the switching means is controlled at a predetermined period only when the output difference of the differential photoelectric conversion elements is small. Detection method 0