JPH01244310A - Distance detecting device for camera - Google Patents

Abstract

PURPOSE:To perform the measurement of distance efficiently and with good reliability, by obtaining a plurality of measured distance data through the generation of lights from a light emitting element by two or more times and determining whether the measurement is continued thereafter, on the basis of the identity of said data. CONSTITUTION:A light emitting element 1 and a light receiving element 2 are spaced a predetermined distance L. A driving circuit 4 for driving the light emitting element is controlled by a control signal from a microcomputer 3, so that the element 1 generates light singly to project the same to an object S to be photographed. The light receiving element 2 receives the light reflected by the object S and inputs to the microcomputer 3 through a distance measuring circuit 7. A distance adjusting mechanism A is controlled by an output of the microcomputer 3. In this construction, the light emitting element 1 is so designed as to generate light by two or more times during the distance measuring occasion thereby to obtain a plurality of data of the measured distances. The microcomputer 3 checks the identity of the data. If the data are identical with each other, the measuring number of times is reduced. On the contrary, if the data are not identical, the measuring number of times is increased.

Description

TECHNICAL FIELD The present invention relates to a device that projects light onto a subject and detects the distance to the subject based on the reception position of reflected light.

(Prior art) To detect distance in a camera, a light emitting element and a light receiving element are arranged at a certain distance, the light from the light emitting element is projected onto the subject, and the reflected light is received as a light spot by the light receiving element.
A so-called active distance measuring device is used, which measures the distance to a subject based on the position of a light spot using the principle of triangulation.

Such active distance detection devices are roughly divided into two types depending on the light emission form of the light emitting element. There is a one-shot method in which the light is emitted singly for each distance measurement operation.

In the former method, by selectively extracting only the signal components tuned to the modulation frequency of the light emitting element using a bandpass filter, the shadow VI of external light is reduced as much as possible and the reliability of distance measurement data is improved. However, since it requires capacitors and reactance coils that make up the band-pass filter, there is a problem in that the number of external parts increases, making the circuit configuration larger and making it difficult to incorporate it into the camera.

On the other hand, according to the latter method, the light-emitting element can be activated according to the instantaneous rating and emit a powerful light, making it possible to expand the distance measurement range and eliminate the need for a band-pass filter, simplifying the circuit configuration and making it more compact. On the other hand, the ability to distinguish between light from blinking lighting equipment, such as fluorescent lights, neon signs, and strobe devices, and light from light emitting elements is low, so distance measurement data cannot be used. There is a problem in that there is a possibility that a large error may be included.

(Purpose) The present invention was made in view of the above-mentioned problems, and its purpose is to provide a distance measurement system for cameras that can obtain highly reliable distance measurement information while taking advantage of the single-shot flash method. The purpose is to provide a detection device ff18.

(Summary of the Invention) In other words, the present invention is characterized in that a light emitting element and a light receiving element are arranged at a certain distance, and a signal from a microcomputer causes the light emitting element to emit light and illuminate the subject. On the other hand, in distance detection drawing in which reflected light from a subject is converted into an electrical signal by a light receiving element as the position of a spot light related to the distance to the subject, the light emitting element does not have to receive light during the distance measurement period. The present invention is characterized in that a plurality of distance measurement data are obtained by emitting light, and it is determined whether or not to continue the subsequent distance measurement operation based on the identity of the distance measurement data.

(Example) The details of the present invention will be described below based on illustrated examples.

FIG. 1 shows an overview of the present invention, and shows a - constant distance M
A light-emitting element 1 and a light-receiving element 2 are arranged with a distance L between them, and a signal from a light-emitting element drive circuit 4 activated by a signal from a microcomputer 3 is applied to cause the light-emitting element 1 to emit light singly, and this light is transferred to a condenser. While illuminating the subject S through the lens 5, the reflected light from the subject S is transmitted through the condenser lens 6.
converts it into a spot light, receives it at the light receiving element 2, converts the position of the spot light related to the distance to the object into an electrical signal, converts this signal into a pulse width signal by the distance measuring circuit 7, and sends it to the microcomputer 3. The pulse motor M drives the distance adjustment mechanism to the photographing lens.

FIG. 2 shows the details of the above-mentioned apparatus, in which reference numeral 1 indicates a condenser lens 5 in the optical axis direction of the photographing lens.
When a high-level signal is output from the microcomputer 3, the transistors 41 and 42 become conductive and output the electric charge of the capacitor 43 to the light emitting element 1. According to a signal from the light emitting element driving circuit 4 configured as above, light is emitted singly at a predetermined number of times, for example, about 8 times, at fixed time intervals, for example, every 10 milliseconds.

2 is a spot light position detector which receives light from the optical axis direction of the photographic lens at the focal position of the condenser lens 6, and has a cando terminal 2a and two anode terminals 2b, 2cV;
It is configured to output a current signal 11 and signal 2 corresponding to the position of the spot light.

Reference numerals 71 and 72 denote head amplifiers that receive signals from the spot light position detector 2, and transmit current signals from the anode terminals 2b and 2c of the spot light position detector 2 to the amplifiers 71a,
72a converts it into a voltage, charges it to the capacitor 7 C172c via the amplifier 711) and 72b, controls the transistors 71d and 72d, and converts it into a voltage that is lower than the frequency component of the pulsed signal caused by the light emitting element 1, that is, external light. This structure is designed to bypass signals caused by pulse-like signals, thereby further improving dynamic precision with respect to pulsed signals.

73 is a logarithmic conversion circuit, which includes an operational amplifier 73a that logarithmically compresses the current signal 1 from one head amplifier 71, and the sum of the current signals ■□ and I2 from the head amplifiers 71 and 72 (
An operational amplifier circuit 73b that logarithmically compresses the signal (II +I2) and a signal 109 from each operational amplifier circuit 73a, 73b.
and 109 (t+I2), and is configured to output a current signal 109/(IL+I2) proportional to the distance to the subject, which is output from the microcomputer. Voltage follower 74 that operates in response to a data hold signal
A current signal Il/(11+I2) proportional to the distance is outputted to a double integration circuit 76, which will be described later.

76 is the aforementioned double integration circuit, which includes an operational amplifier 76a;
Capacitor 7 having a capacity capable of holding each current signal
6b receives a current signal through the switch S1 which is turned on by the data hold signal mentioned above, and receives a current from the current source 77 through the switch S2 which is turned on by the read signal from the microcomputer 3. configured to receive.

A pulse width conversion circuit 78 converts the read signal into a pulse width proportional to the time required to charge the capacitor 76 of the double integration circuit 76 to a constant potential VO, and converts the pulse width into a pulse width proportional to the time required to charge the capacitor 76 of the double integration circuit 76 to a constant potential VO. This is what is output to.

Reference numeral 3 in the figure is the aforementioned microcomputer,
A distance measurement operation control section 31 receives a signal from a switch B that is linked to the release button of the camera, and executes a series of operations based on a flowchart to be described later to control the entire distance measurement operation, and a distance measurement circuit 7 It is composed of an A/D converter 32 that converts a pulse representing a distance signal from a distance into a digital signal based on a clock, and an arithmetic processing section 33 that processes this digital signal and converts it into distance information.

The arithmetic processing unit 33 includes a memory means 333a that can store a plurality of distance data, and a distance/near distance that compares the plurality of distance data with a reference value to determine whether the distance data represents far or near. It is composed of a determining means 33b, an average value calculating means 33c for calculating the average value of the distance data in the memory means 33a, and a step number determining means 33d for converting the calculation result into a step number.

Next, the operation of the apparatus configured as described above will be explained based on the waveform diagram shown in FIG. 3 and the flowchart shown in FIG. 4.

When the power of the camera is turned on to perform distance measurement, the voltage caused by the external light incident on the spot light position detector 2 is charged in the capacitors 71c and 72c, and the transistor 71d
, 726%, the current corresponding to the external light component is bypassed to ground, and the integrating capacitor 76b is connected to the switch 5.
21Fi and is supplied with current from the current source 77 to be charged to the initial potential Vo.

In this state, when you turn on the distance measurement switch B by pointing the camera at the subject and operating the release button, the distance measurement operation control section 31
The first light emission signal is output from the light emitting element drive circuit 4.
The light emitting element 1 is caused to emit light through the light emitting device 1 to irradiate the subject with light. This light is reflected by the subject, converted into a spot light by a condenser lens 6, and then detected by a spot light position detector 2.
incident on . As a result, the spot light position depth detector 2
A current corresponding to the spot light position is output from each terminal 2b, 2C. This current signal is the head amplifier 71J72
Since the distance signal is smaller than the time constant of , the distance signal passes through this time constant and becomes a distance signal logarithmically compressed by the logarithmic conversion circuit 73. The distance measurement operation control unit 31 outputs a data hold signal when a certain period of time ΔT1 has elapsed from the start of light emission, that is, when the distance signal becomes stable, and outputs the logarithmic signal to the logarithmic expansion circuit 75 via the voltage follower 74. output and convert it to a current signal,
Integrating circuit 76 for a certain period of time ΔT2 via switch S1
input. As a result, the potential of the integrating capacitor 76b reaches the initial potential V. This decreases by ΔV1.゛When the first light emission is completed, the supply of drive current is cut off to the light emitting element 1 and it naturally cools down in preparation for the next light emission.At the same time, the ranging operation control circuit section 31 outputs a readout signal and switches the switch S2. is turned on to charge the capacitor 76b with a constant current from the current source 77. Since this charging time Δt1 is proportional to the amount of charge ΔV1 accumulated in the capacitor 76b, the pulse width Δt4 becomes a distance signal.

This pulse signal is converted into a digital signal by the analog-digital converter 32 and then stored in the memory means 33.
It is stored in a.

When the set interval ΔT3 has elapsed, the integrating capacitor 76b is supplied with current from the current source 77 via the switch S2, and returns to the initial potential Vof. The distance measuring operation control unit 3] outputs a second light emission signal to cause the light emitting element 1 to emit light to irradiate the same subject with light. As a result, a current signal corresponding to the distance to the subject is output from the optical spot position detector 2, and this current signal is converted into a distance signal by the logarithmic conversion circuit 73, and then logarithmically expanded by the data hold signal before being sent to the switch. St'
A is input to the capacitor 76b for a certain period of time ΔT2, and the potential of the capacitor 76b is lowered by a potential difference ΔV2 that matches the distance signal, thereby generating a signal with a pulse width Δt2. This distance signal is digitized and stored in memory means 33.
It is stored in a.

When distance measurement has been completed the prescribed number of times N1 in this manner, the distance measurement operation control section 31 causes the distance determination means 33b to output N1 pieces of distance data stored in the memory means 33a, and then outputs the N1 pieces of distance data stored in the memory means 33a to the distance determination means 33b. or long-distance data.

As a result of this distance determination, if it indicates a short distance, the reflection intensity of the measurement light emitted by the light emitting element 1 is strong and the data reliability is high, so the subsequent distance measurement operation is stopped and the data is stored in the memory. The stored data is averaged by means 33c.
After calculating the average value, the step number conversion means 33d
to the number of steps (reshape and output.

On the other hand, if the distance measurement data indicates a long distance or cannot be judged as either, in other words, if there are variations in the distance measurement data, such as indicating a long distance and sometimes indicating a short distance, the distance measurement operation is continued further. The distance data is stored in the memory means 33a.

At the stage where the distance measuring operation has been completed for the prescribed number of times N2 (N2 > Nt), the distance measuring operation control circuit section 31 stores the memory means 3.
3a (The stored distance data for N2 times is read out and the average value is calculated by the average value calculation means 33c, and then converted into the number of steps and output.

As a result, even if the intensity of reflected light from the subject is low and a distance measurement error occurs 1.2 times during a series of distance measurement operations,
This error is reduced to (1/predetermined number of times), making it possible to obtain distance information as reliable as possible.

FIG. 5 shows a second embodiment of the present invention, in which reference numeral 34 denotes an arithmetic processing section that receives distance data from the analog-digital conversion section 32, and a calculation processing section that receives the distance data from the analog-to-digital conversion section 32. , CL to C2...C6 to C7 as addresses and step number So, SL...S7 as data, and a step number conversion means 34a consisting of a dictionary (Fig. 7), and stores this step number. memory means 34b for
, a difference determination means 34c that determines whether the number of steps of the specified number N1 from the start of distance measurement is different, and an extreme value elimination means 34c that excludes and outputs the maximum and minimum values of the number of steps stored in the memory means 34b. It consists of a means 34d and an average value calculating means 34e for calculating the average value of the number of steps.

Next, the operation of the device configured in this way will be explained based on the flowchart shown in FIG.

The distance signal outputted from the distance measurement circuit 7 at the start of distance measurement is converted into a digital signal, and then converted into a step number by the step number conversion means 34a and stored in the memory means 34.
It is stored in b. In this way, when distance measurement is performed a prescribed number of times N1 and the prescribed number of steps N1 is stored in the memory means 34b, the number of steps is read out from the memory means 34b, and the sameness of the step numbers is determined by the difference determination means 34c. do.

As a result of this judgment, if the number of steps is the same, it means that the distance measurement up to now has not been performed reliably, so the subsequent distance measurement operation is aborted and this number of steps is output as distance information. do.

On the other hand, if the result of the determination is that there is variation between the number of steps, the reliability of the distance measurement operation is low, so distance measurement is performed further for the specified number of times N2 (N2 > N). - Determine the number of steps and store it in the memory means 34b. When distance measurement has been completed N2 times in this way, the number of steps is read from the memory means 34b to the extreme value eliminating means 34d, and the remaining number of steps after excluding the maximum and minimum values is calculated by the average value calculating means 34e. It is averaged and output as distance information. Due to this, non-? Distance information based on highly reliable measurement data can be obtained without importing real data.

In this embodiment, the total distance measurement data is divided by the number of distance measurement operations, but since the number of distance measurement operations is constant, the converted data obtained by the arithmetic processing section may be used as is, or by a constant number M. It is clear that the same effect can be achieved even if the divided value is used as distance information.

(Effects) As described above, according to the present invention, the light emitting element is emitted multiple times to obtain a plurality of distance measurement data even if the light emitting element is not received during the distance measurement period, and a plurality of distance measurement data are obtained based on the identity of the distance measurement data. Next distance measurement operation! Since the system determines whether or not the distance measurement continues, if the distance measurement operation is being performed reliably, the number of distance measurements can be reduced to reduce power consumption as much as possible. If the operation is uncertain, the number of distance measurement data can be increased to obtain highly reliable distance information.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an overview of the present invention, Fig. 2 is a circuit diagram showing details of the above device, Fig. 3.4 is a waveform diagram and flow chart showing the operation of the above device, and Fig. 5.6
The figures are a block diagram of an apparatus showing other embodiments of the present invention, a flowchart showing its operation, and FIG.
FIG. 2 is a schematic diagram showing an embodiment of a number conversion means. 1...Light emitting element 2...Light spot position detection element 3...Microcomputer 32...Analog-digital converter 33.34.
... Arithmetic processing unit 7 ... Distance measurement circuit 71, 72 ... Head amplifier 73 ... Logarithmic conversion circuit 74 ... Voltage follower 75 ... Logarithmic expansion circuit 76 ... -Double integration circuit 76b...Integration capacitor 78...Pulse width conversion circuit Sl, S2...Switch A...Photographing lens M...Pulse motor

Claims (1)

[Claims] A light-emitting element and a light-receiving element are arranged at a certain distance apart, and a signal from a microcomputer causes the light-emitting element to emit light and illuminate the subject, while the reflected light from the subject is reflected at a spot related to the distance to the subject. In a distance detecting device that converts the position of light into an electrical signal by a light receiving element, the light emitting element is made to emit light at least a plurality of times during a distance measurement period to obtain a plurality of distance measurement data, and when the distance measurement data is the same A distance detection device for a camera that determines whether or not to continue subsequent distance measurement operations based on the distance.