KR970003453Y1 - Device for automatic focusing of a camera - Google Patents

Abstract

None.

Description

Camera automatic distance measuring device

1 is a block diagram of an automatic distance measuring apparatus of a conventional camera,

2 is a detailed circuit diagram of an automatic distance measuring apparatus of a camera according to an embodiment of the present invention.

The present invention relates to an automatic distance measuring device of a camera that receives and processes light reflected from a subject. More specifically, it is necessary to block external light such as visible light, sunlight, and fluorescent light in a system for measuring the distance of an object. The present invention relates to an automatic distance measuring apparatus of a camera for improving an autofocus function by minimizing disturbance light effects by using a light receiving unit circuit that detects only an infrared band.

In order to reduce the influence of the disturbance light, the light receiving signal processor of the conventional camera automatic distance measuring device uses a filter to reduce the influence of the disturbance light by blocking a frequency above or below a certain band or by using a differential amplifier. By using a device that senses the distance according to the comparison between the amplified signal and the comparator voltage by amplifying the difference between the disturbance light and the signal received from the near and far side.

The prior art will be described with reference to the accompanying FIG. 1. 1 is a block diagram of an automatic distance measuring apparatus of a conventional camera.

According to FIG. 1, the conventional automatic distance measuring apparatus of the camera includes infrared light receiving devices D1 and D2 that output current corresponding to the intensity of the detected infrared light, and infrared light receiving devices D1 and D2. A current-voltage converter 100 for converting the output current into a voltage and amplifying the output current; a multiplexer 200 for outputting a signal output from the current-voltage converter 100 by a control signal input; and the multiplexer 200 Bandpass filter unit 300 that passes only the signal frequency band of the subject from the signal output from the signal, an amplifier 400 for amplifying the output of the bandpass filter unit 300 as an input, and the amplifier ( Integrating the signal amplified in the 400, the integral portion 500 is connected to the multiplexer 200, and the signal integrated in the integrator 500 is input to the integral signal of the integrating unit 500 is set level City A signal processor 1 comprising a comparator 600 which detects the liver and compares it with a reference time, a light-emitting infrared drive unit 700 for reflecting infrared rays from the light emitting diode D1, and AF (Auto Focus) The motor driver 900 and the infrared light driver 700 turn on the light emitting diode D1 to emit infrared light, and in accordance with the output signal of the comparator 600 of the light receiving signal processor 1, the AF motor driver The micro controller 800 drives the 900 and inputs a control signal to the multiplexer 200.

The operation of the automatic distance measuring apparatus of the conventional camera configured as described above is as follows.

Under the control of the microcontroller 800 while the power is applied, the infrared light driving unit 700 operates and the light emitting diode D1 is turned on to emit infrared rays. The infrared rays emitted by the light emitting diodes D1 are reflected on a subject (not shown), and the infrared rays are incident on the light receiving diodes D1 and D2 to output current corresponding to the intensity of the received infrared rays.

The output current is input to the current-voltage converter 100, converted into voltage, and amplified. The voltage is input to the multiplexer 200 having a built-in synchronous switch, and the synchronous switch is operated by the control signals of the integrator 500 and the microcontroller 800 to select and output one of the two input terminals. Output signal is output to terminal.

The output signal becomes an input terminal of the bandpass filter 300 and passes only the signal reflected from the subject. The signal passing through the bandpass filter 300 is amplified through the amplifier 400 and input to the integrator 500 to be integrated.

When the integrated signal is input to the comparator 600 and the integrated signal reaches the set leveling level, the integrated synchronous switch is operated again so that the multiplexer 200 is operated to compare the signal output from the integrator 500. In comparison with the reference numeral 600, the time at which the integrated signal rises to the set level is determined and input to the microcontroller 800. Therefore, the microcontroller 800 drives the AF motor driver 900 by determining whether the focal length is correct based on the output signal of the comparator 600.

However, the conventional camera automatic distance measuring device uses a filter to pass only the infrared light frequency, which is the frequency of the required band, and cuts out the disturbance light band, but it is difficult to manufacture the filter to pass the frequency of the correct band. It is difficult, and beyond the error range of the filter, due to the limitation of the performance improvement, the focusing according to the distance detection is not accurately performed. In addition, there is a disadvantage in that the accuracy of the distance measurement is reduced by affecting the input signal according to the reflectance of the light reflected from the subject and the change rate according to the change in power.

As another example of the prior art of the automatic distance measuring device of the camera, the configuration of the above configuration by the integrated circuit so that it can be easily carried out in accordance with the trend of miniaturization, Republic of Korea Utility Model Registration Application No. 91-18825 (Application Date: November 7, AD 91).

The automatic focusing apparatus also has a disadvantage in that the accuracy of accurate distance measurement is deteriorated by reflectance of light and power fluctuation rate.

Also, in the conventional triangulation method, since the amount of current output from the light receiving diode is affected by the difference in reflectance of light reflected by the subject, the accurate distance cannot be measured. Therefore, the received light is changed by the reflectance of the subject. The technique for correcting the change in the amount of output current of the diode to recognize the distance of the subject only by the incident light incident on the light-receiving diode without being affected by the reflectance is disclosed in Korean Utility Model Registration Application No. 91-18822. November 7, 1991 AD).

The auto focusing circuit of the camera passes an appropriate frequency band, reduces the efficiency of a band pass filter that blocks external light, and has a disadvantage in that a signal value changes according to a change rate caused by power fluctuation.

Accordingly, an object of the present invention is to solve the above-mentioned disadvantages, and by using a light receiver circuit that passes only a proper frequency band necessary for a light receiving signal processor instead of a band pass filter, minimizes disturbance light effects and By reducing the change in reflectance and power, the distance detection function is improved to provide a camera's automatic distance measuring device that can accurately adjust the focus.

The construction of the present invention for achieving the above object is, a light receiving unit for detecting the light reflected from the subject and passing only the appropriate frequency band, the current-voltage converter, to reduce the influence of the power fluctuation, and to amplify the signal A light receiving signal processor comprising an amplifier, a comparator for reducing the influence of light reflectance and outputting a digital signal, an infrared light driver for emitting infrared light, a microcontroller and an AF motor driver for controlling the light.

When described in detail with reference to the accompanying second embodiment a preferred embodiment for easily carrying out this invention by the above configuration as follows.

2 is a circuit diagram of an automatic distance measuring apparatus for a camera according to an embodiment of the present invention. As shown in FIG. 2, the configuration of the automatic distance measuring apparatus of the camera according to the embodiment of the present invention includes: a light receiving unit 10 which receives light reflected from a subject, passes only necessary infrared bands, and blocks external light; The current-voltage converter 20 converts the current of the infrared light processed by the light receiving unit 10 into a voltage, and amplifies and outputs the difference between the voltages output from the current-voltage converter 20 and reduces the influence of power fluctuation. A light receiving signal processing unit including an amplifying unit 30 and a comparing unit 40 which reduces the influence of reflectance of light and outputs a digital signal by comparing the voltage output from the amplifying unit 30 with a reference voltage ( 2), an infrared light driver 700 for emitting infrared light to the light emitting diode D3, an AF motor driver 900, and AF according to the output signal of the comparator 40 of the light receiving signal processor 2; A microphone for driving the motor driver 900 It consists of a controller (800).

In the light receiving unit 10, one terminal of the resistors R11 and R12 is grounded, the other terminal is connected to the anode side of the light receiving elements D1 and D2, and the resistors R13 and R14 are connected to the anode side of the light receiving element. This is connected to the capacitor (C1, C2). The output from the light receiving unit 10 is connected to the inverting terminals of the amplifiers A1 and A2 of the current-voltage converter 20, and the resistor R21 is connected to the non-inverting terminal to connect the resistors R22 and R23 to ground. It is.

The common element on the cathode side of the light receiving element of the light receiving portion 10 is connected to grounds connected to the resistors R22 and R23 and is connected to the output of the voltage generator 21.

In the current-voltage converter 20, each output of the amplifiers A1 and A2 passes through the capacitors C3, C4, C5 and C6 to the input of the amplifier 30.

A capacitor C3 and a resistor R31 are connected to an inverting terminal of the amplifier A3 of the amplifier 30 and connected to an output of the amplifier A1 of the current-voltage converter 20, and the resistor R30 is input. It is fed back to the output side. To the non-inverting terminal, the output of the amplifier A2 of the current-voltage converter 20 is input by connecting the capacitor C5 and the resistor R32, and the resistor R33 is connected so that the resistor R33 is the resistor R23. Connected to ground).

A capacitor C4 and a resistor R34 are connected to the inverting terminal of the amplifier A4 at the output of the amplifier A1 of the current-voltage converter 20, and the resistor R35 is fed back to the output side. An output of the voltage generator 21 of the current-voltage converter 20 is connected to the non-inverting terminal and connected to the resistor R35. A capacitor C6 and a resistor R37 are connected to the inverting terminal of the amplifier A5 at the output of the amplifier A2 of the current-voltage converter 20, and the resistor R39 is fed back to the output side.

The output of the voltage generator 21 of the current-voltage converter 20 is connected to the resistor R30 and input to the non-inverting terminal of the amplifier A2. The output of the amplifier is input to the comparator 40, the output of the amplifier comparator A4 of the amplifier 30 is input to the buffer A7 of the comparator 40, the output value is the ratio of the comparator A6 The inverting terminal is input to the inverting terminal of the comparator A8. The comparator A6 receives the output of the amplifier A3 of the amplifier 30 at the non-inverting terminal, and the output of the amplifier A5 is input to the non-inverting terminal of the comparator A8.

Operation of the automatic distance measuring device of the camera according to the embodiment of the present invention by the above configuration is as follows.

When the light receiving elements D1 and D2 detect the light emitted from the light emitting diode reflected by the infrared light driver 700 to the subject, the capacitor is set by setting the appropriate frequency band by the resistors R3 and R4. While passing through (C1, C2), low frequency bands of natural light such as ambient sunlight, indoor natural light, and artificial light are blocked, and high frequency bands, which are infrared light bands, pass.

In order to prevent the energy of the input light from being accumulated without being discharged for one period, the resistors R11 and R12 are connected and shortened by bypassing through the capacitor.

When the infrared light output from the light emitting diode D3 is a high frequency band, it does not indicate a frequency band of the infrared light itself but indicates that the light emission time of the light emitting diode D3 is a high frequency band.

That is, the infrared controller 700 repeats the on / off operation of the light emitting diodes D3 by a period corresponding to a high frequency band by the microcontroller 800, thereby being output from the light receiving diodes D1 and D2. The current state changes with alternating current.

The signal passing through the light receiving unit 10 is input to the current-voltage converter 20 is converted into a voltage signal and output. The output voltage signal passes through the capacitors C3, C4, C5, and C6 connected to the outside of the circuit, and once again, the low frequency band is cut off and the high frequency infrared light passes, thereby preventing noise caused by disturbance light.

At this time, the time constant is changed by the capacitors C3, C4, C5, and C6, so that only a signal corresponding to an appropriate frequency band passes.

The signal passed above is input to the amplifier 30, and the amplifier A3 amplifies and outputs a difference between two voltage signals output from the amplifiers A1 and A2 of the current-voltage converter 20, and changes in power supply. By varying the offset voltage level of each amplifier by the same ratio even if the light intensity of the light is changed, the voltage generator 21 of the current-voltage converter 20 in the amplifiers A4 and A5 so as not to be affected by the change in the light intensity. Amplify and output the difference between the voltage output from the amplifier and the respective output signals of the amplifiers A1 and A2.

The variation can be reduced to within 2% in the 32.V to 2.2V variation.

The signal output from the amplifier 30 is input to the comparator 40 to compare the reference voltage determined by the microcontroller 800 with the voltage output from the amplifier A3 by using the comparator A6, which is high or low. Will output a digital signal.

In order to equalize the distance detection rate according to the reflectance of the light reflected from the subject, the signal output through the amplifier A4 is inputted to the inverting terminal of the comparator A8 by amplifying and outputting the signal output by the buffer A7. The digital signal is output by comparing the output value of the amplifier A5 input to the input signal.

The microcontroller 800 receives the output of the comparator A6 and the output of the comparator A8 and determines whether the focal length is correct according to the signals of the two comparators to drive the AF motor driver 900. In the comparison unit 40, the variation due to the variation from 20% to 90% of the reflectance can be reduced to within 3%.

As described above, in the embodiment of the present invention, the influence of noise and disturbance light in any band can be eliminated by changing the resistance of the light receiving unit 10 and the constant of the capacitor without using the band pass filter. In addition, by connecting a capacitor outside the circuit between the current-voltage converter 20 and the amplifier 30 to change the time constant, it is possible to pass the desired frequency band according to the environmental conditions, the number of parts according to the band pass filter The cost reduction and circuit simplification can be achieved by reducing the cost, and low-end cameras can be easily mounted.

In addition, since the amplification unit 30 varies the offset voltage of the amplifier by the same ratio, it is possible to reduce the influence of the power supply variation, thereby providing an effect of reducing the distance change detection according to the reflectance of the received light. This effect of the present invention can be used in fields such as a device for determining the presence or absence of an object using infrared rays, or a distance detector, and the step of detecting the distance according to the comparator configuration of the comparator 40 to 4 to 8 It can be configured and put into practical use.

Claims (5)

A light receiving unit 10 which detects a signal reflected from a subject and passes a frequency of an appropriate band and blocks disturbance light, a current-voltage converter 20 converting the detected current signal into a voltage and outputting the voltage; The amplification unit 30 receives and amplifies the converted voltage signal, reduces the influence of power fluctuation, and reduces the influence of reflectance of the received light, and outputs the digital signal by comparing the amplified signal with a reference voltage. A light receiving signal processor 2 comprising a comparator 40, an infrared light driver 700 for emitting infrared light, and an infrared light driver 700 are driven to the output signal of the light receiving signal processor 2. And a micro controller (800) for driving the AF motor driving unit (90) and the AF motor driving unit (900). The apparatus of claim 1, wherein the light receiving unit (10) uses a resistor and a capacitor to block disturbance light and to pass only a frequency of an appropriate band. The automatic distance measurement of a camera according to claim 1, wherein a capacitor is connected to an outside of the circuit between the current-voltage converter 20 and the amplifying unit 30 so as to pass only a proper frequency band by changing a time constant. Device. 2. The amplifier of claim 1, wherein the amplifier 30 comprises a differential amplifier for differentially amplifying a short range signal and a long range signal, and an amplifier for differentially amplifying a difference between two input signals and a constant voltage. The automatic distance measuring device of a camera, wherein the accuracy of the power fluctuation is equalized and the influence of the power fluctuation is reduced. The method of claim 1, wherein the comparator 40 compares and outputs the differential amplification value between the input signal and the constant voltage of the amplifier 30 in order to reduce the influence of the reflectance of the light reflected by the subject. Automatic distance measuring device of the camera.