KR950007866B1 - Apparatus and method for automatic focus control using a infrared light distantmeasuring type in a camcorder - Google Patents

Abstract

The automatic focusing control apparatus of video camera using the range finder method of infrared ray transforms the minute current signal of two channel being output from the ray receiving part into the wave of integral value. The lens are controlled according as the AF motor is activated by software, and the micro computer decides the signal size detecting the location of A and B channel.

Description

Automatic Focus Control Device and Method of Video Camera Using Infrared Distance Detection Method

1 is a view for explaining the principle of the active method used in the general automatic focusing apparatus.

2 is an electrical equivalent circuit diagram of a general light receiving element.

Figure 3 is a block diagram of the overall configuration of a conventional automatic focusing apparatus.

Figure 4 is a block diagram of the overall configuration of the automatic focusing apparatus according to the present invention.

5 is a view illustrating an embodiment of an automatic focusing apparatus according to FIG. 4.

6 is a detailed circuit diagram of the infrared LED driver employed in FIG.

7 is a waveform diagram of signals output from the integrator voltage controlled oscillator and the microcomputer employed in FIG.

FIG. 8 is a flowchart illustrating a process of controlling each part in the microcomputer employed in FIG. 4 to drive an infrared LED and an AF motor to complete autofocus control.

* Explanation of symbols for main parts of the drawings

10 light emitting unit 20 light receiving unit

30,40: current voltage conversion unit 50: switching unit

60: detector 70: amplification and integration

80: voltage controlled oscillator (VCO) 90: microcomputer

100: motor drive unit M: motor

The present invention relates to an automatic focus control apparatus and a method of a video camera, and more particularly, to an automatic focus control apparatus and a method of a video camera that employs an active method to measure using infrared rays.

In general, the auto focusing (AF) method of camera integrated video (hereinafter referred to as a video camera) is largely classified into an active method using infrared rays and ultrasonic waves and a passive method using image sensing and image detection.

In particular, the principle of the active method, which emits infrared light to a subject (hereinafter, abbreviated as "subject") and measures it by the reflection distance measuring signal reflected by the subject, is shown in FIG.

According to FIG. 1, the infrared light emitted from the infrared light source is reflected from the subject 4 through the lens 1 of the infrared light emitting diode (hereinafter referred to as infrared LED), and the reflected light is directed to the light receiving element lens 2. It forms on the light receiving element 3 through.

In this case, L is the distance from the lens 1 of the infrared LED to the subject 4, R is the distance between the infrared LED 1 and the light receiving element lens 2, F is the focal length of the light receiving element lens 2, If X is the distance from the light receiving element 3 to the infrared beam passing through the light receiving element lens 2,

L = R Relationship is established.

Therefore, since the distance L from the infrared LED lens 1 to the subject 4 is inversely proportional to the light incident position X of the light receiving element 3, the distance L can be measured.

Here, in the electrical equivalent circuit of the light receiving element 3, when the P-side electrode is A and B and the N-side electrode is C as shown in FIG. 2, Io is generated by the light spot irradiation position. The total current is D1, the ideal diode, Cj is the junction capacitance, Rsh is the classifier resistance, the resistance to the electrode A at the light spot irradiation position, the resistances R2 and S to the electrode B, and the current source and R are the negative resistance.

In this case, the photocurrents I ₁ and I ₂ output from the light receiving element may be expressed as follows.

[Equation 1]

According to the above equation ①, the difference between the output current and the ratio Is proportional to the distance X from the electrodes A and B center points to the light spot irradiation position point.

Therefore, when the subject is in focus, the incident position of the reflected light is formed in the center of the light receiving element, and is changed into a current signal of the same magnitude. If the focus is shifted, the incident position of the reflected light is imaged by being biased to one side of the light receiving element, so that the current magnitude of both channels is different. Where the distance (X) from the center of the electrodes A and B to the light spot irradiation position point and the difference between the output current and the sum While maintaining linearity, the AF motor must be controlled to achieve the correct focus.

Conventionally, as shown in FIG. 3, the automatic focusing apparatus of the video camera of Patent No. 90-15683, which was previously filed by the company, switches the position detection signals of two channels A and B output from the light receiving element 2 to the switching unit ( 5) is switched to time division by one channel and integrated in the amplification and integration section 7. The comparing section 8 outputs the level signal to the microcomputer 9 only when the output value of the amplifying and integrating section 7 is equal to or higher than the set voltage. However, when the reflectance of the subject is low and the distance is far, the output signal of the amplifying and integrating unit 7 becomes relatively small to reach the set voltage, so that the microcomputer 9 cannot recognize the focus and cannot accurately adjust the focus. There was a downside.

In addition, since the overall gain of the entire control loop as described above is 100 dB or more, there is another disadvantage that the power of the infrared LED must be divided into four stages to adjust the dynamic range of the circuit.

In order to overcome the above-mentioned problems, the present invention has been created, and receives a infrared light projected from an infrared LED and reflected on a subject to switch the position detection signals of two channels to a time division by one channel at a predetermined period. It is an object of the present invention to provide an automatic focus control apparatus for a video camera using the infrared ranging method that can automatically adjust focus by recognizing the integrated value of the position detection signals into a frequency.

Another object of the present invention is to provide an automatic focus control method of a video camera using an infrared ranging method that converts two channel position detection signals outputted from a light receiving element into a counter amount in a microcomputer to drive an infrared LED and an AF motor by software. There is a purpose.

In order to achieve the above objects, an automatic focusing apparatus of a video camera using an infrared distance measuring method includes a light emitting part for projecting a distance light beam to a subject, and a light receiving surface of reflected light projected from the light emitting part and reflected by the subject. A light receiving unit for outputting a minute photocurrent according to an imaging position, a first and second current voltage converting unit for converting a current signal output from the light receiving unit into an amplified voltage signal, and from the first and second current voltage converting units A switching unit for time-switching the output signal by one channel, a detector for filtering and amplifying the output signal of the channel switched by the switching unit to have a predetermined frequency band, and amplifying the output signal of the detector, An amplifying and integrating unit for integrating a predetermined period, and a voltage controlled oscillating unit for converting a voltage signal output from the amplifying and integrating unit into a frequency ( VCO), a drive signal for turning on / off the infrared LCD, and a charge / discharge signal transmitted to the integrator, and counting the frequency output from the voltage controlled oscillator as time to output a control signal for driving the AF motor. And a motor driver for controlling a motor for driving the photographing lens to an optimal focus position by the direction of the microcomputer and the direction and speed control signals of the motor M from the microcomputer.

In addition, the automatic focus adjustment method of the video camera using the infrared range detection method according to the present invention is the time-switched position detection signal of the A channel of the position detection signal output to the two channels from the light receiving unit corresponding to the reflected light of the subject An A-channel signal detection step of converting and storing the integral value output from the integrator into a frequency, and after detecting the A-channel position detection signal from the A-channel signal detection step, switch the position detection signal of the B-channel and output it from the integrator. A B channel signal detecting step of converting and storing the value into a frequency, and a counter amount calculating step of calculating a counter amount counting the frequency output from the A and B channel signal detecting steps in time; And a motor control step of controlling the direction and speed of the motor from the count amount calculation step.

Hereinafter, with reference to the accompanying drawings will be described in detail the automatic focus control apparatus and method of the video camera using the infrared distance measuring method according to the present invention.

4 is a block diagram of the overall configuration of the automatic focusing apparatus of the video camera using the infrared distance measuring method according to the present invention.

According to FIG. 4, the light emitter 10 emits infrared light through an infrared LED to a subject (not shown in the drawing) through an infrared LED in response to a driving signal of the infrared LED driver. . At this time, the infrared LED driver inputs a 10kHz buster signal from the microcomputer 90 to set the power of the infrared LED in one step to emit the infrared LED. The reflected infrared rays reflected by the subject are focused by the light receiving lens (not shown in the figure) of the light receiving unit 20 to condense the light incident position on the light receiving surface.

The first and second current voltage converters 30 and 40 output the two-channel microcurrent signals I ₁ and I ₂ output from the light receiver 20 as amplified voltage signals.

Switching section 50 is an analog switch, the output signal transmitted from the first and second current voltage converter 30, 40 to the two channels (A, B) under the control of the microcomputer 90. Output to the detector 60.

The detector 60 passes only the frequency components within a narrow band including the driving frequency of the infrared LED among the output signals of the channel selected by the switching unit 50 to improve the signal-to-noise (S / N) ratio and simultaneously amplify the signal. Output

The amplifying and integrating unit 70 receives a signal obtained by re-amplifying the signal amplified and filtered by the detector 60 and converts it into a current signal corresponding to the amplifying and integrating unit 70. It is output as a voltage signal.

The voltage controlled oscillator 80 converts the voltage signal output from the amplification and integration unit 70 into a frequency signal and outputs the frequency signal to the microcomputer 90. That is, when the integral value of the amplification and integration unit 70 is large, the microcomputer 90 recognizes the high frequency, and when the integral value of the amplification and integration unit 70 is small, the microcomputer 90 recognizes the low frequency. Done.

The microcomputer 90 controls the motor driver 100 using a signal obtained by counting an output signal of the voltage controlled oscillator 80 at a counter.

The motor driving unit 100 inputs the speed control signal V and the direction control signals F and B output from the microcomputer 90 to drive the motor M for driving the photographing lens to the optimum focus position. do.

A preferred embodiment of the automatic focus control apparatus for a video camera using the infrared distance measuring method according to the present invention having the above configuration will be described.

5 is a detailed circuit diagram of the automatic focusing apparatus according to FIG.

5 shows the operation of the light receiving unit 20, the first and second current voltage conversion units 30 and 40, the switching unit 50, the detector 60, the amplifying and integrating unit 70, and the like. Since the present disclosure is disclosed in the patent application No. 90-15683, detailed operation description will not be mentioned.

In the voltage controlled oscillator 80, a current I flows through the voltage signal Vc output from the amplification and integration unit 70, and is charged in the capacitor C. The resistor R and the capacitor C determine the time constant.

When the output of the operational amplifier OP7 becomes "high" by the resistor R22 for giving a hysteresis band, the transistor TR4 conducts and is discharged in the capacitor C.

P ₁ point is the driving voltage It is pulled up by.

At this time, the output of the operational amplifier OP7 generates a square wave while the capacitor C is discharged.

6 is a detailed circuit diagram of the light emitting unit 10 employed in FIG.

According to FIG. 6, when the 10 kHz buster signal output from the microcomputer 90 is "low", the transistors TR5 and TR6 are cut off and the transistor TR7 is turned on.

When the buster signal output from the microcomputer 90 is "high", transistors TR5 and TR6 are turned on and transistor TR7 is cut off.

Therefore, when the buster signal output from the microcomputer 90 is "low", current flows through the load resistor R29, the infrared LED is emitted, and when the buster signal is "high", the transistor I7 is cut off. No current flows through the load resistor R29.

At this time, the waveform of the 10kHz buster signal output from the microcomputer 90, that is, the signal having a period of 100μsec is as shown in Figure 7A.

The infrared LED buster signal output from the microcomputer 90 causes the infrared LED to emit for 10 msec, thereby converting the reflected light reflected from the subject into the electrical signal by the two-split light receiving element 20.

The electrical signal is converted into a counter amount in the microcomputer 90 to control the motor driving unit 100 for 40 msec.

FIG. 7B shows waveforms of signals in which the A and B channel position detection signals output from the two-component photodetector are integrated during the sampling period T in the amplification and integration section 70. FIG.

The amplitude of the signal detected by integrating the position detection signal of the A channel during the sampling period T by the amplification and integrating unit 70 corresponds to I ₁ , and the position detection signal of the B channel is amplified after a predetermined time dT. The amplitude of the signal integrated and output during the sampling period T that is the same as the integration period of the A channel in the integrating unit 70 corresponds to I ₂ .

7C and 7D are waveform diagrams of signals obtained by converting the integrated values of the A-channel and B-channel position detection signals into the frequency in the voltage controlled oscillator 80, respectively.

FIG. 8 is a flowchart illustrating a process of controlling each unit in the microcomputer 90 employed in FIG. 4 to drive an infrared LED and an AF motor to complete autofocus control.

8 will be described with reference to FIGS. 4 to 7.

In step S1, the port C of the microcomputer 90 is initialized, the memory and the count mode are cleared, and the capacitor C9 of the integrator 72 is discharged for 1 msec to prevent noise.

In steps S2 to S3, a control signal is output to the switching unit 50 among the position detection signals of the A and B channels output from the light receiving unit 20 to select the A channel (step S2), and amplify the transmitted signal of the A channel. And the integrating unit 70 (step S3).

In steps S4 to S5, the 10 kHz buster signal for driving the infrared LED is turned “on” and the counter is turned “on” for 50 μsec (step S4), and the infrared LED buster signal having a cycle of 100 μsec is turned off by turning off the buster signal for 50 μsec. Output (step S5).

In steps S6 to S7, it is determined whether there are n or more buster signals (step S6). When the number of buster signals is n or more, the integral value output from the amplifying and integrating unit 70 from the voltage controlled oscillator 80 is determined. The value converted into the frequency is input to the microcomputer 90 (step S7), the frequency is counted and stored in the counter (step S8), and delayed by 1 msec (step S9).

In steps S10 to S11, it is determined whether the B channel is selected by the switching unit 50 from step S9 (step S10). If the B channel is not selected, the channel B is selected and fed back to the step S3 (step S11). ).

In steps S12 to S14, the difference between the product and the difference of the counter amount calculated by converting the integral value of the position detection signals of the two channels A and B from the step S10 into frequency. Is stored in the register r5 (step S12), and the sum of the counter amounts and the product Is stored in the register r4 (step S13), and the ratio of the value stored in the register r5 and the value stored in the register r4, that is, the difference between the counter amounts and the sum The value is stored in the register r3 (step S14).

In steps S15 to S17, it is determined whether a carry has occurred from the value stored in the register r5 (step S15). If a carry occurs, the motor is moved in the reverse direction (step S16). Otherwise, the motor is moved forward (step S17). ).

In steps S18 to S19, the difference and the sum of the counter amounts stored in the register r3 The value is compared with the epsilon (ε) value representing the hysteresis band (step S18). When the value is less than the epsilon value, the motor is stopped to complete the autofocus control and then fed back to step S2 (step S19).

In this case, the epsilon value ε refers to a value when the value stored in the register R3 is 5% or less.

In steps S20 to S23, when the value stored in the register R3 is greater than or equal to the epsilon value ε from step S20, it is determined whether the value stored in the register R3 is greater than or equal to the K value (step S20). The motor M is controlled by pulse width modulation (PWM) (steps S21 and S23), and when it is less than or equal to K value, the motor is controlled by pulse width modulation (PWM) at low speed to focus and then feed back to step S2 ( Steps S22 and S23).

At this time, the K value refers to when the value stored in the register r3 is 20% or less.

As described above, the automatic focus control apparatus and the method of the video camera using the infrared ranging method according to the present invention frequency and the integral value of the amplification and integrator composed of one channel of the micro-current signal of the two channels output from the light receiving unit By converting to, the microcomputer determines the position detection signal size of the A and B channels and software-drives the AF motor to adjust the focus even when the reflectance of the subject is low and the distance is far. There is an effect of increasing the reliability and stability of the system by processing the output position detection signal in a one-channel integration method.

Claims (5)

A light emitting unit 10 which transmits a distance measuring light beam to a subject, and a light receiving unit 20 which outputs a minute light current according to an imaging position on a light receiving surface of the reflected light projected from the light emitting unit 10 and reflected by the subject; First and second current voltage converters 30 and 40 converting the micro current signal output from the light receiver 20 into an amplified voltage signal, and the first and second current voltage converters 30 and 40. A switching unit 50 for switching the output signal from the signal to time division, a detector 60 for filtering and amplifying the output signal of the channel switched by the switching unit 50 to have a predetermined frequency band, and An amplifying and integrating unit 70 for amplifying a signal output from the detector 60, integrating for a predetermined period, and a voltage controlled oscillating unit for converting and outputting a voltage signal output from the amplifying and integrating unit 70 into a frequency; 80 and a main output from the voltage controlled oscillator 80 A microcomputer 90 for outputting a control signal for driving the AF motor with a counter amount counting the number of times, and controlling the light emitting unit 10, the switching unit 50, the amplifying and integrating unit 70; And a motor driver 100 for outputting a direction (F, B) and a speed control signal (V) for driving the motor by the AF motor driving control signal output from the microcomputer (90). Automatic focusing device for video camera using infrared distance measuring method. According to claim 1, wherein the voltage-controlled oscillator 80 is a current flowing through the resistor (R) and the capacitor (C) connected to the inverting terminal of the operational amplifier (OP6) the output signal of the amplification and integration unit 70 ( A square wave pulse comprising an integration means for charging electric charges to the capacitor C by I), an operational amplifier OP7 pulled up according to the output voltage of the operational amplifier OP6, and a resistor R22 for determining the hysteresis band. And a switching means composed of a pulse generating means for generating a voltage and a transistor (TR4) for controlling to discharge from the capacitor (C) according to the output signal of the operational amplifier (OP7). Automatic focusing device for video camera. 2. The light emitting unit (10) according to claim 1, wherein the light emitting unit (10) is constituted by current limiting means consisting of active elements (TR5, TR6) which are blocked or conducted in accordance with a control signal output from the microcomputer (90). An automatic focus control apparatus for a video camera using an infrared range detection method, comprising a switching means for driving an infrared LED, which is composed of an active element (TR7) and a load resistor (R29) that are blocked or conductive. An A-channel signal detection step of integrating an electrical signal output from the light receiving unit transmitted to the A-channel during a sampling period and then frequency-converting, and detecting a position detection signal of the A-channel from the A-channel signal detection step The B channel signal detection step of selecting the B channel and integrating the electrical signal output from the light receiving unit transmitted to the B channel during the sampling period and converting the frequency into a frequency; and the frequency output from the A and B channel signal detection steps as a counter amount. And a motor control step of controlling a direction and a speed of the motor from the counter amount calculation step. The method of claim 4, wherein the detecting of the A and B channel signals comprises: an integration step of outputting a control signal so as to charge the position detection signal of the light receiving unit to the condenser of the integrator from the initialization step; A buster signal on / off step of outputting a buster signal, and a frequency conversion step of determining whether the number of buster signals is greater than or equal to a predetermined number from the buster signal on / off step and recognizing a frequency output from the voltage controlled oscillator Automatic focus control method of a video camera using an infrared ranging method characterized in that it comprises a.