KR920008980Y1 - Signal detecting circuit for auto-focus controlling system of camera - Google Patents

Abstract

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Description

Subject signal detection circuit of auto focusing system

(A)-(d) of FIG. 1 is explanatory drawing for demonstrating the general triangulation method.

2 is a block diagram showing an auto focusing system configured with a subject signal detection circuit of the present invention.

3 is a detailed circuit diagram showing an embodiment of the disturbance light blocking unit and the filter unit of FIG.

* Explanation of symbols for main parts of the drawings

8, 9: light receiving diode 10: disturbance light blocking unit

11,12: current-voltage converter 13: amplification degree control unit

20: filter part 21, 22: high pass filter

23, 24: bandpass filter

The present invention is an automatic focusing system that automatically adjusts the focus by triangulation using a light emitting diode, which is an infrared light emitting device, and a light receiving diode, which detects the infrared light. It relates to a subject signal detection circuit of the auto focusing system for detecting a.

The auto focusing system is a system that automatically shifts and sets the focal length according to the distance to the subject so that the photographer can obtain a simple and clear image without any exposure and distance adjustment and without any difficulty in operation. Such an auto focusing system is required in many devices such as a CDD (Charge Coupled Device) camera, a stereoscopic camera, an electronic still video camera, a video camera and a camcorder as well as an automatic camera. The auto focusing system developed in response to these demands is a focus detection method and a range detection method.

The focus detection method uses light passing through the photographing lens, and directly adjusts the focus by detecting the contrast or the position of the subject image in the vicinity of the focus position. The focus detection method includes a contrast detection method and a phase detection method.

The distance measuring method is a method of measuring a distance from a subject and feeding the result back to adjust the focus. The ultrasonic propagation time method calculates a distance based on the time when the ultrasonic wave is emitted and the emitted ultrasonic wave is reflected from the subject and returned. And, there is a triangulation method for measuring the distance to the subject by detecting the angle to see the subject.

In the triangulation method, images of the subjects incident on the two measurement windows arranged at regular intervals are imaged on the photodiodes, and the angle displacements of the movable mirror are detected by comparing the images of the subjects formed on the photodiodes. Double phase matching method to measure the distance from the subject using the angle displacement of one movable mirror, and the light emitting device that emits enemy ships and the light receiving device that receives the infrared rays are installed at regular intervals. There is a projection method for measuring the distance by detecting the angle of the incident light formed on the light receiving element after the infrared light is reflected from the subject.

Among the many auto focusing methods, the triangulation method by infrared light transmission has a merit that the control principle and circuit configuration are simple and are not affected by the ambient brightness. The principle of this method will be described.

In the triangulation method by infrared light emission, as shown in (a) of FIG. 1, the one-dimensional image sensor 2 is disposed at a predetermined distance from the light emitting element 1, and the light emitting element 1 and the subject 3 The light emitting beam collimation lens 4 is interposed between the light emitting beam imaging lens 5 between the one-dimensional image sensor 2 and the object 3. The infrared ray emitted from the light emitting element 1 is reflected on the object 3 through the light beam collimation lens 4 and interposed on the same central axis, and then through the light receiving beam imaging lens 5. The focus is adjusted by moving the light receiver in accordance with the amount of current formed in the sensor 2 and corresponding to the formed image.

In other words, the distance between the object 3 and the center of the optical axis of the light emitting beam collimation lens 4 is L, and the distance between the centers of the light emitting beam collimating lens 4 and the light receiving beam imaging lens 5 is W, and the light receiving beam imaging is performed. The distance between the center of the lens 4 and the one-dimensional image sensor 2 is F, and the distance between the center of the light receiving beam imaging lens 5 and the point where the object 3 is imaged to the one-dimensional image sensor 2. If T, L: W = F: T is established, a relation of L = WXF / T can be obtained.

(B)-(d) of FIG. 1 show a state in which an object is imaged on the two-segmented light-emitting diodes 6 and 7, which are one-dimensional image sensors 2, according to the distance from the object 3. (b) shows the case where the focal length of the focus lens unit is exactly correct, (c) of FIG. 1 shows the case where the focal length with the subject 3 is near, and (d) of FIG. 1 shows the subject 3 The distance from) is long distance. As can be seen here, according to the position of the phase formed on the two-split light receiving diodes 6 and 7, the two-split light-emitting diodes 6 and 7 respectively output the current amounts of the signals corresponding to the phases, and the current amounts of the two signals. The focal length of the focus lens unit is adjusted by driving the focus lens unit and the two-segmented light-receiving diodes 6 and 7 that are mechanically interlocked so as to be the same.

In such a triangulation type auto focusing system, the weak signal, that is, the two-segmented light-emitting diodes (6) (7), is a very weak signal with a current amount nA output by the two-segmented light-emitting diodes (6) (7). It is very important to detect the signal of the image of the subject entrapped in.

In detecting a signal of an image of the subject, a custom integrated device is conventionally used. However, the custom integrated device is expensive to be expensive, has a lot of influences from external noise signals, and is external to the two-segment light-receiving diodes 6 and 7 so that the amplifying unit for amplifying the signal of the subject is saturated. When the strong disturbance light is incident, the effect of blocking the disturbance light is insufficient, and when the focus is automatically adjusted, hunting occurs that moves the focus ring to the left and right, and a puntover phenomenon occurs. There was a problem.

Therefore, an object of the present invention is to provide a subject signal detection circuit that blocks the disturbance light when strong disturbance light is incident and smoothly detects a signal of the subject.

The present invention having the above object consists of a disturbance light blocking unit for converting a current flowing into the light-emitting diode into a voltage and blocking strong disturbance light, and a filter unit for passing only the signal of the subject in the output signal of the disturbing light blocking unit.

The disturbance light blocking unit includes a current-voltage converter for converting a current flowing into the light-emitting diode into a voltage using an operational amplifier, and a transistor for controlling the amplification degree of the operational vapor while being turned on and off according to the intensity of the disturbance light. If it is weak, the transistor is turned off, and the signal of the subject detected by the light-emitting diode is amplified and output by the op amp with high amplification, and when the intensity of disturbance light is strong, the transistor is turned off to reduce the amplification of the op amp. By converting the signal of the subject into amplification and voltage with an operational amplifier with low amplification, the operational amplifier is prevented from saturation and effectively outputs the signal of the subject.

The filter unit includes a high pass filter for blocking a low frequency noise signal, and a band pass filter for amplifying and passing only a signal of a subject having a certain frequency in the output signal of the high pass filter, thereby subjecting the subject to an output signal of the disturbance light blocking unit. Only signal of is detected.

In particular, the present invention effectively detects a subject's signal by shielding it with a shield box so that the disturbance light blocking unit and the filter unit are not affected by external noise signals.

Hereinafter, the subject signal detection circuit of the present invention will be described in detail with reference to the accompanying drawings of FIGS. 2 and 3.

2 is a block diagram showing an auto focusing system in which a subject signal detecting circuit of the present invention is constructed. As shown in FIG. 2, strong current disturbances are obtained by converting a current according to the intensity of infrared light received by the light receiving diodes 8 and 9 into voltage. The disturbance hole blocking unit 10 for blocking light, the filter unit 20 for passing only the signal of the subject from the output signal of the disturbance hole blocking unit 10, and amplifying the output signal of the filter unit 20 An amplifying unit 30, an integrating unit 40 for integrating the output signal of the amplifying unit 30, and a multiplexer for discharging the integrated signal when the integrated signal of the integrating unit 40 reaches a set setting level ( 50, a comparator 60 for detecting a time at which the integrated signal of the integrator 40 is set to a setting level using the output signal of the multiplexer 50, and comparing it with a reference time, and a light emitting diode driver 80 The light emitting diode 81 is turned on to emit infrared rays As well as the motor driving section 90 in accordance with an output signal of the comparing section 60 is composed of a central processing unit (70) for adjusting the focus to thereby control the drive motor 91.

In the auto focusing system configured as described above, under the control of the central processing unit 70 in a state where 5 V power is applied, the LED driver 80 lights the LED 81 to emit infrared rays to the subject. Infrared rays reflected from the incident light enters the light-emitting diodes 8 and 9, and thus, the current of the subject flows in the light-emitting diodes 8 and 9 according to the intensity of the received infrared light.

Then, the disturbance hole blocking unit 10 detects the current flowing through the light receiving diodes 8 and 9 and converts it into a voltage, and blocks and outputs a signal of the disturbance light incident on the light receiving diodes 8 and 9 and outputs the disturbance hole. The filter unit 20 passes only a signal of a subject having a predetermined frequency from the output signal of the blocking unit 10, and a signal of the subject output from the filter unit 20 is amplified by the amplifying unit 30, and the integrating unit Integrated at 40, the multiplexer 50 operates to discharge the integrated signal when the level of the integrated signal reaches the set setting level, causes the integral unit 40 to start integration again, and outputs the multiplexer 50. As a signal, the comparator 60 determines the time when the integrated signal of the integrator 40 rises to the setting level, compares the time with the reference time, and outputs the result to the CPU 70.

Therefore, the central processing unit 70 controls the motor driving unit 90 while driving the rudder 91 in the forward and reverse directions while determining whether the focal length is correct by the output signal of the comparing unit 60.

In this case, the automatic focusing system includes a one-dimensional image sensor having the light receiving diodes 8 and 9 and a focus lens unit mechanically installed in association with the driving of the motor 91. The focal length is adjusted by adjusting the driving of the motor 91 so that the levels of the two signals output from the unit 60 are the same.

3 is a detailed circuit diagram illustrating an embodiment of the disturbance hole blocking unit 10 and the filter unit 20 of FIG. 2.

The disturbance hole blocking unit 10 includes an operational amplifier OP ₁₁ (OP ₁₂ ) and a resistor (R ₁₁ -R ₁₃ ) (R ₁₄ -R ₁₆ ) for converting a current flowing through the light receiving diodes 8, 9 into voltage. and the voltage converter 11 and 12, the current-) and capacitor (C _11, the current to C _12), an operational amplifier (OP ₁₁₎ in accordance with the output signal level of the voltage converter (11) (12) (OP Amplification degree control unit 13 comprising transistors TR ₁₁ (TR ₁₂ ), resistors R ₁₇ (R ₁₈ ), and capacitors C ₁₃ (C ₁₄ ) for adjusting the amplification degree so that ₁₂ ) does not become saturated. It consists of 14.

The filter unit 20 includes a capacitor C ₂₁ (C ₂₂ ) and a resistor R ₂₁ (R ₂₂ ) that allow a frequency signal equal to or greater than a signal of a subject having a constant frequency in the output signal of the disturbance hole blocking unit 10. An operational amplifier OP ₂₁ for detecting and amplifying a signal of a subject from the output signals of the high pass filters 21 and 22 and the output signals of the high pass filters 21 and 22 to the amplifying unit 30 ( OP ₂₂ ), band pass filters 23 and 24 composed of resistors R ₂₁ and R ₂₂ (R ₂₃ and R ₂₄ ) and capacitors C ₂₃ and C ₂₄ (C ₂₅ and C ₂₆ ).

The disturbance hole blocking unit 10 and the filter unit 20 according to the present invention configured as described above include a light receiving diode after the infrared ray emitted by the light emitting diode 81 is reflected from the subject in a state where power of 5V and 2.5V is applied. When the light is received by 8) (9), the light receiving diodes 8 and 9 flow a weak current of several nA depending on the intensity of the received infrared rays, and the current flowing through the light receiving diodes 8 and 9 is a current. It is converted into a voltage in the voltage converters 11 and 12 and output.

In this case, when the intensity of the disturbance light incident on the light receiving diodes 8 and 9 is weak, the current flowing through the light receiving diodes 8 and 9 is small, so that the output signal level of the operational amplifier OP ₁₁ and OP ₁₂ is high. The voltage across both ends of the resistors R ₁₇ and R _{18 of the} amplification degree adjusting unit 13 and 14 becomes low.

Therefore, transistor (TR ₁₁₎ is because a resistance (R ₁₇₎ (R ₁₈₎ off the voltage between the base and the emitter becomes lower than its bias voltage transistor (TR ₁₁₎ (TR ₁₂₎ of (TR ₁₂₎ is in blocking state, The current flowing through the light receiving diodes 8 and 9 is converted into a voltage according to the values of the resistors R _11- R ₁₃ and R _14- R ₁₆ of the current-voltage converters 11 and 12 and output.

When the intensity of the disturbance light incident on the light receiving diodes 8 and 9 is strong, the current flowing through the light receiving diodes 8 and 9 is large, so that the level of the output signal of the operational amplifiers OP ₁₁ and OP ₁₂ is increased. Will be lowered.

At this time, as the output signal level of the operational amplifier OP ₁₁ (OP ₁₂ ) is lowered, the voltage across the resistors R ₁₇ (R ₁₈ ) becomes high, and thus the transistors TR ₁₁ (TR ₁₂ ) have their biases. Over voltage is applied to turn on transistors TR ₁₁ and TR ₁₂ .

Therefore, the resistors R ₁₇ (R ₁₈ ) are connected in parallel with the resistors R ₁₃ (R ₁₆ ), and the current flowing through the light receiving diodes 8, 9 is transferred to the resistors R _11- R ₁₃ , R ₁₇ (R). ₁₄ -R ₁₆ , R ₁₈ ) is converted into a voltage according to the value of the output.

That is, the disturbance light blocking unit 10 has a high amplification degree by the value of the resistors R _11- R ₁₃ and R _14- R ₁₆ when the intensity of the disturbance light incident on the light receiving diodes 8 and 9 is weak. When the signal of the light receiving diodes 8 and 9 is amplified and converted into voltages, and the intensity of the disturbance light is strong, the transistors TR ₁₁ and TR ₁₂ are turned on and the resistors R _{11 to} R ₁₃ and R _{17 are} provided. ₁₄ -R ₁₆ , R ₁₈ to amplify and convert to a voltage with low amplification to prevent op amp OP ₁₁ (OP ₁₂ ) from saturating negatively.

As such, the signal output from the disturbance hole blocking unit 10 is input to the filter unit 20 so that the basic noise signal such as 60 Hz is removed from the high pass filter 21, and only a frequency signal of about 1 KHz or more passes and the high pass. The output signals of the filters 21 and 22 are input to the band pass filters 23 and 24 so that only a subject signal of about 10 KHz, which is infrared rays reflected from the subject, passes through the band pass filters 23 and 24. The output signal of the subject is input to the amplifier 30.

This invention devises 128 times the voltage of the subject signal output from the band pass filter 23, 24 of the filter unit 20 when reflecting plates reflecting infrared rays by 90% and 20%, respectively, for each distance. Was obtained to obtain the average value shown in Table 1.

TABLE 1

In particular, the present invention prevents external noise signals from entering by shielding the disturbance light blocking unit 10 and the filter unit 20 with a shield box, thereby accurately adjusting the focus of the subject even in a region having a lot of noise signals. can do.

As described above, the present invention amplifies the subject signal while controlling the amplification degree according to the intensity of the disturbance light incident from the disturbance light blocking unit to the light receiving diode, thereby preventing the operational amplifier from saturation and accurately detecting only the subject signal from the filter unit. Hunting or puncturing is not only prevented, and the focal length can be precisely adjusted without being influenced by external noise signals.

Claims (4)

In a triangulation distance autofocusing system that adjusts a focal length according to the intensity of infrared rays reflected from a subject and incident on the light receiving diodes 8 and 9, a current flowing through the light receiving diodes 8 and 9 is applied to a voltage. A filter for passing only the infrared signal reflected by the subject from the output signal of the disturbance light blocking unit 10 and the disturbance light blocking unit 10 to block the disturbance light when a strong disturbance light is incident thereto. 20) the subject signal detection circuit of the auto focusing system, characterized in that the configuration. The disturbance light blocking unit 10 includes: a current-to-voltage converter (11) (12) for converting and amplifying a current flowing through the light-receiving diode (8) (9) into a voltage; (11) An automatic amplification degree adjusting section (13) (14), which adjusts the amplification degree of the current-voltage converter (11) and (12) according to the output signal level of the signal to prevent saturation. Subject signal detection circuit of focusing system. 2. The filter unit (20) of claim 1, wherein the filter unit (20) includes a high pass filter (21) and a high pass filter (21) to remove a low frequency noise signal from the output signal of the disturbance light blocking unit (10). And a band pass filter (23) (24) for passing only the infrared signal reflected from the subject among the output signals of (22). The object signal detection circuit of claim 1, wherein the disturbance light blocking unit (10) and the filter unit (20) are shielded with a shield box so that external noise signals are not introduced.