KR920011061B1 - Camera auto-focus controlling apparatus by sense - Google Patents

Abstract

The focus adjustor adopts the passive sensor focus method of driving a camera lens according to the brightness surrounding a subject, instead of an active auto-focus method in a conventional camera. The focus adjustor comprises a circuit (10) driving the lens toward an optimal focus range; a release switch (11) for selecting a mechanical part, an ootical part or a power source; a sensor (20) selectively operated by transistors (23,24) according to current variations in a photo transistor (21) and a variable resistor (22) ; a focus lock (30) having a SCR (31) driven by a control signal generated from the sensor (20); AF driver (40) driving the lens (41) according to a solenoid actuation.

Description

Camera focusing device by sensor

1 is a circuit diagram of an apparatus of the present invention.

* Explanation of symbols for main parts of the drawings

10 circuit portion 11 release switch

20: sensor detection unit 21: photo transistor

22: variable resistor 23: first transistor

24: second transistor 30: focus lock portion

31: SCR 40: AF Composition

41: mirror lens 42: solenoid

43: diode VCC: power

The present invention relates to an apparatus for adjusting a camera focus by a sensor, wherein the brightness of a subject to be scanned is detected by a visible light sensor, and the photographing lens is moved and adjusted by using a subject depth by an aperture.

Active AF cameras, which are currently commercially available, irradiate infrared spot beam light into parallel light through an aspheric lens toward a subject to be photographed, and receive a portion of infrared reflected light from the subject surface for distance measurement. The shape of the light distribution is imaged on the surface of the light receiving element through the lens. At this time, the light distribution on the light-receiving surface varies according to the distance of the subject, and the tilted amount at the center of the device is converted into the form of an electrical signal for photoelectric conversion. The photoelectrically converted signal is amplified by the electronic processor through I / V conversion. Through circuits such as filters, comparisons, sample hold, latches, encoders, magnet drives, and generators, the focusing is controlled by moving the friction lens to an appropriate focus position for the object distance.

Such an active two-point AF method has problems such as a relatively complicated circuit configuration, a high price of a device, and a possibility of error in AF operation under a high brightness condition.

The present invention uses a passive sensor focus method that drives the lens according to the luminance condition of the subject, and utilizes the principle that the lens is set to the near point in the high brightness condition and the near point in the high brightness condition. It was. Generally speaking, when the distance between the circle and the near point in the two-point AF camera is about 2.5m, the low luminance condition is the fresh use area.The shooting distance is generally closer to the near distance by the fresh guide number. It is limited, and in high brightness conditions, it is EE area, so general users take a lot of back and long distance shooting before 3m, and even if shooting near, the camera's aperture FNO increases, which increases the depth of field, making it an active AF camera. You can get a prize similar to

The present invention has been completed using this principle, and will be described in detail below with reference to the accompanying drawings.

1 is a circuit diagram of the apparatus of the present invention, which operates in three stages of the circuit portion 10 for driving the photographing lens to an appropriate focus region, the mechanism portion and the optical portion driven by the circuit portion 10 to provide a power supply Vcc. A release switch 11, wherein the circuit unit 10 includes a sensor detection unit 20 configured to selectively operate in the transistors 23 and 24 according to a current change by the phototransistor 21 and the variable resistor 22, It includes an AF driver 40 for driving the photographing lens 41 in accordance with the solenoid operation by the digital signal of the focus lock unit 30 made of the SCR 31 is operated according to the control signal by the sensor detection unit 20.

In addition, the sensor detecting unit 20 includes a photo transistor 21 which is operated when the release switch 11 is in a single state, a variable resistor 22 for adjusting the amount of current of the photo transistor 21, and a photo transistor 21. The first transistor 23 is switched in accordance with the current, and the second transistor 24 is switched in reverse depending on the switching of the first transistor (23). In addition, the AF driver 40 includes a solenoid 42, a diode 43, and a photographing lens 41, and is configured to move the photographing lens 41 to an appropriate focal region position by operating the solenoid 42.

In the circuit unit 10, the transistors 23 and 24 are provided with an output voltage by the resistors R1 and R2, and the output current controls the SCR 31 via the resistor R3 and the capacitor C1, and is released. The switch 11 has a normal position a position, a release 1 stage state in which the circuit unit 10 is operated, a b position, a release 2 stage state in which the mechanism unit is operated, a c position, and the power supply Vcc is the main switch 12 It is a configuration that is turned on and off. According to this configuration, in the present invention, when the release switch 11 is released from the normal state to the first stage of release (moving from the a position to the b position), the circuit unit 10 is operated, and the separation of the circle and the near point of the photographing lens 41 is performed. In the design, the appropriate EV brightness (subject brightness) can be set so that the variable resistor 22 can be adjusted.

Under such a high brightness condition, when the release switch 11, which is a photographing button, is pressed from the normal stage to the release stage 1, the photo transistor 21 detects the brightness of a high-brightness subject and receives a high-brightness light. Since the transistor 21 is turned on to lower the internal resistance value, a power supply Vcc is provided to the transistor 23 to turn on the transistor 23 and the transistor 23 is turned on, so that the base of the transistor 24 is turned on. The transistor 24 and the SCR 31 are turned off at the low potential, and the SCR 31 is turned off, so that the AF driver 40 causes the solenoid 42 not to be driven so that the photographing lens 41 remains at the home position. do.

On the contrary, in the low luminance condition, when the release switch 11 is pressed from the normal stage to the release stage 1, the photo transistor 21 detects the brightness of the low luminance subject, and the subject (not shown) is low. Because of the luminance, the phototransistor 21 is turned off to increase the internal resistance value. Accordingly, the transistor 23 is turned off because no bias is provided, and the transistor 23 is turned off, so that an applied voltage is provided to the base of the transistor 24 to provide a transistor. 24 and the SCR 31 are turned on. When the SCR 31 is turned on, a current flows in the solenoid 42 to be magnetized, and the photographing lens 41 is moved to a position set to satisfy the low luminance condition in the release two-stage state. In addition, since the SCR 31 maintains its state once it is turned on due to its characteristic, the SCR 31 has a focus lock function of continuously fixing the photographing lens 41 at the set position by the solenoid. That is, since the release switch 11 is positioned at point c of the second stage of the release after the point b of the first stage of the release, the release switch 11 is returned to the point a of the first stage. The photographing lens 41 is fixed while the mechanism operating part for adjusting focus is operated. In optical analysis, the lens source is f = 35mm, F = 3.8, δ '= 1 / 30mm (δ': minimum allowable particle size on the film surface based on minimum contact-resolution resolution). As an example of a general compact camera, the formula for calculating the front and rear depth based on the finite distance and the shooting distance of the lens is as follows.

h: Infinity of lens

a: Distance between objects (distance between the subject and the photographing lens 41)

ℓ1: Depth of field

ℓ2: Depth of field

According to the equations (1-1 to 1-3), the optical analysis data such as the infinity of the lens according to the F NO, the aperture diameter of the camera, the EV, F NO value, the brightness of the subject, and the front and rear of the subject, were tested. 1 is shown. In this case, the fresh shooting distance is calculated by the fresh guide number ÷ F NO.

TABLE 1

When the brightness of the subject is set to EV 10 or less under low luminance conditions as shown in Table 1, the front and rear depths at a shooting distance of 2.0 m (near proximity) are about 1.6 m to 2.5 m depth ranges based on the shooting distance, This area becomes the focal point of the near point, and the fresh shooting distance when the camera aperture diameter on the fresh start EV is set to F NO 4.5 in fresh guide number 10 is divided by the fresh guide number 10 divided by F NO 4.5. It can be seen that there is a limit. Also, in high brightness conditions, the brightness of the subject is EE mode with EV 11 or higher, so the front and rear depth when the subject distance is 3.5m (origin) is about 2.28 ~ 5.22m based on the subject distance, and about 1.13 ~ com in EV 15 In addition, it can be seen that the depth of field is corrected by the depth of field.

As described above, the present invention avoids the automatic focus adjustment method according to the subject distance by the active two-point AF method of the compact camera which is currently generalized, and automatically uses the depth of field range according to the change of the aperture value by the brightness of the subject. By using the sensor focus method that can be adjusted to the focus area, the photographic characteristics are similar to the active AF method, but the complexity of the electronic processor according to the active AF method and the error occurrence factor in the AF operation in the high luminance area are reduced, and accordingly the cost is reduced. And it has the effect of reducing the work, adjustment labor.

Claims (4)

A circuit portion 10 for driving the photographing lens to an appropriate focus region, a mechanism portion driven by the circuit portion 10, an optical portion, and a release switch 11 for selecting and supplying power. The circuit portion 10 includes a photo transistor. A sensor detector 20 configured to be selectively operated by the transistors 23 and 24 according to a current change by the 21 and the variable resistor 22, and an SCR 31 operated according to a control signal by the sensor detector 20. And a AF lock unit 40 for driving the photographing lens 41 according to the solenoid operation of the focus lock unit 30 by the digital signal of the focus lock unit 30, and detecting the luminance condition of the subject by the sensor detection unit. Camera focusing device by the sensor, characterized in that for adjusting the shooting lens to the focus position. The photoelectric sensor of claim 1, wherein the sensor detector 20 includes a phototransistor 21 that is operated when the release switch 11 is in the first stage, a variable resistor 22 that adjusts the amount of current in the phototransistor 21, and a photo. Camera focusing apparatus by a sensor, characterized in that the first transistor 23 is switched according to the current of the transistor 21, and the second transistor 24 is switched in reverse according to the switching of the first transistor (23) . According to claim 1, AF driver 40 is composed of a solenoid 42, a diode 43 and a photographing lens 41, so that the photographing lens 41 is moved to a predetermined focus position by the operation of the solenoid 42. Camera focusing device by the sensor, characterized in that the configuration. The signal locked to the condition of the photographing subject in the first stage of the release lock stage 30 remains unchanged at the position of the photographing lens 41 according to the initial brightness even if the brightness (condition) of the subject changes. Camera focusing device by the sensor, characterized in that to be fixed.