JPH04220629A - Focus demand - Google Patents

Abstract

PURPOSE:To improve the operability of a focus demand. CONSTITUTION:When the action of a servo means which controls the action of a focusing lens is controlled by comparing the manipulated variable detection signal of a focus control means with the lens position signal of a lens position detection means using a comparator and outputting a servo control signal proportional to the difference between both of the signals, a characteristic converting means comprising a potentiometer, an amplifier and a focus characteristic setter, etc., is used and characteristics of the focusing lens are changed by the characteristic converting means in such a manner that when the focusing lens is at close range the amount of movement of the focusing lens relative to the manipulated variable is increased while when the focusing lens is at infinite far side the amount of movement of the focusing lens is decreased.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to focus demand in television cameras and the like.

0002

BACKGROUND OF THE INVENTION In a television camera, lens focusing is performed by servo means consisting of a drive member such as a motor and a control mechanism that controls the operation of this drive member. A focus demand is used to provide a servo control signal to the control mechanism. This focus demand is
A focus operation means such as a handle that is manually operated by a photographer, and an operation amount detection means such as a potentiometer that detects the operation amount of the focus operation means and outputs an electric signal proportional to this operation amount. Roughly composed. Then, the output signal of the detection means is input as a servo control signal to the control mechanism of the servo means, and the drive member is operated based on the servo control signal to focus in a range from a close object to an infinitely distant object. It is made possible to do so. As methods for operating the focus lens using this focus demand, there are a speed control method and a position control method.The speed control method moves the focus lens at a speed corresponding to the amount of operation of the focus operation means. Further, in the position control method, the focus lens is moved by an amount corresponding to the amount of operation of the focus operation means. For this purpose, a lens position detection means for detecting the current position of the focus lens is provided, a signal of the current position of the focus lens is acquired from the lens position detection means, and the focus is determined based on this signal and the operation amount of the focus operation means. The movement of the lens is controlled.

[0003] When moving the focus lens using the position control method described above, in the prior art, the focus lens was moved in proportion to the amount of operation of the focus operation means. However, the relationship between the object distance and the amount of movement of the focus lens, ie, the focus curve, changes exponentially, as shown by the curve FC in FIG. Therefore, if the focus lens is moved in proportion to the amount of operation of the focus operation means, the sensitivity will be too high at infinity, making it impossible to focus finely. On the other hand, on the close side, the ability of the focus lens to follow the operation of the focus operation means deteriorates.

Therefore, in order to improve the operability of the focus operation on the infinity side, it is sufficient to widen the operation stroke range of the focus operation means, and also to improve the responsiveness of the focus lens to the focus operation on the close side. In order to achieve good results, the operating stroke range of the focus operating means may be narrowed. However, if the operating stroke range of the focus operating means is widened, the followability of the focus lens at close range becomes worse, and if the operating stroke range is narrowed, the sensitivity at infinity becomes even higher, making the operability extremely difficult. It gets worse.

Considering the above points, when focusing on the infinity side, the operation stroke range of the focus operation means is widened, and when focusing on the close side, the operation stroke range of the focus operation means is narrowed. Devices that can be switched in this manner have been known for some time.

[0006]

As described above, by changing the operation range of the focus operation means depending on the position of the subject, the operability of the focus demand can be improved to some extent. However, there are problems in that performing such a switching operation during photographing is troublesome and troublesome. Moreover, simply changing the operation stroke range of the focus operation means in two stages according to the object distance cannot improve the operability to the desired degree over the entire range of object distances from close objects to infinitely distant objects. This is difficult to achieve, and there are still limits to the improvement of focus demand operability.

The present invention has been made in view of the above points, and its purpose is to further improve the operability of focus demand.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention detects the operation amount of the focus operation means by the operation amount detection means, and uses this operation amount detection signal and the current position of the focus lens. A comparator compares the lens position signal from the lens position detection means that detects the lens position, outputs a servo control signal according to the difference between the two signals, and controls the operation of the servo means that controls the operation of the focus lens. In the above, the structure includes a characteristic conversion means for changing characteristics so that when the focus lens is on the close side, the amount of movement of the focus lens relative to the operation amount is large, and on the infinity side, the movement is small. This is a characteristic feature.

[0009]

[Operation] By adopting such a configuration, when the focus operation means is operated, the focus operation means can largely displace the focus lens with a small amount of operation on the close side of the focus curve where the slope is gentle and the sensitivity is low. can be done. Thereby, the focus lens can be quickly moved to the focus position in response to the operation of the focus operation means on the close side. Also,
At the infinity side, where the focus curve has a steep slope and sensitivity is high, the amount of movement of the focus lens due to the amount of operation of the focus operation means is small, so focusing at this infinity side can be easily performed, and fine details can be Operation becomes possible.

0010

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, in FIG. 2, reference numeral 1 indicates a focus operation means, and the focus operation means 1 is composed of a rotating drum, a rotating lever, etc., which are manually operated by a photographer. Reference numeral 2 denotes a manipulated variable detection means composed of, for example, a potentiometer, and the manipulated variable detecting means 2 can detect the manipulated variable of the focus operating means 1. Furthermore, 3 is a lens position detecting means for detecting the current position of the zoom lens, which is constituted by a potentiometer or the like.

Reference numeral 4 denotes a comparator, and this comparator 4 can compare the signal from the manipulated variable detection means 2 and the signal from the lens position detection means 3 and output the difference. ing. The signal from the comparator 4 is input to the servo means 5 as a servo control signal, and the focus lens driving motor 6 is operated based on the signal from the servo means 5 to move the focus lens 7. It is designed to let you do so.

Therefore, when this focus operation means 1 is operated, this is detected by the operation amount detection means 2, and
This signal is input to comparator 4. The signal related to this operation amount is compared with the signal related to the current position of the focus lens 7 detected by the lens position detection means 3, and based on the comparison result, the lens is moved by a predetermined amount to the near side or to the infinity side. A servo control signal for moving the lens 7 is input to the servo means 5, and the servo means operates the motor 6, so that the focus lens 7 is moved by an amount corresponding to the focus operation.

By the way, the operation amount detection means 2 and the lens position detection means 3 are set to change proportionally in accordance with the focus operation amount and the position of the lens 7, respectively, as shown by imaginary lines in FIG. In this case, the sensitivity becomes unnecessarily high on the infinity side, and on the other hand, the ability of the lens 7 to follow the operation of the focus operation means deteriorates on the close side. Therefore, the output signal from the lens position detection means 3 corresponding to the amount of movement of the lens 7 should be changed in a curve as shown by the solid line in FIG. 3, or the output signal corresponding to the operation amount from the operation amount detection means 2 should be Set it so that it changes as shown by the dotted line. This allows the lens 7 to move along the focus curve FC. As a result, the lens 7 can be quickly moved to the focus position in response to the operation of the focus operation means on the close-up side, and the amount of operation of the focus operation means on the infinity side, where the inclination is steep and the sensitivity is high. Since the amount of movement of the lens 7 due to this decreases, focusing on the infinity side can be easily performed, and fine operations become possible.

Next, FIG. 4 shows a second embodiment of the present invention. In this embodiment, an amplifier is used to adjust the amount of movement of the focus lens 7 with respect to the amount of operation of the focus operation means 1 along a focus curve. It is configured to control the This amplifier may amplify the output signal from the manipulated variable detection means 2 as shown by A1, or
Further, as shown at A2, the output signal from the lens position detection means 3 may be amplified, and furthermore, as shown at A3, it may be provided on the output side of the comparator 4. When the amplifier A1 or A3 is provided, the amplification gain has a characteristic that changes as shown by the solid line in FIG. 3, and when the amplifier A2 is used, the characteristic changes as shown by the dotted line in FIG. Provide amplification gain. This also makes it possible to improve the operability of the lens 7, as in the first embodiment described above.

Furthermore, as shown in FIG. 5, in place of the comparator 4, a comparison means 8a for comparing the signal from the operation amount detection means 2 and the signal from the lens position detection means 3, and a comparison means 8a for comparing the signal from the operation amount detection means 2 and the signal from the lens position detection means 3, It has a focus characteristic setting device 8b which is preset to the optimum focus characteristic FC based on the lens position from the means 3, and output signals from the operation amount detection means 2 and output signals from the lens position detection means 3. It is also possible to provide a focus control means 8 composed of, for example, a microcomputer, which is configured to be able to output a servo control signal corresponding to the set focus characteristic by comparing the set focus characteristics. It becomes possible to input a signal having characteristics along the focus curve FC to the servo means 5.

[0016]

As explained above, the present invention utilizes a characteristic conversion means to convert the output signal from the operation amount detection means for detecting the operation of the focus operation means and the lens for detecting the current position of the focus lens. A comparator compares the lens position signal from the position detection means, outputs a servo control signal according to the difference between the two signals, and performs characteristic conversion when controlling the operation of the servo means that controls the operation of the focus lens. By inputting a servo control signal to the servo means via the means, the signal is converted into an output signal characteristic that changes like a quadratic curve, with a steep slope on the close side and a gentle slope on the infinite side. As a result, the output signal corresponding to the operation amount of the focus operation means will change rapidly at the close side, and when the focus operation means is operated at the infinity side, the output signal will change rapidly depending on the operation amount of the focus operation means at the infinity position. The change in the signal becomes gradual, the focus curve is corrected and converted into a nearly straight line, and the operability of the focus demand is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a focus curve.

FIG. 2 is a circuit diagram of focus demand showing the first embodiment of the present invention.

FIG. 3 is a diagram showing signal characteristics of operation amount detection means and lens position detection means.

FIG. 4 is a circuit diagram of a focus demand showing a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a focus demand showing a third embodiment of the present invention.

[Explanation of symbols]

1 Focus operation means 2 Operation amount detection means 3 Lens position detection means 4 Comparator 5 Servo means 6 Motor 7 Focus lens 8 Focus control means 8a Comparison means 8b Focus characteristic setter

Claims (4)

[Claims] 1. The operation amount of the focus operation means is detected by the operation amount detection means, and the operation amount detection signal and the lens position signal from the lens position detection means for detecting the current position of the focus lens are detected by a comparator. In the apparatus for controlling the operation of a servo means for controlling the operation of a focus lens by outputting a servo control signal according to the difference between the two signals, when the focus lens is on the close side, the focus for the operation amount is A focus demand characterized by having a structure including a characteristic conversion means for changing characteristics so that the amount of lens movement is large and the movement is small on the infinity side. 2. The characteristic converting means converts the manipulated variable detecting means into a potentiometer having an output signal characteristic that changes in a curve such that the slope is steep on the close side and gentle on the infinity side. The focus demand according to claim 1, characterized in that: 3. The characteristic converting means converts the lens position detecting means by a potentiometer having an output signal characteristic that changes in a curve such that the slope is gentle on the close side and steeply on the infinity side. The focus demand according to claim 1, characterized in that: 3. The characteristic converting means comprises an amplifier that amplifies the output signal of any one of the operating flow detecting means, the lens position detecting means, or the comparator, and by changing the gain of the amplifier in a curved manner. 2. The focus demand according to claim 1, wherein the servo control signal characteristics are set to change exponentially from the closest side to the infinity side. 4. The characteristic conversion means indexes a servo control signal for the operation amount detected by the operation amount detection means from a close side to an infinity side based on a lens position signal from the lens position detection means. 2. The focus demand according to claim 1, further comprising a focus characteristic setting device that changes the focus characteristic functionally.