JPH022291A - Camera with automatic focus function - Google Patents

Abstract

PURPOSE:To reduce the change in the image magnification (picture angle) due to the movement of a lens and to decrease the adverse effect on a video signal by adjusting a focus of the lens by means of the inner focus system in the contrast detection AF system. CONSTITUTION:A camera section 10 converts an incident light made incident through an optical system lens 50 into a video signal sequentially, the video signal is separated into a luminance signal and a composite synchronizing signal. The composite synchronizing signal is separated into vertical and horizontal synchronizing signals by a synchronizing signal processing section 16 and a gate signal generating circuit 18 sends a control signal controlling the timing of the sampling of the picture area to be sampled to a gate circuit 20. The gate circuit 20 samples the luminance signal of the high frequency component for a prescribed period and an arithmetic circuit 22 integrates the sampled luminance signal for a prescribed period and outputs it as an AF evaluation data to an MPU 24. The MPU 24 uses the AF evaluation data to apply comparison calculation of the time series by the down hill servo method and moves the compensator lens system 56 on the optical axis 70 via a motor control circuit 26.

Description

[Detailed description of the invention] Technical field TECHNICAL FIELD The present invention relates to cameras, and more particularly to automatic focusing mechanisms thereof.

BACKGROUND TECHNOLOGY As is well known, the automatic focus adjustment method (hereinafter referred to as
It's called the AF method. ), there are seven measurement methods, including an external measurement method that uses infrared irradiation, phase difference detection AF that uses the light flux from the imaging lens, and contrast detection AF that uses the contrast of the subject. .

For example, a conventional camera with a contrast detection AFa structure that uses a video signal obtained from an imaging device such as a COD extracts the high frequency component of the video signal in a predetermined area on the screen, integrates it for a predetermined period, and then Focusing was achieved by moving the so-called front lens of the optical system lens so that the integral value was the highest.

As is well known, when the front lens of an optical system lens moves, the image magnification (
angle of view), that is, the size of the image changes.

Accordingly, the video signal obtained by the imaging device also changes accordingly. In the contrast detection AF method, refined values of high-frequency components of a predetermined image area of a video signal obtained from an imaging device are compared and calculated in time series, and the movement of the front lens is controlled using, for example, a hill-climbing servo method. therefore,
When the angle of view changes, the precision value of the high frequency component in a predetermined area may also change accordingly. In other words, even though the subject image has not changed, the bait calculation value may change due to a change in the size of the image. In such a case, the servo control system repeats changes in the integral value and movement of the lens in an infinite loop, resulting in a problem of hunting in which the servo mechanism vibrates.

OBJECTS It is an object of the present invention to overcome the drawbacks of the prior art and to provide a camera with an autofocus function that has good focusing accuracy and a stable focusing function.

DISCLOSURE OF THE INVENTION According to the present invention, a camera with an autofocus function includes: an imaging lens made up of a plurality of lenses constituting an inner focus mechanism; an imaging means for converting light input through the imaging lens into a video signal; A video signal processing means and gate means that utilize only a predetermined band and a predetermined range of the signal, and an inner side of a plurality of lenses designed to reduce changes in image magnification due to focusing using the extracted video signal. and a driving means for moving the at least one lens according to the result of the calculation.

Further, according to the present invention, the calculation means of the camera with an autofocus function calculates the moving direction of at least one lens using a hill-climbing control method.

DESCRIPTION OF EMBODIMENTS Next, embodiments of a camera with an autofocus function according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, the configuration of an example of a video camera in which the camera with an autofocus function of the present invention is applied is shown. The camera of this embodiment includes four groups of zoom lenses 50 and a solid-state image sensor 30 , the contrast detection is performed using the video signal obtained by the solid-state image sensor 30, and the zoom lens 50 is controlled by an inner focus method according to the detection result.

The camera unit 10 includes a solid-state image sensor 30 made of a charge transfer device such as a CC port including a plurality of image sensor arrays 32, and an optical system lens 50. converted into a signal. The converted video signal is separated into an H degree signal and a composite synchronization signal.The luminance signal after eight separations is output from the output 102 to the video signal processing circuit 12, and the composite synchronization signal is output from the output 10B to the synchronization signal. It is output to the processing section 18. Note that the luminance signal separated by one is output to the AF mechanism related to the present invention, and is also output from the connection line 130 to other circuits such as a recording system.

The camera unit 10 also includes a zoom motor 34 and a focus motor 36 that drive a movable lens of an optical system lens 50, which will be described later, and each motor is driven according to control signals input from an output 124 and an output 128 of the motor control circuit 2B. do.

Referring to FIG. 2, the optical system lens 50 of the camera section 10
The principle structure of is shown in more detail. In the optical system lens 50 of this embodiment, four groups of zoom lenses are configured by a focusing lens system 52, a variator lens system 54, a compensator lens system 56, and a mask lens system 58. It is located in As described above, this camera employs an inner focus system, and the focusing lens system 52 and master lens system 58 are fixed. Further, the variator lens system 54 is movable back and forth in the direction A of the optical axis 70, and the compensator lens system 58 is also movable back and forth in the direction B of the optical axis 70. To adjust the focus,
This is done by moving the compensator lens system 56 back and forth on the optical axis 70. In addition, the focal length due to the so-called zoom operation and the focus adjustment due to changes in the focal length are adjusted by driving the zoom motor 34 and the focus motor 36 to move the variator lens system 54 and the compensator lens system 56 back and forth on the optical axis 701-. This is done by moving.

Returning to FIG. 1, the video signal processing circuit 12 includes a bandpass filter and a clamp circuit. The video signal processing circuit 12 extracts a high frequency component from the luminance signal inputted from the output +02 of the camera unit 1O, clamps the extracted high frequency component signal, and then outputs the signal from the output 104 to A/
It is output to the D converter 14.

The A/D converter 14 outputs +0 from the video signal processing circuit 12.
The analog signal of the high frequency component input from 4 is converted into digital and output to the gate circuit 20.

On the other hand, the synchronization signal processing unit 16 outputs the output 10 of the camera unit 10.
The composite synchronization signal input from 8 is converted into a nail direct synchronization signal (Vsy
nc) and horizontal synchronization signal (Hsync).

Each signal after separation is output to the gate signal generation circuit 18 from output +10. In addition, these synchronization Shinso Vsync
and Hsync can be taken out directly from the camera unit 10, for example, if the camera unit IO is equipped with a synchronization divider.

In the gate signal generation circuit 18, setting values for the horizontal direction and superposition direction of the area on the screen to be sampled are set in the gate circuit 20, and in addition to this, the synchronous signal processing section 16
The scanning status of the screen scanning line by Vsync and Hsync which are manually inputted from the screen will be compared. Based on the comparison result, a control signal for controlling the sampling timing in the gate circuit 20 is outputted to the output 112.

The gate circuit 20 has 11 AND gate circuits (not shown), and has an A/D signal input from the output 10B of the A/D converter 14.
The luminance signal after D conversion is output from the gate signal generation circuit 18 +
According to a control signal manually input from 12, sampling is performed for a predetermined period. The sampled signal is output to the arithmetic circuit 22 from the output +14.

The arithmetic circuit 22 refines the sampled signal input from the output 114 of the gate circuit 20 for a predetermined period. The data after integration (AF evaluation data) is output from output 116 to M
It is output to PU 24.

The MPU 24 compares the AF evaluation data inputted from the output 11B of the arithmetic circuit 22 with the immediately preceding AF evaluation data, and performs a time series comparison at the so-called hill-climbing servo method.
Do calculations. The MPU 24 is also connected to the camera section 10, and outputs 118 and 12 of the camera section 10.
Position information of the variator lens system 54 and the compensator lens system 56 of the optical system lens 50 is input from 0. The MPU 24 refers to the position information of the compensator lens system 56 and determines the rotational direction and drive time of the focus motor 3B that moves the compensator lens system 56 (i.e., the movement of the compensator lens system 56) according to the result of the comparison calculation in the mountain climbing servo method. When the zero rotation direction and drive time for determining the distance) are determined, a control signal for controlling the focus motor 3B is output from the output 12B to the motor control circuit 26.

The motor control circuit 2B is connected to the MPU 24 and the camera unit 10, and outputs a focus motor drive signal 1 according to the control signal input from the output 12B of the MPU 24.
Output to 28.

Here, the AF operation of the camera shown in FIG. 1 will be specifically explained.

When the main power of the camera is turned on and light from a subject enters through the optical system lens 50, the camera section 10 sequentially converts the incident light into a video signal, and uses the converted video signal as a luminance signal and a composite synchronization signal. The luminance signal after 0 separation is sent from the output +02 to the video signal processing circuit 12, and is also output to other circuits such as the recording system via the connection line 130. On the other hand, the composite synchronization signal is sent to the synchronization signal processing unit 1 via the output 108.
Output to 6.

Next, the video signal processing circuit 12 extracts only the high frequency component of the luminance signal, and the A/D converter 14 converts the extracted signal into a digital signal. The digitized high-frequency component luminance signal is sent to the gate circuit 20 via the output 10B.

On the other hand, the composite synchronization signal separated by the camera unit IO is separated into a vertical synchronization signal and a horizontal synchronization signal by the synchronization signal processing unit 16.
It is sent to the gate signal generation circuit 18.

The gate signal generation circuit 18 compares the set values in the horizontal and vertical directions of the image area to be sampled with the actual scanning situation of the video signal.
A control signal for controlling sampling timing is sent to the gate circuit 20.

In the gate circuit 20, the digitalized high-frequency component luminance signal is sampled for a predetermined period, that is, a predetermined area on the screen. Therefore, the arithmetic circuit 22 integrates the sampled luminance signal for a predetermined period, for example, one field, and outputs the integrated data to the MPU 24 as AF evaluation data.

The MPU 24 uses the AP evaluation data to perform time series comparison calculations using the mountain climbing servo method.On the other hand, the position information of the compensator lens system 58 is transmitted from the camera unit 10 to the MPU 24.
24 at all times. The MPU 24 refers to this position information and determines the rotation direction of the focus motor 36 according to the result of the comparison calculation. When the 0 rotation direction is determined, the MPU 24 controls the motor control circuit 2B accordingly to focus. A motor drive signal is sent to the camera unit IO. The focus motor 38 is driven by the focus motor drive signal, and the compensator lens system 56 is connected to the optical axis 7 via an interlocking member such as an AF ring.
Move above 0.

The focus is adjusted by moving the compensator lens system 56 on the optical axis 70 in this manner, and these operations are continuously repeated until the camera is powered off.

As described above, the camera of this embodiment determines the moving direction of the optical system lens using the high frequency component of the video signal, and adjusts the focus by moving the compensator lens system 56 of the optical system lens 50. Therefore, changes in image magnification (angle of view) due to lens movement are reduced, and adverse effects on video signals can be reduced. Therefore, M
The calculated values used in the mountain climbing servo method performed in the PU 24 are stabilized, and problems such as hunting can be reduced.

Furthermore, since the AF operation is performed by the compensator lens system 56, there is no need to provide the optical system lens 50 with an optical system dedicated to AF, so the optical system lens 50 can be made smaller and lighter than before.

In this embodiment, the AF operation was mainly explained, but in the case of a so-called zoom operation, the AF operation follows the change in focal length due to the movement of the variator lens system 54, similar to the operation of a normal zoom lens. Consensator lens system 5
The focus is adjusted by moving 6.

In this case, the MPU 24 compares the position information of the variator lens system 54 inputted from the camera unit IO with the position information of the compensator lens system 56, and outputs a control signal for moving each lens system! 22 and output 12B are output to the motor control circuit 26. The motor control circuit 2B sends a focus motor drive signal and a zoom motor drive signal from output 128 and output 12B, respectively, to the camera unit IO, and
and the focus motor 36 is driven.

Such an operation realizes a zoom operation.

In this embodiment, the camera with an autofocus function of the present invention is applied to a video camera, but it can also be applied to other cameras other than video cameras, such as an electronic still camera having a solid-state imaging device.

Effects According to the present invention, in the contrast detection 111AF method that performs automatic focus adjustment using high-frequency components of a video signal, the lens focus is adjusted by the inner focus method, so that the image magnification by moving the lens can be adjusted. (
This reduces changes in angle of view) and reduces negative effects on video signals. Therefore, evaluation data used for automatic focus adjustment is stabilized, and problems such as hunting can be reduced.

[Brief Description of the Drawings] Fig. 1 is a functional block diagram showing an embodiment of the camera with an autofocus function according to the present invention, and Fig. 2tA shows the principle configuration of the optical system lens of the camera with an autofocus function shown in Fig. 1. FIG. Explanation of symbols of main parts 10. Camera section 12. Video signal processing circuit 1B. Synchronization signal processing section 1B. Gate signal generation circuit 20.9. , Gate circuit 22, , Arithmetic circuit 24, , MPU 213, , Motor control circuit 34, , Zoom motor 3B, , Focus motor 50, , Optical system lens patent applicant Fuji Photographic Film Co., Ltd. Managing Director Takao Katori Takao Maruyama

Claims (1)

[Claims] 1. An imaging lens made up of a plurality of lenses constituting an inner focus mechanism, an imaging means for converting light input through the imaging lens into a video signal, and a predetermined band of the video signal. and video signal processing means and gate means that utilize only a predetermined range; and at least one inner lens of the plurality of lenses designed to reduce changes in image magnification due to focus using the extracted video signal. A camera with an autofocus function, comprising: calculation means for calculating a moving direction of a lens; and driving means for moving the at least one lens according to the result of the calculation. 2. The camera according to claim 1, wherein the calculation means calculates the moving direction of the at least one lens using a hill-climbing control method.