JPH11109215A - Focusing method for camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing method for a camera capable of surely, instantly and automatically focusing, as for the camera for focusing with high accuracy by moving a zoom lens to a telephoto end at the time of performing an automatic focusing operation. SOLUTION: When an AF(automatic focusing) start switch 51 is turned on, first, the focusing lens 12 is wobbled, the increasing direction of a focal evaluation is detected and the moving direction of the focusing lens 12 is decided. And, thereafter, the zoom lens 14 is moved to the telephoto end, then, the focusing lens 12 is operated so as to ascend in the decided direction, then, the focusing lens 12 is set at the maximum point of the focal evaluation value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of adjusting the focus of a camera, and more particularly to a method of adjusting the focus of a camera that performs autofocus based on a focus evaluation value.

[0002]

2. Description of the Related Art Conventionally, in a camera such as a television camera, when an auto focus start switch is turned on,
After moving the zoom lens to the telephoto end, focus adjustment is performed by moving the focus lens to the hill-climbing direction in the direction of increasing the focus evaluation value and moving the focus lens to the maximum point of the focus evaluation value, and after the focusing is completed. A camera that performs focus adjustment such as returning a zoom lens to an original position has been proposed.

The focus evaluation value is the amount of high frequency components of a video signal indicating a captured image. The hill-climbing operation of the focus lens moves the focus lens in a direction in which the focus evaluation value increases, and the focus evaluation value has a maximum value. It is to detect points. According to this, when performing focus adjustment by autofocus, the zoom lens is moved to the telephoto end before the focus lens is moved up the hill, so the focus adjustment is performed with the zoom lens set to the wide side. The focus accuracy can be higher than that of performing the zooming. For example, it is possible to prevent a problem that the focus is shifted when the zoom lens is moved after performing the focus adjustment.

[0004]

When the focus lens is operated to climb a mountain, it is necessary to first move the focus lens or a lens dedicated to wobbling by a small amount back and forth (wobbling) to detect the direction in which the focus evaluation value increases. There is. Conventionally, this wobbling is performed after the zoom lens is moved to the telephoto end.

However, when the zoom lens is at the telephoto end, if the focus lens position deviates greatly from the maximum point of the focus evaluation value, it is difficult to detect the increasing direction of the focus evaluation value even if wobbling is performed. There is a problem that the autofocus operation takes time. The present invention has been made in view of such circumstances, and when performing auto-focusing based on a focus evaluation value in a state where the zoom lens is moved to the telephoto end, immediately detects the increasing direction of the focus evaluation value. It is another object of the present invention to provide a method of adjusting the focus of a camera, which shortens the time of the autofocus operation and improves the autofocus performance.

[0006]

According to the present invention, in order to achieve the above object, when an auto focus start switch is turned on, the zoom lens is moved to a tele end, and then the focus lens is moved to a focus evaluation value by auto focusing. In the method of adjusting the focus of the camera to be moved to the maximum point, when the auto focus start switch is turned on, a direction in which the focus evaluation value is increased by wobbling of the lens before moving the zoom lens to the telephoto end is detected. After the zoom lens is moved to the telephoto end, the focus lens is moved up and down in a direction in which the detected focus evaluation value increases to set the focus lens at a maximum point of the focus evaluation value.

According to the present invention, the moving direction of the focus lens, that is, the direction in which the focus evaluation value increases, is determined by performing wobbling before moving the zoom lens to the telephoto end. The direction in which the focus evaluation value increases can be detected more reliably and immediately than in the case where wobbling is performed after being moved to the end, so that the time for the autofocus operation can be reduced and the autofocus performance can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a camera focus adjusting method according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing the internal configuration of a television camera to which the camera focus adjustment method according to the present invention is applied. As shown in FIG. 1, the photographing optical system 10 includes a focus lens 12, a zoom lens 14, a master lens 1,
6, an aperture 18 and the like, and a subject image is formed on an imaging surface of a CCD 20 serving as an image sensor via these lenses and the aperture 18.

The focus lens 1 of the photographing optical system 10
2 and the zoom lens 14 are each provided with a motor drive circuit 6
The motor drive circuits 60 and 62 are driven by motors 64 and 66 driven by
The motors 64 and 66 are driven based on drive signals input from the D / A converter 32 and D / A converters 68 and 70.

The positions of the focus lens 12 and the zoom lens 14 are adjusted by potentiometers 72 and 74, respectively.
Are detected by the A / D converter 7
The data is input to the CPU 32 through the CPU 6 and 78. CPU32
Detects the positions of the focus lens 12 and the zoom lens 14 from the potentiometers 72 and 74,
By outputting drive signals to the motor drive circuits 60 and 62, the focus lens 12 and the zoom lens 14 are moved to desired target positions.

The CCD 20 photoelectrically converts a subject image formed on an image forming surface and inputs the image to an image pickup circuit 22 as an image signal. The image pickup circuit 22 outputs, for example, N
A TSC video signal is generated, and this video signal is output to the viewfinder 48 or the like. The imaging circuit 22 includes a high-pass filter (HPF) 24 for obtaining a focus evaluation value indicating the sharpness of an image, an A / D converter 26, and a gate 2
8, the adder 30 is connected in order, and the imaging circuit 22 outputs a luminance signal generated from the image signal to the HPF 24 and outputs a synchronization signal to the focus area selection gate 28, the adder 30, and the CPU 32 in accordance with the video signal. I do.

The HPF 24 extracts a high-frequency component contained in the luminance signal. The higher the sharpness of the image, the more the extracted high-frequency components are included. Therefore, by integrating the high-frequency components, the average sharpness of the image in the integration range can be quantified. And HPF
The high frequency component that has passed through 24 is converted into a digital signal by an A / D converter 26 and input to a focus area selection gate 28. The focus area selection gate 28 is a circuit that extracts only a signal corresponding to a focus area at the center of the imaging screen, and extracts only information on a subject (main subject) captured in the focus area.

The digital signal extracted by the focus area selection gate 28 is input to an adder 30, where the digital signals for one field are integrated. This integrated value is used as a focus evaluation value indicating the sharpness of the image by the CPU.
32. The CPU 32 includes an auto focus start switch (AF start switch) 5 shown in FIG.
When 1 is turned on, the focus evaluation value is input from the adder 30, the focus lens 12 is moved to a position where the focus evaluation value becomes maximum by the hill-climbing operation, and the focus is automatically adjusted. Although details will be described later, when autofocus is performed by the AF start switch 51, the zoom lens 14 is moved to the tele end in order to obtain high focusing accuracy. Also, the AF start switch 5
When 1 is off (the AF start switch is normally off and an ON signal is transmitted only when the photographer presses the AF start switch), a lens controller (not shown) manually operated by the photographer ), The focus lens 12 and the zoom lens 14 are moved based on the instruction signal.

Next, the processing contents of the CPU 32 will be described. FIG. 2 is a flowchart showing a processing procedure of the CPU 32. When the power is turned on, first, the CPU 3
2 executes the initial setting to make it possible to take a picture (step S10), and thereafter executes the processing at the time of a normal manual operation (step S12). That is, as described above, the focus lens 12 and the zoom lens 14 are moved based on the instruction signal from the lens controller.

[0015] Further, during the execution of the above-described normal processing,
It is monitored whether or not the AF start switch 51 is turned on (step S14), and if NO, the above-described normal processing is repeatedly executed. On the other hand, when the AF start switch 51 is turned on, the following auto focus operation is executed.
When the AF start switch 51 is turned on, the CPU 32
First, wobbling of the focus lens 12 is executed (step S16). That is, a wobbling drive signal is output to the motor drive circuit 60 so that the focus lens 12
Is moved back and forth by a small amount, and a focus evaluation value is input from the adder 30. Thereby, the direction in which the focus evaluation value increases is detected, and the moving direction of the focus lens 12 is determined as the direction in which the focus evaluation value increases (step S1).
8).

Next, the current position of the zoom lens 14 is input from the potentiometer 74, the position is stored, and the zoom lens 14 is moved to the telephoto side (step S20). Then, it is determined whether or not the zoom lens 14 has reached the tele end (step S22), and it is confirmed that the zoom lens 14 has reached the tele end. Since the wobbling of the focus lens 12 is performed in step S16 before the zoom lens 14 is moved to the telephoto end, the wobbling is performed more reliably and immediately than when the wobbling is performed after the zoom lens 14 is moved to the telephoto end. The direction in which the focus evaluation value increases can be detected.

When it is confirmed that the focus lens 12 has reached the telephoto end, the focus lens 12 is moved in the direction determined in step S18 (in the direction in which the focus evaluation value increases), and the focus evaluation value is added to the adder 30. To start auto-focusing by a hill-climbing operation (step S24). Then, it is determined whether or not the focus lens 12 has reached the maximum point of the focus evaluation value, that is, whether or not to end the autofocus operation (step S2).
6) When the focus lens 12 reaches the maximum point of the focus evaluation value, the focus lens 12 is set at that position.

Then, the zoom lens 14 is moved to the original position stored in step S20 (step S28). When the above auto focus operation is completed, the process returns to step S12, and the above processing is repeatedly executed. As described above, when the AF start switch 51 is turned on to start the auto focus, the focus lens 12 is moved before the zoom lens 14 is moved to the tele end.
By wobbling, the moving direction of the focus lens 12 can be reliably and immediately determined.

In the above-described embodiment, the focus lens 12 is wobbled to detect an increasing direction of the focus evaluation value. However, when a lens for wobbling is provided, the zoom lens 14 is moved to the tele end. Before this, the lens is wobbled to detect the increasing direction of the focus evaluation value. Further, in the above-described embodiment, a case has been described in which the focus adjustment method according to the present invention is applied to a television camera. However, the present invention is not limited to this, and can be applied to other cameras such as a still camera.

[0020]

As described above, according to the method of adjusting the focus of the camera according to the present invention, the moving direction of the focus lens, that is, the focus evaluation value is obtained by performing wobbling before moving the zoom lens to the telephoto end. Since the increasing direction is determined, it is possible to detect the direction in which the focus evaluation value increases more reliably and immediately than in the case of wobbling after moving the zoom lens to the tele end,
The time for the autofocus operation can be reduced and the autofocus performance can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an internal configuration of a television camera to which a camera focus adjustment method according to the present invention is applied.

FIG. 2 is a flowchart illustrating a procedure of an autofocus process;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Photographing optical system 12 ... Focus lens 14 ... Magnification lens 16 ... Master lens 18 ... Aperture 20 ... CCD 22 ... Imaging circuit 24 ... HPF 28 ... Focus area selection gate 30 ... Adder 32 ... CPU 60, 62 ... Motor drive Circuit 64, 66: Motor 72, 74: Potentiometer

Claims (1)

[Claims] 1. A focus adjustment method for a camera, comprising, when an auto focus start switch is turned on, moving a zoom lens to a telephoto end, and then moving a focus lens to a maximum point of a focus evaluation value by auto focusing. When the focus activation switch is turned on, a direction in which the focus evaluation value increases due to a minute movement of the lens is detected before moving the zoom lens to the tele end, and the detection is performed after moving the zoom lens to the tele end. A focus adjustment method for a camera, wherein the focus lens is set to a maximum point of the focus evaluation value by performing a hill-climbing operation in a direction in which the focus evaluation value increases.