JPH02163713A - Automatic focus adjustor - Google Patents

Abstract

PURPOSE:To attain fast focusing capable of front-rear decision in accordance with the variation of a focus signal owing to zooming by combining a compensator focusing type inner focus lens with automatic focusing by a video signal. CONSTITUTION:A zoom lens 10 has an object measuring lens 11, a variator lens 12 for zooming, a compensator lens 13 for focusing, and an image measuring lens 14. For example a subject is at a distance of 2m, lenses 12 and 13 are positions A and (a), and the focus signal is Va (non-peak value). In such a case, when a zoom state B is entered by moving the lens 12, the difference between the position (b) of the lens 12 and a focusing position 2m is larger than in a front state and the focus signal decreases to a value Vb. It is evident from the contents of a focusing information storage circuit 29 that an extension quantity curve rises rightward between A and B, so a control circuit 26 decides a focusing direction is on a short-distance side and outputs a signal for moving the lens 13 in the short-distance side to a motor driving circuit 25. Namely, it is not necessary to make the front-rear decision after zooming operation and the time required for the decision can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention provides a method for calculating tW from a video signal of an image sensor such as a CCD.
The present invention relates to an automatic focus adjustment device for a video camera or the like that performs focus detection by obtaining eH, and more specifically to an improved automatic focus adjustment device that shortens the focusing time by improving a hill-climbing automatic focus adjustment method.

(Prior Art) Conventionally, there have been many proposals regarding devices that perform autofocusing based on high frequency components of video signals.

There has also been a proposal (Japanese Unexamined Patent Publication No. 195632/1983) that combines autofocus with a zoom lens configuration in which zooming is performed by a variator lens, which is a variable magnification lens, and focusing is performed by a compensator.

(Problem to be solved by the invention) In the conventional autofocus method (mountain climbing method) using video signals, it was not possible to determine whether or not the focus was approaching unless the focusing lens was used. .

A method has also been proposed in which the optical path is slightly moved and optically modulated to determine the front and back, but this method requires a complicated configuration.

In addition, the lens configuration used in the invention according to the above proposal (Japanese Patent Application Laid-open No. 195632/1983) has a smaller lens barrel,
The focus lens is characterized by low load and small stroke.

In the present invention, focus detection is performed using a well-known phase difference method for focus correction.

Focus detection using a phase difference method is inherently advantageous in terms of determining the front and back of the focus, but requires securing optical path space, optical/light path adjustment, etc.

An object of the present invention is to improve an automatic focus adjustment device that performs focus detection by obtaining information from a video signal of an image sensor such as a CCD, and to provide an automatic focus adjustment device that can shorten focusing time. It's about doing.

(Means for Solving the Problems) In order to achieve the above object, an automatic focus adjustment device according to the present invention adjusts the focus of a zoom lens that performs zooming using a variator lens and focusing using a compensator lens using a focus signal obtained from an imaging unit. In an automatic focusing device, means for driving the variator lens and the compensator lens using a lens drive signal, a lens position information detecting means for detecting the position of the variator lens and the position of the compensator lens, and a means for detecting the position of the variator lens and the subject. storage means for storing compensator focus position information determined by the distance; means for generating a focus signal from a video signal obtained from an imaging section during movement of the variator; refer to the focus signal and the contents of the storage means; The control circuit includes a control circuit that determines the moving direction of the compensator and generates a lens drive signal.

The means for generating a focus signal from the video signal includes focus signal detection area setting means that can change the area so that the same subject is always included in the area based on variator position information, and the control circuit is configured to increase or decrease the focus signal by moving the variator. The lens drive signal may be configured to detect this, determine the front and back of the compensator lens from the focus position information stored in the storage means and the detected increase/decrease information, and generate a lens drive signal.

The means for generating a focus signal from the video signal includes focus signal detection area setting means for extracting a signal from a fixed detection area, and the control circuit detects that the focus signal increases or decreases due to movement of the variator. It is also possible to determine the front and back of the compensator lens from the focus position information stored in the storage means and the detected increase/decrease information, and generate the lens drive signal.

(Example) The present invention will be described in more detail below with reference to the drawings and the like.

FIG. 1 is a block diagram showing an embodiment of an automatic focusing device according to the present invention.

The zoom lens 10 includes an object side lens 11, a variator lens 12 for zooming. It has a compensator lens 13 and an image side lens 14 that perform focusing.

The variator lens 12 and the compensator lens 13 are provided movably in the optical axis direction by feed mechanisms 3i and 32 each having a lead screw directly connected to the shaft of a motor 27,28.

The motors 27 and 28 each have a control circuit 2.
Motor drive circuit 24.2 driven by signals from 6
5.

The variator lens 12 and the compensator lens 13
The axis of the position is that the lens position information detection means is the motor 27,
Position information is detected from the rotation amount of 2B and inputted to the control circuit.

A contrast detection circuit 22 outputs a signal (focus signal) at a level corresponding to the focus state to the control circuit based on the video signal from the 1m @ abandoned child 20 via the signal processing circuit 21.

Note that the area gate circuit 23 selects and sets which area on the screen is to be the detection area.

These signal processing circuit 21 and contrast detection circuit 22
, the area gate circuit 23 forms means for generating a focus signal from the video signal.

The area gate circuit 23 forms a focus signal detection area setting means and is configured to always include the same subject within the area based on the variator position information.

Note that signals from a fixed detection area may be extracted.

The focus information storage circuit 29 stores the zoom state (variator 12
The distance, subject distance, and compensator lens 1
The data of the relationship between the positions of the three positions (see FIG. 2) is stored.

FIG. 2 is a graph for explaining the focus adjustment operation of the zoom lens.

In the automatic focus adjustment operation, the variator lens 12 is moved to perform zooming, a focus signal is taken in at that angle of view, and while being compared, the compensator lens 13 is moved to perform focusing.

The fi shadow area of the lens 10 of this embodiment (the amount of extension of the compensator lens 13 for focusing at a certain subject distance depending on the zooming state) forms a curve as shown in FIG.

For example, to focus on a subject at a distance of 1 m, the compensator lens only needs to lie on the curve indicated by 1 m in accordance with the zoom state.

Assume that the subject is now at a distance of 2 meters.

The position (zoom state) of the variator lens 12 is A
, the position of the compensator is a.

Here, the focus signal has a certain value Va that is not a peak, and if the compensator is located at a position on the curve indicated by 2m, it will be a peak value.

After this, move the variator lens 12 and change the zoom state to B.
Assuming that, when the compensator is positioned without moving, the difference from the in-focus position 2m becomes larger than in the previous state.

In other words, the focus signal decreases to vb.

Let us assume that autofocus operation is performed at this position.

Normally, it is not known in which direction the focusing lens should be moved, so first try moving it in a certain direction (for example, to the close-up side), and if the focus signal increases, you know that it is in the focusing direction.

Also, if the signal decreases, we know that we need to move it in the opposite direction. In other words, front and back judgment operations are essential.

However, in the present invention, when it is found that the current vbO value is smaller than the value of Va that was taken in earlier, the control circuit 26 determines that this feeding amount curve is to the right from the contents of the focus information storage circuit 29 between A and B. Since it is known that the direction is upward, the focus direction is the closest side.

Therefore, the control circuit 26 is connected to the compensator lens 1.
3 in the closest direction (upward in FIG. 2) is output to the motor drive circuit 25.

In other words, after the zooming operation, there is no need to perform forward/backward determination for autofocus, the time required for this can be shortened, and the focusing speed can be shortened.

Here, since the angle of view changes due to zooming by moving the variator lens 12, the area area setting by the area gate 23 is changed according to the zooming so that the subject content within the detection area does not change at the same time. It is effective to configure the system so that it fits within the area.

Further, in the illustrated area, the curve of the ll11 shadow area is upward-sloping to the right, but since this slope differs depending on the zoom state, the data corresponding to the position information of the variator and the typical extension amount curve are stored in the focus information storage circuit 29. It is already understood from the content of

In addition, even if the size of the detection area does not change with zooming, it is possible to determine the front and back from a slight change in the focus signal (before the angle of view or subject content begins to change significantly), so this is a simpler configuration. The size of the area may be fixed.

(Effects of the Invention) As described in detail above, the focal joint device according to the present invention is capable of zooming using a variator lens.

The combination of a lens configuration that performs focusing using a compensator lens (compensator focusing inner focus lens) and autofocus using a video signal is advantageous for miniaturization.

■When the lens is ¥IAwJ, the stroke is small and the load is small.

In addition, high-speed focusing is now possible because front and back judgment can be made based on changes in focus signals caused by zooming.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an automatic focusing device according to the present invention. FIG. 2 is a diagram for explaining the focus adjustment operation of the zoom lens. 10...Zoom lens 11...Object side lens 12...Variator lens 13...Compensator lens 14...Image side lens 20...Image sensor 21...Image 1 image signal processing circuit 22... ...Contrast detection circuit 23...Area gate circuit 24.25...Motor drive circuit 26...Control circuit 27.28...Lens drive motor 29...Focusing information storage circuit 31.32...・Feeding mechanism

Claims (3)

[Claims] (1) In an automatic focus adjustment device that adjusts the focus of a zoom lens that performs zooming with a variator lens and focusing with a compensator lens using a focus signal obtained from an imaging section, means for driving the variator lens and the compensator lens using a lens drive signal; , lens position information detection means for detecting the position of the variator lens and the compensator lens;
a storage means for storing compensator focus position information determined by the variator position information and the subject distance; a means for generating a focus signal from a video signal obtained from an imaging section during movement of the variator; An automatic focus adjustment device comprising a control circuit that determines the moving direction of the compensator with reference to the contents of a storage means and generates a lens drive signal. (2) The means for generating a focus signal from a video signal includes a focus signal detection area setting means that can change the area so that the same subject is always included in the area based on variator position information, and the control circuit is configured such that the focus signal is 2. A lens drive signal is generated by detecting an increase or decrease in the compensator lens and determining the front and back of the compensator lens based on the focus position information stored in the storage means and the detected increase or decrease information. Automatic focus adjustment device. (3) The means for generating a focus signal from a video signal includes focus signal detection area setting means for extracting a signal from a fixed detection area, and the control circuit detects that the focus signal increases or decreases due to movement of the variator. 2. The automatic focus adjustment device according to claim 1, wherein a front/backward determination of the compensator lens is made based on the focus position information stored in the storage means and the detected increase/decrease information, and a lens drive signal is generated.