JPH02163715A - Automatic focus adjustor - Google Patents

Abstract

PURPOSE:To preclude disablement of focusing in macrophotography and to attain high-accuracy automatic focus adjustment by providing an area setting means, a mode detecting means, and a control means and changing a detection area automatically between normal photography and macrophotography. CONSTITUTION:The signal from an image pickup element 20 is passed through a video signal processing circuit 21 and part of it is inputted to a contrast detecting circuit 22 through an area gate circuit 23. An AF control circuit 25 puts a lens in focus by sending its output to a lens driving part 26 so as to move the focusing lens 11 to the position where the contrast value is maximum with the output signal of the circuit 22. The circuit 23 switches a video signal with the signal of the circuit 25 to extract only the signal of a necessary area. Here, the circuit 25 detects macrophotography time (whether a macrophotography switch 19 is on or the lens is moved to the macrophotography side) and sends its output to the circuit 23 so that the detection area is widened at the start of AF operation. In the normal photography, the detection area is switched to a narrow detection area. Consequently, the failure in focusing in macrophotography is precluded and high-accuracy AF operation is enabled.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to selecting a focus detection signal detection area in accordance with the operation mode of a camera lens in order to improve the focusing accuracy of an automatic focus adjustment device of a camera. This invention relates to an automatic focusing device.

(Prior Art) An automatic focus adjustment device (Japanese Unexamined Patent Application Publication No. 1982-219505) has been proposed which is capable of changing a focus detection area and has a variable video signal detection area for generating a focus signal indicating a focus adjustment state. ing.

This invention is particularly intended to solve the problem that when using a zoom lens in a television camera or the like and performing TTL focus detection, if the focus detection area is fixed, the focus detection accuracy will be impaired depending on the condition of the subject. That is. This device is a phase difference type focus detection device as an embodiment.

(Problem B to be Solved by the Invention) To perform automatic focus adjustment even in an automatic focus adjustment device using a lens capable of macro photography that drives a focus adjustment lens based on a detected focus signal. teeth,
Special consideration is required especially when taking macro photographs.

That is, during macro photography, since the subject is magnified and exists at the center of the screen, the probability that there will be a part where contrast is likely to occur near the center is small.

Furthermore, during macro photography, the depth of field is shallow, so highly accurate focus adjustment is required.

An object of the present invention is to provide an automatic focus adjustment device that solves the problem of automatic focus adjustment particularly in macro photography mode.

(Means for Solving the Problems) In order to achieve the above object, an automatic focus adjustment device according to the present invention uses a lens capable of macro photography that drives a focus adjustment lens based on a detected focus signal. In the automatic focus adjustment device, an area setting means for setting a plurality of detection areas having different areas in a signal corresponding to a screen, a mode detection means for detecting whether the lens is in a macro mode, and when in the macro mode, The apparatus is configured to include a control means for selecting a wide one of the detection areas, and selecting a narrow one of the detection areas when not in the macro mode.

(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 photographing lens 10 is composed of a focusing lens 11 and an image side lens 12.
1 is driven forward and backward to the in-focus position by a lens driving section 26, as will be described later.

Further, this lens 10 is capable of macro photography, and when the macro mode is selected, the macro switch 19 is turned on, and the fact that the macro mode has been selected is input to the AF control circuit 25.

An image sensor 20 such as a CCD detects the image formed by this lens 10.

A signal from the image sensor 20 passes through a video signal processing circuit 21 and a portion thereof is inputted to a contrast detection circuit 22 via an area gate circuit 23.

The area gate circuit 23 is a circuit that switches the video signal in response to a signal from the AF control circuit 25 and increases only the signal in a necessary area, that is, masks it.

Based on the output signal from the contrast detection circuit 20, the AF control circuit 25 sends an output to the lens drive circuit for focusing so as to move the focusing lens 11 to the position where the contrast value is maximum.

In the present invention, when the AF operation starts (detecting when the operator turns on the macro switch 19 or moves the lens to the macro side), the AF control section controls the area gate circuit. The output is sent to 23 to expand the detection area.

FIG. 2 is a diagram for explaining the relationship between the detection area and the photographic screen.

In FIG. 2(A), a wide detection area when the macro mode is selected is shown by a broken line.

Similarly, FIG. 2B shows the detection area during normal photographing.

Normally, in macro layered photography, the subject is often placed across the screen, as shown in FIG. 2(A). In this case, in a narrow detection area, parts where it is easy to obtain contrast, such as the outline of the subject, fall into the area, making it easy to focus.

On the other hand, in a wide detection area in normal photography, objects located at various distances may enter the detection area, making it easy to capture information other than the subject object.

Therefore, in this case, the AF control circuit 25 switches to a narrower detection area.

As described above, by changing the detection area during macro photography, more accurate AP operation can be realized.

In the embodiment described in detail above, an autofocus method for detecting focus using a video signal has been described, but the autofocus method is not limited to this method.

As another example, in autofocus using the phase difference method, conventionally one line sensor was used to detect focus on only a single area, but by arranging multiple sensors,
This is possible by selecting a plurality of detection areas obtained by combining these.

Also, in the active method using infrared reception and emission,
The detection area can be selected by changing the area of the light receiving element.

(Effects of the Invention) As explained in detail above, the present invention relates to an automatic focusing device using a lens with a macro function.

The apparatus is provided with an area setting means for setting a plurality of detection areas having different areas in a signal corresponding to the screen, and a mode detection means for detecting whether the lens is in macro mode.

The apparatus is configured to include a control means for selecting one of the wide detection areas when in the macro mode, and selecting one of the narrow detection areas when not in the macro mode.

This allows the detection area to be automatically changed between normal photography and macro photography.

This provides the following effects.

■Prevents inability to focus during macro photography.

■No malfunctions occur during normal shooting.

[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 relationship between the detection area and the photographic screen. 10...Photographing lens 11...Focusing lens 12...1st side lens 19...Macro switch 20...Image sensor 21...Video signal processing circuit 22...Contrast detection circuit 23...・Area gate circuit 25...AF control circuit 26...Lens drive section

Claims (1)

[Claims] In an automatic focus adjustment device using a lens capable of macro photography that drives a focus adjustment lens based on a detected focus signal, an area setting means sets a plurality of detection areas having different areas in a signal corresponding to a screen. and mode detection means for detecting whether the lens is in macro mode.
An automatic focus adjustment device comprising a control means for selecting a wide one of the detection areas when in macro mode, and selecting a narrow one of the detection areas when not in macro mode.