JPH0795136B2 - Auto focus device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus device, and more particularly to an autofocus device for performing focus adjustment on a desired subject within a field frame.

[Prior Art] In a camera or the like that performs focus detection using an image signal from a distance measuring field in an output image signal of an image pickup device, a target in the peripheral area of the entire field of view can be obtained by arbitrarily selecting a distance measuring field position. Japanese Unexamined Patent Publication No. 60-226280 discloses a technical means that enables automatic focus detection or automatic focus adjustment for a subject and removes a constraint when determining a composition in a conventional apparatus.

[Problems to be Solved by the Invention] However, in the above technical means, since the selection of the distance measuring field of view (focus area) is manually performed using the joystick, the push button switch, etc., the operation is troublesome. Since it takes a long time to shoot, there is a risk of missing a shutter chance in shooting requiring fast shooting, which is particularly unsuitable for a still camera. In a still camera, unless an operability and a quick-shooting property are improved, even if an expensive electronic circuit is used, the effect is small. On the contrary, it is often easier to apply AF lock.

In view of such problems, an object of the present invention is to automatically select an arbitrary area in a screen very easily and quickly, and to detect a focus state based on an image signal of the selected area. It is to provide a focus device.

[Means and Actions for Solving the Problems] An autofocus device according to the present invention divides a display unit for displaying a subject image on a screen and a screen displayed on the display unit into a plurality of areas, Switching means fixed to each of them, and this switch means being turned on.
A focus for selecting a detection means for detecting the off state and a standard area in which the size of the focus detection area of the subject image corresponds to a normal recording screen displayed on the display means or an area smaller than the standard area. A detection area selecting means, and means for enlarging the first divided area selected by the first selecting operation by the switch means when an area smaller than the standard area is selected by the focus detecting area selecting means. , When the second divided area is selected from the enlarged first divided area by the second selection operation by the switch means, the focus state is set based on the subject information corresponding to the second divided area. And a focus detecting means for detecting.

[Example] FIG. 1 shows an example of a still video camera to which the autofocus device of the present invention is applied. The infrared light cut filter 3 is arranged in front of the solid-state image sensor 1, and therefore, when the optical image of the object 5 is formed on the light-receiving surface of the solid-state image sensor 1 by the imaging lens 4, the object light is After the infrared light is excluded by the infrared light cut filter 3,
The light is received by each pixel of the solid-state image sensor 1. Solid-state image sensor 1
Is scanned by the drive pulse generated by the drive pulse generation circuit 6, and the photoelectric conversion signal is read out as a color signal from each pixel. This color signal is guided to the preamplifier 7 and amplified, and then subjected to various processes such as gamma correction and gain adjustment by the process circuit 8 to be converted into a video signal. The output of the process circuit 8 is the recording circuit 9
Is guided to the magnetic head 10 via. The magnetic disk 11 is driven by a motor 12 whose rotation is controlled by a servo circuit 13. The track control circuit 14 is a control circuit for moving the magnetic head 10 in the radial direction of the magnetic disk 11. The system controller 15 sends a control signal to the drive pulse generating circuit 6, the process circuit 8, the recording circuit 9, the servo circuit 13 and the track control circuit 14.

The output of the preamplifier 7 is a high-pass filter (HP
It is led to the gate circuit 17 via 16). The gate circuit 17 is a gate that opens and closes according to a control signal from the system controller 15, and passes only an image signal of a focus detection area (hereinafter referred to as a focus area) set by the photographer, as described later. The output of the gate circuit 17 is analog-digital converted by the A / D converter 18 and then guided to the image memory 19. The microcomputer (hereinafter referred to as CPU) 20 receives the output of the image memory 19, calculates the contrast of the image, and sends a rotation control signal of the motor to the motor drive circuit 21 according to the state.
The motor drive circuit 21 is a circuit for moving the taking lens 4 to the focus matching position.

As will be described later in detail, the transparent panel switch 22 is composed of a plurality of transparent focus area selection switches 22a arranged in a matrix on the display screen of the liquid crystal display unit 23 (see FIGS. 5A and 5B). )reference). The operation switch SW ₁ connected to the CPU 20 is a reset switch. When the reset switch SW ₁ is turned on, all the modes selected by the photographer are returned to the initial state. Operation switch SW ₂ ,
SW ₂ is a switch for selecting the size of the focus area. When the operation switch SW ₂ is turned on, a large focus area is selected, and when the operation switch SW ₃ is turned on, a small focus area is selected. The CPU 20 detects the on / off state of the operation switches SW _{1 to} SW ₃ , and also detects which focus area selection switch 22 a of the transparent panel switches 22 is on. Any focus area selection switch 22a in the transparent panel switch 22
By selecting, the area where the switch 22a exists is set as the focus area. Then, the CPU 20 changes the states of the operation switches SW _{1 to} SW ₃ and the transparent panel switch 22 to the system controller.
15 and the liquid crystal drive circuit 24. System controller
15 receives a signal from the CPU 20, and sends a control signal to the liquid crystal drive circuit 24 and the gate circuit 25. This control signal causes the gate circuit 25 to pass the area of the output pixel signal of the process circuit 8 according to the size of the focus area. That is, the gate circuit 25 passes all the pixel signals of the solid-state imaging device 1 when the focus area is large, and only the pixel signals of a partial area of the screen to be enlarged and displayed when the focus area is small. The output of the gate circuit 25 is the liquid crystal drive circuit 24.
Since the output of the driving circuit 24 is guided to the liquid crystal display section 23, the liquid crystal display section 23 displays the subject image in the pixel signal area that has passed through the gate circuit 25.

The transparent panel switch 22 and the liquid crystal display section 23 are constructed as shown in FIG. The name and position of the switch are printed on the graphic sheet 26 which is the operation surface of the transparent panel switch 22. A transparent upper electrode 27 and a lower electrode 28 are arranged below the graphic sheet 26 via a spacer 29, and at a position where the spacer 29 does not exist, an electrode X integrated with the upper electrode 27 and an electrode integrated with the lower electrode 28. Y and Y are provided so as to face each other so that they do not contact each other, and one focus area selection switch 22a of the transparent panel switch 22 is configured. By pressing the graphic sheet 26 corresponding to the positions of the electrodes X and Y with a finger or a pen, the electrodes X and Y come into contact with each other and the switch is turned on. The lower electrode 28 of the transparent panel switch 22 is adhered on the display screen of the liquid crystal display unit 23 with an adhesive tape 31.

As shown in FIG. 3 (A), a plurality of electrodes X of the transparent panel switch 22 (focus area selection switch 22a) are connected to the lines X ₁ , X ₂ and X _{3, respectively,} and a plurality of electrodes Y of the transparent panel switch 22 are also connected. Connected to Y ₁ , Y ₂ , and Y ₃ , a plurality of switches are arranged in a matrix shape crossing each other. Now, in the transparent panel switch 22 arranged in the matrisk pattern, when the CPU 20 sequentially transmits repetitive pulses to the lines X ₁ , X ₂ , and X ₃ as shown in FIG. Which focus area selection switch 22a of switch 22a
Is turned on, which of the lines Y ₁ , Y ₂ and Y ₃ outputs the pulse of which of the lines X ₁ , X ₂ and X ₃ is determined. For example, assuming that the focus area selection switch 22a at the intersection of (X ₂ , Y ₂ ) is turned on as shown in FIG. 3 (A), FIG. 3 (B)
As shown in, the pulse of line X ₂ is detected in line Y ₂ . The pulses detected on the lines Y ₁ , Y ₂ , Y ₃ are read by the CPU 20. In the state shown in FIGS. 3A and 3B, the focus area selection switch 22a at the position (X ₂ , Y ₂ ) of the transparent panel switch 22 is turned on.
Read by

FIG. 4 is a schematic view of the appearance of a still video camera to which the present invention has been applied. Connection cord for camera body 32 and display 33
It is designed to be detachably attached by 34.
The display unit 33 is provided with the liquid crystal display unit 23, and the display unit 23
The transparent panel switch 22 is displayed on the screen of
The operation switches SW _{1 to} SW ₃ are respectively arranged below.

Next, the operation of the above embodiment will be described with reference to the time chart shown in FIG.

First, the photographer selects the size of the focus area by selecting the operation switch SW ₂ or SW ₃ . Now, when the operation switch SW ₂ is on, the CPU 20 determines that a large focus area has been selected. Then the CPU20
This focus area size information is output to the liquid crystal drive circuit 24 as an area display signal S ₀ , and the system controller 25
Is output as a screen size signal S ₁ , signals S ₀ and S ₁ are signals that indicate whether the display is a normal display or an enlarged display,
In this case, normal display is instructed. When the focus area selection switch 22a of the transparent panel switch 22 is turned on by pushing it with a finger or the like, the CPU 20 sends an area signal S ₂ indicating the position of the focus area to the system controller 15. When the system controller 15 receives these signals S ₁ and S ₂ , it opens the gate circuit 17 and A / A outputs only the image signal in the focus area designated by the photographer.
The signal is led to the D converter 18, and the gate circuit 25 is opened to lead the pixel signals of the entire region to the liquid crystal drive circuit 24. As a result, the liquid crystal display unit 23 displays, for example, a display as shown in FIG. That is, in FIG. 5 (A), the liquid crystal display unit
The screen area surrounded by the broken line in the central part of the screen of 23 is selected by the focus area selection switch 22a, and the image signal in this screen area is stored in the image memory 19
Is stored in, and the CPU 20 calculates the contrast. If the contrast value does not reach the peak, the taking lens 4 is driven and the contrast is calculated again. If the contrast value reaches a peak, it means that the focus is matched, and the driving of the taking lens 4 is stopped.
After that, the system controller 15 controls the recording circuit 9, the track control circuit 14, and the servo circuit 13 to record an image on the magnetic disk 11.

Next, it is assumed that the operation switch SW ₃ is turned on. At this time, small is selected as the focus area.
Then, the CPU 20 sends the information about this small focus area to
The area display signal S ₀ is output to the liquid crystal drive circuit 24, and the screen size signal S ₁ is output to the system controller 15. At this time, enlarged display is instructed by the signals S ₀ and S ₁ .
Then, when the focus area selection switch 22a of the transparent panel switch 22 is pressed by a finger or the like to turn it on, in this first focus area selection operation of the transparent panel switch 22, the area signal S ₂ is sent from the CPU 20 to the system controller 15
Sent to the liquid crystal drive circuit 24 through the gate circuit 25 from the system controller 15 only the image signal of the selected screen area (the area of the central figure surrounded by the alternate long and short dash line in FIG. 5A). It is sent and enlarged and displayed on the liquid crystal display unit 23 as shown in FIG. 5 (B). Note that N is displayed in the upper right of the screen of the liquid crystal display unit 23 in the normal display (see FIG. 5A), but W is displayed in the upper right of the screen in the enlarged display. Next, on this enlarged screen,
The photographer again operates an arbitrary focus area selection switch 22a of the transparent panel switch 22 to select the focus area. Then, at this time, the CPU 20 sends an area signal S ₂ instructing the position of the focus area to the system controller 15 to cause the selection switch 22a to operate.
The focus area designated by is detected and displayed. As a result, the display screen of the liquid crystal display unit 23 displays the fifth
The display as shown in FIG. That is, the fifth
In FIG. 3B, the face of the person in the upper center of the screen of the liquid crystal display unit 23 is selected and is displayed surrounded by a broken line.

Next, as described above, the pixel output in the focus area is stored in the pixel memory 19 and then the CPU 20 calculates the contrast of the image. Then, when the driving of the taking lens 4 is stopped at the peak position of the contrast, the image is recorded on the magnetic disk 11. Of course, the image recorded here is the image shown in FIG.

In this way, focus detection based on a narrow area of the screen can be easily performed by a simple operation of the operation switches SW ₂ and SW ₃ and the transparent panel switch 22 having a simple structure.

Although the embodiments of the present invention described above are applied to an electronic still camera, the present invention can also be applied to a silver salt film camera. Further, although the transparent panel switch 22 is a mechanical type, it is also possible to use an electromagnetic type or electrostatic type switch using a known pointing pen.

[Effects of the Invention] As described above, according to the present invention, it is possible to easily and quickly select an arbitrary region of the screen, and to provide an ergonomically excellent autofocus device. It is also possible to select a small area on the screen with a simple circuit configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an electric circuit showing an embodiment of a still video camera to which the autofocus device of the present invention is applied, and FIG. 2 is a transparent panel switch shown in FIG. 3A and 3B are electrical wiring diagrams showing an example of the transparent panel switch and time charts of its input / output signals, and FIG. 4 is a diagram showing the configuration of the present invention. FIG. 5 (A) and FIG. 5 (B) are schematic views of the external appearance of the still video camera, and FIG. 5 (A) and FIG. 5 (B) are front views showing a state in which the focus area is selectively displayed in each of the normal display and enlarged display states of the liquid crystal display screen. FIG. 6 is a flow chart for explaining the autofocus operation of the embodiment shown in FIG. 20 …… CPU (detection means, focus detection means) 22 …… Transparent panel switch (switch means) 22a …… Focus area selection switch (switch means) 23 …… Liquid crystal display (display means) SW ₂ , SW ₃ …… Switch (selection means)

Claims (1)

[Claims] 1. Display means for displaying a subject image on a screen, and a screen displayed on the display means divided into a plurality of areas,
Switching means fixedly provided in each of the divided areas, and turning on of the switching means. The detection means for detecting the off state and the size of the focus detection area of the subject image are selected from the standard area corresponding to the normal recording screen displayed on the display means or an area smaller than the standard area. Focus detection area selection means, and means for enlarging the first divided area selected by the first selection operation by the switch means when an area smaller than the standard area is selected by the focus detection area selection means. And when the second divided area is selected from the enlarged first divided area by the second selection operation by the switch means, the focus is obtained based on the subject information corresponding to the second divided area. An autofocus device comprising: a focus detection unit that detects a state.