JPH02294168A - Camera with auto-focusing function - Google Patents

Abstract

PURPOSE:To photograph after easily focusing on an object by extracting an electrical signal generated at a designated image pickup area, and controlling the focusing position of a lens. CONSTITUTION:An output signal at every picture element corresponding to horizontal scan from a solid-state image pickup element 19 is also supplied to a switching circuit 33 via a sample-and-hold circuit 31, an exposure control part 26, and an AGC(automatic gain control) circuit 32. A switching control part 34 detects the scan timing of a focus area selected and designed by a focus area selection key 12 in advance based on a timing signal representing the scan timing of the solid-state image pickup element from a timing signal generation part 29, and turns on the switching gate of the switching circuit 33. And only the output signal from the solid-state image pickup element 19 corresponding to the focus area is supplied to an auto-focus control part 33. Thereby, it is possible to surely perform focusing at a state where desired composition is decided even when the object desired to focus is located at any position in an image pickup area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a camera with an autofocus function.

[Prior art and its problems] Conventionally, in cameras equipped with an autofocus function, the focus area is usually fixed at the center of the finder.

That is, when a subject is captured at the center of the viewfinder and the release switch is operated, the distance to the subject corresponding to the focus area is optically measured, and the focal length is automatically adjusted.

However, if the upper self-focus area is fixed at the center of the finder, for example, if you want to take a picture with the subject placed to the right or left of the finder, the focal length will match the background of the subject. For this reason, general autofocus cameras are provided with a focus lock function as a countermeasure in cases where the subject to be focused does not correspond well to the focus area. In other words, this focus lock function means that when you align the focus area with the subject and press the release switch halfway, the focal length will be fixed for the subject (
After that, even if the subject is moved to an arbitrary position within the finder and the shutter is released, the subject can be photographed with the focal length adjusted to the subject.

However, if the focus lock function is activated every time the subject moves out of the focus area, there is a problem that, for example, the shutter may be released even though the focus is supposed to be locked, or the user may make an operation error due to carelessness.

[Purpose of the Invention] The present invention was made in view of the above-mentioned problems, and it is possible to easily take pictures that focus on the subject without having to perform a focus lock operation even when the subject is not captured in the center of the viewfinder. The purpose of the present invention is to provide a camera equipped with an autofocus function that enables automatic focusing.

[Summary of the Invention] In other words, a camera with an autofocus function according to the present invention includes a lens, an image sensor that generates electricity/i according to the amount of light incident through the lens, and an image sensor that generates electricity/i according to the amount of light incident through the lens. imaging signal output means for sequentially outputting the electrical signals generated as image signals; area specifying means for specifying an arbitrary area of the image sensor; and a specified area for extracting the electric signals generated in the designated imaging area by the specifying means. The image pickup apparatus includes a signal extraction means and a focus control means for controlling the focal position of the lens based on the electrical signal from the designated imaging area by the signal extraction means.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of the electronic circuit. In the figure, 11 is a main control section;
The operation of each part of the circuit is controlled by The main control unit 10 includes a release switch 11 that is operated when photographing a subject, and a focus area that includes four operation keys: "up", "down", "left", and "right" for selecting the focus area within the shooting area. Selection key 12 is connected. Also,
Reference numeral 13 denotes a finder for viewing and setting the photographing area, and a liquid crystal shutter 14 is provided inside this finder 13. This liquid crystal shutter 14 displays the focus area on the photographing area in accordance with the selection of the focus area by the focus area selection key 12. The drive is controlled through the drive section 15.

On the other hand, 16 is an imaging lens, 17 is a zoom lens, and 18 is an iris (aperture), and the subject image captured by the finder 13 is captured by the imaging lens 16. zoom lens 17
, and the solid-state image sensor (CCD) 1 through the iris 18.
9 is optically imaged.

The imaging lens 16 is driven by a focus motor 20, and the zoom lens 17 is driven by a zoom motor 21, and the focus motor 20 and zoom motor 21 are driven and controlled by an Aremo lens control section 22. . An autofocus control signal for obtaining the optimum focal length corresponding to the focus area is input to the lens control section 22 from the autofocus control section 23 . Further, the iris 18 is driven by an iris motor 24, and the iris motor 24 is drive-controlled by an iris control section 25. The iris control section 25 receives an iris control signal from the exposure control section 26 that indicates the aperture opening corresponding to the optimum exposure value.

The solid-state image sensor 19 has a large number of pixels made up of photodiodes arranged horizontally and vertically, and converts image information formed into an image into an electrical signal at a level corresponding to the amount of light of the image and outputs it. A large number of pixels of this solid-state image sensor are horizontally scanned by an H driver 27 and vertically scanned by a V driver 28. The horizontal scanning timing of each pixel of the image sensor for the H driver 27 and the vertical scanning timing for the V driver 28 are output in synchronization with the timing signal from the timing signal generator 29. Here, the timing signal control section 30 detects a horizontal scanning signal corresponding to the focus area selected by the focus area selection key 12, and changes the imaging scanning timing in the timing signal generation section 29 to a variable I.
II glI.

Further, the electrical signals output from each pixel of the solid-state image sensor 19 are sampled and held in the sample-hold circuit 31 in synchronization with timing signals from the two timing signal generators, and sequentially sent to the AGC ( The signal is output to the image processing circuit via the automatic gain control (gain control) circuit 32.

Here, the exposure control section 26 calculates an optimum exposure value according to the total amount of incident light to the solid-state image sensor 19 based on the image output signal from the solid-state image sensor 19, and calculates an aperture opening according to this optimum exposure value. An iris fiIi control signal is output to the iris control section 25 to obtain the iris fiIi control signal.

On the other hand, the output signal for each pixel corresponding to horizontal scanning from the solid-state image sensor 19 is sent to the sample hold circuit 31. It is also provided to the switching circuit 33 via the exposure control section 26 and the AGC circuit 32. This switching circuit 33 provides only the output signal from the solid-state image sensor 19 corresponding to the focus area to the autofocus control section 23, and the on/off operation of the switching gate in this switching circuit 33 is controlled by the switching control section 34. controlled. That is, the switching control section 34 detects the scanning timing of the focus area selected and designated in advance by the focus area selection key 12 based on the timing signal indicating the solid-state image sensor scanning timing from the timing signal generation section 29, and the switching circuit 33 Turn on the switching gate.

FIG. 2 shows the internal configuration of the solid-state image sensor 19, which includes a large number of pixels (photodiodes) 401, 402, .・
..., 40m, the charges corresponding to the imaging level are read out to the V-CCD 41 in accordance with the readout clock, and are sequentially stored in corresponding storage areas according to the scanning signal φVn. 21,422,... 42n. And this storage area 42+, 42■,...
・Transferred from 42n to H-CCD 43, scanning signal φH
The signals are sequentially output through the output amplifier 44 in synchronization with n.

Here, when the scanning signal φVn is applied at a timing opposite to that of normal scanning, each image signal read out to the V-CCD 41 is swept out via the drain 45. In this case, when reading out the 7JS charge of each pixel, the scanning signal φVn is applied at a timing of 63.5 μs per horizontal scan corresponding to the television signal, but for sweeping out the charge, for example, The scanning signal Vφn is applied in reverse scanning at a high-speed timing of 800 kHz.

FIG. 3 shows the selected state of the focus area 51 in the finder 13, and the focus area 51 can be moved to any position 51a, 5lb, . . . in the imaging area by scanning the focus area selection key l2. can be set to move, and displayed on the liquid crystal shutter 14 by the liquid crystal driving section 14.

FIG. 4 shows AF unnecessary charge areas 52a and 52b and AP charge area 5 for the focus area 51 within the imaging area.
3, and the solid-state image sensor 1 in FIG.
9, the charges in the horizontal pixel columns corresponding to the AF unnecessary areas 52a and 52b are sequentially swept out at high speed via the drain 45 by the 800 kHz timing signal, and AF'? The charges in the horizontal pixel column corresponding to the 3-load area 53 are read out by the 63.5 μs timing signal, and only the charges corresponding to the focus area 51 at each horizontal scanning timing are read out by the switching circuit 3.
3 to the autofocus control section 23.

Note that 54 is a camera shake warning lamp, 55 is a focus matching lamp, and 56 is a flash lamp.

Next, the photographing operation of the camera equipped with the autofocus function configured as described above will be explained with reference to the timing chart shown in FIG.

In FIG. 5, AFS is an autofocus start clock, V1+TG is a vertical transfer clock+read clock, H1 is a horizontal transfer clock, and AFGATE is a gate ON signal in the switching circuit 33.

FIG. 6 is a flowchart showing the photographing operation. First, the user looks through the finder 13, captures the subject at an arbitrary position, and sets the composition of the photographing area. Here, the user operates the focus area selection gear 12 to set the focus area 51 at an arbitrary position, for example, as shown in FIG. 3 above. Then, in order to perform AF control, the release switch 11 is pressed halfway. Then, an AFS pulse signal is generated and output from the main control section 10, and the aperture of the iris 18 is opened by the iris motor 24 via the exposure control section 26 and the iris control section 25 (step Sl). Then, the accumulated charges in all pixels of the solid-state image sensor 19 in FIG. It is cleared at high speed (step S2). In this way, when all accumulated electric currents in the solid-state image sensor 19 are cleared, 1/2 5
At a sampling timing of 0 sec, t songs are accumulated according to the incident light on the solid-state imaging element 9 (step S3). Each image sensor 4 of the solid-state image sensor] 9
When 71i 6:j corresponding to the subject image is accumulated uniformly for 0, 402, . In other words, A up to the front of the focus frame
The charge of each pixel accumulated in the F unnecessary charge region 52'a is
The data is swept out from the drain 45 side by the 800 kHz high-speed reverse transfer process in FIG. 2, and becomes invalid data (step S4). Next, focus area 51
The focus frame of the AF charge area 53 where there is
The storage area 42. in FIG. ．． 422. ..., called by 42n,
The signal is output to the sample and hold circuit 31 via the H-CCD 43 and the output amplifier 44.

At this time, in each horizontal scanning period in the AF charge area 53, only the imaging charge corresponding to the focus area 51 is provided to the autofocus control section 23 through the switching circuit 33. That is, since the switching control section 34 is given in advance the position data of the focus area 51 selected and designated by the focus area selection key 12 through the main control section 10, the solid-state image sensor obtained from the timing signal generation section 29 Based on the horizontal scanning timing of 19, the focus area 51
By detecting the corresponding scanning period and sequentially turning on the gate of the switching circuit 33 for each horizontal scanning period of the AF charge area 53 only in that focus frame, only the imaging charge of the focus area 51 is sent to the autofocus control unit 23. It will be given to you. After this, the charge of each pixel accumulated in the AF unnecessary charge region 52b from the focus frame to the final frame, beyond the A P charge area 53 where the middle focus area 51 exists, is calculated as shown in FIG. By the high-speed reverse transfer process of 800k Ilz, data is swept out from the drain 45 side at high speed and becomes invalid data (step S6).In this case, only the AF charge region 53 where the focus area 51 exists, for example, N
63 per horizontal scan according to TSC television signal
．． Extracting the imaging charge at a scanning timing of 5 μs,
In the other AF-unnecessary charge regions 52a and 52b, the accumulated tM (4) is rapidly reversely transferred at a scanning timing of 800 kHz and swept out from the drain 45.
Imaging charges corresponding to the focus area 51 can be extracted faster.

In this way, when the autofocus control unit 23 is given an imaging charge signal corresponding to the focus area 51 of the solid-state image sensor 19, the autofocus control unit 23 calculates the optimum focal length based on the focus area 51. The focus motor 20 and zoom motor 21 are driven through the lens control section 22 in order to S! Then, the focal positions of the imaging lens 16 and the zoom lens 17 are controlled to correspond to the optimum focal length.

Then, when the movement ill iH corresponding to the optimum focal length of the imaging lens l6 and zoom lens 17 is completed,
AFE (autofocus end) indicating focus alignment
The signal is sent from the autofocus control section 23 to the main control section 1.
0 (step S7).

In this case, the autofocus control unit 23 determines the point at which the contrast of the subject image in the focus area 51 of the solid-state image sensor 19 is maximum, that is, the high-frequency component of the imaging signal in the focus area 51 obtained via the switching circuit 33 is the maximum. It detects a point where the image is in focus, determines that it is in focus, and outputs an AFE signal.

Then, the timing signal generator 2 is output from the main controller 10.
By controlling the H driver 27 and the {circle around (2)} driver 28 through 9, all charges in the solid-state image sensor 19 are swept out to the drain 45 side by the high-speed reverse transfer process and cleared (step S8).

Then, the exposure control section 26 is connected to the iris control section 25.
Drive and adjust the iris motor 24 through the iris 1
The aperture opening degree at No. 8 is controlled to open or close according to the optimum exposure value. After this, when the release switch 11 is fully pressed,
The solid-state image sensor 19 is exposed to and accumulated charges according to the subject image by normal vertical/horizontal scanning processing (step S9).
. As a result, the effective image data imaged and accumulated on the solid-state image sensor 19 is transferred to the storage areas 421, 422, . . . in FIG. 2 at the normal sampling timing of 63.5 μs per horizontal scan. H-CCD via 42n
43 and are sequentially transferred and output (step S10). This valid image data is sent to the image signal processing circuit via the sample hold circuit 31, exposure control section 26, and AGC circuit 32, and after being subjected to A/D conversion processing, lffl processing, etc., it is stored in the memory as digital image data. is stored in

Therefore, according to the camera with the autofocus function configured as described above, the focus area 5 for the subject image is
1 to an arbitrary position using the focus area selection key 12, and only the imaging signal from the solid-state image sensor 19 corresponding to the focus area 51 is extracted to the autofocus control unit 23 to perform automatic focusing control. Therefore, no matter where the subject you want to focus on is located within the imaging area, you can easily move the focus area 51 and achieve reliable focus with the desired composition determined. .

[Effects of the Invention] As described above, according to the present invention, there is a lens, an image sensor that generates an electrical signal according to the amount of light incident through the lens, and an image sensor that converts the electrical signal generated by the image sensor into an image. an imaging signal output means for sequentially outputting as a signal; an area designation means for designating an arbitrary area of the imaging device; a designated area signal extraction means for extracting an electrical signal generated in a designated imaging area by the designation means; Since the camera is configured to include a focus control means for controlling the focal position of the lens based on the electrical signal from the designated imaging area by the signal extraction means, there is no need to perform a focus lock operation even when the subject is not captured at the center of the viewfinder. It is possible to provide a camera equipped with an autofocus function that allows photographing to be easily focused on the above-mentioned subject.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an electronic circuit of a camera equipped with an autofocus function according to an embodiment of the present invention;
FIG. 2 is a diagram showing the configuration of the solid-state image sensor of the camera equipped with the autofocus function, FIG. 3 is a diagram showing the state of selection and movement of the focus area in the finder of the camera equipped with the autofocus function, and FIG. 5 is a diagram showing the AF unnecessary charge area and the AF charge area for the focus area within the imaging area by the camera equipped with the autofocus function, and FIG. 5 is the extraction operation of focus area data by the camera equipped with the autofocus function. FIG. 6 is a flowchart showing the photographing operation of the camera equipped with the autofocus function. DESCRIPTION OF SYMBOLS 10... Main control unit, 11... Release switch, 12... Focus area selection key 13... Finder, 14... Liquid crystal shutter, 15... Liquid crystal drive unit, 16... Imaging lens , 17... Zoom lens, 18... Iris, 19... Solid-state image sensor, 20
・・・． Focus smoke, 21...Zoom motor, 2
2... Lens control section, 23... Auto focus control section, 24... Iris motor, 25...
Iris control section, 26... Exposure control section, 27
...H driver, 28...V driver, 29...
Timing signal generation section, 30... Timing signal control section, 31... Sample hold circuit, 32... AG
C circuit, 33... Switching circuit, 34... Switching control section, 401 to 40+... Pixel (photodiode), 41... V-CCD, 421 to 42n
...Storage area, 43...H-CCD, 44
...Output amplifier, 45...Drain, 51...
Focus area, 52a, 52b... AF unnecessary charge area, 53... AF charge area, 54... Camera shake warning lamp, 55... Focus match lamp, 56...
flash lamp. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] A lens, an imaging device that generates an electrical signal according to the amount of light incident through the lens, and an imaging signal output means that sequentially outputs the electrical signals generated by the imaging device as an image signal. an area specifying means for specifying an arbitrary area of the image sensor; a specified area signal extracting means for extracting an electrical signal generated in the specified imaging area by the specifying means; A camera equipped with an autofocus function, comprising: a focus control means for controlling the focal position of the lens based on an electric signal; and a camera equipped with an autofocus function.