JP2007264119A - Autofocus system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an autofocus (AF) system capable of appropriately performing exposure adjustment for the video of an imaging device for AF so that a desired subject may be brought into focus by AF by allowing the exposure adjustment for the imaging device for AF by manual operation. <P>SOLUTION: In a lens device for television broadcasting, for example, the focus of a photographic lens is set to a focused state based on the contrast of the video (image) obtained from the imaging device for AF provided for AF. The brightness of the video taken by the imaging device for AF is adjusted by operating an exposure correction volume 70 in an AF part 12, and the exposure adjustment is performed so that the desired subject may be brought into focus. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an autofocus system, and more particularly to an autofocus system that automatically performs focus adjustment using a contrast method.

  Autofocus (AF) adopted in video cameras such as TV cameras detects the contrast of the subject image from the video signal obtained by the image sensor, and controls the focus so that the contrast becomes maximum (maximum). The method is common. The contrast of a subject image is quantitatively detected by, for example, an integrated value obtained by extracting a high frequency component from a video signal (luminance signal) obtained by an image sensor and integrating the signal of the high frequency component for each field. Is done. Note that the integrated value is a value indicating the degree of focusing and the high contrast of the subject image, and is referred to as a focus evaluation value in this specification.

  In contrast AF, the entire imaging range of the camera, that is, the subject or the entire subject image that is effectively captured by the imaging element of the camera is not set as the AF target range, but one of the imaging ranges. The range of the part is often set as the AF target range. For example, by extracting a video signal within a predetermined range as an AF target range from the video signal obtained from the image sensor, and detecting a focus evaluation value based on the video signal in the extracted range, The target range is limited to a part of the imaging range. In this specification, an AF target range is referred to as an AF area, and a frame indicating the range of the AF area (an outline of the AF area) is referred to as an AF frame. In addition, for example, as disclosed in Patent Document 1, an AF area position or the like within an imaging range that can be changed according to an operation by an operator is also known.

By the way, if the luminance signal obtained from the image sensor is saturated, the contrast with respect to the subject in the AF area cannot be properly evaluated, and there is a possibility of causing an AF malfunction. There has been proposed an autofocus system for the purpose of preventing malfunction of AF due to signal saturation. According to this, an image pickup device (AF image pickup device) for acquiring a video signal for AF is provided separately from an original image pickup device (video image pickup device) for acquiring a video signal for recording or reproduction. The focus evaluation value is detected based on the video signal (luminance signal) obtained from the AF image sensor. In this case, the image pickup device for image and the image pickup device for AF can perform exposure adjustment without affecting the other image. Therefore, an appropriate exposure adjustment is performed on the image of the image pickup device for video as an image for recording or reproduction, and the exposure adjustment for the image of the image pickup device for AF is the exposure adjustment for the image of the image pickup device for image. Irrespective of this, exposure adjustment is automatically performed so that the luminance signal obtained from the AF image sensor is not saturated.
JP 2002-365519 A

  However, even when exposure adjustment is performed so that the luminance signal obtained from the AF image sensor does not saturate, there is a problem that the subject to be truly focused may not be in focus. For example, if there is a high-luminance subject other than the subject you want to focus on, the brightness level of the subject you want to focus on will be too low, and it is appropriate to adjust the exposure so that the luminance signal does not saturate. In some cases, focusing could be prevented. In addition, there may be high-luminance subjects other than the subject to be focused in the AF area. Even if exposure adjustment is limited to the AF area, exposure adjustment for the subject to be focused is appropriate. Instead, the subject was sometimes out of focus.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an autofocus system capable of appropriately performing exposure adjustment on an image of an AF image sensor so that a desired subject is focused by AF. Objective.

  In order to achieve the above object, the autofocus system according to claim 1 is a dedicated AF for autofocus, apart from an image pickup unit that captures an image formed by an optical system as an image for recording or reproduction. In an autofocus system that includes an image pickup unit and automatically sets the focus of the optical system to a focused state based on an image picked up by the AF image pickup unit, the brightness of the image picked up by the AF image pickup unit Brightness detection means for detecting brightness, target setting means for setting a target brightness for an image captured by the AF imaging means in accordance with an operation of a manual operation member, and detection of the image detected by the brightness detection means Based on the brightness and the target brightness set by the target setting means, the brightness of the image picked up by the AF image pickup means is determined. It is is characterized in that and an exposure adjustment unit to perform exposure adjustment so that the brightness of the target.

  According to the present invention, the image obtained from the AF image sensor can be changed to a desired brightness by manual operation, so that the operator appropriately sets the brightness of the subject image to be focused by AF. This makes it possible to focus on the subject reliably by AF.

  According to a second aspect of the present invention, there is provided the autofocus system according to the first aspect of the invention, wherein the target setting means determines the target image brightness when the exposure is automatically adjusted according to the operation of the manual operation member. The target brightness is set by correction. According to the present invention, the exposure adjustment is not performed completely manually, but is automatically performed by the operator manually when necessary using the automatic exposure adjustment (when the desired subject cannot be focused). The brightness of the image can be corrected.

  According to a third aspect of the present invention, the autofocus system includes a dedicated AF imaging unit for autofocusing, apart from an imaging unit that captures an image formed by the optical system as an image for recording or reproduction. In the autofocus system that automatically sets the focus of the optical system to the in-focus state based on the image captured by the image capturing unit, the brightness of the image captured by the AF image capturing unit is adjusted by a plurality of photometric methods. Detected by brightness detection means for detecting by weighted average of detected brightness, weight coefficient changing means for changing the weighting coefficient in the weighted average in the brightness detection means in accordance with the operation of a manual operation member, and the brightness detection means The brightness of the image captured by the AF imaging means is determined based on the brightness of the image An exposure adjusting unit to perform exposure adjustment so that the brightness of the target, further comprising a are characterized.

  In the present invention, there are various photometry methods in automatic exposure adjustment, such as average photometry and peak photometry, and automatic exposure adjustment is performed by weighted average of image brightness detected by these photometry methods. By enabling the operator to change the weighting factor for the method, the operator can appropriately set the brightness of the subject image to be focused by AF, and the subject is surely focused by AF. Can do.

  According to a fourth aspect of the present invention, in the invention according to the first, second, or third aspect, the brightness detection unit is a luminance level of an image signal indicating an image captured by the AF imaging unit. Thus, the brightness of the image is detected.

  The present invention is limited to an aspect in which the brightness of an image is detected by the luminance level of the image signal.

  The autofocus system according to a fifth aspect is the invention according to the first, second, third, or fourth aspect, wherein the brightness of the image and the target brightness are set so that the focus of the optical system is in a focused state. It is characterized in that it indicates the brightness related to the image within the range of the AF area that is the target range to be set.

  In the present invention, processing in each means of claims 1 to 4 is performed only in the AF area.

  According to the autofocus system of the present invention, it is possible to appropriately perform exposure adjustment on the image of the AF image sensor so that a desired subject is focused by AF.

  Hereinafter, preferred embodiments of an autofocus system according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the overall configuration of a lens system to which the present invention is applied. The lens system shown in the figure is a system used for a television camera for television broadcasting, for example, and includes a photographing lens (optical system) and a control system. Even if the photographic lens and the control system are configured as a lens device integrated as a whole, a part of the control system (demands 18, 20, etc. described later) is different from the other as in the present embodiment. Any device configuration may be used, such as a configuration in which a cable or the like is connected to a lens device integrated with a control system component and a photographing lens.

  Although not shown, the photographic lens has a configuration in which various optical components are arranged in a lens barrel that is mounted and coupled to the TV camera. In FIG. 1, the optical component can be moved in the optical axis direction for focus adjustment. A focus lens (group) FL disposed in the zoom lens, a zoom lens (group) ZL disposed movably in the optical axis direction for zoom adjustment (focal length adjustment), and an aperture I that opens and closes for light amount adjustment. Has been. A fixed lens group other than that shown in FIG. 1 is disposed on the lens barrel of the photographing lens.

  The subject light incident on the photographic lens is imaged on the imaging surface (imaging surface) of the imaging element (not shown) of the camera body (camera head) that is mounted with the photographic lens, and after photoelectric conversion by the imaging element, the camera body Predetermined signal processing is performed by the internal signal processing unit. As a result, a video (subject image) captured by the imaging element of the camera body via the photographing lens is generated by the camera body as a video signal of a predetermined format (for example, NTSC system).

  The control system of the lens apparatus includes a focus motor FM, a zoom motor ZM, an aperture motor IM, potentiometers FP, ZP, and IP connected to the focus lens FL, the zoom lens ZL, and the diaphragm I, and the entire lens apparatus. Are provided with a lens control CPU 10 for comprehensively controlling the AF, an AF unit 12 for detecting focus information (focus evaluation value, etc.) during autofocus (AF) control, which will be described in detail later. In addition, a focus demand 18 for a focus operation and a zoom demand 20 for a zoom operation are connected to the lens device by a cable or the like as an accessory device.

  The focus lens FL, the zoom lens ZL, and the diaphragm I are electrically driven by a focus motor FM, a zoom motor ZM, and a diaphragm motor IM, respectively. The motors FM, ZM, and IM are lens controlled. The drive signal output from the CPU 10 is supplied to the amplifiers FA, ZA, IA via the D / A converter 16, so that the drive signal is driven at a rotational speed corresponding to the value of the drive signal. . Further, information on the current positions of the focus lens FL, the zoom lens ZL, and the aperture stop I is provided to the lens control CPU 10 from the potentiometers FP, ZP, and IP.

  Thus, the lens control CPU 10 can drive the motors FM, ZM, and IM to control the positions and operating speeds of the focus lens FL, the zoom lens ZL, and the diaphragm I.

  Control (focus control) of the focus lens FL includes manual focus (MF) and auto focus (AF), and MF and AF can be switched by a predetermined operation.

  At the time of MF, the focus control signal output from the focus demand 18 in accordance with the operation of a predetermined manual operation member (focus knob) of the focus demand 18 is read by the lens control CPU 10 via the A / D converter 14, and the focus The position or operation speed of the focus lens FL is controlled by the lens control CPU 10 so as to coincide with the target position or target speed (generally the target position) designated by the control signal.

  On the other hand, at the time of AF, the focus evaluation value indicating the contrast level of the subject image detected by the AF unit 12 to be described in detail later is read by the lens control CPU 10, and the focus state is set based on the focus evaluation value. Thus, the focus lens FL is controlled.

  In the control of the zoom lens ZL (zoom control), the zoom control signal output from the zoom demand 20 according to the operation of a predetermined manual operation member of the zoom demand 20 is read by the lens control CPU 10 via the A / D converter 14. Then, the position or operation speed of the zoom lens ZL is controlled by the lens control CPU 10 so as to coincide with the target position or target speed (generally target speed) designated by the zoom control signal.

  In the control of the aperture I (aperture control), for example, an iris control signal given from a camera body (not shown) is read by the lens control CPU 10 so as to coincide with a position (opening degree) designated by the iris control signal. The position of the diaphragm I is controlled by the lens control CPU 10.

  Next, the AF process will be described in detail. FIG. 2 shows a processing unit related to the AF processing, and shows a specific configuration of the lens control CPU 10 and the AF unit 12 in FIG. As shown in the figure, the AF unit 12 includes an AF image sensor (CCD or the like) 42, an AF CPU 30, an A / D converter 32, a high-pass filter (HPF) 34, a gate circuit 36, an adder circuit 38, a luminance level. It comprises a detection circuit 40 and the like.

  The AF image sensor 42 captures an image having an angle of view and a subject distance (distance to the in-focus subject) that matches the image captured by the image sensor (video image sensor) of the camera body for recording or reproduction. . For example, a light splitting optical system such as a half mirror is disposed downstream of the focus lens FL and the zoom lens ZL in the optical system, and the subject light passes through two different optical paths (image optical path and AF optical path) in the light splitting optical system. ). The subject light branched into the image optical path is guided to the image pickup device of the camera body in the same manner as the subject light incident on the normal photographing lens, and forms an image on the image pickup surface of the image pickup device.

  On the other hand, in the AF optical path, an optical component that acts in the same manner as an optical component (lens or the like) arranged downstream of the light splitting optical system is arranged, and an imaging surface of the AF imaging element 42 is arranged. . As a result, an image that matches the image captured by the video image sensor is captured by the AF image sensor 42. The AF image sensor 42 does not need to acquire a color image, and captures a monochrome image. A video signal indicating an image (video) sequentially captured by the AF image sensor 42 is luminance. It shall correspond to a signal.

  The video signal (luminance signal) obtained from the AF image sensor 42 is first converted into a digital signal by the A / D converter 32. Subsequently, only the high frequency component of the frequency component of the luminance signal is extracted by the HPF 34, and the luminance signal of the high frequency component is input to the gate circuit 36. In the gate circuit 36, the luminance within the AF area that is the AF target range in the imaging range (shooting range) of the video image sensor of the camera body, that is, the video screen range when the video signal is reproduced. Only the signal is extracted. The AF area will be described later.

  The luminance signal of the high frequency component in the AF area extracted by the gate circuit 36 is then input to the adder circuit 38 and integrated by one screen (one field) by the adder circuit 38. Thus, the integrated value obtained sequentially for each luminance signal for one screen is a focus evaluation value indicating the contrast height of the video (subject image), and the focus evaluation value is read into the AF CPU 30.

  The lens control CPU 10 controls the focus lens FL so that the focus evaluation value acquired from the AF CPU 30 as described above is maximized (maximum), thereby focusing the photographing lens on the subject in the AF area. To burn. Specifically, for example, the focus lens FL is moved a small amount back and forth in the optical axis direction (wobbling), and the focus evaluation values at the front and rear moving ends are acquired from the AF CPU 30 of the AF unit 12. Then, the direction in which the focus evaluation value increases is detected by comparing the focus evaluation values at the moving ends, and the focus lens FL is moved in that direction by a predetermined amount or a predetermined speed. This is repeated, and the focus lens FL is stopped when the increasing direction of the focus evaluation value is not detected by wobbling, that is, when the focus evaluation value reaches a maximum. As a result, the focus lens FL is set at a position where the focus of the photographing lens is brought into focus.

  Here, the AF area will be described. As shown in FIG. 3, in the imaging range 50 in which the subject image is effectively captured by the imaging element of the camera body, the AF area 52 as the AF target range is, for example, a rectangular range. Set as When the position of the AF area 52 is fixed, it is generally set at the center of the imaging range. However, by changing the luminance signal extraction range in the gate circuit 36 in accordance with the operation of the operator with a predetermined controller, the AF area 52 It is also possible to change the position and size of the area 52. Note that the AF target range may be the entire imaging range, and in this case, the entire imaging range can be regarded as the AF area.

  In this embodiment, a controller connected to a lens device such as the focus demand 18 is provided with an AF operation unit 60 for performing operations related to AF such as the AF area range as shown in FIG. By operating the joystick 62 of the operation unit 60 back and forth and right and left, the position of the AF area can be changed vertically and horizontally within the imaging range. When the AF operation unit 60 as shown in FIG. 4 is provided in a controller such as the focus demand 18, information from the controller is acquired by the lens control CPU 10 by serial communication or the like between the controller and the lens control CPU 10. Keep it available. Of the information from the controller, only the information necessary for the AF unit 12 is supplied from the lens control CPU 10 to the AF CPU 30 of the AF unit 12. As a result, the AF CPU 30 can set the processing required in the AF unit 12 based on the operation of the AF operation unit 60, for example, the extraction range of the luminance signal in the gate circuit 36 based on the operation of the joystick 62. However, a controller dedicated to the AF operation unit 60 as shown in FIG. 4 may be connected to the lens device by a cable or the like, and the AF CPU 30 directly acquires information from the controller without going through the lens control CPU 10. You may do it.

  In the AF operation unit 60 of FIG. 4, an AF mode switch 64 is a switch for selecting an off mode, a momentary AF mode, and a continuous AF mode. In a state where the momentary AF mode is selected, an AF start switch The AF process is executed in the lens control CPU 10 only when 66 is on, and the MF process is executed otherwise. In a state where the continuous AF mode is selected, once the AF start switch 66 is turned on, the lens is operated until a predetermined operation for releasing AF is performed (for example, until the AF start switch 66 is turned on again). The AF process is continuously performed in the control CPU 10, and when the AF is released, the MF process is executed. In the off mode, even when the AF start switch 66 is turned on, the lens control CPU 10 always executes the MF process. The brightness level adjustment mode switch 68 and the exposure correction volume 70 will be described later.

  Next, luminance level adjustment (exposure adjustment) in the AF unit 12 will be described. In FIG. 2, the charge accumulation time (electronic shutter speed) in the AF image sensor 42 can be controlled by the AF CPU 30, and the exposure value can be changed by adjusting the electronic shutter speed. Yes.

  On the other hand, the luminance signal obtained from the AF image sensor 42 is input to the luminance level detection circuit 40 in the AF unit 12, and the luminance level detection circuit 40 determines the luminance level of the image on one screen from the signal level of the luminance signal. Are detected by a predetermined method. The brightness level detected by the brightness level detection circuit 40 is read into the AF CPU 30 and the AF image sensor uses the AF image sensor so that the image captured by the AF image sensor has an appropriate brightness based on the brightness level. The electronic shutter speed is controlled.

  Note that the luminance level detection in the luminance level detection circuit 40 may be any method such as an average photometry method that averages the luminance level of each pixel in one screen or a peak photometry method that obtains the maximum luminance level in one screen. Such a method may be used. Also, instead of detecting the luminance level in the entire screen, the AF area range currently set is given from the AF CPU 30 to the luminance level detection circuit 40, and the luminance level in the AF area range is detected. May be.

  Here, the AF operation unit 60 shown in FIG. 4 is provided with a brightness level adjustment mode switch 68, and exposure adjustment can be switched between the automatic mode and the exposure correction mode by the mode switch 68. . As shown in FIG. 2, the setting state of the brightness level adjustment mode switch 68 is read into the AF CPU 30, and the AF CPU 30 is in a state where the brightness level adjustment mode switch 68 is set to the automatic mode. Based on the luminance level read from the luminance level detection circuit 40 as described above, the electronic shutter speed in the AF image sensor 42 is set so that the brightness of the image is appropriate. When the luminance level detection circuit 40 detects the luminance level of only the image in the AF area range, the electronic shutter speed is set so that the brightness of the image in the AF area range is appropriate.

  On the other hand, in the state in which the exposure correction mode is set by the brightness level adjustment mode switch 68, the electronic shutter speed in the AF image sensor 42 is set based on the brightness level read from the brightness level detection circuit 40 as in the automatic mode. At the same time, the electronic shutter speed is corrected according to the rotation position of the knob of the exposure correction volume 70 of the AF operation unit 60 shown in FIG. The exposure correction volume 70 outputs a positive / negative voltage value corresponding to the rotation direction and the rotation amount of the knob with a predetermined rotation position of the knob as a reference (0), and the value is used for AF as shown in FIG. It is read by the CPU 30. For example, the AF CPU 30 corrects the electronic shutter speed so that the electronic shutter speed decreases as the value of the exposure correction volume 70 increases, that is, the image becomes brighter. The electronic shutter speed decreases as the value of the exposure correction volume 70 decreases. Correction is performed so that the image becomes faster, that is, the image becomes darker.

  There are several modes as the processing procedure of the AF CPU 30 for changing the brightness of the image obtained from the AF image sensor in accordance with the value of the exposure correction volume 70. For example, as a first aspect, a target value is set for the luminance level detected by the luminance level detection circuit 40 and the luminance level detected by the luminance level detection circuit 40 is set as described below. When the electronic shutter speed is set so as to be the target value, there is an aspect in which the target value is changed based on the value of the exposure correction volume 70. As a second aspect, there is an aspect in which an exposure value (EV value) for obtaining an image having a predetermined brightness is changed based on the luminance level detected by the luminance level detection circuit 40. Further, as a third aspect, when the luminance level detection circuit 40 gives a weighted average of luminance levels obtained by a plurality of photometry methods to the AF CPU 30, its weighting coefficient is based on the value of the exposure correction volume 0. There is a mode to change. In this case, how the brightness of the image is changed with respect to the value of the exposure correction volume 70 is indefinite, but exposure adjustment can be performed with a weight assigned to a photometric method considered appropriate depending on the subject. Become. Specifically, the luminance level detection circuit 40 obtains the weighted average of the luminance levels obtained by the peak metering method and the average metering method, and changes the weighting coefficients according to the value of the exposure correction volume 70. .

  In the present embodiment, the brightness (electronic shutter speed) automatically set in the automatic mode is changed (corrected) by the exposure correction volume 70. The brightness (electronic shutter speed) may be completely set only at the operation position of the manual operation member so that the exposure adjustment can be performed only by manual operation.

  Further, as shown in FIG. 2, a video monitor 46 is shown in the AF unit 12. The video monitor 46 can be attached to and detached from the lens device with a cable or the like, and is connected to the output of the A / D converter 32 via the D / A converter 44. According to this, the video signal (luminance signal) obtained from the AF image sensor 42 is input to the video monitor 46, and the video imaged by the AF image sensor 42 is displayed on the video monitor 46. Thus, the operator can confirm the brightness of the image captured by the AF image sensor 42, and can confirm whether the subject image to be focused has an appropriate brightness for AF. it can. Then, the user can adjust the desired subject image to an appropriate brightness by operating the exposure correction volume 70 while viewing this video.

  Further, in the D / A converter 44, not only the function of converting an analog signal into a digital signal but also information on the AF area currently set by the gate circuit 36 is taken in and the current image is output to the video monitor 46. It is also possible to provide a function of superimposing an image of an AF frame indicating the range of the AF area. According to this, the range of the currently set AF area can also be confirmed on the video monitor 46.

  FIG. 5 is a flowchart showing a processing procedure related to exposure adjustment in the AF CPU 30. When the power is turned on, the AF CPU 30 performs necessary initial settings (step S10) and then performs processing other than exposure adjustment (step S12). Subsequently, the state of the brightness level adjustment mode switch 68 is read to determine whether or not the exposure correction mode is set (step S14). If YES is determined, the value of the exposure correction volume 70 is read (step S16). If it is determined NO, the value of the exposure correction volume 70 is set to 0. In other words, the value of the exposure correction volume 70 is not considered (step S18).

  Next, the AF CPU 30 adds the value of the exposure correction volume read in step S16 or the value (0) set in step S18 to the current target value of the luminance level (step S20). Subsequently, the current luminance level is read from the luminance level detection circuit 40 (step S22).

  Next, the AF CPU 30 determines whether or not the current luminance level matches the target value obtained in step S20 (step S24). When it determines with YES, it returns to step S12. On the other hand, when it is determined NO, it is determined whether or not the current luminance level is higher than the target value (step S26). If YES is determined, the electronic shutter speed in the AF image sensor 42 is set to a low speed (step S28). If NO is determined, the electronic shutter speed in the AF image sensor 42 is set to a high speed (step S30). And after the process of step S28 or step S30, it returns to step S12. It should be noted that an electronic shutter speed such that the luminance level matches the target value is obtained based on the current luminance level in the processing of step S28 and step S30, and the electronic shutter speed may be set to that speed. The brightness level may coincide with the target value by shifting to the high speed or low speed side by a predetermined value and repeating the processing of step S12 to step S30.

  As described above, in the above embodiment, in the AF process, the focus evaluation value is detected based on the video signal obtained from the AF image sensor 42, and the focus is set to the in-focus state. The present invention can also be applied to an autofocus system that employs a so-called optical path length difference type AF that has a plurality of imaging surfaces arranged at different positions. In this system, a plurality of (for example, two) imaging surfaces are arranged at positions with different optical path lengths as imaging surfaces of the AF imaging element 42. These imaging surfaces may be imaging surfaces of individual AF imaging elements, or may have optical path length differences on the imaging surfaces of the same imaging element. Then, a subject image that is imaged at, for example, a position equidistant from the front and back of the image pickup surface of the image pickup device is picked up by each image pickup surface of the AF image pickup device. Each focus evaluation value is detected from a video signal (luminance signal) obtained by imaging on each imaging surface of the AF imaging element. Then, by comparing these focus evaluation values, a focus state (focus, front pin, rear pin) is detected, and control is performed so that the focus of the photographic lens is brought into focus based on the focus state. Even in such a system, the brightness of an image obtained from each imaging surface of the AF imaging element can be adjusted in the same manner as in the above embodiment.

FIG. 1 is a block diagram showing the overall configuration of a lens system to which the present invention is applied. FIG. 2 is a configuration diagram illustrating a processing unit related to the AF process. FIG. 3 is an explanatory diagram used for explaining the AF area. FIG. 4 is a front view showing the AF operation unit. FIG. 5 is a flowchart showing a processing procedure related to exposure adjustment in the AF CPU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Lens control CPU, 12 ... AF part, 18 ... Focus demand, FL ... Focus lens (group), FM ... Focus motor, FP ... Potentiometer, 30 ... AF CPU, 32 ... A / D converter, 34 DESCRIPTION OF SYMBOLS ... High-pass filter (HPF) 36 ... Gate circuit 38 ... Adder circuit 40 ... Luminance level detection circuit 42 ... AF image sensor 44 ... A / D converter 46 ... Video monitor 60 ... AF operation part 62 ... Joystick, 68 ... Brightness level adjustment mode switch, 70 ... Exposure compensation volume

Claims (5)

In addition to the image pickup means for picking up an image formed by the optical system as an image for recording or reproduction, a dedicated AF image pickup means for autofocusing is provided, based on the image picked up by the AF image pickup means. In an autofocus system that automatically sets the focus of the optical system to a focused state,
Brightness detection means for detecting the brightness of the image captured by the AF imaging means;
Target setting means for setting a target brightness for an image picked up by the AF image pickup means in accordance with an operation of a manual operation member;
Based on the brightness of the image detected by the brightness detection unit and the target brightness set by the target setting unit, the brightness of the image captured by the AF imaging unit becomes the target brightness. Exposure adjusting means for performing exposure adjustment;
An autofocus system characterized by comprising   The target setting means sets the target brightness by correcting the brightness of an image targeted when the exposure is automatically adjusted according to an operation of the manual operation member. Autofocus system. In addition to the image pickup means for picking up an image formed by the optical system as an image for recording or reproduction, a dedicated AF image pickup means for autofocusing is provided, based on the image picked up by the AF image pickup means. In an autofocus system that automatically sets the focus of the optical system to a focused state,
Brightness detection means for detecting the brightness of an image captured by the AF imaging means by a weighted average of brightness detected by a plurality of different photometry methods;
A weight coefficient changing means for changing a weight coefficient in the weighted average in the brightness detecting means according to an operation of a manual operation member;
Exposure adjusting means for performing exposure adjustment based on the brightness of the image detected by the brightness detecting means so that the brightness of the image captured by the AF imaging means becomes a predetermined target brightness;
An autofocus system characterized by comprising   4. The autofocus according to claim 1, wherein the brightness detecting unit detects the brightness of the image based on a luminance level of an image signal indicating an image captured by the AF imaging unit. system.   The brightness of the image and the target brightness indicate brightness relating to an image within an AF area that is a target range for setting the focus of the optical system to a focused state. 3, or 4 autofocus system.

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