WO2014156383A1

WO2014156383A1 - Autofocus device and method of controlling operation thereof

Info

Publication number: WO2014156383A1
Application number: PCT/JP2014/053970
Authority: WO
Inventors: 愛子関谷; 隆久佐藤; 江波戸　尚
Original assignee: 富士フイルム株式会社
Priority date: 2013-03-29
Filing date: 2014-02-20
Publication date: 2014-10-02
Also published as: JP2016114614A

Abstract

The purpose of the present invention is to preemptively prevent hunting, and a feeling of strangeness when using both an optical path-length difference AF and a phase difference AF. A focus lens is moved at a first relatively high speed using the phase difference AF until a focus lens is moved to a first threshold position (P1) near the focusing position (P0). When the position of the focus lens is closer to the focusing point (P0) than the first threshold position (P1), the focus lens is moved at a second speed which is almost imperceptibly slower than the first moving speed using the optical path-length difference AF. The speed the focus lens moves gradually slows as the focus lens approaches the focusing position (P0).

Description

Auto-focus device and operation control method thereof

The present invention relates to an auto-focus device and an operation control method thereof.

The camera auto focus includes phase difference AF (auto focus), contrast AF, and the like. In the phase difference AF, light entering from a lens is divided into two parts and guided to a sensor for phase difference AF, and the direction and amount of focus are determined from two intervals formed. Contrast AF searches for a place where the contrast is high while moving the focus lens based on the image captured on the image sensor, and focuses. In contrast AF, there are two imaging elements arranged at different optical path lengths, one that searches for the focus / lens position that maximizes the contrast of the image formed on one imaging element (focus evaluation AF). There are two types of contrast AF (optical path length difference AF) that images a subject and focuses on the image signal obtained from each image sensor, and both are used as AF of a television camera (Patent Document 1). , 2).

Patent No.4189674 JP 2004-212458 A

In phase difference AF, the amount of lens movement until the subject is in focus can be obtained directly, which is high speed, but there is a problem that the distance measurement accuracy is poor and the subject cannot be fully focused. In contrast AF, the subject image is used. Since the focus evaluation is performed, the accuracy of focusing on the subject is high, but there is a problem that it takes a long time to focus to move the lens while searching for the focus position. On the other hand, in contrast AF, the focus lens moving speed is set by amplifying the focus evaluation value signal indicating the amount of focus deviation by applying a gain coefficient. Although it is possible to reduce the time to focus, increasing the gain factor increases the moving speed of the focus lens, but it becomes difficult to stop at the focus position. A phenomenon called hunting in which the lens touches back and forth may occur.

For this reason, combining the high speed of phase difference AF with the high accuracy of contrast AF, such as moving the lens with phase difference AF when the focus is greatly out of focus, and focusing with high precision with contrast AF when approaching the in-focus position When the speed difference between the phase difference AF and the contrast AF is large when the operation is performed, the rapid speed change at the time of switching becomes uncomfortable and gives the user an unpleasant feeling. Increasing the gain factor of contrast AF to solve this sense of incongruity causes the above-described hunting, and decreasing the speed of phase difference AF decreases the speed of the entire AF, leading to a decrease in product performance.

In Patent Document 1, the frequency characteristic of a video signal used for auto-focusing is changed according to the focus accuracy priority mode and the stability priority mode. In Patent Document 2, a diaphragm is used for the contrast AF optical system. In this case, the characteristics near the peak of the focus evaluation value are adjusted, and any of the problems that occur when both the phase difference AF and the contrast AF are used are not considered.

An object of the present invention is to solve the problems that occur when both phase difference AF and contrast AF are used.

The autofocus device according to the present invention is based on the amount of focus deviation in the pupil division direction of the two subject images formed by dividing the light incident through the focus lens into two by pupil division. A first focus evaluation value output unit that outputs a first focus evaluation value signal indicating a position where light path lengths are different from each other in an optical path of light incident through the focus lens (images are formed by the focus lens) The first image sensor and the second image sensor, which are optically arranged at equal intervals in front and rear with respect to the position of the subject image, the output signals of the first image sensor and the output signals of the second image sensor And a second focus evaluation value output unit for outputting a second focus evaluation value signal indicating the amount of focus shift based on the first focus evaluation value signal, and a focus position calculated based on the first focus evaluation value signal. Focusing the first image sensor If it is not between the focusing position and the second imaging element focusing position, the focus lens is moved at the first moving speed based on the first focusing evaluation value signal output from the first focusing evaluation value output unit. If the in-focus position calculated based on the first in-focus evaluation value signal is between the in-focus position of the first image sensor and the in-focus position of the second image sensor, the second in-focus position is obtained. A second moving speed that is slower than the first moving speed based on the second focus evaluation value signal output from the evaluation value output unit, and becomes slower as the focus lens is closer to the position where the subject image is in focus. The focus lens is controlled so that the focus lens is moved by the first focus evaluation value output unit until the position of the focus lens is near the threshold position near the position where the subject image is in focus. Based on the first focus evaluation value signal output from A second focus evaluation value output unit when the focus lens is moved closer to the position where the subject image is in focus than the threshold position. Based on the second focus evaluation value signal output from the second focus evaluation speed signal, which is faster than the threshold movement speed slower than the first movement speed, and becomes slower as the focus lens is closer to the position where the subject image is in focus. The focus lens is moved at a moving speed of, and the focus lens is moved at a third moving speed that is slower than the threshold moving speed as the subject lens approaches the position where the subject image is in focus. It is characterized by having a focus / lens controller for controlling the lens.

The present invention also provides an operation control method suitable for an autofocus device. That is, in this method, the first focus evaluation value output unit shifts the position in the pupil division direction of two subject images formed by dividing the light incident through the focus lens into two by pupil division. The first focus evaluation value signal indicating the amount of focus shift is output based on the amount, and the second focus evaluation value output unit has optical path lengths in the optical paths of light incident through the focus lens. Based on the output signals of the first image sensor and the second image sensor arranged at different positions, a second focus evaluation value signal indicating a focus shift amount is output, and the focus / lens controller When the focus position calculated based on the first focus evaluation value signal is not between the focus position of the first image sensor and the second image sensor focus position, the first focus evaluation value is output. Based on the first focus evaluation value signal output from the The in-focus position calculated based on the first focus evaluation value signal is the in-focus position of the first image sensor and the in-focus position of the second image sensor. If it is in between, the position is slower than the first moving speed based on the second focus evaluation value signal output from the second focus evaluation value output unit, and the focus lens is in a position where the subject image is in focus The focus lens is controlled so as to move the focus lens at a second moving speed that becomes slower as the distance from the second lens moves closer.

According to the present invention, when the focus position calculated based on the first focus evaluation value signal is not between the focus position of the first image sensor and the second focus position, the first focus position is calculated. The focus lens is moved at the first moving speed based on the first focus evaluation value signal output from the focus evaluation value output unit. The focus lens can be moved quickly. When the in-focus position calculated based on the first focus evaluation value signal is between the in-focus position and the second in-focus position of the first image sensor, the first movement speed is used. However, the focus lens is moved at a second moving speed that becomes closer as the focus lens is closer to the position where the subject image is in focus. Immediately after switching from the movement of the focus lens based on the first focus evaluation value signal output from the first focus evaluation value output unit, the first focus evaluation value output unit outputs from the first focus evaluation value output unit. Since the focus lens is moved at a speed not much different from the movement speed of the focus lens based on the focus evaluation value signal of 1, the movement speed of the focus lens does not change so much and the user does not feel uncomfortable.

The focus / lens control unit, for example, when the focus position calculated based on the first focus evaluation value signal is between the focus position of the first image sensor and the focus position of the second image sensor And the focus lens is switched to a movement at the second movement speed from a movement at the first movement speed when the subject lens is close to a position where the subject image is focused. It may be controlled.

The focus / lens control unit includes a focus motor that moves the focus / lens in accordance with a given focus control signal, a first focus evaluation value signal output from the first focus evaluation value output unit, and a second focus evaluation value signal. The second focus evaluation value signal output from the focus evaluation value output unit is input, and the input first focus evaluation value signal or second focus evaluation value signal is input in accordance with a given gain coefficient. A gain control amplification circuit that amplifies the level and gives the focus motor control signal as a focus motor control signal, and a focus position calculated based on the first focus evaluation value signal are the focus position of the first image sensor. If it is not between the focus positions of the second image sensor, the focus lens is moved at the first moving speed based on the first focus evaluation value signal output from the first focus evaluation value output unit. , 1st When the in-focus position calculated based on the evaluation value signal is between the in-focus position of the first image sensor and the in-focus position of the second image sensor, the second focus evaluation value output unit outputs it. The focus lens is moved at a second movement speed that is slower than the first movement speed based on the focus evaluation value signal 2 and slower as the focus lens is closer to the position where the subject image is in focus. A gain coefficient control unit that provides a large gain coefficient to the gain control amplifier circuit may be provided.

The structure of an imaging lens unit is shown. The relationship between the image sensor for optical path length difference AF and the imaging position of a subject image is shown. The relationship between the AF evaluation value and the focus / lens position is shown. The relationship between the phase difference AF evaluation value and the focus / lens position is shown. The relationship between the differential AF evaluation value and the focus / lens position is shown. It is a flowchart which shows a focusing process procedure. It is a flowchart which shows a focusing process procedure. It is a flowchart which shows a focusing process procedure. The relationship between the movement time and position of the focus lens is shown.

FIG. 1 shows an embodiment of the present invention, and shows an optical configuration of a part of a photographing lens unit 1 and a camera body 20 used for broadcasting or the like.

The taking lens unit 1 is detachably attached to the camera body 20.

The photographic lens unit 1 includes a focus lens (focus lens group) 2, a zoom lens (zoom lens group) 3, and a front relay so as to have an optical axis common to the optical axis O1 of the photographic lens unit 1 A lens (front relay / lens group) 5 and a rear relay / lens (rear relay / lens group) 7 are included. A diaphragm 4 is arranged between the zoom lens 3 and the front relay lens 5 so that the optical axis O1 of the photographing lens unit 1 passes through the center. A half mirror 6 is arranged between the front relay lens 5 and the rear relay lens 7.

The camera body 20 is provided with a color separation prism 21 having an optical axis common to the optical axis O1 of the photographing lens unit 1 when the photographing lens unit 1 is mounted. The color separation prism 21 includes a first prism 22, a second prism 23, and a third prism 24, and incident light is separated into a red component, a green component, and a blue component. The first imaging CCD 25, the second imaging CCD 25, the second imaging prism 25, the second prism 23, the third prism 24, the second prism 23, the second prism 23, and the third prism 24, respectively. An imaging CCD 26 and a third imaging CCD 27 are arranged.

Further, the photographing lens unit 1 includes an AF relay lens (AF relay lens) that uses a part of the light reflected at the center of the half mirror 6 as an optical axis [optical axis for AF (auto focus)] O2. Lens group) 8 is provided. A half mirror 40 (which may be a reflecting prism) is provided downstream of the AF relay lens 8. A total reflection mirror 9 is provided after the half mirror 40.

An optical path length difference AF sensor 55 is provided in the total reflection direction of the total reflection mirror 9. The optical path length difference AF sensor 55 includes a split prism 10 composed of a first prism 11 and a second prism 12. A first AF CCD 13 and a second AF CCD 14 are provided on the exit surface of the first prism 11 and the exit surface of the second prism 12, respectively.

The light beam incident on the photographic lens unit 1 passes through the focus lens 2, zoom lens 3, aperture 4, front relay lens 5, half mirror 6 and rear relay lens 7, and enters the camera body 20. Led. In the light decomposing prism 21 included in the camera body 20, the light beam is decomposed into a red light component, a green light component, and a blue light component, respectively, and the first image pickup CCD 25, the second image pickup CCD 26, and the third image pickup device. A subject image is formed on each of the CCDs 27 for use. Video signals representing subject images of the red light component, the green light component, and the blue light component are output from the first imaging CCD 25, the second imaging CCD 26, and the third imaging CCD 27, respectively.

The light beam incident on the taking lens unit 1 is partially reflected by the half mirror 6. The light beam reflected by the half mirror 6 passes through the AF relay lens 8 and is guided to the half mirror 40.

A part of the light incident on the half mirror 40 is reflected and incident on the phase difference sensor 41 included in the phase difference AF sensor 45.

The phase difference sensor 41 includes a condenser lens, a separator lens, and an image sensor (all not shown). The light incident on the phase difference sensor 41 is condensed by the condenser lens and divided into two by the separator lens. The light divided into two forms an image on the image sensor as two images. The focus lens 2 can be controlled so that the focus lens 2 is focused from the interval between the two images. The phase difference sensor 41 outputs video signals representing two images, and the evaluation value calculation circuit 42 generates a phase difference AF evaluation value representing the degree of focusing of the subject image obtained by imaging. A signal representing the phase difference AF evaluation value is input to the selector 33 via the amplifier circuit 43.

The light transmitted through the half mirror 40 is totally reflected by the total reflection mirror 9. The light beam totally reflected by the total reflection mirror 9 is incident on the splitting prism 10, a part of which is incident on the first optical path length difference AF CCD 13, and the other is incident on the second optical path length difference AF CCD 14. An AF signal is output from each of the first optical path length difference AF CCD 13 and the second optical path length difference AF CCD 14.

Signals output from the first optical path length difference AF CCD 13 and the second optical path length difference AF CCD 14 are input to the evaluation

value calculation circuits

51 and 52, respectively, and indicate the degree of focusing of the focus lens 2. Is evaluated. Signals representing the evaluation values calculated in the evaluation

value calculation circuits

51 and 52 are supplied to the subtraction circuit 53. The signal representing the evaluation value calculated in the evaluation value calculating circuit 52 is subtracted in the subtracting circuit 53 from the signal representing the evaluation value calculated in the evaluation value calculating circuit 51 to obtain a differential AF evaluation value. A signal representing the difference AF evaluation value is amplified by the amplifier circuit 54 and is supplied to the selector 33.

The phase difference AF evaluation value signal output from the amplifier circuit 43 and the difference AF evaluation value signal output from the amplifier circuit 54 are also input to the focus control circuit 31. The selector 33 is controlled based on the input phase difference AF evaluation value signal and the difference AF evaluation value signal, and the phase difference AF evaluation value signal output from the amplifier circuit 43 or the difference AF evaluation value signal output from the amplifier circuit 54 Either one is supplied to the gain control amplification circuit 34. The gain coefficient is calculated in the focus control circuit 31, and data representing the calculated gain coefficient is supplied to the gain control amplification circuit. The input signal is amplified using the given gain coefficient, and is supplied to the focus motor 35 as a control signal representing the rotation direction and rotation speed. The focus lens 2 is moved by the focus motor 35.

Further, as will be described in detail later, the moving direction of the focus lens 2 represented by the phase difference AF evaluation value signal output from the amplification circuit 43 and the focus represented by the difference AF evaluation value signal output from the amplification circuit 54. The focus control circuit 31 controls the warning device 32 to warn when the moving direction of the lens 2 does not match. The warning device 32 gives a warning to the cameraman who uses the photographing lens unit 1 by, for example, sound, light, vibration, etc., and the cameraman will manually focus in response to the warning. This prevents the loss of photographing opportunities.

Further, a control device 30 is provided in the photographing lens unit 1 in order to control the above-described circuits and the like.

FIG. 2 shows the relationship between the optical distances of the first imaging CCD 25, the second imaging CCD 26, the third imaging CCD 27, the first optical path length difference AF CCD 13, and the second optical path length difference AF CCD 14. Is shown.

An optical system for causing light to enter the first imaging CCD 25, the second imaging CCD 26, the third imaging CCD 27, the first optical path length difference AF CCD 13, and the second optical path length difference AF CCD 14 is provided. Represented by lens 30.

The optical distances until the light enters the first imaging CCD 25, the second imaging CCD 26, and the third imaging CCD 27 are all equal. On the other hand, the optical distance until the light enters the first optical path length difference AF CCD 13 is a predetermined distance from the first imaging CCD 25, the second imaging CCD 26, and the third imaging CCD 27. The optical distance until the light enters the second optical path length difference AF CCD 14 is equal to a predetermined distance from the first imaging CCD 25, the second imaging CCD 26, and the third imaging CCD 27. The first imaging CCD 25, the second imaging CCD 26, the third imaging CCD 27, the first optical path length difference AF CCD 13, and the second optical path length difference so as to be equal when they are arranged after a distance. The positional relationship of the AF CCD 14 (optically equidistantly spaced positions) is defined. Temporarily, the first imaging CCD 25, the second imaging CCD 26, the third imaging CCD 27, the first optical path length difference AF CCD 13, and the second optical path length difference AF CCD 14 are arranged on the same optical axis. The first optical path length difference AF CCD 13 and the second optical path length difference AF CCD 14 are arranged at equally spaced positions before and after the first imaging CCD 25, the second imaging CCD 26, and the third imaging CCD 27. It is equivalent to what is done.

FIG. 3 shows the relationship between the AF evaluation value and the position of the focus lens 2.

A graph G51 is obtained from the evaluation value signal calculated by the evaluation value calculation circuit 51 based on the signal output from the first optical path length difference AF CCD 13, and the signal output from the second optical path length difference AF CCD 14 is obtained. A graph G52 is obtained from the evaluation value signal calculated by the evaluation value calculation circuit 52 based on the above.

As described above, the first imaging CCD 25, the second imaging CCD 26, the third imaging CCD 27, the first optical path length difference AF CCD 13, and the second optical path length difference AF are assumed to be on the same optical axis. When the CCD 14 is arranged, the first optical path length difference AF CCD 13 and the second optical path length difference are arranged at equal intervals before and after the first imaging CCD 25, the second imaging CCD 26, and the third imaging CCD 27. Since this is equivalent to the arrangement of the AF CCD 14, at the intersections of the graphs G51 and G52 obtained from the signals of the first optical path length difference AF CCD 13 and the second optical path length difference AF CCD 14, respectively. A certain focus lens position P0 is the position of the focus lens 2 where the subject image is focused on the first imaging CCD 25, the second imaging CCD 26, and the third imaging CCD 27.

FIG. 4 shows the relationship between the phase difference AF evaluation value and the position of the focus lens 2. The horizontal axis indicates the position of the focus lens 2, and the vertical axis indicates the phase difference AF evaluation value.

When the phase difference AF evaluation value is calculated in the evaluation value calculation circuit 42, the position of the focus lens 2 is determined from the relationship between the calculated phase difference AF evaluation value and the graph G0. For example, if the phase difference AF evaluation value calculated by the evaluation value calculation circuit 42 is D1, D2 or D3, the position of the focus lens 2 is P1, P2 or P3. If the phase difference AF evaluation value is 0, the position P0 of the focus lens 2 is substantially equal to the in-focus position at which the subject image is in focus.

In FIG. 4, the graph G0 is indicated by a straight line. However, since the AF evaluation value is obtained in steps according to the resolution of the AF sensor, the position of the focus lens 2 that is actually obtained is the position of the AF sensor. It becomes a discrete numerical value according to the resolution, and when the phase difference AF evaluation value is 0, the focus position P0 may not correspond completely.

FIG. 5 is a graph G53 showing the relationship between the differential AF evaluation value signal output from the subtraction circuit 53 and the position of the focus lens 2. The horizontal axis is the focus lens position, and the vertical axis is the differential AF evaluation value.

Between the positive peak value D11 and the negative peak value D12 of the differential AF evaluation value, the positional relationship between the differential AF evaluation value and the focus lens 2 corresponds one to one. If the differential AF evaluation value is known, the position P11 of the focus lens 2 corresponding to the positive peak value D11 [the in-focus position of the first optical path length difference CCD 13 (first imaging element)] and the negative peak The position of the focus lens 2 between the position P12 of the focus lens 2 corresponding to the value D12 and the in-focus position of the second optical path length difference CCD 14 (second image sensor) is also known. The position of the focus lens 2 at which the differential AF evaluation value is 0 is the in-focus position.

As shown in FIG. 4, in the phase difference AF, the amount of displacement from the focus position P0 of the focus lens 2 is calculated from the phase difference AF evaluation value, and the focus lens 2 is directly moved to the target position. Even when the lens is moved at high speed, so-called hunting does not occur because there is no operation for searching for the in-focus position P0. On the other hand, when the focus lens 2 is positioned at the focus position P0 using the differential AF evaluation value, as shown in FIG. 5, the change in the evaluation value with respect to the lens movement near the focus position P0 is large. Even if the lens slightly exceeds the in-focus position P0, the evaluation value fluctuates greatly. Therefore, if the moving speed of the focus lens 2 is fast, the focus lens 2 is moved and the focus position P0 is moved. While determining whether or not the focus position has been reached, the in-focus position P0 is exceeded, and the operation of reversing and reversing the in-focus position is repeated, thereby causing hunting.

For this reason, when the focus lens 2 is positioned at the focus position P0 using the differential AF evaluation value, the focus lens 2 must be moved relatively slowly. However, after calculating the position shift amount with respect to the focus position P0 of the focus lens 2 from the phase difference AF evaluation value and moving the focus lens 2 so that the calculated position shift amount disappears, the focus lens is thereafter moved. When the moving speed of the focus lens 2 is changed so that the focus lens 2 is moved relatively slowly so that hunting does not occur using the differential AF evaluation value in order to position 2 at an accurate in-focus position, When it changes, a sense of incongruity occurs. For this reason, in this embodiment, in order to prevent a sense of incongruity at the time of the change, if the moving speed of the focus lens 2 does not change much at the time of the change and approaches the in-focus position, focus is prevented to prevent hunting. The gain coefficient of the gain control amplification circuit 34 is determined (defined) so that the moving speed of the lens 2 becomes slow.

6 to 8 are flowcharts showing the focusing processing procedure. FIG. 9 shows the relationship between the position of the focus lens 2 and the time until the focus lens 2 is positioned at the in-focus position.

First, the phase difference AF sensor 45 is driven, and based on the phase difference AF, the phase difference AF evaluation value indicating the amount of displacement from the in-focus position of the focus lens 2 and the optical path length difference AF sensor 55 are driven. A difference AF evaluation value based on the difference AF is calculated (step 61).

The selector is switched by the focus control circuit 31 so that a phase difference AF evaluation value signal indicating the amount of positional deviation from the focus position of the focus lens 2 based on the phase difference AF is given to the gain control amplification circuit 34. The gain control amplification circuit 34 is given a predetermined gain coefficient G. In the gain control amplification circuit 34, a signal obtained by multiplying the input AF evaluation value signal by the gain coefficient G is generated, and the generated signal is sent to the focus motor 35 as a signal for controlling the rotation speed of the focus motor 35. Given. The focus lens 2 is moved based on the phase difference AF evaluation value (step 62). The difference AF evaluation value signal obtained based on the optical path length difference AF

image pickup devices

13, 14 and the like is input to the focus control circuit 31, and the moving direction of the focus lens 2 and the step which can be understood based on the graph G53 shown in FIG. In 62, it is determined whether or not the moving direction of the focus lens 2 moved based on the phase difference AF evaluation value matches. If they match, it is confirmed that the moving direction of the focus lens 2 is correct. If they do not match, the moving direction of the focus lens 2 is incorrect. If the moving direction of the focus lens 2 is wrong (NO in step 64), the warning device 32 warns (step 60).

If the moving direction of the focus lens 2 is correct (YES in step 64), whether or not the position of the focus lens 2 is closer to the focus position P0 than the first threshold position P1 in the vicinity of the focus position P0. Confirmed (step 65). As shown in FIG. 9, the focus lens 2 is driven based on the evaluation value of the phase difference AF until the position of the focus lens 2 reaches the first threshold position P1 (NO in step 65). Therefore, the moving speed of the focus lens 2 is high, and the time t1 until the focus lens 2 reaches the first threshold position P1 is short (the gain G is determined in advance).

When the focus lens 2 reaches the first threshold position P1 (YES in step 65), the selector 33 is switched so that the evaluation value signal output from the amplifier circuit 54 is supplied to the gain control amplifier circuit 34. The moving speed of the focus lens 2 is slower than the first moving speed before the focus lens 2 moves to the first threshold position P1, but is close to the first moving speed, and A gain coefficient G1 that gives a second moving speed faster than the threshold moving speed is given to the gain control amplification circuit 34. Such a gain coefficient G1 (predetermined) is multiplied by the differential AF evaluation value signal output from the amplifier circuit 54 and given as a control signal to the focus motor 35. The lens 2 is moved (step 66). The process of step 66 is repeated until the focus lens 2 is closer to the focus position P0 than the second threshold position P2 that is closer to the focus position P0 than the first threshold position P1 ( Step 67). As shown in FIG. 9, the first movement when the focus lens 2 is moved based on the evaluation value of the phase difference AF until the position of the focus lens 2 reaches the second threshold position P2. Since the gain coefficient of the gain control amplification circuit 34 is determined so that the focus lens 2 moves at a second moving speed that is not much different from the speed, from the movement control of the focus lens 2 based on the evaluation value of the phase difference AF. , There is no sense of incompatibility even when switching to the movement control of the focus lens 2 based on the differential AF evaluation value. Further, as shown in FIG. 9, since the moving speed of the focus lens is relatively fast until the position of the focus lens 2 reaches the second threshold position P2, the focus lens 2 has the second threshold value. The time t2 until the position P2 is reached is also relatively short.

When the focus lens 2 is closer to the in-focus position P0 than the second threshold position P2 (YES in step 67), a gain coefficient smaller than the gain coefficient G1 is set so that the moving speed of the focus lens 2 becomes slower. G2 (this gain coefficient G2 is also predetermined) is applied to the gain control amplification circuit 34. The gain coefficient G2 is multiplied by the differential AF evaluation value signal output from the amplifying circuit 54 and provided to the focus motor 35 as a control signal. The focus lens 2 is moved at a third moving speed that is slower than the second moving speed (step 68). The process of step 68 is repeated until the focus lens 2 is closer to the focus position P0 than the third threshold position P3 (step 69). As shown in FIG. 9, the focus lens 2 is moved at a third movement speed that is slower than the second movement speed until the position of the focus lens 2 reaches the third threshold position P3. .

When the focus lens 2 is closer to the focus position P0 than the third threshold position P3 at time t3 shown in FIG. 9 (YES in step 69), the moving speed of the focus lens 2 is further decreased. , A gain coefficient G3 smaller than the gain coefficient G2 (this gain coefficient G3 is also predetermined) is applied to the gain control amplification circuit 34. The gain coefficient G3 is multiplied by the differential AF evaluation value signal output from the amplifier circuit 54, and is provided to the focus motor 35 as a control signal. The focus lens 2 is moved at a fourth moving speed that is slower than the third moving speed (step 70). When the focus lens 2 is moved at the third moving speed, the position of the focus lens 2 when the differential AF evaluation value becomes 0 as shown in FIG. The movement of the lens 2 is stopped (step 71).

As shown in FIG. 9, the phase difference AF evaluation value obtained based on the phase difference sensor 41 is used until the focus lens 2 reaches the first threshold position P1 in the vicinity of the position where the subject image is focused. Then, the focus lens 2 is moved at the first moving speed (gain coefficient G). When the focus lens 2 is closer to the position where the subject image is in focus than the first threshold position P1, the first moving speed is based on the differential AF evaluation value obtained based on the optical path length

difference image sensors

13 and 14. The focus lens 2 is moved at a second moving speed slower than the first moving speed and faster than the threshold moving speed (gain coefficient G1). Furthermore, as the focus lens approaches the position where the subject image is in focus, the focus lens is gradually moved at a third movement speed that is slower than the threshold movement speed (gain coefficients G2, G3). Since the focus lens 2 is moved in this manner, even when two types of AF sensors are switched and used, a sense of incongruity does not occur and hunting can be prevented.

In the above-described embodiment, the focus lens 2 is driven at the first moving speed using the phase difference AF evaluation value signal until the focus lens 2 is between the positions P11 and P12 shown in FIG. When the focus lens 2 is between these positions P11 and P12, the focus lens 2 is driven at a moving speed slower than the first moving speed by using the differential AF evaluation value signal. Also good. In this case, the focus lens 2 becomes slower as it approaches the position P0 where the subject image is focused. In addition, since the focus lens 2 is located between the positions P11 and P12, the movement speed of the focus lens 2 is not switched from the first movement speed to the second movement speed, but more accurately. When approaching the focal position P0, the first movement speed using the phase difference AF evaluation value signal may be switched to the second movement speed using the difference AF evaluation value signal.

Furthermore, control may be performed as follows. The target position of the focus lens 2 is calculated based on the phase difference AF evaluation value signal indicating the amount of displacement from the focus position of the focus lens 2 based on the phase difference AF, and driving to move the lens toward the target position is started. To do. Simultaneously with the movement of the lens, the focus determination is performed with the differential AF evaluation value by the second AF sensor, and when it is determined that the subject image is closer to the in-focus position than the first threshold position P1, The difference AF evaluation value signal obtained based on the optical path length difference AF

image pickup devices

13, 14 Image sensor for optical path length difference AF
30 Control unit
31 Focus control circuit
33 Selector
34 Gain control amplifier circuit
41 Phase difference sensor
42, 51, 52 Evaluation value calculation circuit

Claims

A first focus evaluation value indicating the amount of focus deviation based on the amount of positional deviation in the pupil division direction of two subject images formed by dividing the light incident through the focus lens into two by pupil division. A first focus evaluation value output unit for outputting a signal;
A first imaging device and a second imaging device arranged in positions where the optical path lengths are different from each other in an optical path of light incident through the focus lens;
A second focus evaluation value output unit for outputting a second focus evaluation value signal indicating a focus shift amount based on the output signal of the first image sensor and the output signal of the second image sensor; In addition, when the focus position calculated based on the first focus evaluation value signal is not between the focus position of the first image sensor and the second image sensor focus position, the first focus is obtained. Based on the first focus evaluation value signal output from the evaluation value output unit, the focus lens is moved at the first moving speed, and the focus is calculated based on the first focus evaluation value signal. When the position is between the in-focus position of the first image sensor and the in-focus position of the second image sensor, based on the second focus evaluation value signal output from the second focus evaluation value output unit. It is slower than the first moving speed and the focus lens is close to the position where the subject image is in focus. A focus lens control unit for controlling the focus lens so as to move the focus lens at a second moving speed that becomes slower.
Auto focus device with
The focus lens control unit
A focus position calculated based on the first focus evaluation value signal is between the focus position of the first image sensor and the focus position of the second image sensor, and the focus lens; However, the focus lens is controlled so that the movement at the first movement speed is switched to the movement at the second movement speed when the subject image is close to the in-focus position. is there,
The autofocus device according to claim 1.
The focus lens control unit
A focus motor for moving the focus lens in accordance with a given focus control signal;
The first focus evaluation value signal output from the first focus evaluation value output unit and the second focus evaluation value signal output from the second focus evaluation value output unit are input and given. A gain control amplification circuit that amplifies the level of the input first focus evaluation value signal or the second focus evaluation value signal and gives it to the focus motor as a focus motor control signal, When the focus position calculated based on the first focus evaluation value signal is not between the focus position of the first image sensor and the second image sensor focus position, the first focus evaluation is performed. A focus position calculated based on the first focus evaluation value signal by moving the focus lens at a first moving speed based on the first focus evaluation value signal output from the value output unit Is the in-focus position of the first image sensor and the in-focus position of the second image sensor If it is between the positions, it is slower than the first moving speed based on the second focus evaluation value signal output from the second focus evaluation value output unit, and the focus lens is the subject image. A gain coefficient control unit that provides the gain control amplification circuit with a gain coefficient that moves the focus lens at a second moving speed that becomes slower as the position becomes closer to the in-focus position;
The autofocus device according to claim 1, further comprising:
The first focus evaluation value output unit is configured to focus on the amount of positional deviation in the pupil division direction of the two subject images formed by dividing the light incident through the focus lens into two by pupil division. Outputting a first focus evaluation value signal indicating the amount of deviation;
The second focus evaluation value output unit outputs each of the first image sensor and the second image sensor that are arranged at positions having different optical path lengths in the optical path of the light incident through the focus lens. A second focus evaluation value signal indicating the amount of focus deviation is output based on the signal;
When the focus / lens controller does not have a focus position calculated based on the first focus evaluation value signal between the focus position of the first image sensor and the second image sensor focus position. The focus lens is moved at a first moving speed based on a first focus evaluation value signal output from the first focus evaluation value output unit, and based on the first focus evaluation value signal. Second focus output from the second focus evaluation value output unit when the calculated focus position is between the focus position of the first image sensor and the second image sensor focus position. Based on the evaluation value signal, the focus lens is moved at a second movement speed that is slower than the first movement speed and slower as the focus lens is closer to the position where the subject image is in focus. Control the focus lens;
Operation control method of auto focus device.