Imaging device

A lens control device, for controlling driving of a second lens unit for correcting image movement regarding movement of a variating first lens unit, comprises: a storage unit for storing data indicating the position of the second lens unit corresponding to the position of the first lens unit created for a predetermined focal distance; a control unit for generating information to control driving of the second lens unit based on the data, and for controlling driving of the second lens unit based on this information; and a distance detecting unit for detecting distance to the focus object; wherein the control unit restricts the range of the generated information based on the detection results from the distance detecting unit. Or, the control unit controls driving for the second lens unit to generate the information, and performs weighting based on detection results from the distance detecting unit relating to driving control.

This application claims priority from Japanese Patent Application Nos. 2003-354372 filed Oct. 14, 2003, and 2003-361291 filed Oct. 21, 2003, which are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical equipment such as a video camera, digital camera, and so forth.

2. Description of the Related Art

With regard to cameras with non-interchangeable lenses, there are demands for reduction in size, the ability to photograph subjects from as close as possible, and so forth. Therefore, rather than interlocking a correcting lens and a variable power lens mechanically by a cam, a so-called inner focus type lens is becoming mainstream, wherein the movement locus of the correcting lens is input in advance as lens cam data within a microcomputer, which drives the correcting lens according to this lens cam data, and further sets the focus by means of this correcting lens.

FIG. 8is a figure that illustrates the configuration of a lens system with the current inner focus type. Here, reference numeral901denotes a fixed front lens,902denotes a zoom lens for variable power (also referred to as a variator lens: first lens unit),903denotes an aperture diaphragm,904denotes a fixed lens that is fixed, and905denotes a focus lens (second lens unit) to be used as a correcting lens, which provides a focal point adjusting function and a function that corrects the movement of the image based on the variable power. Further,906denotes an imaging plane.

With a lens system configured as inFIG. 8, the focus lens905provides both a compensator function and a focal point adjusting function, therefore even if the focal point distance is equal, the position of the focus lens905for converging with the imaging plane906differs based on the subject distance. When the subject distance is changed with regard to each focal point distance, and when the position of the focus lens905is continuously plotted to focus with the subject image on the imaging plane906, the result is as shown inFIG. 9. While zooming in or out, selecting a locus corresponding to the subject distance from the multiple loci illustrated inFIG. 9moves the focus lens905according to the selected locus, thereby enabling variable power (zooming) while storing the focused state.

Now, with regards to the type of a lens system where the front lens performs the focusing, a focus lens independent of the zoom lens is provided, and further, the zoom lens and the focus lens are mechanically linked to a cam ring. Therefore, in the case of trying to rotate the cam ring manually and change the focal point for example, even if the cam ring is moved very fast, the cam ring follows and rotates. The zoom lens and the focus lens move in the direction of the optical axis, according to the cam formed by the cam ring, and therefore, is the focus lens is in a converging position, the image will not blur due to zooming.

In contrast to this, a lens system of an inner focus type generally records in memory the information of the multiple loci illustrated inFIG. 9(also called electronic cam locus) or the information corresponding to this (in other words, either information indicating the locus itself, or a function wherein the lens position is a variable, is suitable), selects a locus based on the positions of the focus lens and the zoom lens, and performs zooming while moving along the selected locus.

Now, in the case that the zoom lens moves in the direction from telephoto to wide angle, focus can be maintained using the above-described locus following method, because it converges from a state wherein multiple loci have a given amount of spacing in between, as is apparent fromFIG. 9. However, in the direction from wide angle to telephoto, the focus lens that was at the convergence point is uncertain which locus to follow, and therefore focus cannot be maintained with a similar locus following method.

Therefore, Japanese Patent No. 2,795,439 (Claims, FIGS. 3 and 4, and the description thereof) discloses a control method (zigzag movement) wherein, using an AF evaluation value signal (sharpness signal) obtained from the high frequency component of the image signal by using a TV-AF method, when moving the zoom lens (variable power), the focus lens is forced to move so as to be off focus from the focus position, and further, performs repeated control of switching and moving the focus lens toward the direction of focus (changing the following speed to the locus), thereby correcting the following locus. Further, Japanese Patent No. 2,795,439 discloses a method of changing the increase/decrease cycle of the sharpness signal by means of changing the amount of change of the following speed corresponding to the subject, the focal point distance, and the depth of field, and attempts improvement of selection (generating) accuracy of the following locus selection.

The zigzag movement disclosed in the aforementioned Japanese Patent No. 2,795,439 specifies the following locus based on the change of the AF evaluation value. Further, the evaluation value changes not only according to the status of blurring of the image, but also changes according to the pattern changes of the subject. Therefore, considering that there may be cases wherein the focus lens movement switching is switched in the wrong direction, the correction range of the following locus is set as a wide range so as to be able to return to the correct locus even if initially moving in the wrong direction.

On the other hand, when the setting is for such a wide correction range, in the event that the movement deviates from the locus that should be used, the image may blur until moved back to the correct locus. Further, in the case of moving the focus lens in the wrong direction, image blurring may occur wherein the AF evaluation value level in particular is greatly decreased, or when image-taking a subject with low contrast, the correct locus may not be found, and there is the possibility that the image blur is carried all the way to the telephoto edge.

Further, in the case of image-taking a subject with a high frequency, when the following locus is trying to be set by means of the zigzag movement, arbitrary image blurring can occur. In order to make this type of image blurring less conspicuous, the AF evaluation value level, which determines the reverse timing of the drive direction of the focus lens wherein the zigzag movement can be adjusted according to the subject conditions, can be adjusted, but eliminating the occurrence of all image blurring of the subject related to the zigzag movement is difficult.

Further, with the TV-AF method, due to the signal detection cycle obtained by the AF evaluation value being a vertical synchronizing signal cycle, the sharpness of locus selection becomes poorer as the zooming speed becomes faster, and consequently, the rate of mistaken following locus selection increases.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a lens control device, optical equipment, and a lens control method for performing high quality zooming that is not affected by the photography scene or camera work, while maintaining a state of focus, even with a high speed zoom.

To this end, according to one aspect of the present invention, a lens control device, for controlling the driving of a second lens unit for correcting image movement in the event of movement of a variating first lens unit, comprises: a storage unit for storing data indicating the position of the second lens unit corresponding to the position of the first lens unit created for a predetermined focal distance; a control unit for generating information to control the driving of the second lens unit based on the data, and for controlling the driving of the second lens unit based on this information; and a distance detecting unit for detecting the distance to the focus object; wherein the control unit restricts the range of the generated information based on the detection results from the distance detecting unit.

According to another aspect of the present invention, a lens control method, for controlling the driving of a second lens unit for correcting image movement in the event of movement of a variating first lens unit, comprises: a storage step for storing data indicating the position of the second lens unit corresponding to the position of the first lens unit created for a predetermined focal distance; a control step for generating information to control the driving of the second lens unit based on the data, and for controlling the driving of the second lens unit based on this information; and a distance detecting step for detecting the distance to the focus object; wherein, in the control step, the range of the generated information is restricts based on the detection results from the distance detecting unit.

Here, the information may be locus information for showing the position of the second lens unit as relates to the first lens unit or a parameter for identifying this locus, or may be position information for driving the second lens unit.

According to another aspect of the present invention, a lens control device, for controlling the driving of a second lens unit for correcting image movement in the event of movement of a variating first lens unit, comprises: a storage unit for storing data indicating the position of the second lens unit corresponding to the position of the first lens unit created for a predetermined focal distance; a control unit for generating information to control the driving of the second lens unit based on the data, and for controlling the driving of the second lens unit based on this information; and a distance detecting unit for detecting the distance to the focus object; wherein the control unit controls the driving for the second lens unit to generate the information, and performs weighting based on the detection results from the distance detecting unit relating to the drive control.

According to another aspect of the present invention, a lens control method, for controlling the driving of a second lens unit for correcting image movement in the event of movement of a variating first lens unit, comprises: a storage step for storing data indicating the position of the second lens unit corresponding to the position of the first lens unit created for a predetermined focal distance; a control step for generating information to control the driving of the second lens unit based on the data, and for controlling the driving of the second lens unit based on this information; and a distance detecting step for detecting the distance to the focus object; wherein in the control step, the driving of the second lens unit for generating the information is controlled, and weighting is performed based on the detected distance, relating to the driving control.

Here, weighting may be weighting relating to the drive direction or drive speed of the second lens unit, or relating to the conditions for switching the driving conditions in the case of driving the aforementioned second lens unit while switching the driving conditions.

Further, the information may be locus information for indicating the position of the second lens unit as relates to the first lens unit or a parameter for identifying this locus, or may be a position information for driving the second lens unit.

Further objects, features and advantages of the imaging device, the focus control method, and the processing program, according to the present invention, will become apparent from the following description of the preferred embodiments with reference to the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to describing the embodiments of the present invention, the technology that is the premise to the present invention will be described.

FIG. 10is a diagram for describing one example of the locus following method for a focus lens in an inner focus type lens system.

InFIG. 10, Z0, Z1, Z2, . . . Z6indicate the position of the zoom lens, and a0, a1, a2, . . . a6and a0, b1, b2, . . . b6indicate the position of the focus lens corresponding to the subject distance stored in an unshown microcomputer beforehand. The group of these focus lens positions (a0, a1, a2, . . . a6and a0, b1, b2, . . . b6) becomes the focus loci that the focus lens of the representative subject distances should follow (representative locus).

Further, p0, p1, p2, . . . p6are the locations on the focus locus that the focus lens should follow, calculated based on the aforementioned two representative loci. The Equation for the positions on this focus locus will be illustrated below.
P(n+1)=|p(n)−a(n)|/|b(n)−(a)|×|b(n+1)−a(n+1)|+a(n+1)(1)

According to the above Equation (1), for example in the case ofFIG. 10wherein the focus lens is at p0, the ratio wherein p0 internally divides the line segment b0−a0is calculated, and the point that internally divides line segment b1−a1according to this ratio is taken as p1. From the difference in location of this p1−p0and from the time required for the zoom lens to move from Z0to Z1, the movement speed of the focus lens in order to maintain focus is determined.

Next, a case in which the stopping position of the zoom lens is not restricted to the boundary of the zoom area that has the stored representative locus data will be described.FIG. 11is a diagram for describing the interpolation method of the zoom lens movement direction, wherein one portion ofFIG. 10is extracted and the position of the zoom lens is arbitrary.

Now, in the case wherein the zoom lens position is at Zxwhich is not on the zoom area boundary, and the focus lens position is Px, then axand bxare calculated as follows:
ax=ak−(Zk−Zx)×(ak−ak−1)/(Zk−Zk−1)  (2)
bx=bk−(Zk−Zx)×(bk−bk−1)/(Zk−Zk−1)  (3)

In other words, following the current zoom lens position and the two zoom area boundary positions that are on either side (for example, Zkand Zk−1inFIG. 11) thereof and the division ratio obtained therefrom, axand bxcan be calculated by dividing those with the same subject distance of the stored four representative locus data (ak, ak−1, bk, bk−1inFIG. 11) using the above-described division ratio.

Next, following the division ratio obtained from ax, px, and bx, pkand pk−1can be calculated by dividing that of the previously stored aforementioned four representative data with identical focal distance, by the above-described division ratio as in Equation (1).

Then, when zooming from wide angle to telephoto, the movement speed of the focus lens in order to maintain focus is determined from the difference in focus position pkwhere the following movement is headed, and the current focus position px, and from the time required for the zoom lens to move from Zxto Zk.

Further, when zooming from telephoto to wide angle, the movement speed of the focus lens in order to maintain focus is determined from the difference in focus position pk−1where the following movement is headed, and the current focus position px, and from the time required for the zoom lens to move from Zxto Zk−1.

FIG. 12illustrates an example of the table data of the focus locus information stored in the microcomputer beforehand.FIG. 12illustrates the focus lens position data A(n, v)based on subject distance, which changes according to the zoom lens position. The subject distance changes with according to a variable n in the row direction, and the zoom lens position (focal distance) changes according to a variable v in the column direction. Here, n=0 denotes an infinitely distant subject distance, and as n grows larger, the subject distance changes towards the greatest close-up distance side. n=m indicates a subject distance of 1 cm. On the other hand, v=0 denotes the wide-angle end. Further, as v grows larger and the focal distance increases, v=s denotes the zoom lens position on the telephoto end. Therefore, one row of table data plots one representative locus.

Next, as described above, a locus following method will be described for solving the problem wherein the focus lens cannot find which locus to follow when zooming from the wide angle to the telephoto direction.

InFIGS. 13A and 13B, the horizontal axis illustrates the position of the variable power lens. Further, the vertical axis inFIG. 13Aillustrates the AF evaluation signal obtained from the imaging signal by means of the TV-AF Equation. This AF evaluation signal illustrates the level of the high frequency components of the imaging signal (the sharpness signal). Further, the horizontal axis inFIG. 13Billustrates the focus lens position. InFIG. 13B, reference numeral1304denotes the cam locus (grouping of the focus lens positions) that the focus lens should travel when zooming while obtaining focus of the subject at a given distance position.

Here, the standard movement speed for focus locus following when further at the wide angle side than the zoom lens position1306(Z14) is made to be positive (moving in the direction of focus lens close-up), and the standard movement speed for focus locus following when moving in the infinitely distant direction when further at the telephoto side than the position1306is made to be negative. As the focus lens moves over the target locus1304while maintaining focus, the strength of the AF evaluation signal becomes the level denoted by1301inFIG. 13A. Generally, with zooming wherein focus is maintained, the AF evaluation signal is approximately a set value.

InFIG. 13B, the standard movement speed of the focus lens that traces the target locus1304while zooming is Vf0. The actual focus lens movement speed is Vf, and in the event of zooming while increasing and decreasing this movement speed Vfcompared to the standard movement speed Vf0, the locus thereof becomes a zigzag locus as in1305(hereafter, this is called “zigzag correction operation”).

At this time, the AF evaluation signal level changes so as to produce mountains and valleys as indicated by1303inFIG. 13A. Here, at the position wherein the target locus1304and the actual zigzag locus1305intersects, the AF evaluation signal level1303becomes the greatest level1301(the even-numbered points of Z0, Z1, Z2, . . . Z16), and at the odd-numbered points of Z0, Z1, Z2, . . . Z16wherein the movement direction vector of the actual locus1305switches, the AF evaluation signal level1303becomes the smallest level1302.

Then, conversely, if the value TH1of the smallest level1302of the AF evaluation signal level1303is set in advance (in other words, the focus tolerance is set wherein the AF evaluation signal of the smallest level TH1that can be considered to be focused is the lower limit), and if the movement direction vector of the locus1305is switched each time the AF evaluation signal level1303becomes the same size as TH1, the focus lens movement direction after switching can be set in the direction closer to the target locus1304. In other words, whenever the image is blurred by the difference of the greatest level1301and the smallest level1302(TH1) of the AF evaluation signal, zooming can be performed while controlling the occurrence of blurring by controlling the drive direction and drive speed which are drive conditions for the focus lens to reduce this blurring.

By using this type of method, as illustrated inFIG. 9, with zooming from wide angle to telephoto wherein the focus loci of different subject distances spread out from convergence, even if the standard movement speed Vf0that maintains focus is not the most appropriate for the subject distance at that time, the movement speed Vfcan be controlled against the standard movement speed (calculated using P(n+1)obtained from Equation (1)), and by repeating the switching operation indicated in locus1305according to the changes of the AF evaluation signal level, focus locus re-identifying (re-generating) can be performed without the AF evaluation signal level moving below the smallest level1302(TH1), in other words, without producing any more than a predetermined amount of blurring. Further, by setting TH1appropriately, zooming is realized wherein the blurring is imperceptible to the naked eye.

Here, with the focus lens movement speed Vfcompared to the standard movement speed set at Vf+for the positive direction correction speed, and at Vf−for the negative direction correction speed,
Vf=Vf0+Vf+(4)
or
Vf=Vf0+Vf−(5)
hold. At this time, the correction speeds Vf+and Vf−are determined by the direction vector of Vf0so as to equally divide the interior angle of the two Vfdirection vectors obtained by Equations (4) and (5), so as not to produce any imbalanced selection of the following locus according to the aforementioned zooming method.

The zooming control described above generally performs processing synchronizing to the image vertical synchronizing signal, from the relationship wherein the focus detection is performed using the imaging signal from the imaging device.

FIG. 7is a flowchart of the zooming control performed within the microcomputer. Upon processing beginning in step S701, initial settings are made in S702. At the time of initialization, the RAM within the microcomputer and each port is initialized.

In S703, the state of the camera main unit operating system is detected. The microcomputer receives the information of the zoom switch unit for the photographer to operate here, and displays the variable power operation information such as the zoom lens position on the display to advise the photographer that it is in the process of zooming. In S704, AF processing is performed. In other words, automatic focus adjustment processing is performed corresponding to the changes in the AF evaluation signal.

In S705, zooming processing is performed. In other words, the processing is performed for the compensator operation for maintaining the focus while zooming. Specifically, calculations are performed for the focus lens standard drive direction and standard drive speed, in order to trace the locus illustrated inFIG. 10closely.

S706is a routine that selects which to use of the drive direction or drive speed of the zoom lens or focus lens, that were calculated in the S704to S705processing routine, in the case of AF or zooming, and drives the zoom lens and focus lens between the telephoto edge and wide angle edge, or between the close-up edge and the infinity edge, under control provided by software so as not to hit the mechanical edge.

In S707, a control signal is output to the motor driver, corresponding to the drive direction information and drive speed information for zooming and focusing determined in S706, and controls the drive/stop of the lens. After completing processing in S707, the flow returns to S703. The series of processes illustrated inFIG. 7is performed synchronously with the vertical synchronizing signal (stands by in the processing of S703until the next vertical synchronizing signal is input).

FIGS. 3A through 4Billustrate the control flow executed within the microcomputer once every vertical synchronizing signal, and illustrate in detail the content of the processing executed in S705ofFIG. 7. Now, InFIGS. 3A through 4B, the portions indicated by the same circled numeral are connected to one another.

The descriptions below will make reference to FIG.5throughFIG. 7, andFIG. 10.

In S400inFIG. 5, the drive speed Zsp of the zoom motor is set so as to perform natural zooming operations, corresponding to the operation information of the zoom switch unit.

In S401, the distance from the current position of the zoom lens and focus lens to the subject (subject distance) is identified (estimated), and that subject distance information is stored memory region such as RAM, as three locus parameters (data for obtaining the target position information) α, β, and γ. Here, the processing illustrated inFIG. 5is performed. Now, in order to simplify the description, the processing illustrated inFIG. 5will be described as if the focus state is maintained at the current lens position.

In S501ofFIG. 5, with the wide angle edge to the telephoto edge in the data table illustrated inFIG. 12divided into s equal segments, at which zoom area v the current zoom lens position Zxis currently located, is calculated.

In S601, the zoom area variable v is cleared. In S602, the zoom lens position Z(v)on the boundary of the zoom area v is calculated, according to the following Equation (6). This Z(v)is equal to the zoom lens position Z0, Z1, Z2, . . . illustrated in FIG.10.
Z(v)=(telephoto edge zoom lens position−wide angle edge zoom lens position)×v/s+wide angle zoom lens position  (6)

In S603, whether the Z(v)obtained in S602is equal to the current zoom lens position Zxis determined. If equal, in S607, 1 is raised as the boundary flag, as the zoom lens position Zxis positioned on the boundary of the zoom area v.

If not equal in S603, in S604whether Zx<Z(v)is determined. If Yes in S604, then Zxis between Z(v−1)and Z(v), and the boundary flag in S606is 0. If No in S604, then in S605the zoom area v is incremented and the flow returns to S602.

By repeating the above process, whether or not the current zoom lens position Zxexists in the v=k′th zoom area on the data table inFIG. 12, and whether or not Zxis on the zoom area boundary, can be told at the time of completing the flow shown inFIG. 6.

Returning toFIG. 5, the current zoom area is set in S501by the process inFIG. 6, and according the following process calculates where on the data table inFIG. 12the focus lens is positioned.

First, in S502the subject distance variable n is cleared, and in S503whether the current zoom lens position exists on the boundary of the zoom area is determined. If the boundary flag is 0, it is assumed not to be on the boundary, and the flow continues to the process starting at S505.

On the other hand, in the event that S503determines the boundary flag to be 1, in S504the focus position A(n, v)corresponding to the zoom lens position (v in this case) of the subject distance n, and A(n+1, v)corresponding to the zoom lens position of the subject distance n+1, are called up and each stored in memory as axand bx, respectively.

In S508whether the current focus lens position pxis greater than axis determined. If greater than ax, in S509whether or not the current focus lens position pxis greater than bxis determined. If not greater than bx, the focus lens position pxis determined to be between the subject distances n and n+1, and the locus parameters at this point are recorded in memory from S513to S515. At S513, α=px−ax, at S514, β=bx−ax, and at S515, γ=n.

S508is negative in the case that the focus lens position pxis at the far infinite distance position. At this time, in S512α=0 is set and continued from the process of S514, and the locus parameter for infinite distance is stored in memory.

S509is positive in the case that the focus lens position pxis at the far close-up position, and in this case, in S510the subject distance n is incremented, and in S511whether n is on the side of infinite distance from the position m corresponding to the far close-up distance is determined. If to the side of infinite distance from the far close-up distance position m, the flow returns to S503. S511is negative in the case that the focus lens position pxis at the far close-up position, and the locus parameters for the far close-up distance are stored in memory by continuing from the process starting at S512at this time.

Returning toFIG. 4A, in S401, the locus parameters is stored in memory in order to know which position on the locus illustrated inFIG. 9the current zoom lens position and the focus lens position are located.

In S402, the zoom lens position Zx′ (the target position from the current position) wherein the zoom lens will arrive after one vertical synchronizing period (1V), is calculated. Here, if the zoom speed determined in S400is Zsp (pps), the zoom lens position Zx′ after one vertical synchronizing period can be found from the Equation (7) below. A pps is an increment of the rotation speed of the stepping motor, and denotes the step amount (1 step=1 pulse) of rotation during 1 second. Further, the symbols in Equation (7) represent the movement direction of the zoom lens, + meaning the telephoto direction and − meaning the wide angle direction.
Zx′=Zx±Zsp/vertical synchronizing frequency  (7)

Next, S403determines which zoom area v′ wherein Zx′ exists. In S403, the same process as the process inFIG. 6is performed, and ZxinFIG. 6is substituted with Zx′, and v with v′.

Next, in S404, whether the zoom lens position Zx′ after one vertical synchronizing period exists on the zoom area boundary is determined, and if the boundary flag=0, the zoom lens position Zx′ is not considered to be on the boundary, and the flow continues from the process starting in S405.

In S405, Zk←Z(v′), and Zk−1←Z(v′−1)are set. Next, in S406, the four table data sets A(γ, v′−1), A(γ, v′), A(γ+1, v′−1), A(γ+1, v′)wherein the subject distance γ is specified by the process inFIG. 5, and calculates ax′ and bx′ from the Equations (2) and (3) described above in S407. On the other hand, in the case that S403yields Yes, in S408the focus position A(γ, v′)corresponding to the zoom area v′ of the subject distance γ, and the focus position A(γ+1, v′)corresponding to the zoom area v′ of the subject distance γ+1 are called up, and stored in memory as ax′ and bx′, respectively.

Then in S409, the focus lens focus position (target position) px′ when the zoom lens position has reached Zx′ is calculated. Using Equation (1), the following target position after one vertical synchronizing period can be expressed as follows.
Px′=(bx′−ax′)×α/β+ax′  (8)

Therefore, the difference ΔF of the following target position and the current focus lens position becomes
ΔF=(bx′−ax′)×α/β+ax′−Px

Next, in S410the focus standard moving speed Vf0is calculated. Vf0is obtained by subtracting the focus lens position difference ΔF from the movement time of the zoom lens required to move this distance.

The calculation method for the correcting speed for performing the focus lens movement speed correction (zigzag operation) illustrated inFIG. 13Bwill be described below.

In S411, each parameter is initialized, and the “reversal flag” used in the later processes is cleared. S412calculates the correction speed Vf+and Vf−for the “zigzag correction operation” from the focus standard movement speed Vf0obtained in S410.

Here, the correction amount parameter δ and the correction speeds Vf+, Vf−are calculated as follows. FIG.14, which is a diagram to describe the calculation method of the correction speeds Vf+and Vf−corresponding to the correction amount parameter δ, illustrates the zoom lens position on the horizontal axis, and the focus lens position on the vertical axis.1304is the target locus to be followed.

Now, the focus speed at which the focus lens position changes by an amount of y when the zoom lens position changes by an amount of x, (in other words, arrives at the target position), is the standard speed Vf0calculated in1403. The focus speed at which the focus lens position changes by an amount of n or m, with displacement y as a reference, when the zoom lens position changes by an amount of x, is the correction speed Vf+and Vf−to be calculated. Here, n and m are determined so that the direction vector1401of the speed to drive closer to the close-up side than the displacement y (the speed wherein the correction speed Vf+is added to the standard speed Vf0in the positive direction), and the direction vector1402of the speed to drive closer to the infinite distance side than the displacement y (the speed wherein the correction speed Vf−is added to the standard speed Vf0in the negative direction), have direction vectors separated equal angles δ as to the direction vector1403of the standard speed Vf0.

Here the correction angle δ is a variable for parameters such as the depth of the subject field depth or focal distances. By using this, the increase/decrease cycle of the AF evaluation signal level that changes corresponding to the focus lens drive state can be kept constant as to the assigned focus lens position change amount, and the possibility of missing the focus locus that the focus lens should be following during the zooming can be reduced.

Within the memory of the microcomputer according to the value of δ, the value of k is stored as the data table, and by reading out as necessary, the Equations (11) and (12) are calculated.

Here, in the case that the zoom lens position changes by an amount of x each time unit,Zoom speed Zsp=x,Focus standard speed Vf0=y, andCorrection speed Vf+=n, Vf−=m hold, and the correction speeds Vf+and Vf−(negative speed) are obtained by Equations (11) and (12).

In S413, whether or not zooming is being performed is determined, according to the information illustrating the operational state of the zoom switch unit obtained in S703ofFIG. 7. In the event that zooming is being performed, the process starting at S416is carried out. In the event that zooming is not being performed, a value TH1is set, wherein a arbitrary constant μ is subtracted from the current value of the AF evaluation signal level at S414. This TH1determines the AF evaluation signal level that is the switchover base point for the correction direction vector (switchover base point for the zigzag correction operation), as described inFIG. 13A. This TH1is to be determined immediately prior to the start of zooming, and corresponds to the smallest level of1302inFIG. 13A.

Next, in S415the correction flags are cleared, and this process ends. Here, the correction flag is a flag indicating whether the locus following state is under correction in the positive direction (correction flag=1) or under correction in the negative direction (correction flag=0).

In the event that S413determines that zooming is being performed, determination is made whether or not the zooming direction is from wide angle to telephoto in S414. If from telephoto to wide angle, in S419Vf+=0 and Vf−=0 is set, and the processing starting from S420is performed. If from wide angle to telephoto, in S417whether or not the current AF evaluation signal level is smaller than TH1is determined. If TH1or greater, the flow continues to S420, and if smaller than TH1, in S418the reversal flag is set to 1 to perform correction direction switching since the current AF evaluation signal level has dropped to below the TH1(1302) level inFIG. 13.

In S420, whether the reversal flag is 1 is determined, and in the event that the reversal flag=1, then in S421whether the correction flag is 1 is determined. If the correction flag is not 1 in S421, then in S424the correction flag is set to 1 (correction state in the positive direction). Further, according to Equation (4),
focus lens movement speedVf=Vf0+Vf+(whereinVf+≧0).

On the other hand, if the correction flag=1 in S421, then in S423the correction flag is set to 0 (correction state in the negative direction), and according to Equation (5),
focus lens movement speedVf=Vf0+Vf−(whereinVf−≧0).

Further, in the event that the reversal flag is not 1 in S420, S422determines whether the correction flag=1. If the correction flag=1 the flow continues to S424, and if not, the flow continues to S423.

After completing this process, in S706inFIG. 7the focus lens and zoom lens drive direction and drive speed are selected, according to the operation mode. In the case of zooming operation, the focus lens drive direction is set to the close-up direction or the infinite distance direction, depending on whether the focus lens movement speed Vfobtained in S423or S424is positive or negative. Thus, the locus to be traced is re-identified as the focus lens zigzag driving is performed.

The above-described is the underlying conventional art upon which the present invention has been made, and the description below will be made primarily contrasting the embodiments of the present invention with the conventional art.

First Embodiment

FIG. 1shows an embodiment according to the present invention of an imaging device (optical device) provided with a lens control device, as the configuration of a video camera. Now, the present embodiment describes an example applying the present invention to a imaging device with non-interchangeable image-taking lens, however the present invention can also be applied to an interchangeable lens (optical equipment) of an imaging system possessing an interchangeable lens and the camera main unit to which this is attached. In this case, a microcomputer within the lens performs the later-described zooming operation in response to a signal that is sent from the side of the camera main unit. Further, the present invention is not limited to a video camera, and may be used for a digital camera or various imaging devices.

InFIG. 1, in order from the object side, reference numeral101denotes a fixed front lens unit101,102denotes a zoom lens unit (first lens unit) that performs variation by moving along the optical axis,103denotes an aperture diaphragm,104is a fixed lens unit that is fixed,105denotes a focus lens unit (second lens unit), which provides a focus adjusting function and a compensator function that corrects the image movement from the variator, moving along the optical axis. The image-taking optical system configured of these lens units is a rear focus optical system configured of four lens units possessing the optical power of positive, negative, positive, positive in order from the object side (left side of diagram). Now, the diagram is drawn showing one lens making up each lens unit, but in actuality, each lens unit may be made up of either a single or multiple lenses.

Reference numeral106is a imaging device, such as a CCD or a CMOS sensor. The light flux from an object that passes through the image-taking optical system forms an image on the imaging device106. The imaging device106takes the formed object image and performs photoelectric conversion, and outputs image-taking signals. The image-taking signals are amplified to the optimum level with an amplifier (AGC)107and input into the camera signal processing circuit108. The camera signal processing circuit108outputs the input imaging signal to the amplifier110after the input imaging signal is converted to a standard television signal. The television signal that is amplified to the optimum level by the amplifier110is output to a magnetic recording/playing device111, and is recorded on a magnetic recording medium such as a magnetic tape. Or, other different recording media may be used, such as semiconductor memory or an optical disk.

Further, the television signal amplified by the amplifier110is also sent to a LCD display circuit114, and is displayed on a LCD115as a taken image. Now, the LCD115also displays images such as the photography mode, image-taking conditions, warnings, etc., to be communicated to the user. Such images are superimposed on the taken image and displayed, by means of a camera microcomputer116controlling a character generator113, and mixing the output thereof with television signals on the LCD display circuit114.

On the other hand, the imaging signals input to the camera signal processing circuit108can be simultaneously compressed with internal memory and stored on a still image recording medium112such as a card medium.

Further, the imaging signal input into the camera signal processing circuit108is also input into an AF signal processing circuit109as a focus information production means. The AF evaluation value signal (focus signal) that is formed in the AF signal processing circuit109is read out as data through transmission with a camera microcomputer116.

Further, the camera microcomputer116reads in the zoom switch130and AF switch131states, and further detects the state of the photo switch134.

In the state wherein the photo switch134is pressed halfway, the focus operation by the AF begins, and locks the focus when at a focused state. Further, in the fully pressed (deep press) state, this locks the focus regardless of whether in focus or out of focus, reads images into the memory (not shown) within the camera signal processing circuit108, and performs still image recording to the magnetic tape or still image recording medium112.

Now, the camera microcomputer116determines whether to use a moving-image image-taking mode or a still-image image-taking mode, according to the state of the mode switch133, and controls the magnetic recording/playing device111or still image recording medium112via the camera signal processing circuit108. Thus, suitable television signals are provided to the recording medium, or in a case wherein the mode switch133is set to the playing mode, playing control of the recorded television signals from the magnetic recording/playing device111or still image recording medium112is performed.

A computer zoom unit (control means)119that is within the camera microcomputer116outputs a signal to the zoom motor driver122by the program within the computer zoom unit119wherein the AF switch131is off and the zoom switch130is operating, for driving the zoom lens unit102in the telephoto or wide angle direction corresponding to the operational direction of the zoom switch130. The zoom motor driver122receives this signal and drives in this direction of the zoom lens unit102via the zoom motor121. Further at this time, the computer zoom unit119drives a focus motor125via a focus motor driver126, based on the lens cam data (representative locus data or locus parameter data according to the multiple subject distances, as illustrated inFIG. 11) previously stored in cam data memory120, and drives the focus lens unit106so as to correct the image movement that accompanies zooming.

Further, an AF control unit117in the camera microcomputer116drives the zoom lens unit102and focus lens unit105based on the distance information to the subject (focus object) obtained from the output of the subject distance detecting circuit127or the AF evaluation signal that is sent from the AF signal processing circuit109, wherein the AF switch131is on and the zoom switch130is operating, a variating operation is necessary to maintain the focus state, and therefore the computer zoom unit119sends also the lens cam data stored on the cam data unit120through the internal program.

Now, the output signal from the subject distance detecting circuit127is calculated and processed at the distance information processing unit128within the camera microcomputer116, and is output to the computer zoom unit119as the subject distance information.

Further, in the event that the AF switch131is on and the zoom switch130is not operating, the AF control unit117outputs a signal to the focus motor driver126to drive the focus lens105so as to make the AF evaluation value signal sent from the AF signal processing circuit109as great as possible, and drives the focus lens unit105via the focus motor125. Thus, the automatic focus adjusting operation is performed.

Here, the subject distance detecting circuit127measures the distance to the subject with triangulation using an active sensor, and outputs the distance information that is the measurement result thereof. The active sensor in this case can be an infrared sensor that is widely used in compact cameras.

Now, the present embodiment is described with the example of performing distance detection using triangulation, but other distance detection methods can also be used for the present invention. For example, distance detection with phase-difference detection can also be used. In this case, for example, an element (half prism or half mirror) is provided to divide the light that passes through the exit pupil of the image-taking lens (i.e., TTL (Through The Lens) method), the light exited from this element is guided to no fewer than two line sensors via a sub mirror or image forming lens, and by taking the correlation of the output of these line sensors, the offset direction and offset amount of these outputs can be detected, and the distance from these detection results to the subject is found.

A principal diagram of the distance calculation using triangulation or phase-difference detection is illustrated inFIG. 15andFIG. 16. InFIG. 15, reference numeral201denotes a subject,202denotes an image forming lens for a first optical path,203denotes a line sensor for the first optical path,204denotes an image forming lens for a second optical path, and205denotes a line sensor for the second optical path. The line sensors203and204are installed apart by the distance of a base line B. Of the light from the subject201, the light that passes through the first optical path by the image forming lens202forms an image on the line sensor203, and the light that passes through the second optical path by the image forming lens204forms an image on the line sensor205. Here,FIG. 16illustrates an example of the signal readout from the line sensors203and205which have received the two subject images formed by passing through the first and second optical paths. Because the two line sensors are apart by the distance of the base line B, the subject image signal has only the offset of X number of pixels, as shown inFIG. 15. Therefore the correlation of the two signals can be calculated by offsetting the pixels, and X can be calculated by obtaining the amount of pixel offset wherein the correlation becomes greatest. Using the principle of triangulation, the distance L to the subject can be obtained from L=B×f/X, using this X and the base line B, and the focal distance f of the image forming lens202and204.

Further, as a distance detection means, an ultrasound sensor may be used to measure the propagation speed and detect the distance to the subject.

The distance information from the subject distance detecting circuit127is sent to the distance information processing unit128. The distance information processing unit128performs the three types of processing below.

1. Calculates cam locus of which distance inFIG. 9to which the zoom lens unit102and focus lens unit105positions correspond. The calculation for the cam locus outputs a virtual cam locus that internally divides the cam locus of the γ′th row and the γ′th+1 row of the row direction inFIG. 12for the locus parameters α, β, and γ, by the ratio of α/β, as the subject distance and to how many meters this is equivalent to, for example, as described in process S401inFIG. 4A, based on the current lens unit position. The locus parameters α, β, and γ, and the subject distance are converted at the fixed correlation table data, and the actual distance of the main subject can be output.

2. By inverting the actual distance of the subject from the subject distance detecting circuit127, using the correlation table mentioned above in 1, the cam locus inFIG. 9above that is denoted by the locus parameters α, β, and γ are found. At this time, the inverting process of the correlation table does not use the data from the wide angle side wherein the cam loci inFIG. 9converge, and the loci are scattered. The data from the telephoto side is used as much as possible, and locus parameters with the highest possible resolution.

3. The actual distance difference and the differential direction is calculated for the above 1 and 2.

Of these processes 1, 2, and 3, the process 2 can identify the cam locus data correlating to the detection distance detected with the subject distance detecting circuit127.

On the other hand, the camera microcomputer116also performs exposure control. The camera microcomputer116references the brightness level of the television signal formed in the camera signal processing circuit108, controls the iris driver124so as to make the brightness level appropriate for exposure, and controls the opening of the aperture diaphragm103. The opening amount of the aperture diaphragm103is detected using an iris encoder129, and feedback control of the aperture diaphragm103is performed. Further, in the case that sufficient exposure control cannot be performed with the aperture diaphragm103alone, a timing generator (TG)132is used to control the exposure time of the imaging device106, which handles anywhere from a high speed shutter to a so-called slow shutter for extended exposure. Further, when exposure is insufficient such as image-taking under low lighting, the television signal gain is controlled using the amplifier107.

By operating a menu switch unit135, the photographer can manually operate the image-taking mode or camera function switching appropriate for the image-taking state.

Next, the algorithm during zooming operation will be described with reference toFIGS. 3A and 3B. With the present embodiment, the computer zoom unit119in the camera microcomputer116executes the below-described operation flow processes, including the aforementioned various operation flows (programs).

Further, with the present embodiment, the cam locus to be followed is identified (formed) according to the distance information obtained from the subject distance detecting circuit127, and zooming operation is performed. The operation flow inFIGS. 3A and 3Bis an example of a method for zooming operation while establishing (producing) a zoom tracking curve which is the cam locus to be followed, using the distance information. This method is particularly effective in the case that the detection cycle of the AF evaluation value such as very high speed zoom becomes less fine, and sufficient contrast to establish the zoom tracking curve cannot be obtained from the TV-AF reference signal alone (AF evaluation value signal).

FIGS. 3A and 3Billustrate a process performed in S705ofFIG. 7as described previously, and where the processes (steps) are the same as those inFIGS. 4A and 4B, the same reference numerals will be used and the description thereof will be omitted.

In S400, the zoom speed during zooming operation is determined. In S300, the distance to which cam locus of the representative locus illustrated inFIG. 9the current main subject image-taking distance corresponds to is determined, according to the output signal of the subject distance detecting circuit127, and the locus parameters α, β, and γ are calculated. Further, in the same way, the locus parameters αnow, βnow, and γnow corresponding to the current zoom lens position and focus lens position as described in S401inFIG. 4Aare calculated.

The αnow, βnow, and γnow are α, β, and γ calculated in the process from S512to S515inFIG. 5and stored in memory under the respective names αnow, βnow, and γnow. On the other hand, the locus parameters based on the distance information obtained from the subject distance detecting circuit127are calculated as α, β, and γ using for example the following method.

First, in order to obtain the correlation between the output distance information and the representative locus (cam locus) illustrated inFIG. 9, the correlation between the distance change and the locus parameters are placed in a table data form in advance, within the range wherein the cam loci (cam curve) form of the representative subject distance is uniform. Therefore, the locus parameters are calculated using the distance information as input. As for the subject distance wherein the cam loci form changes, a lookup table is provided that shows a separate correlation, and having these multiple tables enables the locus parameters for each of the subject distances to be obtained.

Regarding the focal distance, of the discrete cam locus information inFIG. 9that is within the memory as data, the locus parameters at the long focal distance side can be output so as to make the greatest resolution of the locus parameters α, β, and γ. Therefore, even if the current lens position is at the position wherein the cam loci are converging at the wide angle side as illustrated inFIG. 9, the locus parameters can be extracted at the point on the telephoto side wherein the cam loci are scattered, according to the distance information. Therefore, at the point wherein the zoom lens102is positioned on the wide angle side, one cam locus upon which the focus lens105should travel can be identified by calculating (interpolating) based on the locus parameters on the telephoto side.

Now, S300is executed every certain cycle (for example, one vertical synchronizing signal). Therefore, even if the subject distance changes during zooming, the newest cam locus to follow is continuously updated according to the output of the subject distance detecting circuit127.

Next, in S301, the correction range of the cam locus, which is a feature of the present invention, is determined based on the output of the subject distance detecting circuit127(in other words, α, β, and γ calculated in S300). This correction range is equivalent to the correction range in the correction operation for the following cam locus wherein the TV-AF signal (AF evaluation value), and may be, for example, the range between the upper limit201and the lower limit202illustrated inFIG. 2.

Here, according to the present embodiment, when the output from the subject distance detecting circuit127for example corresponds to the subject distance of 5 m (203), the correction range is controlled to be a range of ±50 cm of that subject distance. In other words, the upper limit201is a cam locus equivalent to corresponding with a subject distance of 4.5 m, and the upper limit202is a cam locus equivalent to corresponding with a subject distance of 5.5 m. Now, this correction range should be determined according to the detection sharpness of the subject distance detecting circuit127.

In other words, the aforementioned correction range is set so as to control the re-generating range when performing precise re-generating of the following cam locus by the correction operation (zigzag operation) by the TV-AF signals, after a general following cam locus is specified based on the distance information from the subject distance detecting circuit127.

Thus, the detecting resolution (detecting accuracy) of the subject distance detecting circuit127does not have to be so high, and as a result, a smaller imaging device can be provided at a lower cost. In addition, due to restricting the correcting range of the following cam locus, the number of times of directional switching when re-identifying the following cam locus using the TV-AF signal can be increased, and due to reducing the frequency of continuing to correct in the same correction direction, the occurrence of blurring can be prevented wherein perfect focus and image blurring were cyclically repeated according to the zigzag operation in the cases of image-taking a subject with a high frequency. Further, image blurring in the case of following an incorrect following cam locus or image blurring when recovering to the correct cam locus can be reduced.

Regarding the actual operation, the correction operation (zigzag drive) of the following cam locus using the TV-AF signal is performed within the range between the upper limit201and the lower limit202, and in the case of deviating from this range, the focus lens105drive direction is reversed so as to return to this correction range. As a result, re-generating of the cam locus outside the range of the upper limit201and the lower limit202is prohibited.

According to the present embodiment, the correction range is set according to the detection resolution of the subject distance detecting circuit127, and by allowing generating of the precise following cam locus by the TV-AF signal only within that range, erroneous movement resulting from dual use of the TV-AF signal or erroneous image blurring is reduced. In other words, by allowing re-generating of the following cam locus only when the generating results of the two types of cam locus generating methods agree, which are the generating method of a cam locus based on the output from the subject distance detecting circuit127and the generating method of a cam locus based on the detecting signal at the focus state of the TV-AF signal, an extremely highly precise cam locus following method can be realized by combining only the strengths of each generating method.

Specifically, when identifying the following locus by the TV-AF signal as described in the conventional art, the focus lens drive speed (correction speed) for the zigzag operation needed to be set to a speed capable of covering from the cam locus on the infinity side to the cam locus on the close-up side. In comparison, according to the present embodiment, by limiting the correction range of the cam locus, for example even if the focus lens correction speed is the same as the conventional art, the drive range has become narrower, and so the number of zigzag operations can be increased for each unit of time. Therefore, even at a high speed zoom, the cam locus generating precision by the TV-AF signal can be improved.

On the other hand, the setting value of the correction speed can be lowered by having the normal number of zigzag operations, the occurrence of blurring can be prevented wherein focusing and image blurring were cyclically repeated according to the correction operation when image-taking a subject with a high frequency (details will be described in the second embodiment). Therefore, an imaging device zooming system that has a high degree of freedom for implementing zoom functionality with the best control method according to the product use can be provided, such as priority for zoom speed or priority for appearance, even though using the same method. This is an addition advantage of the present embodiment and the present invention.

Returning to the description ofFIGS. 3A and 3B, in S302whether or not the “AF correction flag” is in the set state is determined. If set, the flow continues to S303, and in S311, which will be described below, whether or not the locus parameters αAF, βAF, and γAF, which are updated with each detection that the AF evaluation value reaches the peak state1301level described inFIG. 13, are included in the correction range (the range between the upper limit201and the lower limit202) illustrated inFIG. 2, is determined. If within this correction range, S304sets each of these αAF, βAF, and γAF, to α, β, and γ, and controls the focus lens105to trace the cam locus re-specified by this correction movement.

On the other hand, in the case that the locus parameters αAF, βAF, and γAF, are outside the correction range in S303, or in the event that the “AF correction flag” has been cleared in S302, the locus parameters α, β, and γ, that are specified based on the distance information from the subject distance detecting circuit127, that were already decided in S300, are held, and the focus lens105is controlled to trace the cam locus specified by these locus parameters α, β, and γ.

Here, the “AF correction flag” is a flag showing whether or not the following cam locus has been re-specified by the later-described TV-AF signal, and in the case that generating is made based only on the distance information from the subject distance detecting circuit127(in the case where re-generating is not performed, or in the case that the cam locus is outside the correction range inFIG. 2and the possibility of erroneous generating is high), in S305the “AF correction flag” is cleared, and from the next time and thereafter, until the re-generating of the cam locus by the correction movement is performed, the locus trace control is performed giving priority to the generating results based on the distance information.

Hereafter, a process similar to that inFIGS. 4A and 4Bis performed. In S402the position Zx′ (the position to which it should move from the current position) wherein the zoom lens102will arrive after one vertical synchronizing period (1V) is calculated. In the event that the zoom speed determined in S400is Zsp (pps), the zoom lens position Zx′ after one vertical synchronizing period can be obtained from the above-described Equation (7). Here, pps is an increment that shows the rotation speed of the stepping motor which is the zoom motor121, and represents the step amount (1 step=1 pulse) of rotation during 1 second. The symbols in Equation (7) represent the movement direction of the zoom lens, + for the telephoto direction and − for the wide angle direction.
Zx′=Zx±Zsp/vertical synchronizing frequency  (7)

Next, in S403, which zoom area v′ Zx′ exists is determined. In S403, the same process as the process illustrated inFIG. 6is performed, and ZxinFIG. 6is substituted with Zx′, and v with v′.

Next, in S404, whether the zoom lens position Zx′ after one vertical synchronizing period exists on the zoom area boundary is determined, and in the event that the boundary flag=0 this it not considered to be on the boundary, and the flow continues from the process starting with S405. In S405, Z(v′)is set to Zk, and Z(v′−1)to Zk−1.

Next, in S406, out the four table data sets A(γ, v′−1), A(γ, v′), A(γ+1, v′−1), A(γ+1, v′)wherein the subject distance γ is specified by the process illustrated inFIG. 5are read out, and ax′ and bx′ are calculated from the Equations (2) and (3) described above in S407.

On the other hand, in the case of Yes in S403, in S408the focus lens positions A(γ, v′)and A(γ+1, v′)corresponding to the zoom area v′ of the subject distance γ are called up and stored in memory as ax′ and bx′, respectively. Then, in S409the focus lens focus position (target position) px′ when the zoom lens position has reached Zx′ is calculated. Using Equation (1), the target position of the focus lens105after one vertical synchronizing period can be expressed as follows.
Px′=(bx′−ax′)×α/β+ax′  (8)

Therefore, the difference of the target position and the current focus lens position becomes
ΔF=(bx′−ax′)×α/β+ax′−Px

Next, S410calculates the focus standard moving speed Vf0. Vf0is obtained by subtracting the focus lens position difference ΔF from the movement time of the zoom lens102required to move this distance.

After completing the present process, the flow continues to S706inFIG. 7, and in the event that zooming is being performed, movement is made at the focus speed determined in S410in the direction of the symbol (positive for the close-up direction, and negative for the infinite distance direction) of this focus speed, thereby carrying out compensator actions.

In S411, each parameter is initialized. Here, the “reversal flag” used in the later processes is cleared. In S412the correction speed Vf+and Vf−is calculated for the “zigzag correction operation” from the focus standard movement speed Vf0obtained in S410. Here, the correction amount parameter δ and the correction speeds Vf+and Vf−are calculated using Equations (9) through (12) as described above, usingFIG. 14.

In S413, whether or not zooming is being performed is determined, according to the information illustrating the operational state of the zoom switch130obtained during S703illustrated inFIG. 7. In the even that zooming is being performed, the process from S416on is carried out. Otherwise, in S309the “AF correction flag is cleared, and preparation is made for the next zooming operation from the wide angle to the telephoto direction. Then in S414, a value TH1(the level indicated by1302inFIG. 13A) is set, wherein a arbitrary constant μ is subtracted from the current value of the AF evaluation signal level. This TH1determines the AF evaluation signal level that is the switchover base point for the correction direction vector (switchover base point for the zigzag correction operation), as described inFIG. 13A.

Next, in S415the “correction flags” are cleared, and the process ends. Here, the “correction flag” is a flag indicating either a state wherein the cam locus following state is when the correction is in the positive direction (correction flag=1) or a correction state in the negative direction (correction flag=0), as described above.

If determination is made in S413that zooming is being performed, determination is made whether or not the zooming direction is from wide angle to telephoto in S414. If No, the “AF correction flags” are cleared and preparation is made for the next wide angle to telephoto direction zooming operation to be performed (S308), similar to S309. Then at S419, Vf+=0 and Vf−=0 are set, and the process from S420is performed and zigzag drive is not executed.

If Yes in S413, in S306determination is made whether or not the focus lens position in relation to the current zoom lens position surpasses the upper limit201of the correction range illustrated inFIG. 2. If so, the flow continues to S423to return the focus lens position to within the correction range.

In S423, the calculated focus speed (standard movement speed) Vf0is added to the negative correction speed Vf−(corrected to the infinite distance direction). By doing so, the focus lens105is forced to return to the direction of the lower limit202rather than the upper limit201of the correction range.

Further, in the event that the upper limit201has not been exceeded in S306, determination is made in S307whether or not the focus lens position relating to the current zoom lens position is below the lower limit202of the correction range inFIG. 2. If so, the flow continues to S423to return the focus lens position to within the correction range. In S423, the calculated focus speed (standard movement speed) Vf0is added to the positive correction speed Vf+(corrected to the close-up direction). By doing so, the focus lens105is forced to return to the direction of the upper limit201rather than the lower limit202of the correction range. Thus, the drive range of the focus lens105is controlled within the correction range, and as a result, the cam locus re-specified by the zigzag movement is also controlled within this correction range.

In the event that the focus lens position in S306or S307is not outside the correction range, determination is made in S417whether or not the current AF evaluation signal level is smaller than TH1, in order to execute the zigzag movement. If Yes, the current AF evaluation level has moved lower than the level of TH1(1302) inFIG. 13A, and therefore S418sets a reversal flag to perform switching of the correction direction.

Determination is made in S420whether the reversal flag=1, and if Yes, the flow continues to S421and determination is made whether the correction flag is 1 or not. If S421yields No, then the flow continues to S424and sets the correction flag to 1 (correction state in the positive direction). According to Equation (4),
Focus speedVf=Vf0+Vf+(wherein Vf+≧0)

On the other hand, in the event that S421is Yes, then the flow continues to S423and sets the correction flag=0 (correction state in the negative direction), and according to Equation (5),
Focus speedVf=Vf0+Vf−(whereinVf−≧0)

If S420is determined to be No, S422determines whether or not the correction flag=1. If Yes the flow continues to S424, and if No, the flow continues to S423.

After completing this process, in S706inFIG. 7the drive direction and drive speed of the focus lens105and zoom lens102are selected, according to the operation mode.

In the case of a zooming operation, the focus lens105drive direction is set to the close-up direction or the infinite distance direction depending on whether the focus lens movement speed Vfobtained in S423or S424is positive or negative. Thus, the cam locus to be traced is re-specified as the focus lens105zigzag drive is performed.

During the process from S417through S424while performing the zigzag drive, the AF evaluation value signal is detected to have reached the peak level1301described inFIG. 13A. When S417is No, S310determines whether or not the peak level1301is detected. In the case that the peak level is detected, in S311, with the “AF correction flag=1” and the current values of the locus parameters as re-generating locus parameters by TV-AF,
αAF←αnow, βAF←βnow, γAF←γnow
is set. Then, the next time that the conditions are fulfilled in S302and S303(in the case that the determination results of both steps are Yes), in S302the identified cam locus is updated.

This time, the locus parameters updated and re-specified in S304are updated to the specified cam locus based on the distance information, by the correction range in S301changing by the change of the detected distance information, or by the zooming operation stopping, or by the zooming direction reversing.

In the case that the next time the conditions are not fulfilled in S302and S303, each time a new peak level is detected (S310), the updating of αAF, βAF, and γAF is repeated and the most appropriate cam locus is continuously updated during zooming operation.

Now, in the case that the AF evaluation value level is not detected to have reached the peak level in S310, the flow continues on to S420, and without switching the correction direction by the zigzag operation, drives the focus lens105whiles correcting in the correction direction predetermined by the previous time.

By performing the above processes, the cam locus generating accuracy using the TV-AF signal can be greatly improved by limiting the identification range (correction range) in the case of identifying the cam locus to be followed using the TV-AF signal, based on the distance information to the subject. Therefore, problems such as disadvantages that accompany the detection cycle of the AF evaluation value with TV-AF, or problems that erroneously determine the wrong cam locus to be traced because of influence the TV-AF signal receives not only from the distance change but also from a change in the appearance of subject, or erroneous movement problems wherein the switching timing is incorrect for the zigzag movement, can be reduced. Therefore, the occurrence of image blurring can be reduced.

Specifically, the cam locus to be the standard in the distance information is specified, and by using the method of the present embodiment wherein the correction range is limited and the cam locus is corrected (re-specified) using the TV-AF signal, the correction resolution of the following cam locus based on the TV-AF signal can be improved. Therefore, the detecting resolution of the subject distance detecting circuit127does not need to be so fine, and a smaller and less costly type of subject distance detecting circuit127can be employed.

Second Embodiment

The first embodiment has been described regarding a case in which the correction speed of the correction movement for the focus lens105by the TV-AF signal is calculated in the same way as with the conventional art described inFIGS. 4A and 4B. Because of this, in the first embodiment, the movement distance (drive range) of the focus lens105is lessened because of the limits on the correction range, and as a result, the frequencies of the zigzag operation within the correction range increases. Therefore, a system is provided wherein the generating functionality of the following cam locus is high, even at a high speed zoom and so forth.

In contrast, according to the second embodiment, the correction speed is set slower than in the case of the first embodiment, and attempts to reduce the cyclical image blurring that accompanies the zigzag movement and so forth.

For example, if the correction speed is set at half the amount of the first embodiment, the overshooting amount of the drive direction reverse timing of the focus lens105illustrated inFIG. 13Bis reduced, and therefore the type of phenomenon wherein focusing and image blurring are cyclically repeated according to the zigzag operation can be prevented from occurring.

In order to change the correction speed to ½, the process wherein the correction speed Vf+and Vf−is calculated in S412illustrated inFIGS. 3A and 3Bis cut in half may be added, for example. Further, computations can be made by providing a coefficient to Equations (4) and (5).
Focus speedVf=Vf0+Vf+/2 (whereinVf+≦0)  (4)′
Focus speedVf=Vf0+Vf−/2 (whereinVf−≦0)  (5)′

Now, the aforementioned embodiments have been described regarding a case of controlling the range for when the cam locus (α, β, γ) to be followed is identified (generated) based on the distance information to the subject, but the present invention may also be applied in the case of controlling the range based on the distance information to the subject, when the focus lens target position is calculated (generated).

As described in the first embodiment and the second embodiment, the range of information (locus information and so forth) that is generated to control the drive of the second lens unit, based on the distance to the detected focus object, is limited, and therefore can avoid producing information that does not correspond to the distance to the object for which focus is actually desired, and image blurring during zooming can be reduced.

Here, the aforementioned information is generated based on the distance to the focus object detected and the aforementioned data, and as a basis for this aforementioned generated information, and in the case of performing forming processing wherein new information is generated using the focus signal representing the focus state of the optical system based on this detected distance in the event that the range of information generated by this forming process is limited, problems such as disadvantages that accompany the detection cycle of the focus signal, or problems wherein incorrect information is generated because of influence the focus signal receives, not only from the distance change but also from change in the appearance of the focus object, or erroneous movement problems wherein the switching timing is incorrect for the zigzag movement, can be avoided, and the occurrence of image blurring during the forming process can be reduced, and focus maintenance control with high precision during zooming can be performed.

Further, in the re-generating process, in the case of changing the driving conditions of the lens unit to move this second lens unit towards the position wherein the focus signal represents the most focused state corresponding to the drive state when driving based on this aforementioned standard information, the second lens unit drive range is limited based on the detected distance, and by doing so, the second lens unit can avoid driving based on incorrect information. In addition, even in the case wherein the switching timing of the zigzag movement is wrong, the image blurring amount can be reduced, and can quickly make transition to driving based on the correct information.

Third Embodiment

The zigzag movement disclosed in the aforementioned Japanese Patent No. 2,795,439 specifies the following locus based on the change of the AF evaluation value. However, the evaluation value changes not only according to the status of blurring of the image, but also changes according to changes in appearance of the subject. Therefore, there may be a case wherein the focus lens movement switching is switched in the wrong direction. In the event that the movement deviates from the locus that should be used, the image may blur until moved back to the correct locus. Further, in the case of moving the focus lens in the wrong direction, image blurring may occur wherein the AF evaluation value level in particular is greatly reduced, or when image-taking of a subject with low contrast, the correct locus may not be found, and the possibility exists that the image blur may be carried all the way to the telephoto edge.

Specifically, when starting zooming from the wide angle side wherein the cam locus spacing is crowded, if the drive starting direction by the zigzag driving is in the opposite direction from the direction of the cam locus (focus locus) to be specified, the image blurring is noticeable even if the offset from the position of the focus locus is small because the focus depth is shallow at the wide angle side. Further, as described above, on the wide angle side wherein the subjects from infinity to several 10 cm away are all focused on at the same focus position, in the event that multiple objects with differing subject distances exist within the wide angle, the image of these subjects all become blurred, and the quality of the image becomes very poor.

The algorithm during zooming operation will be described with reference toFIGS. 17 and 18. According to the present embodiment, the computer zoom unit119in the camera microcomputer116executes the later-described operation flow processes, including the aforementioned various operation flows (programs). Now, inFIGS. 17 and 18, the portions indicated by the same circled numeral are connected to one another.

Further, according to the present embodiment, the cam locus to be followed is established (formed) according to the distance information obtained from the subject distance detecting circuit127, and zooming operation is performed. The operation flow shown inFIGS. 4A and 4Bis an example of a method as described above for zooming operation while precisely establishing (generating) a zoom tracking curve which is the cam locus to be followed, using the distance information. This method is particularly effective for recovering image blurring in the case that the focus lens105is moved off the focus cam locus during zooming, or reducing image blurring at the start of the zooming operation.

FIGS. 17 and 18are processes performed in S705ofFIG. 7as described previously, and wherein the processes (steps) are the same as those inFIGS. 4A and 4B, the same reference numerals will be used and the description will be omitted.

In S1400, the zoom speed during zoom operation is determined. In S1401, which position on the cam locus inFIG. 9the main subject being photographed is, is determined, from the current zoom lens position and the focus lens position. Here, from the interpolation process based on the cam locus data table (FIG. 12) storing the representative locus illustrated inFIG. 9as discrete data, the cam locus where the current zoom lens and focus lens positions exist, including virtual cam locus, in other words three locus parameters that correspond to this cam locus are calculated as α, β, and γ, and are stored in a memory region such as RAM. This process is the same process as that described with reference toFIG. 5.

In S1300, the calculated locus parameters α, β, and γ are temporarily saved as αnow, βnow, and γnow, and additionally the locus parameters α, β, and γ are calculated regarding how many meters in actual the subject distance (estimated distance). The correlation between the locus parameters and the estimated distance can be calculated by creating in advance a table data of the correlation between the estimated distance and the locus parameter within the range wherein the cam curve form of the representative subject distance is uniform, with the locus parameters as input. At a subject distance wherein the cam curve form changes, a lookup table can be made to show different correlations, and by having these multiple tables, all of the estimated distances B can be obtained for each zoom lens position and focus lens position.

Next, in S1301, the output from the subject distance detecting circuit127is obtained. Then, the distance to the image-taking subject shown by the output from the subject distance detecting circuit127(actual distance) A is compared with the estimated distance B found from the current lens position in S1300, and determination is made whether the actual distance A is nearer (close-up direction) or farther (infinity distance direction) as compared to the estimated distance B.

Next, determination is made in S1302whether or not the “AF correction flag” is in the set state. If set, the flow continues to S1303, and the locus parameters αAF, βAF, and γAF to be decided in the following S1311are set as α, β, and γ respectively (stored in memory). Here, the changes in the AF evaluation signal are detected while performing the zigzag operation of the focus lens unit105, and the locus parameters αAF, βAF, and γAF are the cam locus parameters when at the peak level1301inFIG. 13A. In other words, these are the cam locus information detected by the AF evaluation signal peak level, and represent the cam locus that the microcomputer116has confirmed as the true focus cam locus.

Thus, the locus parameters α, β, and γ that are updated in S1303represent the cam locus re-specified based on the AF evaluation signal, and by continuing to perform re-specification of the cam locus repeatedly with a continuous zooming operation thereafter, the result is that the focus lens unit105can be made to trace (follow) the true focus cam locus.

On the other hand, in the event that the “correction flag” is cleared in S1302, the locus parameters α, β, and γ specified based on the distance information from the subject distance detecting circuit127that have already been decided in S1300are held, and the focus lens105is controlled to trace the cam locus specified by these locus parameters α, β, and γ.

Here, the “correction flag” is a flag showing whether or not the cam locus to be followed has been re-specified by the below described AF evaluation signal, and once set (when the following cam locus is re-specified), it will not be cleared unless the zooming direction is switched or the zooming operation is stopped. The re-specified cam locus information (α, β, and γ) is re-specified (updated) continually based on the detection results of the AF evaluation signal, and at the focal distance wherein the cam loci are scattered, identified on the focus locus.

Hereafter, a process similar to that inFIGS. 4A and 4Bis performed. In S1402, the position Zx′ (the position to move to from the current position) where the zoom lens102will arrive after one vertical synchronizing period (1V), is calculated. In the event that the zoom speed determined in S400is Zsp (pps), the zoom lens position Zx′ after one vertical synchronizing period can be obtained from the above-described Equation. (7). Here, pps is an increment that shows the rotation speed of the stepping motor which is the zoom motor121, and represents the step amount (1 step=1 pulse) of rotation during 1 second. The symbols in Equation (7) represent the movement direction of the zoom lens, + for the telephoto direction and − for the wide angle direction.
Zx′=Zx±Zsp/vertical synchronizing frequency  (7)

Next, in S1403, which zoom area v′ where Zx′ exists is determined. S1403is the same process as the process illustrated inFIG. 6, and the ZxinFIG. 6is substituted with Zx′, and v with v′.

Next, determination is made in S1404whether the zoom lens position Zx′ after one vertical synchronizing period exists on the zoom area boundary, and if the boundary flag=0 is it not considered to be on the boundary, and the flow continues from the process starting with S1405. In S1405Z(v′)is set to Zk, and Z(v′−1)to Zk−1.

Next, in S1406the four table data sets A(γ, v′−1), A(γ, v′), A(γ+1, v′−1), A(γ+1, v′)wherein the subject distance γ is specified by the process illustrated inFIG. 5are calculated, and ax′ and bx′ are calculated from the Equations (2) and (3) described above in S1407.

On the other hand, in the case that S1403is determined to be Yes, in S1408the focus lens positions A(γ, v′) and A(γ+1, v′) corresponding to the zoom area v′ of the subject distance γ are called up and stored in memory as ax′ and bx′, respectively. Then, in S1409the focus lens focus position (target position) px′ when the zoom lens position has reached Zx′ is calculated. Using Equation (1), the target position of the focus lens105after one vertical synchronizing period can be expressed as follows.
Px′=(bx′−ax′)×α/β+ax′  (8)

Therefore, the difference ΔF of the following target position and the current focus lens position becomes
ΔF=(bx′−ax′)×α/β+ax′−Px

Next, in S1410the focus standard moving speed Vf0is calculated. Vf0is obtained by subtracting the focus lens position difference ΔF from the movement time of the zoom lens102required to move this distance.

After completing the present process, the flow continues to S706inFIG. 7, and if zooming is being performed, moves at the focus speed determined in S1410in the reference numeral direction (positive for the close-up direction, and negative for the infinite distance direction) of this focus speed, thereby performing compensator actions.

In S1411, each parameter is initialized. Here, the “reversal flag” used in the later processes is cleared. In S1412the correction speed Vf+, Vf−for the “zigzag correction operation” is calculates from the focus standard movement speed Vf0obtained in S1410. Here, the correction amount parameter δ and the correction speeds Vf+, Vf−are calculated using Equations (9) through (12) as described above withFIG. 14.

Determination is made in S1413whether or not zooming is being performed, according to the information representing the operational state of the zoom switch130obtained during S703inFIG. 7. If zooming is being performed, the process from S1416is performed. If Yes the process from S1416is performed. If No is determined, in S1313the “zoom flag” and the “correction flag are cleared, and preparation is made for the next zooming operation from the wide angle to the telephoto direction. Then at S1414, a value TH1(the level denoted by1302inFIG. 13A) is set, wherein a arbitrary constant μ is subtracted from the current value of the AF evaluation signal level. This TH1is decided immediately prior to zooming, and this value is the level of1302inFIG. 13A.

Next, S1415clears the “correction flags”, and ends this process. Here, the “correction flag” is a flag denoting either a state wherein the cam locus following state is when the correction is in the positive direction (correction flag=1) or a correction state in the negative direction (correction flag=0), as described above.

In the event that determination is made in S1413that zooming is being performed, determination is made whether or not the zooming direction is from wide angle to telephoto in S1414. If No, the “correction flags” are cleared and the preparation is made for the next wide angle to telephoto direction zooming operation to be performed (S1312), similar to S1313. Then at S1419, Vf+=0 and Vf−=0 are set, and the process from S1420is performed and zigzag drive is not executed.

If S1413is Yes, determination is made in S304whether or not the “zoom flag” is in the cleared state. If cleared, the flow continues to S1305because this is the first case wherein zooming is from the wide angle to the telephoto direction, the “zoom flag” is set, and further, so as to correctly match the correction direction (the drive start direction of the focus lens unit105) of the zigzag movement based on the detecting result of the AF evaluation signal at zoom start time with the object distance direction of the main subject, determination is made in S1306whether the distance information obtained from the output of the subject distance detecting circuit127is in the close-up direction or in the infinite distance direction compared to the distance corresponding to the current focus lens position.

Here, the process of S1306is to determine the relationship between the estimated distance B that is based on the lens position determined in S1300, and the actual distance A that is based on the output of the subject distance detecting circuit127determined in S1301. In the case that the actual distance A is on the closer side of the estimated distance B, in other words, in the case that it is towards the close-up direction, the flow continues to S1424, and starts the zigzag movement correction in the correction direction of the close-up direction. In the case that S1306is No, in other words the actual distance A is on the farther side of the estimated distance B, the flow continues to S1423in order to start the correction movement from the infinite distance direction.

Thus, the present embodiment has a first feature wherein at the point of starting the zooming, the correction direction for the generating movement of the cam locus using the AF evaluation signal sets the distance corresponding to the focus lens unit105position (estimated distance B) so as to be closer to the distance (actual distance B) that is based on the output of the subject distance detecting circuit127, in other words sets weighting relating to the drive direction of the focus lens unit105.

By performing this type of movement, a phenomenon can be avoided wherein, when starting zooming from the wide angle side wherein the cam locus spacing is crowded, the drive starting direction of the focus lens unit105during zigzag operation moves in the opposite direction from the direction of the focus cam locus, which causes the image blurring to be conspicuous even if the offset from the position of the focus locus is small because the focus depth is shallow. Therefore, in the case that the focus cam locus direction at the wide angle and the focus lens unit105drive direction (correcting direction) is in the opposite direction, the problem wherein the images of objects with differing subject distances the image of these subjects all become blurred and the quality of the image becomes very poor can be prevented in advance.

The description will be continued from S1304. Once the “zoom flag” is set in S1306, the flow continues to S1307based on the determination results at S1304(zoom flag=1) from the next time. As with S1306, determination is made in S1307whether or not the distance information based on the output of the subject distance detecting circuit127(actual distance A) is closer than the estimated distance B. If Yes, S309sets Vf+at twice the value, to give priority weighting to the close-up direction of the zigzag movement. On the other hand, in the case that S1307is No, the flow continues to S1308, and adds weighting by doubling Vf−. This is a second feature of the present embodiment wherein weighting is added to the correcting movements for re-generating of the cam locus using the AF evaluation signal, based on the detected actual distance A (according to the relationship between the actual distance A and the estimated distance B).

Because of this weighting correction process, for example, when identifying the cam locus based on the changes in the AF evaluation signal, not only does the AF evaluation signal change due to the image blurring state, but also changes due to the changes in the design of the subject, and therefore, the problem of the correction direction being incorrectly switched (problems such as the image blurring continuing for a long time until returning to the correct locus, or the image blurring being carried all the way to the telephoto edge) can be avoided.

As one example of the weighting process, the present embodiment described the case wherein the focus lens unit105drive speed (correction speed) for the correction process is doubled, based on the detected actual distance A, but the present invention does not need to be limited to this. For example, the weighting ratio of the correction speed can be changed according to the difference between the detected actual distance A and the estimated distance B based on the lens position and the direction thereof.

Further, rather than increasing the correction speed in the direction moving closer to the actual distance A, the correction speed in the opposite direction may be decreased.

Further, the AF evaluation value switching level (TH1)1302shown inFIG. 13Aas a condition for switching the correction direction can be set low in the direction moving closer to the focus lens position corresponding to the actual distance A, and this level1302set high in the correction direction that moves away from the focus lens position corresponding to the actual distance A, whereby the frequency of correction operations in the direction moving closer to the focus lens position corresponding to the actual distance A can be increased.

Thus, zigzag operation is executed by performing the processing after S1417while performing the weighting process of the zigzag operation based on the detected distance information during zooming operation. First, S1417determines whether or not the current AF evaluation signal level is smaller than TH1. If Yes, then in S1418a reversal flag is set to perform correction direction switching, since the current AF evaluation signal level has become lower than the TH1(1302) level inFIG. 13A.

In S1420, determination is made whether the reversal flag=1, and if Yes, the flow continues on to S1421where determination is made whether the correction flag is 1 or not. If No in S1421, the flow continues to S1424, and sets the correction flag to 1 (the correction state in the positive direction). Based on Equation (4),
Focus speedVf=Vf0+Vf+(whereinVf+≧0).

On the other hand, if S1421is Yes, the flow continues to S1423, and sets the correction flag to 0, (the correction state in the negative direction), and based on Equation (4),
Focus speedVf=Vf0+Vf−(whereinVf−≧0).

In the case that S1420is determined to be No, determination is made whether or not the correction flag is 1 at S1422, and if Yes the flow continues to S1424, and if No, to S1423.

After completing this process, in S706inFIG. 7, the direction and drive speed of the focus lens and zoom lens drive are selected, according to the operation mode.

In the case of zooming operation, here the focus lens105drive direction is set to the close-up direction or the infinite distance direction, depending on whether the focus lens movement speed Vfobtained in S1423or S1424is positive or negative. Thus, the cam locus to be traced is re-specified while the focus lens105zigzag drive is performed.

During the process from S1417through S1424while performing the zigzag drive, the AF evaluation value signal is detected to have reached the peak level1301described inFIG. 13A. In the event that S1417is No, determination is made in S1310regarding whether or not the peak level1301has been detected. In the case that the peak level has been detected, in S1311, with the “AF correction flag=1” and the current values of the locus parameters as re-generating locus parameters by TV-AF,
αAF←αnow, βAF←βnow, γAF←γnow
is set. Then, the next S1302determines the “correction flag=1”, and so in S1303the generating cam locus is updated.

This time, as long as the zooming operation does not stop or the zooming direction does not reverse, the locus parameter updated and re-specified in S1303repeats the updating of αAF, βAF, γAF in S1311each time a new peak level is detected (S1310), and the optimal cam locus is constantly updated during zooming operations.

Now, in the case that the AF evaluation value level is not detected to have reached the peak level in S1310, the flow continues on to S420, and without switching the correction direction by the zigzag operation, drives the focus lens105whiles correcting in the correction direction predetermined by the previous time.

According to the present embodiment as above, weighting settings based on the detected distance information are made relative to the drive start direction of the focus lens unit105in the zigzag movement, and therefore the occurrence of image blurring during the zigzag operation can be reduced.

In addition, the possibility exists of the main subject changing distance during zooming operation, but according to the present embodiment, the cam locus can be changed over quickly and smoothly because weighting is added to the drive or drive speed in the direction moving closer to the focus lens position corresponding to the detected distance. Further, even in the event wherein the focus lens unit105is driven in the wrong direction by the correction movement from the AF evaluation signal, moving away from the correct cam locus that it should be following, the occurrence of image blurring can be reduced, and returning smoothly to the correct cam locus is enabled.

Further, using the methods according to the present embodiment enables the generating precision of the following cam locus based on the TV-AF signal (AF evaluation signal) to be improved. Therefore, the detecting precision of the subject distance detecting circuit127can be somewhat less fine, and a smaller and less costly type of subject distance detecting circuit127can be employed.

Therefore, according to the present embodiment, at the time of controlling the second lens drive to generate the aforementioned information (locus information and so forth), weighting is performed based on the distance to the detected focus object, and therefore, the driving of the second lens unit which would make the image blurring greater can be reduced. For example, relating to the drive direction of the second lens unit for generating the aforementioned information, weighting based on the detection results of the aforementioned distance enables driving toward the direction in which the image blurring of the second lens unit increases to be avoided. Further, relating to the drive direction of the second lens unit for generating the aforementioned information, weighting based on the detection results of the aforementioned distance enables driving toward the direction in which the image blurring decreases to be made quickly.

Further, in the case of switching the driving conditions of the second lens unit while driving in order to generate the aforementioned information, performing weighting based on the detection results of the aforementioned distance relating to the conditions to switch the driving condition enables the switching of the driving conditions of the second lens unit to be made according to the detecting distance, and the aforementioned information can be generated quickly.

As described above, according to the present embodiment, at the time of generating the aforementioned information, weighting that corresponds to the detecting distance can be added to the drive control of the second lens unit, whereby the occurrence of image blurring can be reduced, and quick and smooth information generation can be realized. As a result, the focus of the focus objects can be maintained in a sure manner (following the zooming by the first lens unit).

Further, at the time of generating the aforementioned information using a focal point signal that indicates the focal point state of the aforementioned optical system obtained from the photoelectric conversion signals of the optical image formed by the optical system including the first and second lens units (for example, the re-generating process), by using the drive control of the second lens unit or appropriately setting the condition for drive condition switching of the second lens unit for the so-called zigzag operation, problems can be avoided wherein the focal point signal is influenced not only by changes in distance but also changes in the appearance of the focus objects, the second lens unit drives and image blurring becomes noticeable.