JP2006322984A - Variable power imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To move a zoom lens barrel and a focus lens barrel without interfering with each other at high-speed zooming, and to achieve focusing in the zoom area of a wide range in a lens barrel where the moving ranges of a focus lens and a zoom lens in an optical axis direction are overlapped. <P>SOLUTION: In the imaging apparatus where the maximum moving speed of the zoom lens in the optical axis direction is higher than that of the focusing lens, the focusing lens is moved to trace a locus different from the positional information of the focusing lens when a distance between the focusing lens and the zoom lens is equal to or under a fixed value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus including a zoom lens such as an electronic camera or a video camera.

  2. Description of the Related Art Conventionally, some electronic cameras and video cameras equipped with a zoom optical system perform focus adjustment by moving a focus lens in the optical axis direction to change a focus surface due to zoom magnification (hereinafter, zooming).

  An example of a zoom optical system conventionally used in an electronic camera or a video camera is shown in FIG.

  In the figure, 11 is a lens barrel, 12 and 13 are variable magnification lenses that move in the direction of the optical axis and perform a variable magnification operation, 14 is a diaphragm for adjusting the amount of light, and 15 is a focus adjustment and correction of focus plane movement due to variable magnification. A focus lens 16 is a solid-state imaging device (CCD) that converts an object image formed on the focus surface by the focus lens into an electric signal.

  In this optical system, the focus surface moves depending on the subject distance, and the focus surface also moves due to zooming. FIG. 8 shows the position where the focus lens should be in order to correct the subject distance and the focal plane that moves by zooming. The curve in the figure represents the position of the focus lens with respect to some typical subject distances.

  As a mechanism for moving the focus lens in a camera using such an optical system, a focus lens holding frame that is normally held by a stepping motor as a drive source and given rotation to a lead screw so as to be movable in the optical axis direction. Is known to be moved in the longitudinal direction of the optical axis by a lead screw.

  When the zoom magnification is constant, the in-focus point can be found with respect to the subject at a specific distance by moving the focus lens from the position of the infinite cam in FIG. Also, when changing the zoom magnification while focusing on a subject at a certain distance, keep the focused state by moving the focus lens in the optical axis direction according to the curve corresponding to the subject distance. Can do.

  FIG. 9 schematically shows the movable range of the zoom lens barrel adjacent to the movable range of the focus lens barrel. The distance between the two curves at a certain zoom magnification represents the actual distance between the zoom lens barrel and the focus lens barrel. In this optical barrel, it can be seen that the movable range of the zoom lens barrel and the focus lens barrel overlap in the range from WIDE to TELE as shown in the figure.

By the way, the moving speed of the focus lens barrel when the focus lens barrel moves following the cam locus is obtained from the cam locus as follows. Consider the case of moving from the zoom position n to n + 1 in the TELE direction.
Vf (Z (n)) = ΔP (Z (n)) / {ΔZP (Z (n)) / Vz}
... (1)
Here, Z (n): nth zoom position from WIDE Vf (Z (n)): moving speed of focus lens barrel between zoom positions n and n + 1 ΔP (Z (n)): from zoom position n Number of pulses for moving the focus lens in the optical axis direction to n + 1 ΔZP (Z (n)): Number of pulses for driving the zoom lens from zoom position n to n + 1 Vz: Zoom magnification speed (zoom per unit time) Number of drive pulses)
In order for the focus lens to move following the cam trajectory, the stepping motor of the drive source must be able to drive the focus lens barrel at the speed V. From the above equation, it can be seen that the faster the zooming speed is, the faster the driving speed of the focus lens must be.

As a conventional example, for example, Patent Document 1 can be cited.
JP 2002-98880 A

  By the way, the reason why the stepping motor is used for driving the focus lens is mainly that the operation control with relatively high accuracy can be performed by the open loop control and that the operation sound is quiet and suitable for the focus lens driving. However, because of the characteristics of the stepping motor, the generated torque decreases as it rotates at a higher speed. Therefore, an upper limit is determined for the moving speed of the focus lens barrel, which is expressed as Vmax. Since the gradient of the focus cam locus varies depending on the zoom magnification as shown in FIG. 8, the focus lens moving speed Vf varies depending on the zoom magnification even if the zoom magnification speed Vz is constant.

  When the speed Vf (z (n)) exceeds Vmax, the focus lens cannot move following the cam trajectory, and is not in focus from that point and the photographed image is blurred. End up.

  A wavy line “a” in FIG. 9 represents a state in which the cam track does not follow the cam track and moves away from the cam track when zooming from the WIDE end to the TELE end. It can be seen that the cam trajectory of the adjacent zoom lens barrel and the focus cam trajectory d intersect at the zoom position Z (m). This indicates that the zoom lens barrel overtakes the focus lens and interferes. Yes.

  In particular, in recent years, there has been an increasing demand for improving the operability by shortening the startup time and zoom operation time when the power is turned on, and there is a risk that the zoom lens barrel and the focus lens barrel will interfere as the zoom magnification speed increases. It is growing.

  An object of the present invention is to operate the zoom lens barrel and the focus lens tube without interference when zooming at high speed, and to maintain a focused state in a wider zoom range and realize comfortable operability. is there.

  In order to solve the above-described problems, the present invention provides a zoom lens that changes a zoom magnification by moving in the optical axis direction, a driving unit that drives the zoom lens at a plurality of speeds, and the zoom A selection means for selecting a driving speed from a plurality of driving speeds of the lens, a focusing lens for adjusting the focal position by moving in the optical axis direction, and the focusing lens that changes according to the subject distance and zoom magnification. A focus adjustment lens position storage means for storing the focus position; a drive means for moving the focus adjustment lens based on the focus adjustment lens position information stored in the storage means; and a zoom lens that changes according to the zoom magnification. Zoom lens position storage means for storing the position, information on the two storage means and the zoom lens driving speed, the focus adjustment lens and the lens An interval calculating means for calculating an interval of the lens, and a moving range in the optical axis direction of the zoom lens and a moving range in the optical axis direction of the focus adjusting lens have an overlapping range, and the optical axis direction of the zoom lens In an imaging device in which the maximum movement speed of the focus adjustment lens is larger than the maximum movement speed of the focus adjustment lens, when the distance between the focus adjustment lens and the zoom lens becomes a predetermined value or less, a locus different from the focus adjustment lens position information is obtained. The focus adjusting lens is moved by tracing.

  According to a second aspect of the invention, the different trajectory is a trajectory when the focus adjustment lens is moved in the same direction as the zoom lens at a maximum speed.

  According to a third aspect of the present invention, a zoom lens that changes the zoom magnification by moving in the optical axis direction, driving means for driving the zoom lens at a plurality of speeds, and a driving speed based on the plurality of driving speeds of the zoom lens. Selection means for selecting, a focus adjustment lens that adjusts the focus position by moving in the optical axis direction, and a focus adjustment lens position memory that stores a focus position of the focus adjustment lens that changes according to the subject distance and zoom magnification A zoom lens position memory for storing a position of the zoom lens that changes in accordance with a zoom magnification, and a driving means for moving the focus adjustment lens based on the focus adjustment lens position information stored in the storage means. And the distance between the focus adjustment lens and the zoom lens from the information of the two storage means and the zoom lens driving speed. And a focus adjustment lens switching point calculation means for calculating a zoom magnification for switching the movement locus of the focus adjustment lens, and a movement range in the optical axis direction of the zoom lens and light of the focus adjustment lens In the imaging apparatus, the moving range in the axial direction has an overlapping range, and the maximum moving speed in the optical axis direction of the zoom lens is larger than the maximum moving speed of the focus adjusting lens. The focus adjustment lens position to satisfy the minimum distance in the zoom area based on the minimum distance for preventing the lens barrels from interfering with each other, the zoom speed during operation, and the maximum speed of the focus adjustment lens. A zoom magnification for starting the movement of the focus adjustment lens by following a different path from the information is calculated; The focusing lens at maximum speed to drive the zoom lens in the same direction as a starting point, and is obtained by way.

  In a fourth aspect of the present invention, the diaphragm is moved in a direction different from the focus adjustment lens position information, and at the same time, the diaphragm is driven in a direction to narrow down from an appropriate exposure.

  As described above, according to the first invention, when the distance between the focus lens and the zoom lens barrel is equal to or smaller than a certain value, the focus lens is moved in the retraction direction at the maximum speed, so that no complicated calculation is required. The risk of interfering with can be greatly reduced.

  According to the second aspect of the invention, since the distance between the focus lens and the zoom lens barrel is predicted and calculated to determine the retraction timing of the focus lens, it is possible to surely avoid interference and minimize the range where blur occurs. I can do it.

Example 1
FIG. 1 is a block diagram showing the configuration of an electronic camera that well represents the first invention.

  In the figure, reference numeral 100 is a lens barrel, 101 and 102 are zoom lenses that move in the optical axis direction to control zooming, 103 is an optical aperture that has an aperture and adjusts the amount of light by changing the aperture diameter, and 104 is in the optical axis direction. Reference numeral 105 denotes a solid-state image pickup device (hereinafter referred to as a CCD) that converts a subject image formed by the above-described optical system into an electric signal.

  Reference numeral 110 denotes a drive source for moving the zoom lenses 101 and 102, which is a small DC motor in the present invention, 111 is a zoom driver that controls the zoom motor 110 based on an instruction from the CPU 120, and 112 is a drive that operates the diaphragm. Reference numeral 113 denotes a diaphragm driver that controls the drive source 112 based on an instruction from the CPU 120, 114 denotes a focus motor that drives the focus lens, and a pulse motor in the present invention, and 115 denotes a driver that drives the focus motor. Reference numeral 116 denotes a focus cam storage memory which stores the focus lens focus position determined by the zoom magnification and the subject distance as information such as numerical data, matrix data, or an interpolation formula. The stored information is the position of the focus lens. In addition, the position may be stored as the number of driving pulses of the focus motor.

  An A / D converter 121 converts an analog signal output from the CCD into a digital signal. An image processing circuit 122 performs predetermined signal processing on the digital signal. The output signal is an AF evaluation circuit 124, an image. It is given to the display device (LCD) 106 and the image recording device 123.

  The AF evaluation circuit 124 extracts a high frequency component for a predetermined range of the screen, generates an AF evaluation value based on the high frequency component, and provides the AF evaluation value to the AF control circuit 126, and drives the focus lens based on the AF evaluation value. The AF control circuit reads the focus cam data from the above-mentioned cam storage memory 116 and controls the operation of the focus lens described later.

  Reference numeral 125 denotes a zoom switch, which allows the operator to instruct the zoom direction and zoom speed. Based on the input, the CPU 120 passes through the zoom driver 111, the aperture driver 113, the AF control circuit 126, and the focus motor driver 115. Operate each unit.

  A focusing operation and a zooming operation in the electronic camera having the above configuration will be described.

  For the zoom switch 125, for example, a lever, a dial, a seesaw type switch, or the like is used. Normally, the camera has a neutral position, and the zoom direction is indicated by operations in both directions. Further, in this embodiment, a multi-stage zoom speed can be designated according to the operation amount. When the CPU 120 detects the operation direction and operation amount of the zoom switch 125, the CPU 120 determines the rotation direction and rotation speed of the zoom motor 110, gives a drive signal to the zoom driver 111, rotates the zoom motor 110, and zoom lens 101, 102 moves.

  FIG. 2 shows focus cam data in the optical system of the present embodiment. In FIG. 2, the horizontal axis represents the zoom magnification, and the vertical axis represents the focus position of the focus lens. Each curve represents a focal point at a typical subject distance, and the focus cam locus P1 indicates a case where the subject distance is infinity, P2 indicates a case where the distance is 5 m, and P3 indicates a case where the distance is 1 m.

  When the zoom magnification is constant, the AF control circuit 126 calls the cam data for the subject at an infinite distance from the cam data stored in the cam storage memory 116 and drives the focus motor 114 to the position corresponding to the infinite distance. The focus lens 104 is extended. In this embodiment, as shown in FIG. 2, when the focus lens 104 is moved in the feed-out direction, a subject at a close distance is focused.

  After moving the focus lens 104, the CCD 105 reads an image signal, performs image processing, and then extracts an high-frequency component from an area where focus is determined (hereinafter referred to as a focus area) to evaluate the degree of focus. Create a value. This utilizes the fact that the contrast of the photographed image changes depending on the degree of focusing and appears as a change in high-frequency components.

  After obtaining the evaluation value, the AF control circuit 126 repeats the operation of extending the focus lens 104 and obtaining the evaluation value again. FIG. 3 schematically shows evaluation values obtained while extending the focus lens 104 to the closest end. As shown in this figure, for example, when the subject is at a distance Xm, the evaluation value is maximum at the focus lens position corresponding to the distance, and before and after that, the value decreases to form a mountain shape having a peak. Therefore, the focus control circuit moves the focus lens to the peak position, and after stopping, performs exposure correction and actual photographing. The above is generally known as a so-called hill-climbing AF method.

  Next, focus lens driving when the zoom magnification is changed will be described.

  First, it is sufficient that the data stored in advance as the focus cam data is sufficiently detailed with respect to the change in zoom magnification. A method of generating focus cam data at the zoom magnification and subject distance between the values will be described.

  FIG. 4 shows focus cam data. The zoom position before zooming is expressed as Z (n), and the in-focus positions for each subject distance at the zoom position are expressed as P1 (n), P2 (n),..., Pm (n) in order from the infinite distance. . There are various interpolation methods for generating cam data at an intermediate zoom position from these stored data, but here interpolation by proportional distribution is applied. The interpolation method is not particularly limited to this. If the zoom position to be obtained is Z (x), Pm (x) is obtained by the following equation by proportional distribution.

Pm (x) = (Z (x) −Z (n)) / (Z (n + 1) −Z (n)) ×
(Pm (n + 1) −Pm (n)) + Pm (n) (2)
Detailed cam data between representative values can be generated by sequentially calculating while changing the desired zoom position Z (x).

  If the focus position before zooming is on the cam data Pm (x) obtained in this way, the in-focus state is maintained by moving the focus lens to Pm (x) simultaneously with the zooming operation. You can continue. At this time, the focus lens moving speed can be obtained by the following equation.

Vm (x) = (Pm (x) −Pm (n)) / {(Z (x) −Z (n)) / Vz} (3)
Is required. Here, Vz: Zoom drive speed When the focus position before zooming is in focus at Py (n) between the cam data P1 (n) and P2 (n), the zoom position Z The in-focus position Py (n + 1) at (n + 1) can be obtained. This interpolation calculation is also based on proportional calculation, but is not limited to this.

Py (n + 1) = P2 (n + 1) − (P2 (n) −Py (n)) ×
(P2 (n + 1) -P1 (n + 1)) / (P2 (n) -P1 (n))
... (4)
By using Py (n + 1) calculated as described above, the zoom lens is zoomed from the zoom position Z (n) to Z (n + 1), and at the same time, the focus lens is moved from Py (n) to Py (n + 1), thereby enabling the focus cam. It is possible to perform zooming while maintaining the in-focus state even for a subject at a subject distance for which data is not stored in advance.

  By repeating the above operation, the focus lens can keep in focus following zooming throughout the entire zoom range.

  The above description is for the case where the focus lens can follow the movement of the focal point by zooming. When the zoom magnification becomes high, the following problems occur when zooming at a uniform speed.

  Zooming should be performed at a relatively slow speed in order to reliably stop at the zoom position to be stopped. However, in high magnification zooming, zooming between the wide end and the tele end takes a very long time, resulting in poor operability. Conversely, if the zoom speed between the wide end and the tele end is increased, there is a problem that it becomes difficult to stop as desired at the zoom position where it is desired to stop.

  Therefore, there has been a conventional zoom speed that can be selected from a plurality of zoom speeds. The zoom speed is made variable by adjusting the amount of operation of the zoom operation switch. Even in such a case, if zooming is performed at a high speed, the moving speed of the focus lens that follows the cam trajectory in order to maintain the in-focus state increases, and the limit rotational speed of the focus motor that drives the focus lens may be exceeded. FIG. 5 is a diagram illustrating the movement trajectory due to zooming of the focus lens 104 and the lens barrel of the zoom lens 102 closest to the focus lens. The distance between two curves at an arbitrary zoom position is substantially equal to the distance between the two lens barrels. It represents a long interval. In this figure, when zooming from the wide end to the tele end, the focus lens can be moved by following the cam trajectory if the speed is low enough. Since the gradient of the cam curve is large, the cam locus cannot be followed unless the moving speed of the focus lens is high. A wavy line a in the figure represents the locus of the focus lens when the focus motor is driven at the maximum speed during zooming at a speed that cannot follow the cam locus. It can be seen that the wavy line a eventually crosses the locus of the zoom lens barrel on the wide side from the telephoto end, which indicates that the two lens barrels collide.

  In order to avoid such a situation, in the first invention of the present invention, the interval between the two lens barrels is calculated, and when the allowable minimum interval is set and the interval becomes narrower than that value, the focus cam trajectory from that point onwards The movement of the focus lens is stopped and the focus motor is driven at the maximum speed. The locus in this case is indicated by a broken line b, and the zoom position Z (s1) at the allowable minimum interval ΔP1 is moved in the retract direction at the maximum focus speed in the tele direction. It can be seen that when the lens is moved in this way, it does not collide with the zoom lens barrel even if it moves to the telephoto end. It can be seen that the focus lens is still moving at the telephoto end and continues to move even after the zoom lens stops and reaches the cam locus at the time when it reaches the imaginary zoom position Z (e).

  According to such an operation method, the in-focus state can be maintained during zooming from the wide end to the zoom position Z (s1), and the lens barrel interferes although the focus is lost from Z (s1) to the tele end. It is possible to perform zooming at high speed.

  Further, during zooming from Z (s1) to the telephoto end, the aperture is reduced from an appropriate exposure to increase the depth so that blurring is less noticeable.

  In the above description, the allowable minimum interval can be determined in advance from the zoom speed and the two cam trajectories, so that it is not necessary to calculate during the operation of the camera, and the load on the camera system can be reduced. Further, the locus of the zoom lens barrel is stored in the storage memory like the focus lens, and the correction between the zoom positions is calculated as necessary like the focus lens.

  Further, the allowable minimum interval may be changed according to the subject distance.

(Example 2)
Next, in the second aspect of the present invention, the zoom position at which the focus barrel should be started at the maximum speed is calculated so as not to interfere with the zoom barrel, and the focus lens is driven at the maximum speed therefrom. . FIG. 6 shows a cam locus representing the second invention.

  In FIG. 6, the cam locus of the zoom lens barrel and the cam locus of the focus lens are the same as those in FIG. A wavy line c in the drawing represents a trajectory followed by the focus lens moving at the maximum speed in order to maintain a minimum interval ΔP2 that does not interfere at the tele end, and the inflection point is Z (s2).

  Here, Z (s2) is obtained as follows.

  If the subject distance before zooming is a representative point of the cam data, the focus cam data is obtained over the entire area by the interpolation calculation in the zoom direction described above, and the difference from the cam data of the zoom lens barrel is calculated. If the subject distance before zooming is other than the representative point, focus cam data is created by performing the above-described interpolation calculation in the subject distance direction over the entire zoom range.

Next, the zoom position Z (s) at which the focus lens cannot follow is calculated from the above-described equation (3), and then the locus when the focus lens is driven at the maximum speed is drawn in the previous zoom region. Find the zoom position that maximizes the interference. (Tele end in this example)
An inflection point Z (s2) can be obtained by drawing a trajectory c when driving the focus at the maximum speed with a minimum interval ΔP2 allowable at that position and obtaining an intersection with the focus cam trajectory.

  Thus, since the focus lens and the zoom lens barrel are zoomed with a minimum interval, interference can be avoided reliably, and the area where the image is blurred can be reduced to the minimum.

Block diagram of the camera that best represents the present invention Focus cam locus AF evaluation value schematic diagram Focus cam data interpolation method Driving method of focus lens according to the first invention Driving method of focus lens according to the second invention Conventional lens barrel Focus cam locus Focus cam trajectory and zoom barrel cam trajectory

Explanation of symbols

101, 102 Zoom lens 104 Focus lens 105 CCD
114 Focus motor 116 Focus cam memory 120 CPU
124 AF evaluation circuit 126 AF control circuit

Claims (4)

A zoom lens that changes the zoom magnification by moving in the direction of the optical axis;
Driving means for driving the zoom lens at a plurality of speeds;
Selection means for selecting a driving speed from a plurality of driving speeds of the zoom lens, a focus adjusting lens that adjusts a focal position by moving in the optical axis direction, and the focus adjusting lens that changes according to the subject distance and zoom magnification Focusing lens position storage means for storing the in-focus position;
Drive means for moving the focus adjustment lens based on focus adjustment lens position information stored in the storage means; zoom lens position storage means for storing the position of the zoom lens that changes according to the zoom magnification;
An interval calculation unit that calculates an interval between the focus adjustment lens and the zoom lens from the information of the two storage units and the zoom lens driving speed;
The movement range in the optical axis direction of the zoom lens and the movement range in the optical axis direction of the focus adjustment lens have overlapping ranges,
In the imaging device in which the maximum movement speed in the optical axis direction of the zoom lens is larger than the maximum movement speed of the focus adjustment lens,
A variable magnification imaging apparatus according to claim 1, wherein when the distance between the focus adjustment lens and the zoom lens becomes a predetermined value or less, the focus adjustment lens is moved along a path different from the focus adjustment lens position information.   2. The variable magnification imaging apparatus according to claim 1, wherein the different locus is a locus when the focus adjustment lens is moved in the same direction as the zoom lens at a maximum speed. A zoom lens that changes the zoom magnification by moving in the direction of the optical axis;
Driving means for driving the zoom lens at a plurality of speeds;
Selection means for selecting a driving speed from a plurality of driving speeds of the zoom lens, a focus adjusting lens that adjusts a focal position by moving in the optical axis direction, and the focus adjusting lens that changes according to the subject distance and zoom magnification Focusing lens position storage means for storing the in-focus position;
Drive means for moving the focus adjustment lens based on the focus adjustment lens position information stored in the storage means; zoom lens position storage means for storing the position of the zoom lens that changes according to zoom magnification;
An interval calculation unit that calculates an interval between the focus adjustment lens and the zoom lens from information of the two storage units and a zoom lens driving speed;
A focus adjustment lens switching point calculating means for calculating a zoom magnification for switching the movement locus of the focus adjustment lens, and
The movement range in the optical axis direction of the zoom lens and the movement range in the optical axis direction of the focus adjustment lens have overlapping ranges,
In the imaging device in which the maximum movement speed in the optical axis direction of the zoom lens is larger than the maximum movement speed of the focus adjustment lens,
The focus adjustment lens switching point calculation means calculates the zoom lens based on the minimum interval for preventing the lens barrels from interfering with each other in the zoom region, the zoom speed during operation, and the maximum speed of the focus adjustment lens. Calculating a zoom magnification at which the focus adjustment lens should start moving by following a different locus from the focus adjustment lens position information in order to satisfy the minimum interval
The variable magnification imaging apparatus, wherein the driving unit drives the focus adjustment lens at the maximum speed in the same direction as the zoom lens, starting from the zoom magnification.   The variable magnification imaging apparatus according to claim 1 or 2, wherein the zooming device is moved in a direction of narrowing down from a proper exposure while moving along a locus different from the focus adjustment lens position information.

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