JP4441018B2 - Optical equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical device used for a video camera, an electronic still camera, and the like, and more particularly, an optical system (imaging optical system) having a moving lens group that moves on an optical axis at the time of focusing or zooming, for example, a zoom lens In the optical system, the moving lens corrects the difference (image plane displacement) between the image plane position when moving from the wide angle to the telephoto side and the image plane position when moving from the telephoto to the wide angle. It relates to optical equipment.
[0002]
[Prior art]
In recent years, in optical devices used for cameras and the like, downsizing of a photographing optical system and downsizing of an image size of a solid-state imaging device have been progressing rapidly. Due to the downsizing of the photographing optical system, the moving amount of the moving lens unit for focusing tends to be larger than the moving amount of the moving lens unit for zooming, particularly on the telephoto end side. There is a small backlash (hysteresis) between the driving means (lens driving means) such as a step motor and the moving lens group, and the moving lens group for zooming is not moved by the amount of hysteresis when zooming is performed. In some cases, only the moving lens group for focusing with a large amount of movement moves to cause a focus shift (image plane shift).
[0003]
[Problems to be solved by the invention]
In recent optical systems, the photographing optical system and the solid-state imaging device are downsized. For this reason, there has been a problem that the influence of small backlash (hysteresis) between the driving means (lens driving means) such as a step motor and the moving lens group on the planned imaging plane of the optical system used in the optical apparatus becomes larger. . Therefore, how to effectively correct the deviation of the imaging position due to such hysteresis is a big problem.
[0004]
The present invention corrects the deviation of the image plane even when there is the above-mentioned hysteresis when photographing using an optical system (photographing lens) having a moving lens group that moves on the optical axis for focusing and zooming. An object of the present invention is to provide an optical device suitable for a video camera, an electronic still camera, or the like that can maintain high optical performance.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
[0006]
That is, the optical apparatus of the present invention is an optical apparatus that forms an image on an image plane by an optical system including a moving lens group, and a driving unit that drives the moving lens group and a control that controls the driving unit. And a position of the imaging plane when the moving lens group for zooming of the optical system is moved from the wide-angle side to the telephoto side, and a position of the imaging plane when it is moved from the telephoto side to the wide-angle side. Detecting means for detecting a difference (hysteresis) between the recording lens and recording means for recording control information for driving the movable lens group, including information on a difference in position of the imaging plane, and the control means Is characterized in that the driving means is controlled based on the control information to correct a difference in position of the imaging plane. According to such a configuration, even if there is hysteresis in the moving lens group, it is possible to obtain an optical apparatus that can correct the deviation of the imaging plane due to this and maintain high optical performance.
[0007]
In the above configuration, the optical system is preferably a rear focus type zoom lens. By applying the present invention to an optical apparatus having a rear focus type zoom lens, an optical apparatus capable of maintaining high optical performance by correcting a shift of an image plane due to the hysteresis even if there is hysteresis. be able to.
[0008]
It is preferable that the video camera has the optical apparatus having the above configuration. According to such a configuration, it is possible to obtain a video camera capable of obtaining a good image without a focus shift during zooming even if the size is reduced.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0010]
(Embodiment 1)
FIG. 1 is a principal block diagram of an optical apparatus according to Embodiment 1 of the present invention. In the figure, reference numeral 1 denotes an optical system, which comprises a four-group rear focus zoom lens composed of four lens groups.
[0011]
The rear focus zoom lens 1 includes a first lens group (hereinafter referred to as “first group”) 101 which is a fixed lens group, and a second lens group (hereinafter referred to as “second lens”) which is a moving lens group and has a zooming function. Compensator that corrects the focus function and image plane variation accompanying zooming with a third lens group (hereinafter referred to as “third group”) 103 that is a fixed lens group and a moving lens group. And a fourth lens group (hereinafter referred to as “fourth group”) 104 having the functions as described above.
[0012]
Actually, the lens group is composed of a plurality of lenses. For example, in this embodiment, the first group 101 has three lenses, the second group 102 has three lenses, the third group 103 has three lenses, The fourth group 104 is composed of one lens, and is composed of an optical system having four groups and ten elements as a whole.
[0013]
102a is a member for holding the second group 102 (hereinafter referred to as “second group frame”), and 104a is a member for holding the fourth group 104 (hereinafter referred to as “fourth group frame”). These are all manufactured by molding or cutting with a mold using PC (polycarbonate).
[0014]
Reference numeral 2 denotes a member for holding the lens group (hereinafter referred to as “lens barrel”), which is manufactured by molding with a mold or cutting using PC (polycarbonate).
[0015]
The present invention is not particularly limited to the above materials and manufacturing methods. Other than the above, for example, a metal material such as aluminum or titanium is formed by die casting and then manufactured by secondary processing, or directly from a block. A machined product may be used. Further, the lens barrel 2 may be divided into several members and is not particularly limited in the present invention.
[0016]
Further, in the present embodiment, the first group 101 and the third group 103 are fixed to the lens barrel 2 after being fixed to the holding members 101a and 103a, respectively. Good, not particularly limited.
[0017]
Reference numeral 3 denotes a filter unit placed in front of the image sensor 8 and includes an optical low-pass filter 3a such as crystal, an infrared cut filter 3b, and the like.
[0018]
Reference numerals 4 and 5 denote driving means (lens driving means) such as step motors for driving the moving lens groups 102 and 104, respectively. 4a and 5a are lead screw screws whose surfaces are threaded at a predetermined pitch. Reference numerals 102b and 104b denote racks, which are formed as the same member as the second group frame 102a and the fourth group frame 104a, respectively, or integrally formed as separate members by bonding or the like to the second group frame 102a and the fourth group frame 104a. Is done. The racks 102b and 104b mesh with the lead screw screws 4a and 5a, respectively, and the second group frame 102a and the fourth group frame 104a move in parallel to the optical axis 105 when the step motors 4 and 5 are rotated forward and backward. .
[0019]
Reference numerals 6a and 7a denote photo interrupters. Reference numerals 6b and 7b denote light shielding plates, which are formed as the same members as the second group frame 102a and the fourth group frame 104a, respectively. When the light shielding plates 6b and 7b come to the position of the photo interrupters 6a and 7a by the movement of the second group frame 102a and the fourth group frame 104a, the signals from the photo interrupters 6a and 7a change, and this change is detected. Thus, the reference positions of the second group 102 and the fourth group 104 are determined.
[0020]
In this embodiment, relative position information from the reference position of each lens is detected by counting the number of drive pulses for driving the step motors 4 and 5 with respect to the reference position.
[0021]
The photo interrupters 6a and 7a and the light shielding plates 6b and 7b constitute an element of a lens reference position detecting means. Reference numerals 11 and 12 denote detection circuits for detecting signals from the photo interrupters 6a and 7a.
[0022]
In the present embodiment, a combination of a step motor and a lens reference position detection unit is employed, but a combination of a voice coil motor and a lens position detection unit using a magnetoresistive effect element may be used, and is not particularly limited.
[0023]
Reference numerals 13 and 14 denote driving circuits for driving the step motors 4 and 5 as lens driving means.
[0024]
Reference numeral 15 denotes a camera process circuit that processes an output signal from the image sensor 8 and outputs it as an image signal S1. Reference numeral 16 denotes a recording unit such as a ROM that stores driving information of the second group 102 and the fourth group 104. A control circuit 17 controls the drive circuits 13 and 14 that drive the step motors 4 and 5.
[0025]
In FIG. 1, the control circuit 17 and the ROM 16 are separate blocks, but the control circuit 17 and the ROM 16 may be included in the microprocessor.
[0026]
In the rear focus zoom lens 1, the stop position of the fourth group 104 is determined with respect to the stop position (zoom position) on the optical axis 105 of the second group 102 for each subject distance.
[0027]
FIG. 2 shows a plot of stop positions on the optical axis of the second group 102 and the fourth group 104 for each subject distance (hereinafter referred to as “cam curve”). In FIG. 2, the horizontal axis indicates the position of the second group 102, the left side is WIDE (wide angle) and the right side is TELE (telephoto). The vertical axis indicates the position of the fourth group 104, with the upper side being the object side and the lower side being the image plane side (imaging side).
[0028]
In FIG. 2, for example, when the subject distance is infinity, when the second group 102 moves on the optical axis from the wide-angle side to the telephoto side, the fourth group 104 moves the optical axis on the object side as indicated by the curve Y∞. It moves according to the convex trajectory.
[0029]
As described above, in the present embodiment, when zooming from the wide-angle side to the telephoto side or from the telephoto side to the wide-angle side, the cam curve is traced according to the subject distance, based on the cam curve stored in the memory. The fourth group 104 is driven and controlled in accordance with the movement of the second group 102, thereby obtaining a good image with no defocusing.
[0030]
As is apparent from the cam curve in FIG. 2, the inclination angle of the curve is large on the telephoto side, and the movement amount of the fourth group 104 is larger than the movement amount of the second group 102. For this reason, the second group 102 does not move on the optical axis by the amount of play (hysteresis) between the lead screw screw 4a and the rack 102b for the moment when zooming is started, but starts to move with a delay. The cam curve advances by the amount of this delay, resulting in an out-of-focus image. In order to prevent this, it is necessary to measure the hysteresis and correct the cam curve.
[0031]
FIG. 3 is an explanatory diagram showing a method for detecting the shift amount of the image plane position in the present embodiment. The vertical axis indicates the focus (resolution), and the higher the focus is, the better the focus is. The horizontal axis indicates the position of the second lens group 102. The left side is WIDE (wide angle) and the right side is TELE (telephoto).
[0032]
FIG. 4 is a flowchart showing the cam curve correcting operation in the present embodiment.
[0033]
As shown in FIG. 4, when the power is turned on (step 201), the output signals from the photo interrupters 6a and 7a are read by the detection circuits 11 and 12 (step 202). Next, in the control circuit 17, the second group 102 in the direction according to the read signal, that is, the direction that becomes low when the output signals of the photo interrupters 6a and 7a are high, and the direction that becomes high when the output signals are low. The fourth group 104 is driven. The driving is performed until the output signals from the photo interrupters 6a and 7a change, and the positions where the output signals change are set as the reference positions of the second group 102 and the fourth group 104. The position counters of the second group and the fourth group are reset at the position where the output signal has changed. Next, the position of the fourth group 104 and the subject distance are fixed (step 203), and the second group is reciprocated. That is, in this embodiment, the subject distance and the position of the fourth group 104 on the optical axis are fixed, and there is no focus shift when the second group 102 is moved from the telephoto side to the wide angle side in the vicinity of the telephoto side. At the position P1 on the optical axis of the second group 102 (a count number from the reference position of the second group 102), the subject distance, and the position on the optical axis of the fourth group 104 that can obtain a good image, When the second group 102 is moved from the wide angle side to the telephoto side in the vicinity of the telephoto side, a position P2 on the optical axis of the second group 102 (from the reference position of the second group 102) that can obtain a good image without a focus shift. The absolute value HIS of the difference from (the count number) is calculated (step 204, see FIG. 3). That is, the HIS is calculated by the following formula.
[0034]
[Expression 1]
HIS = | P1-P2 |
[0035]
The obtained value is recorded in the recording means 16 (step 205).
[0036]
Hereinafter, a case where zooming is performed from the telephoto side to the wide angle side will be described. Since the same routine is used when zooming from the wide-angle side to the telephoto side, a detailed description is omitted.
[0037]
When zooming is performed from the telephoto side to the wide-angle side, drive control is performed such that the cam curve is moved to the telephoto side by the calculated amount of HIS and the movement of the fourth group 104 is delayed. Accordingly, it is possible to correct a focus shift caused by the second group 102 not starting to move immediately on the optical axis but starting to move with a delay due to the hysteresis of the second group 102.
[0038]
As described above, with the configuration of the present embodiment, it is possible to obtain a good image without a focus shift even when there is a large hysteresis.
[0039]
【The invention's effect】
As described above, according to the present invention, even if there is hysteresis in the moving lens group, the deviation of the image plane caused by this can be corrected, and an optical apparatus that can maintain high optical performance can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a main part of an optical apparatus according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram showing a cam curve of a moving lens group of the optical apparatus shown in FIG. Explanatory drawing which showed the detection method of the difference of the image plane position of the moving lens in Embodiment 1 of the present invention. FIG. 4 is a flowchart showing the operation of the optical apparatus of Embodiment 1 of the present invention.
DESCRIPTION OF SYMBOLS 1 Optical system 101, 103 Fixed lens group 102, 104 Moving lens group 2 Lens barrel 4, 5 Lens drive means 17 Control circuit 16 Recording means 11, 12 Detection circuit 13, 14 Drive circuit

Claims (2)

An optical device that forms an image on an imaging surface by an optical system including a moving lens group,
Driving means for driving the moving lens group;
Control means for controlling the drive means;
The difference between the position of the imaging surface when the moving lens group for zooming of the optical system is moved from the wide-angle side to the telephoto side and the position of the imaging surface when it is moved from the telephoto side to the wide-angle side Detecting means for detecting
Recording means for recording control information for driving the moving lens group, including information on the difference in position of the imaging plane;
An optical apparatus characterized in that the control means controls the driving means based on the control information to correct a difference in position of the imaging plane. The optical apparatus according to claim 1, wherein the optical system is a rear focus type zoom lens.

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