JP2001051179A - Optical equipment - Google Patents

Abstract

(57) [Problem] To provide an optical device comprising an optical system including a moving lens group, capable of correcting a shift of an image forming position of the optical system due to a temperature change and maintaining high optical performance. SOLUTION: A driving means for driving a moving lens group, a control means 18 for controlling the driving means, a measuring means for measuring a movable stroke of the moving lens group, and a storage means 17 for storing control information including the movable stroke. Is provided. Control means 18
Controls the driving means based on the control information to correct the fluctuation of the imaging position of the optical system due to the temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical apparatus used for a video camera, an electronic still camera, and the like, and more particularly, to a temperature change in an optical system having a moving lens group that moves in the optical axis direction during zooming or focusing. The present invention relates to an optical apparatus that corrects a deviation of an image forming position when the image is generated by the moving lens group.

[0002]

2. Description of the Related Art In recent years, optical devices used for video cameras, electronic still cameras, and the like have been rapidly reduced in size and weight. Therefore, as a material of a lens barrel that holds an optical system, a plastic material that has a high degree of freedom in shape, is suitable for miniaturization, and is lightweight is often used as compared with a metal material.

[0003]

However, plastic materials have a larger dimensional change with respect to temperature changes than metal materials. For example, the thermal expansion coefficient of aluminum as a metal material is 2.36 × 10 ⁻⁵ / K, while PC (polycarbonate) as a plastic material is used.
Has a typical thermal expansion coefficient of 5.0 × 10 ⁻⁵ / K, which is about twice that of aluminum. Therefore, in an optical device using a plastic material for the lens barrel, the change in the imaging position with respect to a change in temperature is larger than that in an optical device using a metal material.

[0004] Furthermore, recent optical devices have been improved in resolution by downsizing and higher performance of optical systems and image pickup devices.
For this reason, the influence when the imaging surface of the optical device is displaced due to a change in temperature becomes large, and how to correct the deviation of the imaging position has become a major issue.

According to the present invention, an optical system having a moving lens group moving in the optical axis direction can maintain high optical performance by correcting a shift of an image forming surface even if there is a temperature change. The purpose is to provide equipment.

[0006]

In order to achieve this object, the present invention has the following arrangement.

That is, an optical apparatus according to the present invention is an optical apparatus for forming an image on an image sensor by an optical system including a moving lens group, wherein the driving means drives the moving lens group and controls the driving means. Control means, measuring means for measuring a movable stroke of the movable lens group, and storage means for storing control information for driving the movable lens group, including the movable stroke, wherein the control means comprises: The method is characterized in that the driving unit is controlled based on control information to correct a change in the imaging position of the optical system due to a temperature change.

According to this configuration, even if there is a temperature change,
Detects a change in the movable stroke of the moving lens group due to a temperature change, corrects the tracking curve of the moving lens group based on the detected change in the movable stroke, and corrects the position of the moving lens group based on the corrected tracking curve. By performing the above, it is possible to provide an optical apparatus capable of reducing the deviation of the imaging plane due to a temperature change and maintaining high optical performance.

In the above arrangement, it is preferable that the optical system is an inner focus type zoom lens. By applying the present invention to an optical device having an inner focus type zoom lens, it is possible to obtain an optical device capable of suppressing a deviation of an imaging position due to a temperature change and maintaining high optical performance.

It is preferable that the video camera has the optical device having the above-mentioned configuration. By using the optical apparatus of the present invention for a video camera that requires high miniaturization, high performance, and high resolution, a small and high performance video camera with little deterioration in optical performance due to a temperature change can be realized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of an optical apparatus according to a first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes an optical system, which is an inner focus zoom lens including four lens groups.

The zoom lens includes a first lens group 101 as a fixed lens group, a second lens group 102 as a moving lens group having a variable power function, a third lens group 103 as a fixed lens group, and a moving lens group. Fourth correction and focusing of image plane movement accompanying zooming due to movement of the second lens group
It comprises a lens group 104. The first to fourth lens groups include a single lens or a plurality of lenses.

In FIG. 1, reference numeral 102a denotes a second lens group 1.
A member for holding the second lens group 104 (hereinafter referred to as a “second group moving frame”); 104 a a member for holding the fourth lens group 104 (hereinafter referred to as a “fourth group moving frame”); This is a member for holding the group (hereinafter, referred to as a “barrel”). The second group moving frame 102a, the fourth group moving frame 104a, and the lens barrel 2 are manufactured by injection molding a plastic material such as PC (polycarbonate).

Reference numeral 3 denotes a filter installed in front of the image pickup device 11 such as a CCD, which comprises an optical low-pass filter 3a such as quartz and an infrared cut filter 3b.

Reference numeral 4 denotes driving means such as a stepping motor for moving the second lens group 102 in the direction of the optical axis 105. 4a is a lead screw threaded at a predetermined pitch. Reference numeral 102b denotes a rack provided on the second group moving frame 102a. The rack 102b is engaged with the lead screw 4a, and the second group moving frame 102a moves in the direction of the optical axis 105 as the stepping motor 4 rotates.

Reference numeral 5 denotes a yoke fixed to the lens barrel 2;
Is a magnet fixed to the yoke 5. Reference numeral 7 denotes a coil fixed to the fourth group moving frame 104a by bonding or the like. The yoke 5, the magnet 6, and the coil 7 constitute a linear actuator. The magnetic field generated by applying a current to the coil 7 acts on the magnetic field generated by the magnet 6 and the yoke 5, generating a thrust in the coil 7 in a direction parallel to the optical axis 105.
4a is moved in the direction of the optical axis 105.

Reference numeral 8 denotes a photo interrupter for determining a reference position of the second lens group 102. 2nd group moving frame 10
2a moves in the direction of the optical axis 105, and the light-shielding plate 102b formed on the second group moving frame 102a shields the photo-interrupter 8, so that the signal output from the photo-interrupter 8 changes. By detecting the change by the detection circuit 12, the reference position of the second group moving frame 102a is determined.

Reference numeral 9 denotes a sensor magnet fixed to the fourth group moving sum frame 104a by bonding or the like, and reference numeral 10 denotes an MR sensor. When the sensor magnet 9 moves in the direction of the optical axis 105 together with the fourth group moving frame 104a, the signal output from the MR sensor 10 changes according to the amount of movement. The detection circuit 13 detects a signal from the MR sensor 10 to detect the amount of movement of the fourth-group moving frame 104a. Also, a current is supplied to the coil 7 to move the fourth group moving frame 104a.
Is moved in the image plane direction (rightward on the paper), the reference position of the fourth group moving frame 104a is determined by detecting that the signal of the MR sensor 10 does not change for a predetermined time or more.

Reference numeral 14 denotes a driving circuit for driving the stepping motor 4 as lens driving means, and reference numeral 15 denotes a driving circuit for driving the linear actuator.

Reference numeral 16 denotes a camera process circuit for outputting an output signal from the image sensor 11 as an image signal S1. Reference numeral 17 denotes a storage unit such as a ROM that stores drive information of the second group moving frame 102a and the fourth group moving frame 104a. Reference numeral 18 denotes a second group moving frame 102a and 4 based on lens operation signals such as zooming and focusing, output signals from the detection circuits 12 and 13, and driving information in the storage means 17.
This is a control circuit that controls the drive circuits 14 and 15 of the group moving frame 104a.

Here, in the inner focus lens, the position of the fourth lens group 104 is determined with respect to the position of the second lens group 102 (ie, the zoom position) for each subject distance.

FIG. 2 shows the second lens group 102 for each subject distance.
And a plot (hereinafter, referred to as a “tracking curve”) of a positional relationship between the second lens group 104 and the fourth lens group 104. In FIG. 2, the horizontal axis indicates the position of the second lens group, and the left side is WI.
DE (wide angle) and TELE (telephoto) are on the right side. Also,
The vertical axis indicates the position of the fourth lens group, the upper side is the object side, and the lower side is the image plane side (imaging side). When the second lens group 102 moves from WIDE to TELE when the subject distance is infinity, the fourth lens group moves on a locus convex toward the object side as indicated by a curve C _inf .

As described above, in the present embodiment, when zooming from WIDE to TELE or from TELE to WIDE, the second lens group 102 based on the tracking curve recorded in the ROM as the storage means 17.
Drive control of the fourth lens group 104 according to the moving amount of
A good image without defocus is obtained.

In the present embodiment, when a temperature change occurs, each interval (dimension) between the first lens group 101 and the third lens group 103 and between the third lens group 103 and the image pickup device 11 changes, and the result of the reference temperature To is changed. The image plane deviates from the image plane,
It is out of focus. Therefore, if a temperature change occurs,
It is necessary to correct the tracking curve so as to correct the deviation of the imaging position caused by the temperature change.

FIG. 3 shows tracking curves when the subject distance is infinity when the reference temperature is To = 20 ° C., when the temperature is To + 20 ° C., and when the temperature is To−20 ° C.
In the present embodiment, when the temperature becomes higher than the reference temperature To, the tracking curve of the fourth lens group 104 moves to the image plane side.
The tracking curve of the lens group 104 moves to the object side.

In the present embodiment, the manufacturing error for each optical system,
For example, a movable stroke of the fourth lens group 104 is detected before an initial adjustment (hereinafter, referred to as a focus adjustment) for correcting a focus shift due to a shift in a curvature of a lens surface, a shift in a lens barrel dimension, and the like. Record the value.
The detection method is as follows. First, before the focus adjustment, the fourth-group moving frame 104a is moved in the object direction, and it is detected that the signal from the MR sensor 10 has not changed for a predetermined time or more. Set the edge. Next, the fourth group moving frame 104a
Is moved in the image plane direction, and by detecting that the signal from the MR sensor 10 has not changed for a predetermined time or more, the image plane side end of the movable range of the fourth group moving frame 104a is confirmed. Then, the movable stroke So of the fourth lens group 104 is detected by counting the amount of movement between the two.

After the focus adjustment, the fourth lens group 104 is operated in the same manner in the initial setting process of the camera immediately after the power is turned on.
Is detected. When there is a temperature change, the movable stroke St has a different value from the movable stroke So at the time of focus adjustment.
The tracking curve is corrected based on S = St−So, and a correction position corresponding to a temperature change of the fourth lens group 104 is calculated.

In this embodiment, when the temperature correction coefficient is Kt and the tracking curve at the reference temperature To is Co,
The tracking curve Ct after the temperature correction, that is, the position of the fourth lens group is calculated by the following correction formula.

[0030]

## EQU1 ## Ct = Kt × △ S + Co = Kt × (St−S
o) + Co

However, the present embodiment is not limited to this equation, and a change in the tracking curve due to a temperature change may be calculated by an arbitrary equation (function).

The operation of the embodiment of the present invention will be described below with reference to the flowcharts of FIGS.

First, when the power is turned on (step 20)
1) The output signal from the photo interrupter 8 is read by the detection circuit 12 (step 202). Next, in the control circuit 18, the direction according to the read signal, that is, if the output signal of the photointerrupter 8 is high, it is low.
The second lens group 102 is driven in such a direction as to become “low”, or in the case of “low” when it becomes low (step 203). Driving is performed until the output signal from the photo interrupter 8 changes (step 204). The position where the output signal from the photo interrupter 8 has changed is defined as the reference position of the second lens group 102. That is, the position counter of the second lens group is initially set at the position where the output signal has changed (step 205).

Next, a current is applied to the coil 7 by the drive circuit 15 to drive the fourth lens group 104 toward the object side until the signal from the MR sensor 10 does not change (step 206). In parallel with this, a signal from the MR sensor 10 is read (step 207), and the state of change of the signal is observed (step 208). If the signal has not changed for a predetermined time or more, the position counter of the fourth lens group is cleared (step 209). This position is the object-side end of the movable stroke of the fourth lens group. Next, the coil 7
, And the fourth lens group 104 is driven to the image plane side (step 210). As in the case of the object side, a signal from the MR sensor 10 is read in parallel (step 211), and the state of change of the signal is observed (step 212). When the signal does not change for a predetermined time or more, the driving of the fourth lens group 104 is stopped. This position is the image plane side end of the movable stroke of the fourth lens group 104. The amount of movement from the object side end to the image plane side end, that is, the movable stroke St of the fourth lens group 104 is read from a position counter (step 213), and the fourth lens group 10 is read.
4 is initially set (step 21).
4).

The above-described initial setting operation of the fourth lens group 104 is also performed before the focus adjustment of the optical system as described above, and the movable stroke So as a reference for temperature correction is obtained and recorded in the storage means 17.

After the initialization of the second lens group 102 and the fourth lens group 104 is completed, the control circuit 18 sets the positions of the second lens group 102 and the fourth lens group 104 at the time of turning on the power,
Alternatively, it is moved to a position backed up in the storage means 17. At this time, the control circuit 18 reads the reference movable stroke So and temperature correction coefficient Kt from the storage means 17 (step 215), and calculates the variation ΔS = St-So due to the temperature change of the movable stroke (step 21).
6) The tracking curve is corrected from the temperature correction coefficient Kt by using a correction equation for temperature correction (for example, the above [Equation 1]) (step 217). When the second lens group is moved (step 218), the position of the fourth lens group corresponding to the moved position is calculated from the correction formula, and the fourth lens group 10
4 is moved to that position (step 219). Thus, the initial setting operation ends (step 220).

Thereafter, the drive of the second lens group and the fourth lens group is controlled based on the corrected tracking curve until the power is turned off.

As described above, by adopting the configuration of the present embodiment, it is possible to obtain a good image without a focus shift even when a temperature change occurs due to an environmental change or the like.

[0039]

As described above, the present invention detects a change in the movable stroke due to a temperature change of the movable lens group that moves on the optical axis for zooming and focusing, and detects the change in the movable lens group based on the amount of change in the movable stroke. By correcting the position, the deviation of the imaging position due to temperature change was suppressed small,
An optical device that can maintain high optical performance is 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 tracking curve of a moving lens group of an optical system in the optical device of FIG. 1;

FIG. 3 is an explanatory diagram showing a change in a tracking curve due to a temperature change in the optical device of FIG. 1;

FIG. 4 is a flowchart showing an operation of the optical apparatus according to the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating an operation of the optical apparatus according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating an operation of the optical apparatus according to the first embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 optical system 101 first lens group 102 second lens group 103 third lens group 104 fourth lens group 2 lens barrel 4 lens driving means 5 yoke 6 magnet 7 coil 8 photo interrupter 9 sensor magnet 10 MR sensor 17 storage means 18 Control circuit

Claims (2)

[Claims] 1. An optical apparatus for forming an image on an image sensor by an optical system including a moving lens group, comprising: a driving unit that drives the moving lens group; a control unit that controls the driving unit; Measuring means for measuring the movable stroke of the lens group; and storage means for storing control information for driving the movable lens group, including the movable stroke, wherein the control means performs the driving based on the control information. An optical apparatus, comprising: controlling means for correcting a change in an imaging position of the optical system due to a temperature change. 2. The optical apparatus according to claim 1, wherein the optical system is an inner focus type zoom lens.