JPH05134166A - Lens system control device - Google Patents

Abstract

PURPOSE:To prevent fuzziness due to a change of an object distance at the time of manual focusing by prohibiting tracking a moving locus when a focus lens is separated from the stored moving locus more than a fixed amount. CONSTITUTION:In the case of judging not to be an automatic focus adjusting mode (AF), that is, to be a manual focus mode, a difference from the current position of a focus lens 105 is calculated at the position of a variable magnification lens 102, and it is judged whether the difference is within a fixed distance D or not. When it is judged to be within a fixed distance D, that is, when the current object and an object when the position of the focus lens 105 is stored are judged to be the same, the drive is controlled so that the focus lens 105 traces the stored position. On the other hand, when an object and the current object are judged to be changed, the focus lens (105) tracing the stored position is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens system in which a lens that moves for focus adjustment is arranged on a conjugate side that is shorter than a lens that moves for fluctuations, and an electronic drive control unit for controlling the position of these lenses. Especially, it is suitable for a camera such as a video camera.

[0002]

2. Description of the Related Art Looking at the recent development trend of cameras, a so-called inner focus or rear focus type lens system in which a rear lens group is moved for focus adjustment is widely used for the purpose of downsizing and weight reduction. Has been.

FIG. 3 shows an example of a lens structure in this inner focus type lens system. In the figure, 101 is a fixed first lens group, 102 is a second lens group (magnifying lens) for performing zooming, 103 is a diaphragm, 104 is a fixed third lens group, and 105 is a focus. A fourth lens group (focus lens) which also functions as a minute forward / backward movement for adjustment and focus detection and a function of correcting the movement of the focal plane due to the zooming operation by the second lens group.
Reference numeral 06 is an image pickup surface. The lens system has various modifications such as adding another correction lens group between the second lens group and the third lens group.

In the lens system configured as shown in FIG. 3, when zooming is performed by moving the variable power lens, as described above, the fourth lens group has a focal plane associated with the variable power operation. The movement correction function and the operation for maintaining the in-focus state are performed. This state is shown in FIG.

In FIG. 4, the horizontal axis represents the zooming state (magnifying lens position), and the vertical axis represents the focus lens position. With the object distance as a parameter, the positional relationship between the variable magnification lens and the focus lens for maintaining focus is set. Is shown. As is clear from the figure, during the zoom operation, if the focus lens moves along a unique trajectory for each subject distance, it is possible to perform zooming in a focused state without causing blurring. If it deviates from this locus, blurring will occur.

A method of moving the focus lens along a unique locus according to the subject distance during the zoom operation has been proposed, for example, in Japanese Patent Application Laid-Open No. 1-280709. In this method, the locus of FIG. 4 is divided into regions as shown in FIG. 5 where the slopes are substantially equal, and the focus lens is divided into each of these regions while the zoom lens passes through that region. The driving speed that should be taken is calculated from the inclination of the locus passing through the area and given as a representative speed. During zooming, the position of the area is determined from the positional relationship between the zoom lens and the focus lens, and the drive speed of the focus lens is determined by taking into account the representative speed of the area and the correction from the automatic focus detection device. , To move. This enables zooming while maintaining focus.

However, in the above-described method in the rear focus type lens system, zooming from the wide (W) side to the tele (T) side is performed when the automatic focus adjustment mode is OFF, that is, in the manual focus mode. When performed, as can be seen from FIG. 4, since the loci for maintaining the focus at each subject distance are concentrated within the depth of field on the wide side, the correct locus cannot be selected. There is a drawback that it moves along the trajectory and causes blurring.

The following methods have been proposed as means for compensating for the drawbacks of the rear focus type lens system.

In the manual focus mode, when it is desired to perform zooming from the wide side to the tele side, before that, the same subject is zoomed from the tele side to the wide side. At this time, the movement locus of the focus lens is stored in advance, and when zooming from the wide side to the tele side, the stored locus is traced in reverse to focus from the wide side to the tele side in the manual focus mode. It is intended to enable zooming while maintaining.

[0010]

However, in the above method, for example, when the movement locus of the focus lens is stored by zooming from the tele side to the wide side, and in the manual focus mode, from the wide side to the tele side. If the subject at the time of zooming is different, for example, focus on the subject at infinity on the tele side, then perform zooming to the wide side, store the movement trajectory of the focus lens, and then at the wide end. , If you change the subject to a distance of 1 m and execute zooming to the tele side in manual focus mode, the focus lens will follow the stored trajectory when the subject is at infinity, so zooming is started. The drawback is that it causes blurring.

[0011]

SUMMARY OF THE INVENTION The present invention comprises a lens for zooming, a lens for focus adjustment, position detecting means for detecting the position of each lens, and lens driving means for driving each lens. In an optical device having a lens control unit that controls these lenses and a storage unit that can store the position of the lens that performs focus adjustment, when performing zooming in the wide direction, the position of the lens that performs zooming On the other hand, the position of the focus adjustment lens is stored, and when the magnification is changed from the wide side to the tele side without using the automatic focus detection device (AF system), the stored position of the focus adjustment lens is traced. However, at a certain position of the lens for zooming, the difference between the current position of the lens for focus adjustment and the stored position depends on, for example, aperture information and the position of the lens for zooming. When it becomes more than an amount determined, in which zooming to subsequent telephoto side, includes a configuration to prohibit tracing the position trajectory of the focusing lens stored.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a video camera will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the lens control device according to the present invention.

In the figure, 101, 102, 103,
Reference numerals 104 and 105 are element lenses of an optical system having the same function as described in FIG. 107, 108, 10
Reference numeral 9 is an actuator such as a motor for driving the variable power lens 102, the diaphragm 103, and the focus lens 105, respectively. Reference numerals 110, 111 and 112 denote drivers for driving and controlling the actuators 107, 108 and 109, 113 and 115 denote position encoders for detecting the positions of the zoom lens 102 and the focus lens 105, and 106 denotes an image formed by an optical system. An image pickup device such as a CCD that converts an image into a video signal and outputs the image signal. Reference numeral 116 is an amplifier that amplifies the output signal of the image sensor 106, 117 is a band-pass filter that extracts only the high-frequency component that is effective for detecting the focus state in the output signal of the amplifier 116, and 119 is the band-pass filter 1
Focusing is performed by moving the focus lens 105 in the direction in which the high frequency component is increased by the output signal of 17, or as described in the conventional example, the zoom lens 102 and the focus lens 105 are simultaneously moved to perform the zoom operation. A lens drive control microcomputer 118 for controlling the above, and an aperture control device 118 for keeping the brightness of the subject constant according to the brightness level of the output signal of the amplifier 116. Also 120, 1
Reference numeral 21 is a switch for moving the focus lens 105 to the closest side or the infinity side.

FIG. 2 shows a flow chart of an operation control program stored in the lens drive control microcomputer 119 for operating the lens control device according to the present invention.

In the figure, when the execution of the program is started in step 201, it is determined in step 202 whether or not zooming is performed in the wide direction. When it is determined in step 202 that wide-direction heading is being performed, the process proceeds to step 203.

In step 203, the position of the focus lens 105 with respect to the position of the zoom lens 102 at that time is detected from the output result of the position encoder 115 and stored in a memory (not shown) in the lens drive control microcomputer 119.

While zooming in the wide direction, the processes 201 to 202 and 203 are repeated, and if the zooming is performed while maintaining the focus, one of the loci shown in FIG. One of them is stored in the lens drive control microcomputer 119.

If it is determined in step 202 of FIG. 2 that the zooming is not in the wide direction, the process proceeds to step 204, and it is determined whether or not the zooming is in the tele direction. If it is determined in step 204 that the zooming is in the tele direction, the process proceeds to step 205. If the zoom is not in the tele direction, the process returns to step 201.

In step 205, automatic focus adjustment (AF)
It is determined whether the mode is the mode, that is, the AF mode or the manual focus mode.

When it is determined in step 205 that the AF mode is set, the process returns to step 201 and the normal zooming operation as described in the conventional example is performed. AF in step 205
If it is determined that the mode is not the mode, that is, the manual focus mode, it proceeds to step 206.

In step 206, the current position of the focus lens 105 at the position of the variable power lens 102 at that time and the focus lens 10 stored in step 203.
The difference from the position 5 is calculated, and it is determined whether or not the difference is within a certain amount D. If it is determined to be within a certain amount D, that is, if it is determined that the current subject is the same as the subject when the position of the focus lens 105 is stored in step 203, the process proceeds to step 207.

In step 206, if the difference between the current position of the focus lens 105 and the position of the focus lens 105 stored in step 203 is greater than or equal to a certain amount D, after the position of the focus lens 105 is stored in step 203. , It is judged that the subject is changed, and step 2
Move to 08.

It is rational to determine the fixed amount D in step 206 in consideration of the state of the diaphragm 103 and the position of the variable power lens 102. That is, since the depth of field becomes shallow when the aperture 103 is close to the open state, even if the current position of the focus lens 105 and the storage position in step 203 are slightly different, it is determined that the subject has been changed. Then, the value of D is made small. Conversely, the aperture 103
When the aperture is narrowed down, the depth of field becomes deeper,
Even if the current position of the focus lens 105 and the stored position in step 203 are slightly different, it is not determined that the subject is changed, and the photographer operates the switches 120 and 121 in FIG. 1 to obtain more focus. The value of D is increased so that

Further, in FIG. 4, the loci for maintaining the focus are dispersed on the tele side and concentrated on the wide side.
Therefore, the value of D is set to be small on the wide side and large on the tele side.

In step 207, the focus lens 1
The drive control is performed so that 05 follows the storage position in step 203, and the process returns to step 201.

In step 208, the focus lens 1
05 stops tracing the storage location in step 203 and returns to step 201.

As described above, in zooming in the tele direction in the manual focus mode, steps 201 and 20 are performed.
2, 204, 205, 206, and step 206
Then, if it is determined in step 203 that the subject is the same as the current subject, the processing in step 207 is repeated, and if it is determined that the subject has changed, the processing in step 208 is repeated. As a result, even in the manual focus mode, smooth zooming without extreme blurring is possible.

[0029]

As described above, according to the lens drive control apparatus of the present invention, the locus traced by the focus lens is stored while the magnification change from the tele side to the wide side is executed, and When performing zooming from the wide side to the tele side in the manual focus mode, the position of the previously stored focus lens is traced in reverse, so that a video camera such as a video camera having a rear focus type lens system can be used. The optical device enables zooming in the tele direction while maintaining focus in the manual focus mode, and at the same time, the subject is zoomed to the wide side at this time, and the subject when the moving path of the focus lens is stored It is possible to prevent the occurrence of extreme blur even when the difference is different from the above.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for controlling the operation of the embodiment.

FIG. 3 is a schematic diagram of a known rear focus lens system.

FIG. 4 is a characteristic curve diagram showing a positional relationship between a variable power lens and a focus lens.

FIG. 5 is a diagram showing a state in which a characteristic curve is divided into several areas and a representative speed of a focus lens is set.

[Explanation of symbols]

 102 variable magnification lens 105 focus lens 106 solid-state imaging device 107, 108 actuator 113, 115 encoder 119 control microcomputer 120, 121 focus switch

Claims (3)

[Claims] 1. A lens system including at least a lens that moves for zooming and a focus adjustment lens that moves for focus adjustment, a lens position detection means for detecting the position of each lens, and a drive for these lenses. Drive means for controlling the drive means for moving these lenses, and storage means for storing the movement locus of the focus adjustment lens during the zooming operation in the first direction. In the case where the zooming operation in the second direction, which is the opposite of the above, is performed by the control means so as to follow the movement locus stored by the focus adjusting lens in the storage means in the opposite direction. A lens system controller, wherein the control means prohibits the focus adjusting lens from following the stored movement trajectory when the focus adjustment lens is separated from the stored movement trajectory by a predetermined amount or more. 2. The lens system control device further has an aperture, and the predetermined amount is information about the aperture value of the aperture or the position of the lens operated for zooming, and the information is determined by both. The lens system control device according to claim 1. 3. The lens system controller further comprises electronic detection means for detecting the focus adjustment state of the lens system through the lens system, and in the automatic mode the focus adjustment lens operates the control means based on the output of the electronic detection means. 2. The lens system control device according to claim 1, wherein the position is adjusted via the lens system.