JPH0732483B2 - Focus correction device for color TV camera - Google Patents

Description

The present invention relates to a focus correction device for a color television camera having a zoom lens, and more particularly to a three-color separation type color television using a dichroic mirror or the like. The present invention relates to a focus correction device for a camera.

(Prior Art) Generally, in a color television camera, light for forming an object image is converted into red (R), green (G), and blue (B) light by color separation means such as a color separation prism having a dichroic mirror. It is configured to be separated into three colors, and the separated three-color images are formed on the image pickup surfaces of three image pickup elements such as an image pickup tube or an image pickup plate and converted into electric signals. . On the other hand, a zoom lens mounted in front of a three-color separation optical system such as the color separation prism has an exit pupil with an exit pupil so that color unevenness does not occur on the image surface due to the incident angle of light on the dichroic mirror surface. It is necessary to construct a telecentric optical system located at almost infinity.Generally, in order from the object side, a focusing lens group for focus adjustment, a variable magnification lens group for continuously changing the combined focal length, and a focal position. Is composed of four groups: a correction lens group for maintaining a constant value and an imaging lens group for forming an image on the imaging surface.

In the zoom lens having the above-described basic structure, the focusing lens group moves in the optical axis direction with respect to the other lens groups during focusing, and the zoom lens group is corrected during zooming. Since the lens groups move in the optical axis direction, the aberrations vary due to the relative movement of the lens groups. The fluctuation is that the zoom lens has a large aperture ratio,
It tends to increase as the zoom ratio increases, especially when there are large fluctuations in spherical aberration and field curvature, even if the fluctuations during zooming are corrected by the correction lens group, fluctuations in aberrations due to focusing are not corrected. , Remains as it is, and out of focus particularly at the telephoto end.

In order to be able to correct the focus error due to the above-mentioned aberration variation caused by zooming and focusing each time,
For example, another focus correction lens is added between the imaging lens group and the correction lens group, and the focus correction lens is configured to be movable in the optical axis direction (JP-A-58-205113).
In order to reduce the fluctuation of the above-mentioned aberration, for example, some of the lenses in the imaging lens group are configured to be displaced in the optical axis direction in accordance with zooming (Japanese Patent Publication No. 40-4014).
No. 4), the focusing lens group is divided into a front lens group and a rear lens group, and the air gap between them is changed according to focusing (Japanese Patent Laid-Open No. 58-7610). Has been done.

(Problems to be Solved by the Invention) However, in the method of correcting the focus error due to the aberration variation as described above, not only the number of lenses increases, but also the lens moving mechanism becomes complicated, and further described below. In order to correct the variation of chromatic aberration, it is necessary to increase the number of lenses having different dispersive powers. Therefore, it is difficult for a color television camera to have a large aperture ratio, a large zoom ratio, and a compact zoom lens.

FIG. 5 is a variation curve diagram of chromatic aberration with respect to change (zooming) of the focal length in the zoom lens. The figure shows the amount of chromatic aberration of red (R) and blue (B) with respect to green (G), and the red (R), green (G), and blue (B) light respectively changes according to the change in focal length. It shows that the aberrations are different. Further, as the focusing becomes closer, the amount of spherical aberration due to focusing and the amount of chromatic aberration of field curvature are added. However, since the number of lenses and the lens movement amount are limited, aberration correction on the lens side is also limited, and it is extremely difficult to correct the deviation of the focus position for each color due to the variation of aberration. In addition, as in Japanese Patent Laid-Open No. 58-205113, a method of adding a focus correction lens in front of the imaging lens group cannot focus for each color. Therefore, when variation in chromatic aberration is large,
There is a risk that color bleeding may appear, and the out-of-focus adjustment must be made each time, which makes the operation complicated.

The present invention solves the problem of out of focus due to aberration variation of the zoom lens in the conventional color television camera described above,
An object of the present invention is to provide a focus correction device that can obtain a clear image without complicating the configuration of the zoom lens and without focusing error and color blurring even with variation in aberration.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a focus position for detecting the position of a focusing lens group that is displaced when a zoom lens provided in a color television camera is in focus. A detection means, and a zoom position detection means for detecting the position of the zooming lens group that is displaced during zooming,
Based on the outputs of both the focus position detecting means and the zoom position detecting means and the information stored in advance, the shift amount of the focus position based on the aberration variation caused by the focusing and zooming is decomposed by the three-color separation optical system. An arithmetic circuit for arithmetically operating at least one of the colors and an image sensor position correcting means for correcting the positions of the three image sensors based on the arithmetic result of the arithmetic circuit are respectively provided in the optical axis direction. This is a means for solving the above problems.

(Function) The position of the focusing optical system (L ₁ ) which is displaced in the optical axis direction according to the object distance is detected by the focus position detecting means (11), and the detection signal thereof is sequentially calculated by the arithmetic circuit (13, 2).
It is output to 3). The position of the zoom optical system (L ₂ , L ₃ ) by zooming is detected by the zoom position detecting means (12), and the detection signal is also output to the arithmetic circuits (13, 23). The arithmetic circuit (13, 23) is preliminarily input with the aberration amount due to the color which varies depending on the object distance and the focal length of the zoom lens, and based on this, the focus position detecting means (11) and the zoom position detecting device. From the output from the means (12), the optimum position of the image pickup element according to focusing and zooming is calculated for at least one of the colors separated by the three-color separation optical system (P). The three image pickup devices (4 _R , 4 _G , 4 _B ) are respectively displaced to their optimum positions by the image pickup device position correction means (14, 24, 6, 26) which operates according to the calculation result, and the automatic correction is performed. Is done.

(Example) Next, the Example of this invention is described in detail based on an accompanying drawing.

FIG. 1 is a schematic configuration diagram of a focus correction device showing a first embodiment of the present invention, and FIG. 2 is a perspective view of an image pickup device moving device including a servo motor used in the focus correction device of FIG. Is.

In FIG. 1, in the zoom lens barrel 1, a zoom optical system and an image forming lens group including a focusing lens unit L ₁ , a variable power lens unit L ₂ and a correction lens unit L ₃ are arranged in this order from the object side.
L ₄ is provided, and the focusing lens unit L ₁ is moved in the optical axis direction by the focusing mechanism 2 including a drive motor (not shown). In addition, the variable power lens group L ₂ and the correction lens group
The zoom optical system including L ₃ is configured to relatively move in the optical axis direction by a zooming mechanism 3 including a drive motor (not shown). Imaging lens L ₄ are fixed to the lens barrel 1, cemented dichroic mirror layer mating surface via a 3-color separation prism P provided, the image pickup device 4 _B blue image
A green image is formed on the image pickup device 4 _G and a red image is formed on the image pickup device 4 _R. The three image sensors 4 _B , 4 _G and 4 _R are
Any In this embodiment also formed by the image pickup plate, the imaging surface is held in three imaging plate frame 5 _B so as to face the exit surface, 5 _G, 5 _R, respectively 3-color separation prism. Further, the servo motors M _B , M _G , and M _R are configured to move the respective image pickup plate frames 5 _B , 5 _G , and 5 _R in the optical axis direction via an image pickup plate moving mechanism 6 described in detail later. Has been done.

Imaging plate moving mechanism 6 is slidably fitted to and three-color divided into two fitting holes 5a provided in Figure 2 are shown as respective imaging plate frame _{5 G (5 B, 5 R} ) Two guide columns 7 that are provided in parallel with the optical axis and project from the exit window frame portion H _{a of} the prism housing H that houses the prism P, and the image pickup plate frame 5 _G (5 _B , 5 _R ).
Is driven to rotate by two compression coil springs 8 for urging the three color separation prisms P away from each other and a servo motor M _A (M _R , M _B ), and an image is taken against the urging force of the compression coil spring 8. It is composed of a cylindrical cam 9 that displaces the plate frame _5G ( _5B , _5R ) along the guide column 7.

The displacement of the focusing lens unit L ₁ by the focusing mechanism 2 shown in FIG. 1 is detected by the focus position detection device 11 including a potentiometer (not shown), and the detection signal is sent to the arithmetic circuit 13. Further, the displacement of the variable power lens unit L ₂ and the correction lens unit by the zooming mechanism 3, that is, the zoom position is detected by the zoom position detecting device 12 including another potentiometer (not shown), and the detection signal is also sent to the arithmetic circuit 13. To be

The amount of chromatic aberration according to zooming and the amount of variation of image plane curvature due to color as shown in FIG. 5 are input to the arithmetic circuit 13 in advance, and the spherical aberration and the color of image plane curvature according to focusing are input. Aberration variation amount and the like are input. This arithmetic circuit 13 uses the input focus position detection signal and zoom position detection signal to calculate the red, green,
The optimum position on the optical axis of each imaging plate 4 _R , 4 _G , 4 _B that captures each blue image is calculated, and the calculated signal is used as the servo circuit.
It is configured to send to 14. The servo circuit 14 drives each of the motors M _R , M _G , and M _B by the signal sent from the arithmetic circuit 13 and, at the same time, each position detector 15 _R , 15 _G , 15 including a potentiometer interlocked with each motor. _The servo circuit 14 detects the position signals of the image pickup plates 4 _R , 4 _G , and 4 _B detected by _B.
It is configured to be fed back to the servo control.

The focusing mechanism 2 is driven by a manual operation switch (not shown) or a control signal from an automatic distance measuring device, and the zooming mechanism 3 is controlled by a manual switch (not shown).

Since the first embodiment is configured as described above, when the focusing lens unit L ₁ is moved by the focusing mechanism 2 to perform focus adjustment, the object image formed through the zoom lenses L _{1 to} L ₄ is 3 The color separation prism P separates the three colors of red (R), green (G), and blue (B) and forms images on the image pickup surfaces of the image pickup plates 4 _R , 4 _G , and 4 _B , respectively. Further, the image magnification at that time is determined by the relative position between the variable power lens group L ₂ and the correction lens group L ₃ driven by the zooming mechanism 3. At that time, focusing lens group
The position of L ₁ , that is, the amount of displacement of the focusing mechanism 2 from the reference position is immediately detected by the focus position detection device 11, and the detection signal is sent to the arithmetic circuit 13. Also,
The zoom position detecting device 12 detects the zoom position due to the movement of the zoom system (zooming lens group consisting of L ₂ and L ₃ ), that is, the amount of displacement from the reference position of the zoom mechanism 3, and is sent to the arithmetic circuit 13.

The arithmetic circuit 13 is for each color (R, G, B) based on both detection signals sent from the focus position detection device 11 and the zoom position detection device 12 and the focal length (that is, zoom position) input in advance. Imaging for each color from the amount of aberration (mainly spherical aberration and curvature of field) and the amount of aberration (mainly spherical aberration and curvature of field) for each color (R, G, B) based on the focusing distance (that is, focus position) Calculate the position of the surface,
Servo motors M _R , M _G , M _B via the servo circuit 14 respectively
Drive control.

The cylindrical cam 9 is driven by driving the servo motors M _R , M _G , and M _B.
When (see FIG. 2) rotates, the image pickup plate frames 5 _R , 5 _G , which come into contact with the cylindrical cam 9 by the urging force of the compression coil spring 8,
5 _B slides along the guide column 7, and the imaging plate frame 5 _R , 5 _G , 5 _B
The positions of the image pickup plates 4 _R , 4 _G , and 4 _B , which are respectively held by, are finely adjusted. The positions of the image pickup plates 4 _R , 4 _G , and 4 _B , that is, the rotation amounts of the servo motors M _R , M _G , and M _B are the position detectors 15 _R and 1 _B , respectively.
The signals are detected by 5 _G and 15 _B , respectively, and the detection signals are sent to the servo circuit 14. As a result, the motors M _R , M _G , M _B
Servo control is performed, and each imaging plate 4 _R , 4 _G , 4 _B is an arithmetic circuit.
It is moved and fixed at the optimum position based on the value calculated by 13. Therefore, even if the chromatic aberration is large, or if the variation of the chromatic aberration is large due to focusing or zooming, a clear image is formed on each of the image pickup plates 4 _R , 4 _G , and 4 _B. There is no bleeding, and a clear image can be obtained, which is well corrected for field curvature. If the cam 9 is formed as a straight cam like a heart-shaped cam,
The initial setting (tracking) of the position of each image pickup plate also becomes easy.

The first embodiment described above is an example of the correction method when the variation of chromatic aberration is large not only during zooming but also during focusing. However, the variation of the chromatic aberration during focusing is so small that it can be ignored. In the case of 1, it is possible to share one servo motor for driving the image pickup plate.

FIG. 3 is a focus correction apparatus showing a second embodiment of the present invention in which three image pickup devices are moved by one drive motor and the position of the image pickup plate is corrected with respect to the aberration variation of the zoom lens. FIG. 4 is a perspective view of an image pickup element moving device including a drive motor. Parts having the same functions as those in FIG. 1 and FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 3, the image pickup plate frames 5 _R , 5 _G , and 5 _B , which respectively hold the three image pickup plates 4 _R , 4 _G , and 4 _B , move the image pickup plates driven by one servo motor M _C. Each of them is moved in the optical axis direction by the mechanism 26. The image pickup plate moving mechanism 26 is, as shown in FIG. 4, an image pickup plate frame that holds three image pickup plates 4 _G , 4 _R , and 4 _B.
In addition to 5 _G , 5 _R and 5 _B , the guide column 7 and the imaging plate frame 5 _G , 5 _R and 5 _B which are planted in the prism housing H, the imaging plate frame 5 _G The first cylindrical cam 29 _G for moving the second imaging cam frame 5 _R and the second cylindrical cam 2 for moving the imaging plate frame 5 _R
9 _R, and a third cylindrical cam 29 _B, and a common second cylindrical cam 29 _R and a third cylindrical cam in a first cylindrical cam 29 _G, which is rotated by a servo motor M _C for moving the image plate frame 5 _B It is composed of pulleys 30 _G , 30 _R and 30 _B and belts 31 _a and 31 _b for interlocking with each other. As the amount of movement of the other imaging plate frame 5 _R and 5 _B with respect to the movement amount of the imaging plate frame 5 _G is substantially equal to the amount of fluctuation of chromatic aberration of the red (R) and blue (B) for the green (G), and the pulley The diameters of 30 _G , 30 _R and 30 _B and the cam lifts of the cylindrical cams 29 _G , 29 _R and 29 _B are set to different values. In this case, the lens is constructed so that the fluctuations of red (R) and blue (B) with respect to green (G) due to focusing are extremely small and can be almost ignored. Therefore, only the fluctuation of chromatic aberration due to zooming is considered, and focusing is performed. For, only changes such as spherical aberration and curvature of field for green light are added to the changes in aberration caused by zooming,
It is calculated in the calculation circuit 13.

The electric signals sent from the focus position detection device 11 and the zoom position detection device 12 are red (R) in the arithmetic circuit 23,
A calculation process is performed for one color (green in the embodiment of FIG. 4) of green (G) and blue (B), and the optimum position of the image pickup plate 4 _G for that color is calculated. Further, a signal based on the calculation result is sent to the servo circuit 24. Servo circuit 24
Drives the servo motor M _C by the sent signal and at the same time detects the rotational position of the servo motor M _C by using the position detector 25 including a potentiometer, and feeds back the detection signal to the servo circuit 24 for servo control. Take control. The output of the servomotor M _{C is} the output of the first cylindrical cam 29 _G and the transmission mechanism 3
It is transmitted to the second cylindrical cam 29 _R and the third cylindrical cam 29 _B via 0 _G , 30 _R , 30 _B , 31 _a and 31 _b , whereby green (G),
The red (R) and blue (B) movement ratios are converted, and the image pickup plates 4 _G , 4 _R , and 4 _B are moved so that their image pickup surfaces coincide with the image forming surfaces of the zoom lens.

In the Figure 4, the pulley 30 _G for interlocking with each other the cam _{29 G, 29 R, 29 B} , 30 R, 30 B and the belt 31 _a,
I used 31 _b and, but it can be interlocked. Further, in the first embodiment shown in FIG. 1, when the ratio of aberration variation due to color is substantially equal in zooming and focusing, the cam 9 having a cam lift corresponding to the amount of aberration variation due to each color should be used. , the second embodiment and is calculated only deviation amount of the focal position due to the aberration fluctuation of color in the calculating circuit 13 in the same manner, the servo circuit 14 servo motors M _R, M _G, and M _B, the calculation circuit 13 The servo control may be performed according to the calculated value of.

〔The invention's effect〕

As described above, according to the present invention, the shift of the focus position due to each color due to the aberration variation caused by zooming and focusing is configured to be corrected by moving the image pickup surface of the image pickup element. It is possible to match the image plane for each color. Therefore, it is possible to reduce the adverse effect of aberrations caused by zooming and focusing on the image, and it is possible to obtain an extremely clear image without color blurring.

[Brief description of drawings]

1 is a configuration diagram showing a first embodiment of the present invention, FIG. 2 is a perspective view of an image pickup device moving apparatus used in the embodiment of FIG. 1,
FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG. 4 is a perspective view of an image pickup element moving device used in the embodiment of FIG.
FIG. 5 is a variation curve diagram showing the aberration at each focal length of the zoom lens. (Explanation of symbols of main parts) 1 ... Zoom lens barrel 2 ... Focusing mechanism 3 ... Zooming mechanism 4 _R , 4 _G , 4 _B ... Imaging plate (imaging device) 6, 26 ... Imaging plate moving mechanism (image sensor position correcting means) 14, 24 ...... servo circuit (image sensor position correcting _{means) M R, M G, M} B, M C ...... servomotor (image sensor position correcting means) 11 ...... focus position detection device (Focus position detection means) 12 ...... Zoom position detection device (zoom position detection means) 13, 23 ...... Calculation circuit L ₁ ...... Focusing lens group (focusing optical system) L ₂ ...... Variable lens group (zoom optical system) ) L ₃ ...... correction lens unit (zooming optical system) L ₄ ...... imaging lens group P ...... 3-color separation prism (3-color separating optical system) H ...... prism housing

Claims (3)

[Claims] 1. A color television camera having a zoom lens and three image pickup devices for picking up an image formed by the zoom lens via a three-color separation optical system, wherein the zoom lens is displaced during focusing. Focus position detecting means for detecting the position of the focusing lens group, zoom position detecting means for detecting the position of the zooming lens group which is displaced during zooming, and outputs of both the focus position detecting means and the zoom position detecting means. An arithmetic circuit for calculating a shift amount of a focus position based on variation of aberration due to focusing and zooming for at least one color separated by the three-color separation optical system based on previously stored information; Image capturing is performed by correcting the positions of the three image pickup devices in the optical axis direction based on the calculation result of the circuit. Focusing correction for a color television camera, characterized in that it comprises an element position correcting means. 2. The image pickup device position correcting means drives a cam mechanism (9) for moving the three image pickup devices (4 _R , 4 _G , 4 _B ) in the optical axis direction, and the cam mechanism. A servo motor (M _R , M _G , M _B ) and a servo circuit (14) for controlling each of the servo motors (M _R , M _G , M _B ) based on the calculation result of the calculation circuit (13). The focus correction device for a color television camera according to claim 1, wherein the focus correction device is included. 3. The image pickup device position correcting means displaces each of the three image pickup devices (4 _R , 4 _G , 4 _B ) at a ratio according to a predetermined chromatic aberration variation amount.
Image sensor moving mechanism (2 cams, 29 _R , 29 _G , 29 _B )
6) and driving the three cams (29 _R , 29 _G , 29 _B ) 1
A number of the servomotor (M _C), the scope of the claims, characterized in that it comprises a servo circuit (24) for the controlling of the servomotor (M _C) according to the result of the arithmetic circuit (23) A focus correction device for a color television camera according to item 1.