JP2877324B2 - TV camera optics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical system of a television camera, and more particularly to a method of correcting registration of a television camera using a solid-state imaging device.

(Prior Art) In a color television camera, a luminous flux of a photographic lens is separated into three colors of red, green, and blue by a color separation prism, and respective images are formed on an image sensor to obtain a color signal. .

In a color television camera, a zoom lens is generally used as a photographing lens. However, since the chromatic aberration of magnification changes due to zooming, focus, and aperture, the size of the image of each channel slightly changes. For this reason, a phenomenon in which the sizes of the three color images do not match and shift, that is, a so-called registration error occurs. In a conventional image pickup tube camera, a correction amount of registration is calculated from zoom, focus, and aperture value information, and the electron beam deflection of the image pickup tube is electrically controlled in accordance therewith to correct the chromatic aberration of magnification of the imaging lens. Dynamic registration correction could be performed.

However, in solid-state imaging devices that have been rapidly put into practical use in recent years, since the arrangement of the devices is determined geometrically, it is difficult to perform dynamic correction of registration as in the related art.
Therefore, since the chromatic aberration of magnification of the photographing lens appears on the TV screen as it is, a color shift occurs around the screen, resulting in deterioration of image quality.

For this reason, it is necessary for the solid-state imaging device camera lens to correct the chromatic aberration of magnification more than before, and expensive glass having anomalous partial dispersion is used, or the number of lenses is increased to increase the size.

(Means for Solving the Problem) The present invention relates to a method in which a color separation prism that separates a light beam emitted from an imaging lens system into a plurality of colors and a solid-state imaging device that is located on each of the color-separated image planes. A variable power unit in at least one channel, wherein the variable power unit includes a variable power lens formed of a transparent elastic body, or a movable lens unit that moves along the lens optical axis; The channel has a fixed optical member for making the optical path length equal to that of the one channel, and changes the magnification of the variable power unit based on information from the photographing lens system or information from the outside. Then, the chromatic aberration of magnification of the photographing lens system is corrected so that the sizes of the images on the respective solid-state image sensors substantially match.

(Embodiment) FIG. 1 is a schematic view of a first embodiment of the present invention, and FIG. 2 is a detailed view of a prism portion thereof.

In FIG. 1, reference numeral 1 denotes a photographing lens for forming an image of a subject on a solid-state image sensor, and a first group, 3 and 4, which are movable for focusing, move with the rotation of the cam 5 to change the magnification. A group, 6 is an aperture, and 7 is a master lens.

Reference numeral 12 denotes a color separation prism for separating the image forming light beam from the objective lens into three colors of blue, red, and green. Reference numeral 13 denotes a variable power unit provided for two channels, blue and red. 14
Denotes an image sensor holding unit for a reference green channel.
The imaging device 15 is fixed to 13 and 14 with an adhesive or a molten metal.

Reference numerals 8, 9, and 10 denote position detecting devices for a focus group, a zoom group, and an aperture, respectively, which are encoders or potentiometers. The outputs of 8, 9 and 10 are sent to the arithmetic unit 11,
The chromatic aberration of magnification unique to the lens is calculated from the focus information, zoom information, and aperture information, and a red / blue channel magnification correction signal is output.

This correction signal is sent to the variable magnification unit driving device 16 on the camera side. The driving device 16 drives the red / blue channel magnification unit according to the correction signal from the lens,
By changing the magnification by a predetermined amount, the chromatic aberration of magnification of the photographing lens 1 can be corrected, and an image with registered registration can be obtained.

FIG. 2 shows the prism part of FIG. 1 in detail.

The color separation prism includes a prism 12 having a dichroic film for spectral separation, and a trimming filter adhered to the exit surface of each prism. 17 is a blue trimming filter that allows only blue light, 18 is a red trimming filter that allows only red light, and 19 is a green trimming filter that allows only green light.

The light beam from the photographing lens 1 enters a color separation prism, is divided into three colors of blue, red, and green by a prism 12 and passes through trimming filters 17, 18, and 19, respectively.
Create a spectroscopic image on 15. At this time, if the photographing lens has chromatic aberration of magnification, the sizes of the three images that have been separated are different, so that the above-described registration error occurs.

The portions indicated by reference numerals 20 to 23 in FIG. 2 constitute the variable power unit 13. Reference numeral 20 denotes an outer frame fixed to a trimming filter or a prism base for stably holding the image pickup device 15 integrally with the color separation prism. Reference numerals 21 and 22 denote variable-power lenses, and reference numeral 22 denotes a cylindrical piezo element whose inner diameter can be changed by applying a voltage. Reference numeral 21 denotes an elastic lens formed of a transparent elastic material such as silicon rubber or ethylene propylene rubber. When no voltage is applied to the piezo element 22, the elastic lens 21 has almost no power. When a voltage is applied to the piezo element, the inner diameter of the cylinder changes. For example, when the inner diameter becomes smaller, the surface of the elastic lens 21 becomes a convex surface as shown by a dotted line in FIG. You will have power. With this effect, the magnification of one channel can be controlled independently.

Generally, a shift in the imaging position accompanies a change in magnification. There is no problem if this shift amount is within the depth of focus,
If the depth of focus is deviated, a tracking error occurs, so that it is necessary to correct it. 23 is a tracking correction member for that purpose, and the outer frame 20 and the imaging element 15 are piezo elements.
Connected via 23. 24 is an adhesive or a molten metal.

Since the correction of the registration only needs to correct the difference from one reference channel, in the present embodiment, the green channel is not provided with the refractive power variable action. For the green channel, a fixed outer frame 20 and a glass plate 25 are used. The glass plate 25 is for giving an optical path length equal to other channels.

 Next, the operation of FIG. 2 will be described.

Based on the magnification chromatic aberration correction signal transmitted from the arithmetic unit 11 of the photographing lens system, the variable magnification unit driving device 16 calculates the magnification correction amount of each channel, converts it into the applied voltage of the piezo element, and outputs it. Drive the piezo element.
The shift amount of the imaging position caused by the magnification correction is simultaneously calculated by the driving device 16 and applied to the piezo element 23 as a voltage corresponding to the tracking correction amount, and the expansion and contraction of the piezo element causes the imaging element 15 to shift the imaging position. Follow the shift.

By the above operation, the chromatic aberration of magnification of the photographing lens system is corrected, and a good registered image is obtained.

Note that the signal input to the driving device 16 does not need to be a signal from the taking lens system. May be information on the difference between the sizes of the images.

The function of varying the refractive power of the elastic lens is described in Japanese Patent Application Laid-Open No. Sho 60-144703. In addition, the refractive power variable lens includes not only an elastic lens but also a LiNbO ₃ crystal lens whose refractive index changes according to voltage, and refraction by laterally shifting two aspherical elements disclosed in Japanese Patent Publication No. 43-10034. An element or the like that changes in force can be used.

FIG. 3 shows a second embodiment of the present invention. Variable magnification unit 13
Only the configuration shown in FIG. 20 is an outer frame. Reference numeral 26 denotes a lens having a low refractive power, which is fixed to a cylindrical magnetic body 27.
The magnetic body 27 can slide inside the outer frame 20. 28 is a coil which acts as an electromagnet.

When a current is applied to the coil 28, the magnetic field changes in accordance with the amount of the current, so that the magnetic body 27 and the lens 26 move along the inner surface of the outer frame and change the magnification. The function of the piezo element 23 is the same as in the first embodiment.

In the case of the second embodiment, a glass plate is also used for the reference channel.
It is desirable to insert a lens similar to the lens 26 instead of 25.

As a means for moving the lens 26, a method of driving a cam or a helicoid screw with a motor is also possible.

In the above embodiment, the operation of the piezo element 23 has been described as the shift correction of the imaging position due to the magnification change, but it can be easily extended to the correction of the axial chromatic aberration caused by the focus and zoom of the photographing lens. Further, it goes without saying that the shift correction of the imaging position may be replaced not only with the piezo element but also with the drive of a motor or the like.

In the embodiment, the shift of the imaging position is corrected by moving the imaging device.However, the lens 26 is divided into a plurality of lenses, and the imaging position is kept constant while changing the magnification like a zoom lens. Is also possible. Further, the image forming position may be kept constant by simultaneously changing the center thickness of the elastic lens.

(Effects of the Invention) As described above, the present invention disperses the light into three colors by the color separation prism, and then arranges the variable power unit, and changes the magnification of each channel according to the chromatic aberration of magnification of the imaging lens system.
This is to dynamically correct the chromatic aberration of magnification of the taking lens system so that a television image with good registration can be obtained.

According to the present invention, each channel can be dynamically corrected independently, so that not only high-precision registration correction is possible, but also the photographing lens system requires expensive aberration correction because it can be corrected to the same degree as conventional. It is possible to realize a low-cost and high-performance television camera without using a TV or increasing the number of images.

[Brief description of the drawings]

FIG. 1 is a schematic view of a first embodiment of the present invention, and FIG. 2 is a detailed view of a prism portion thereof. In FIG. 1, 1 is a photographic lens system, 2 is a focus group, and 3 and 4.
Is a zoom group, 5 is a cam, 6 is an aperture, 7 is a master lens group, 8, 9, and 10 are focus, zoom, and aperture detection devices, 11 is an arithmetic unit, 12 is a prism, 13 is a zoom unit, 14 is a holding unit, 15 is an image sensor, and 16 is a driving device. 2, 17, 18, and 19 are trimming filters, 20 is an outer frame, 21 is an elastic lens, 22 and 23 are piezo elements, 24 is an adhesive, and 25 is a glass plate. FIG. 3 shows only one channel of the second embodiment of the present invention, wherein 26 is a lens, 27 is a magnetic material, and 28 is a coil.

Claims (1)

(57) [Claims] 1. A zoom lens system comprising: at least one channel between a color separation prism that separates a light beam emitted from a photographing lens system into a plurality of colors and a solid-state imaging device that is positioned on each of the color-separated image planes; A variable power unit formed of a transparent elastic body, or a movable lens unit that moves along the lens optical axis, and the other channel includes the one channel. And a fixed optical member for equalizing the optical path length, and changing the magnification of the variable power unit based on information from the photographing lens system or information from the outside, etc., and changing the magnification of the photographing lens system. An optical system for a television camera, wherein chromatic aberration is corrected to substantially match the size of an image on each of the solid-state imaging devices.