JPS6091774A - Zoom lens for solid-state image pickup camera - Google Patents

Abstract

PURPOSE:To improve the resolution of a camera utilizing a solid-state image pickup element by shifting a lens in a master system of a zoom lens to an optical axis so as to obtain a fixed picture element registration independently of the variable power operation of the zoom lens. CONSTITUTION:After a picture signal obtained from an image pickup element in response to the timing is amplified and AD-converted before and after the shift of the lens 11, the signal is stored in a frame memory 15. A memory control 16 performs also address control before and after the lens shift so that the picture signal is stored in the frame memory 15 in an arranged form. That is, in storing the signal in the picture signal memory 15 before the lens shift, addresses are skipped at the interval of one each and the picture signal after the shift is written in the addresses skipped at the interval of one each. When signals for one synthesized pattern's share is stored in the frame memory 15 in this way, a read signal is given by the control 16 and one pattern signal with high resolution synthesized in the frame memory 15 is DA-converted and outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens that can improve the resolution of a camera using a solid-state image sensor.

In a camera using a so-called solid-state image pickup device combined with a charge transfer device such as ``AaD'' and a microscopic light-receiving device arranged in an IJ array, there are certain limitations. However, a method of spatial pixel shifting is known as an attempt to overcome these limitations and improve resolution. For example, in order to improve the resolution in the horizontal direction of the screen, the image formed by the objective lens is laterally shifted by 1/2 pitch of the horizontal pitch of the light-receiving element array on the photocathode of the image sensor, that is, the pixel array. This is a method to obtain one screen by combining the image signal outputs of. In order to perform such spatial pixel shifting, a configuration is required to allow relative movement between the image formed by the objective lens and the photocathode of the image sensor.
In the conventional method, an optical wedge is moved in and out of the front surface of the objective lens (υ), or a galvanometer mirror is placed at the same position and swung. However, in this method, the amount of image movement on the imaging plane differs depending on the focal length of the objective lens, that is, the image magnification, so it is necessary to replace the optical rust depending on the focal length of the objective lens, or change the vibration of the galvano mirror. This will involve the hassle of resetting the angle.

In particular, assuming a zoom lens, which has been frequently used as an objective lens in recent years, changing the amount of pixel shift each time the magnification is changed increases the complexity of the structure and is also disadvantageous in terms of reliability.

On the other hand, if a pixel shifting element such as an optical wedge is placed between the objective lens and the solid-state image sensor, there is no need to adjust the amount of pixel shifting due to zooming. Mechanical space is required between the camera element and the back focus of the objective lens is inevitably extended, and the aperture of the rear lens becomes larger, which reduces the weight of the camera.
This will hinder compactness.

The present invention has been made in view of the above circumstances, and provides a zoom lens that is advantageous for increasing the resolution of solid-state imaging cameras.

For this reason, in the present invention, at least one lens in the master system of the zoom lens is shifted with respect to the optical axis so that a constant pixel shift amount is obtained regardless of the zoom lens's magnification changing operation. It is composed of

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, and this zoom lens consists of a so-called zoom magnification variable section 1 and a master section 2. As shown in FIG. Note that 3 indicates a solid-state image sensor arranged on the imaging plane.

Reference numeral 4 denotes a lens in the master section 2, which is a shift lens supported so as to be movable in a plane perpendicular to the optical axis 0, for example in the direction of the arrow x in the figure, for spatial picture element shifting. Reference numeral 5 is a magnetostrictive element made of pure nickel, Alfer, etc., and mechanical distortion is generated by applying a magnetic field. Since one end of this magnetostrictive element is closely fixed to the shift lens 4, its distortion and deformation causes the shift lens 4 to move in the direction of arrow will shift laterally depending on the amount of shift of the lens 4. In addition, in order to give a shift movement to the lens 4, it is also possible to use an electrostrictive vibrator or a combination of a motor and a cam to change the rotation by 1JhK in linear movement.

In performing the above-mentioned pixel shifting, it is also possible to shift the lens in the variable magnification section 1 in FIG. This is not a good idea because the relationship between the two will change depending on the magnification. In this respect, in the master section 2 and later, the angle of the ray toward each point on the imaging plane is determined independently regardless of the magnification change, so a constant amount of image can be produced by a constant amount of lens shift regardless of the magnification change. I can only do it naturally. Of course, the same effect can be obtained by shifting the entire master section 2, although it can be said that this is disadvantageous in terms of the moving mechanism.

Note that in the case of a zoom lens with the lens configuration shown, it is advantageous to shift the lens 4. This is because, in the case of lens 4, for example, a shift of about 8 μ is sufficient to shift the friction surface by about 7 μ. When shifting other lenses even if they are in the master section 2, the amount of lens shift becomes larger than the required amount of image plane shift, which is somewhat disadvantageous due to the structure of the moving mechanism section. Become.

Of course, the amount of image plane shift is first determined by the pixel array pitch or pixel shifting direction on the photocathode of the image sensor, and the setting of the sampling position of the image signal. The amount by which the lens is shifted depends on the optical design.

FIG. 2 shows the system configuration of the lens shift stopper. In FIG. 2, reference numeral 10 denotes a clock pulse generation section, a shift drive section 12 for shifting the shift lens 11, a scan drive section 14 for driving the solid-state image sensor 13,
Frame memory! A clock pulse is applied to the memory control unit 16 which controls the operation of the memory controller 5. The operations of each of the above-mentioned drive sections 12, 14 or memory control section 16 must be mutually synchronized in advance, and their respective operation timings are adjusted based on clock pulses. Further, 11 is an amplifier that amplifies the image signal from the solid-state image sensor 13, a 181 dAD converter, and 19 is a DA converter.
Compartateal.

According to the above system configuration, before and after the lens 11 is shifted, the image signal obtained from the image sensor 13 according to the timing is amplified and AD converted, and then stored in the frame memory 15. Memory control 1
6 also performs address control so that the image signal is stored in the frame memory 15 in an organized form before and after the lens shift.

That is, when storing the image signal before the lens shift in the memory 15, every other address is skipped, and the image signal after the shift is stored at every other skipped address.
Becomes absorbed in it. When the signals for one composite screen are stored in the frame memory 15 in this way, the control 1
A readout signal is given by 6, and the high-resolution one-screen signal synthesized within the frame memory 15 is DA-converted and output.

Note that the picture element shifting method of the present invention is effective not only for still images but also for capturing movie images. In this case, for example, a magnetostrictive A5 element may be driven at high frequency to shift the lens. Furthermore, the image signal may be sampled not only before and after the pixel shifting operation, but also three or more times during one pixel shifting cycle.

As described above, according to the present invention, the spatial picture element shifting method is achieved by shifting the lens in the master section of the zoom lens, so that images that are not affected by zooming can be realized. Not only is it possible to do it without a scratch, but it is also very lightweight and compact.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical system showing an embodiment of the present invention. FIG. 2 is a block diagram showing an example of a control system configuration applied to the present invention. 1... variable magnification section 2. old... master section 3...
...Solid-state image sensor 4...Shift lens 5.
...Magnetostrictive element 10...Clock pulse generation section 12...Shift drive section 14...Scan drive section 15...Frame memory 16...Memory control section Applicant: Fuji Photo Co., Ltd. company

Claims (1)

[Claims] In a zoom lens for a solid-state imaging camera that has a variable magnification system and a master system and forms a subject image on the photocathode of a solid-state imaging device, at least one lens constituting the mask system is attached to the solid-state imaging device. A zoom lens for a solid-state imaging camera, characterized in that a subject imaging position on the photocathode is displaced by shifting in a direction perpendicular to the optical axis in synchronization with driving.