JPH01130677A - Image pickup device - Google Patents

Abstract

PURPOSE:To remarkably reduce a residual reflected distortion by providing a means for changing a relative position relation between a solid-state image pickup element and an image forming lens system so as to shade the optical image of an object formed to the photoelectric transfer part of the solid-state image pickup element by the prescribed quantity. CONSTITUTION:After the image forming lens 4 is adjusted so as to form the optical image of the object 8 on the solid-state image pickup element 5 by the use of an optical finder 6, a focussing motor drive circuit 3 displaces the lens by a focussing adjusting motor 3 according to a signal from a control part 1 to shade the optical image by the prescribed quantity. Thereby, the reflected distortion is effectively reduce to easily generate a picture signal capable of obtaining the reproduced picture of high picture quality without using an expensive and optical low pass filter employing a birefringent material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an imaging device having a solid-state imaging device that generates an image signal corresponding to an optical image of a planar object.

(Prior Art) A photoelectric conversion section of a solid-state image sensor is constructed by disposing areas sensitive to light in a predetermined geometric arrangement.

The image signal generated by the solid-state image sensor is a sampled image of the subject.

By the way, when sampling images in a solid-state image sensor, 1
If the spatial frequency included in the image is higher than 1/2 of the sampling frequency fc in the solid-state image sensor, that is, higher than the Nyquist frequency, the frequency is higher than the Nyquist frequency fn in the spatial frequency of the image. It is well known that the component is aliased into a frequency range below the Nyquist frequency fn in the solid-state image sensor, causing aliasing distortion, and the aliasing distortion causes a large deterioration in image quality in the reproduced image.

Figure 3 shows a COD line as an example of an integrated image sensor.
This is the photosensitive part of the image sensor, and this photosensitive part has a rectangular shape.
This is an example in which the pixels are arranged in the main scanning direction at a pixel pitch of (1'/fc').

The photosensitive part of the COD line image sensor shown in FIG.
Since the sensitivity shape of one pixel is rectangular as shown on the right side of FIG. 3, M T F (Modulation T
transfer function) is M in Figure 4.
It is expressed by a curve as shown as TF characteristic.

Further, the envelope of sideband waves generated by the sampling operation is shown by the broken line in FIG. 4, and frequency components higher than the sampling frequency fc (sampling frequency) become aliasing distortion.

The above-described aliasing distortion will occur even if an ideal low-pass filter is used, as shown by the dashed line in FIG. 4, which exhibits ideal cutoff characteristics at the Nyquist frequency fn. The aliasing distortion (residual aliasing distortion) in the shaded area cannot be removed.

Therefore, an optical low-pass filter that can remove seven spatial frequency components higher than the sampling frequency fc (sampling frequency fc) that causes aliasing distortion is made using a birefringent material such as crystal, and it is connected to the subject. A diagonal shaped pixel as shown in FIG. 6 may be provided between the photoelectric conversion section of the solid-state image sensor, or in the photosensitive section of the photoelectric conversion section of the solid-state image sensor at a pixel pitch of (1/fc). The sensitivity shape of one pixel may be trapezoidal as shown on the right side of FIG. 6, or the solid-state image sensor itself may be arranged at a pixel pitch frequency In some cases, it has been made to wobble at the following frequencies.

(Problems to be Solved by the Invention) However, in the conventional solution using the optical low-pass filter described above, the characteristic of the optical low-pass filter has a comb-shaped passing characteristic as illustrated in FIG. However, since quartz is generally used as the birefringent material used to construct optical low-pass filters, There are limitations to the size that can make this possible due to cost, and there are also problems in that diagonal-shaped pixels as shown in Figure 6 are used in the photosensitive part of the photoelectric conversion part of the solid-state image sensor. If the pixels are arranged in the main scanning direction at a pixel pitch of (1;/fc), the aliasing distortion can be reduced as shown by the characteristic curve shown in Figure 7. A solid-state image sensor has a photosensitive area in which diagonal pixels are arranged in the main scanning direction at a pixel pitch of (1/fc), but it is difficult to manufacture it, and it is not effective in the sub-scanning direction. There is a problem in that, and furthermore, the solid-state image sensor itself is oscillated at a frequency higher than the pixel pitch frequency fc (
The problem with conventional means for causing wobbling is that the configuration of the device for implementing it is complicated.

(Means for Solving the Problems) The present invention provides an imaging apparatus having a solid-state image sensor that generates an image signal corresponding to an optical image of a planar object. means for forming an optical image of a more planar object on the photoelectric conversion section of the solid-state image sensor in an imaging lens system provided between the two; Change the relative positional relationship between the flat object, the solid-state image sensor, and the imaging lens system so that the optical image of the flat object formed on the photoelectric conversion unit is blurred by a predetermined amount. The present invention provides an imaging device comprising means for controlling the image.

(Example) Hereinafter, specific contents of the imaging device of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram of one embodiment of the imaging device of the present invention.

In Fig. 1, 1 is a control unit, 2 is a focus motor drive circuit, 3 is a focus adjustment motor, and 4 is a control unit.
5 is an imaging lens system, 5 is a solid-state image sensor, 6 is an optical finder, 7 is a reflecting mirror (mirror), 8 is a planar object, and 9 is a light source.

In the imaging device shown in FIG. 11, the light corresponding to the optical image of the planar object 8 irradiated with light from the light source 9 is
The light enters a photoelectric conversion section in a line image sensor 5 used as a solid-state image sensor 5 via an imaging lens system 4 .

During the initial focus adjustment by the operator, the optical path between the output side of the imaging lens system 4 and the photoelectric conversion section of the line image sensor 5 used as the solid-state image sensor 5 is as shown in FIG. A reflecting mirror 7 as shown by dotted lines is inserted therein so that light corresponding to the optical image of the object is incident on the optical finder 6 via the reflecting mirror 7.

The optical finder 6 described above is configured such that the distance between the planar object 8 and the imaging plane of the optical image of the object on the optical finder is such that the distance between the planar object 8 and the imaging surface of the optical image of the object on the solid-state image sensor 5 is the same as that of the optical finder 6 . The operator adjusts the imaging lens system 4 so that the optical image of the planar object 8 is projected most clearly on the optical viewfinder 6. When this is done, an optical image of the planar object 8 can be formed on the imaging plane of the photoelectric conversion section in the solid-state image sensor 5.

As described above, after adjusting the imaging lens system 4 using the optical finder 6 so that the optical image of the subject 8 is focused on the imaging plane of the photoelectric conversion section in the solid-state image sensor 5, the control When a start button (not shown) provided in the unit 1 is operated, the reflecting mirror 7 is moved between the exit side of the imaging lens system 4 and the line used as the solid-state image sensor 5 by a mechanism (not shown). It is removed from the optical path between the image sensor 5 and the photoelectric conversion section, and at the same time, the focus motor drive circuit 2 is supplied with drive power to the focus adjustment motor 3 by a signal from the control section 1, and the focus adjustment motor 3 drives the imaging lens. The lens of the system 4 is displaced so that the optical image of the planar object 8 in the photoelectric conversion section of the line image sensor 5 used as the solid-state image sensor 5 is blurred by a predetermined amount. Make it. The displacement of the lens of the imaging lens system 4 by the focus adjustment motor 3 described above may be the entire displacement of the imaging lens system, or the displacement of a part of the lenses of the imaging lens system.

As mentioned above, after the optical image of the planar object 8 in the photoelectric conversion section of the line image sensor 5 used as the solid-state image sensor 5 is blurred by a predetermined amount, the control section 1 Depending on the output signal,
A drive mechanism (not shown) causes the line image sensor 5, which is used as the solid-state imaging probe 5, to
Sub-scanning is started in the direction of arrow 10 indicated by - in the figure.

FIG. 2 is a characteristic curve showing the residual aliasing distortion in the imaging device of the present invention as described above, and the residual aliasing distortion shown in FIG. 2 and the residual aliasing distortion in the conventional example described above It is clear that the amount of residual aliasing distortion in the imaging apparatus of the present invention is greatly reduced compared to the conventional example.

In the embodiment shown in FIG. 1 described above, a line image sensor (CCD line sensor) is used as the solid-state image sensor 5, and the arrow 10 in the first middle is In addition, the initial focus adjustment is performed manually by the operator while observing the state of the optical image of the subject in the optical eyeliner 6. , the planar object 8 is shown to be a light-transmitting object; however, in carrying out the present invention, a two-dimensional image sensor may be used as the solid-state image sensor 5; The focus adjustment may be performed by autofocus↓, and furthermore, the planar object may be a light-reflecting object.

In addition, in the description of the above embodiment, the optical image of the subject 8 is formed on the imaging plane of the photoelectric conversion unit in the solid-state image sensor 5 using the optical finder 6 by the initial focus adjustment by the operator. After the imaging lens system 4 is adjusted so that the light i%! of the line image sensor 5 used as the solid-state image sensor 5 described above is In order to make the optical image of the planar object 8 in the conversion section blurred by a predetermined amount, the focus motor drive circuit 2 is activated by a signal from the control section 1.
Drive power is supplied to the dregs adjustment motor 3, and the lens of the imaging lens system 4 is displaced by the focus adjustment motor 3, so that the photoelectric conversion section of the line image sensor 5 used as the solid-state image sensor 5 described above is Although the optical image of the planar object 8 is blurred by a predetermined amount, the optical image of the planar object 8 in the photoelectric conversion section of the line image sensor 5 used as the solid-state image sensor 5 is To make the optical image blurred by a predetermined amount, for example, one or both of the subject 8 and the solid-state imaging element 5 may be displaced in the optical axis direction, and the solid-state imaging element 5 may be The optical image of the planar object 8 in the photoelectric conversion section of the line image sensor 5 used may be blurred by a predetermined amount.

Furthermore, when the optical image of the planar object 8 in the photoelectric conversion section of the solid-state image sensor is blurred by a predetermined amount as described above, the reproduction that is reproduced by the image signal output from the solid-state image sensor 5 is also performed. The resolution of the image is determined by the solid-state image sensor 5.
A reproduced image in a state where the resolution is lower than the resolution of the reproduced image reproduced by the image signal output from the solid-state image sensor 5 before the optical image of the planar object 8 in the photoelectric conversion unit is blurred by a predetermined amount. However, when the optical image of the planar object 8 in the photoelectric conversion section of the solid-state image sensor 5 is blurred by a predetermined amount as described above, the image signal output from the solid-state image sensor 5 is reproduced. If a solid-state image sensor 5 having a number of pixels that provides a sufficient resolution of the reproduced image is used, the decrease in the resolution of the reproduced image due to the causes described above will not be a problem.

Note that the deterioration of image quality due to a large drop in MTF within the Nyquist limit in the characteristic curve example diagram showing residual aliasing distortion in the imaging device of the present invention illustrated in FIG. 2 also occurs when the resolution of the reproduced image is sufficient. If a solid-state imaging probe 5 having the number of pixels is used, no problem will arise.

(Effects of the Invention) As is clear from the above detailed explanation, an imaging device of the present invention is an imaging device having a solid-state image sensor that generates an image signal corresponding to an optical image of a planar object. means for forming an optical image of the planar object on the photoelectric conversion section of the solid-state image sensor by means of an imaging lens system provided between the object and the photoelectric conversion section of the solid-state image sensor; The planar object, the solid-state image sensor, and the imaging lens system are arranged so that the optical image of the planar object, which is imaged by the imaging lens system on the photoelectric conversion section of the solid-state image sensor, is blurred by a predetermined amount. and a means for changing the relative positional relationship between the imaging device and the imaging device of the present invention. It is possible to provide an inexpensive device that can easily generate an image signal that can be effectively reduced to obtain a high-quality reproduced image. By setting the appropriate settings, it is possible to easily generate both image signals in a state that provides the optimum reproduced image for each subject.1 According to the present invention, the above-mentioned conventional problems can be easily generated. can be solved well.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the imaging device of the present invention,
FIG. 2, FIG. 4, FIG. 5, and FIG. 7 are characteristic curve examples, and FIG. 3 and FIG. 6 are plan views of the photosensitive portion of a conventional solid-state image sensor. DESCRIPTION OF SYMBOLS 1... Control part, 2... Focus motor drive circuit, 3... Focus adjustment motor, 4...
Imaging lens system, 5... Solid-state imaging device, 6... Optical finder, 7... Reflecting mirror (mirror), 8... Planar object. 9...Light source.

Claims (1)

[Claims] In an imaging device having a solid-state image sensor that generates an image signal corresponding to an optical image of a planar object, an imaging lens system installed between the planar object and the photoelectric conversion section of the solid-state image sensor generates an image signal corresponding to an optical image of a planar object. means for forming an optical image of a subject on a photoelectric conversion section of a solid-state image sensor; and an optical image of a planar object formed on the photoelectric conversion section of the solid-state image sensor by the above-described imaging lens system. An imaging device comprising means for changing the relative positional relationship between a planar object, a solid-state imaging device, and an imaging lens system so that the object is blurred by a predetermined amount.