JPS62126777A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To improve a resolution without increasing the number of picture elements by moving in parallel a part of incident light on by every prescribed field with a positive optical element, and increasing spuriously the number of picture elements of a solid-state image pickup element. CONSTITUTION:Reflected light from an object D, after it is polarized in a prescribed direction at a polarization plate 12 through an objective lens 11, is made incident on a TN type liquid crystal 13. On the liquid crystal 13, the impression/non-impression of an AC driving voltage Vc is applied at every field period from a driving control circuit 16, and when impressed, only the ordinary ray of incident polarization light is transmitted, and in a non-impression time, a 90 deg. rotatory characteristic is generated, and only the extraordinary ray of the incident polarization light is transmitted. And on a solid-state image pickup element 15, an optical image moved with a 1/2 of picture element at every field is image-formed. At the element 15, a horizontal read pulse delayed by period of 1/2 of picture element is outputted from the circuit 16, and an image is controlled so as to be always positioned at the same position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a solid-state image device such as COD or MOS using solid me hydrogen atoms, and particularly to resolution improvement thereof.

[Technical background of the invention and its problems] In recent years, solid-state cameras have been used instead of image pickup tubes in imaging devices.
Table devices are increasingly being adopted. However, this solid ac
! CCD used for i1g, MO8W solid 11i
Although i-image elements have advantages over conventional image pickup tubes, such as a longer lifespan and less burn-in and afterimages, they capture video signals discretely, so they are subject to the Nyquist limit depending on the pixel sampling period. This has the drawback that signals exceeding 200 nm are reflected back to lower frequencies and become interfering signals, making it difficult to obtain high resolution. This drawback can be overcome by increasing the number of pixels, but of course there is a limit to increasing the density of semiconductor elements, and it cannot be said that the number of pixels of the solid-state image sensors manufactured to date is sufficient.

Therefore, various methods have been considered to improve the resolution while keeping the number of pixels of a solid-state 1 liter image element the same. As one method, as shown in FIG.
By moving the i-image element B by 1/2 of the pixel pitch for each field in the direction of the arrow in the figure using the piezoelectric element C, the folded signal described above is inverted for each field, and the sum of the two fields is A method has been proposed in which the resolution is improved by calculating the signal and pseudo-doubling the number of pixels. However, in this method, it is necessary to mechanically vibrate the electrically coupled solid-state dancing flA element B, which not only fails to provide sufficient reliability and durability, but also makes it vulnerable to external vibrations. , cameras with an integrated microphone have drawbacks such as the vibration of the image sensor B becoming noise that is picked up by the microphone.
Not very practical.

In addition, as another method, a prism-shaped electro-optical element is placed in the imaging optical system to move the optical image for each field, resulting in high resolution similar to the method shown in Figure 6. There is a method that aims to achieve this. However, since this method uses a prism-shaped electro-optic element between the imaging optical system and the image sensor, the angle of the imaging plane changes as the optical image moves. Since the spatial frequency characteristics between the two leads are different, the above-mentioned folded signal is not completely inverted, and as a result, the effect of increasing the resolution sufficiently is not diminished. In this method, in order to move the optical image without changing the spatial frequency characteristics, the electro-optic element must be placed on the Fourier plane of the imaging optical system, so only a special objective lens can be used.

"Purpose of the Invention" This invention was made to improve the above-mentioned problems, and it is possible to increase the number of pixels of a solid-state image element with a simple configuration and without selecting the type of imaging optical system. It is an object of the present invention to provide a solid-state image device that can improve resolution without reducing image quality.

[Summary of the Invention] That is, the solid silver image device according to the present invention is a solid silver image device according to the present invention.
An active optical element disposed between the element and an imaging optical system moves at least a portion of the incident light in parallel for each predetermined field, and moves the optical image without changing the spatial frequency characteristics of the optical image. Accordingly, the number of pixels of the solid-state imaging device is increased in a pseudo manner, thereby achieving high resolution without increasing the number of pixels of the imaging device.

[Embodiment 1 of the Invention Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

Figure 1 shows its configuration, in which 11 is an objective lens, 12 is a light plate, 13 is a TN type liquid crystal, 14 is a birefringent plate,
15 is a solid-state image sensor. These are each arranged at a predetermined interval perpendicular to a straight line (optical axis) C, and the incident light focused by the objective lens 11 is directed to the polarizing plate 12, T
N-type liquid crystal 13, solid state element 15 via birefringent plate 14
The light is irradiated onto the light-receiving surface of the Reference numeral 16 denotes a drive control circuit which sends an AC drive voltage VC to the TN type liquid crystal 14 and generates and outputs horizontal and vertical readout pulses Ph and Pv to the solid-state image element 11a. Above horizontal and vertical read pulse Ph
, Pv, the video signals of the solid-state waveform element 15 are taken out from the output terminal 18 via the buffer 17.

Here, the polarizing plate 12 deflects the incident light from the objective lens 11 in a predetermined direction. Above T\ type liquid crystal 13
has a non-optical rotation characteristic when an AC driving voltage VC is applied, and transmits only the ordinary incident polarized light, and the AC driving voltage V
When C is not applied, it has a 90° optical rotation characteristic and only the extraordinary light of the incident polarization is transmitted. The birefringent plate 14
has an optical axis m inclined with respect to the light-receiving surface, and the light passing through the TN liquid crystal 13 is divided into 1. /2 width, it divides the light into two parallel east lights: the ordinary light and the extraordinary light. That is, when a driving voltage is applied to the TN liquid crystal 13, only ordinary light passes through the birefringent plate 14, and when no driving voltage is applied, only extraordinary light passes through the birefringent plate 14.

That is, in the above configuration, the drive control circuit 16
AC drive vJ' for each field period for type liquid crystal 13
Application of FR pressure VC is switched between application and non-application, and solid 1
The output timing of the horizontal readout pulse ph to the al11 element 15 is switched to be delayed by a period corresponding to 1/2 pixel every field period.

Here, for example, the reflected light from the subject shown in the figure is T
When the AC drive voltage VC is applied to the N-type liquid crystal 13, only ordinary light passes through the liquid crystal 13, so birefringence tlii14
The light irradiated on takes the optical path shown by the solid line in the figure, and when no voltage is applied, only the extraordinary light passes through the liquid crystal 13, so the birefringent plate 14
The light irradiated on will take the optical path shown by the dotted line. In other words, the optical image formed on the solid-state ill element 15 is moved at a 1/2 pixel pitch for each field, and
Since the readout timing is also shifted by a period corresponding to 1/2 pixel, the image of the image output from the image element 15 is always at the same position. When we apply the pixel positions of the solid wi@filter 15 to this output image, as shown in Fig. 2, in the odd field, the position @a is indicated by the solid line, and in the even field, the position 1 is indicated by the Fli line.
It can be seen that b matches.

Therefore, according to the above configuration, since signals are captured in such a way as to interpolate the pixel position in each of the even and odd fields, the folded signal due to the frequency signal near the pixel repetition period is inverted, and the signal corresponding to two fields is inverted. In the added image, this aliasing signal disappears, and pixels with the same high resolution as captured with twice the number of pixels are obtained. Also, 2
Even if the signal is not raised or lowered by one field, the return signal will be in a flickering state, which will be caught by the human eye and will be noticeable, thereby providing the effect of higher resolution.

Another embodiment of the present invention will be briefly described with reference to FIGS. 3 to 5. However, in FIGS. 3 to 5, the same parts as the first leap are given the same reference numerals, and only the different parts will be described here.

FIG. 3 shows a configuration in which an optical half mirror is used in place of the polarizing plate 12. That is, the light incident on the objective lens 11 is irradiated onto the light receiving surface of the polarizing half mirror 19 via the birefringent plate 12 and the TN type liquid crystal 13. This polarizing half mirror 19 guides the incident light along the optical axis 2 to the first solid-state ML image element 15a, and also deflects a part of the light into the reflected optical axis Q- to the second solid-state image element 15b. It leads to The TN type liquid crystal 13 is switched υII for each field by the AC drive voltage VC from the drive control circuit 16, and the first and second solid state 11
i1 (1 element 15a, 15b has optical axis λ and anti!
II, l are provided to be shifted by 17'4 pixel pitch with respect to the optical axis λ-, and the vertical and horizontal read pulses Pv1. Phl, P v2
．． Reading is controlled by Ph2. 1st and 2nd
The solid 'iA @ Choko 15a.

The video signals read out from 15b are sent to adder 20.
After being incremented by 0, the signal is output from the output terminal 18 via the buffer 17.

In other words, in the above configuration, the incident light of the objective lens 11 is directed to the first and second solid bodies 11i by the birefringence plate 14.
1/4 of the horizontal pixel pitch of i-image elements 15a and 15b
The beam is separated into two parallel beams separated by a width of , that is, an ordinary beam and an extraordinary beam. At this time, the AC drive voltage VC is applied or not applied to the TN type liquid crystal 13 for each field. Therefore, the ordinary light and extraordinary light from the birefringent plate 14 are transmitted to the TN type liquid crystal 1.
3 and a polarizing half mirror 19, they are alternately guided to the first and second solid @oxygen atoms 15a and 15b every field. At this time, the image positions of the transmitted light and the reflected light of the polarizing half mirror 19 are shifted by 1/4 pixel pitch, and the positions are also switched every field. Further, the first and second solid-state image sensors 15a and 15b also have optical axes e and ρ.
Since it is shifted by 1/4 pixel pitch relative to -, the image is formed with interpolation shifted by 1/2 pixel pitch within one field, and further interpolated by shifted by 1/4 pixel pitch for each field. .

Therefore, according to the above configuration, the readout pulses Pvl, Pt+1, Pv are applied so that the positions of the optical images are all aligned with respect to the first and second solid-state image sensors 15a and 15b.
2. By shifting the output timing of Ph2, 1
An image corresponding to four times the number of pixels of one image sensor is obtained.

FIG. 4 shows a configuration using two liquid crystal elements oriented at an angle, and the incident light from the objective lens 11 is transmitted to the first and second liquid crystal elements 21. The solid-state imaging probe 15 is irradiated with the light through the solid-state imaging probe 22 . When the driving voltage Vc is not applied, the liquid crystal elements 21 and 22 divide the incident light into two parallel beams of ordinary light and extraordinary light, and when the driving voltage Vc is applied, all the components of the incident light are transmitted along the optical path of the ordinary light. Transmit. Here, in the first and second liquid crystal elements 21 and 22, the separation directions of ordinary light and extraordinary light are opposite when driving voltage VC is applied, and the separation distance is 1/2 pixel pitch in both cases. During the period corresponding to the odd field of the positive image element 15, the driving voltage Vc is applied to the first liquid crystal element 21, and the driving voltage Vc is applied to the second liquid crystal element 22.
is in an unapplied state. Conversely, during periods corresponding to even fields, the drive voltage is applied to the second liquid crystal element 22, and the first liquid crystal element 21 is in a non-applied state.

That is, in the above configuration, in an odd field, the incident light passes through the first liquid crystal element 21 and passes through the second liquid crystal element 2.
2, it is separated into ordinary light and extraordinary light. At this time, the ordinary light is imaged on the solid-state image sensor 15 along the optical path shown by the solid line in the figure, and the extraordinary light is imaged on the optical path shown by the broken line in the figure. In the even field, the incident light is separated into ordinary light and extraordinary light by the first liquid crystal element 21, and the ordinary light goes through the optical path shown by the solid line in the figure, and the extraordinary light goes through the optical path shown by the dashed-dotted line in the figure, respectively. An image is formed on the solid-state image sensor 15 via the probe 22 . In both fields, the incident light that should originally be focused at one point is
The image is formed at two points 1 pixel apart with a pitch of 7'2 pixels.

Therefore, according to the above configuration, an optical image having the same spatial frequency characteristic can be moved by 1/2 pixel pitch for each field, and by forming the image at two points, it can function as an optical low-pass filter. can be fulfilled at the same time.

FIG. 5 shows a configuration in which a birefringent plate having a separation width of 1/2 of the horizontal pixel pitch is used in place of the first liquid crystal element 21 in FIG. It is a board. A drive voltage VC is applied to the tilted liquid crystal probe 22 in odd fields, and is set to a non-applied state in even fields. That is, the objective lens 11
The incident light is split by the birefringent plate 23 into two parallel beams of ordinary light and extraordinary light, as shown by solid lines and broken lines in the figure. The separation distance is 1/2 pixel pitch. Since the drive voltage Vc is applied to the liquid crystal element 22 during the period corresponding to the odd field of the resistor 15, the ordinary light and the extraordinary light separated by the birefringence plate 23 are respectively transmitted to the liquid crystal element 22.
2 and is imaged on the solid-state '81 imaging element 15. In addition, in the period corresponding to the even field, the incident light is separated into ordinary light and extraordinary light by the birefringent plate 23, and then the ordinary light is separated by the optical path shown by the solid line in the figure by the liquid crystal element 22 in the state where the driving voltage Vc is not applied, and the extraordinary light is are respectively imaged on the solid-state imaging device 15 along optical paths indicated by dashed-dotted lines in the figure. In either field, incident light that should originally be focused on one point is focused on two points separated by a 1/2 pixel pitch. Therefore, according to the above configuration, effects similar to those of the device shown in FIG. 4 can be obtained.

In the above embodiments, all horizontal pixels are interpolated, but this can be similarly performed in the vertical direction or in the diagonal direction. Furthermore, instead of the liquid crystal described above, a crystal or ceramic having electro-optical properties may be used.

Roughly speaking, by combining the above embodiments and switching one field for each field and one field for every two fields, it is possible to achieve a much higher resolution.

[Effects of the Invention] According to the present invention, there is provided a solid-state imaging device that has a simple configuration, can improve resolution without selecting the type of imaging optical system, and without increasing the number of pixels of the solid-state II image element. can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the solid-state wIl device according to the present invention, FIG. 2 is a diagram for explaining the operation of the same embodiment, and FIGS. FIG. 6 is a diagram showing the configuration of a conventional solid-state imaging device. 11... Objective lens, 12... Polarizing plate, 13...
TN type liquid crystal, 14...birefringence plate, 15...solid l!
11@Element, 16... Drive control circuit, 11... Buffer, 18... Output terminal, 19... Polarizing half mirror 120... Screener, 21.22... Liquid crystal element, 2
3... Birefringent plate. Applicant's agent Patent attorney Takehiko Suzue Figure 4 Figure 5 Figure 6

Claims (5)

[Claims] (1) A solid-state image sensor section, an optical system that forms an optical image on the solid-state image sensor section, and a driving signal provided between the solid-state image sensor section and the optical system; an active optical element section that changes the position of the optical image while keeping the spatial frequency characteristics of the optical image constant by moving at least a part of the incident light from the optical system in parallel, and guides the optical image to the solid-state image sensor section; What is claimed is: 1. A solid-state imaging device comprising: control means for switching and deriving a drive signal for an active optical element section for each predetermined field. (2) The active optical element section includes a birefringent plate that separates the incident light from the optical system into two parallel beams of light separated by a certain width of ordinary light and extraordinary light according to the polarization direction, and a polarizing plate that transmits only either one of the birefringent plate and the polarizing plate, and a polarizing plate that transmits only one of the birefringent light and the polarizing plate that transmits the
2. The solid-state imaging device according to claim 1, further comprising an optical rotation element that changes between optical rotation and non-optical rotation. (3) The active optical element section includes a birefringent plate that separates the incident light from the optical system into two parallel light beams separated by a certain width, an ordinary light and an extraordinary light, according to the polarization direction, and a birefringent plate that separates the incident light from the optical system into two parallel light beams separated by a certain width, a polarizing half mirror that transmits one of them and reflects the other in a predetermined direction; and an optically rotating mirror that is disposed between the polarizing half mirror and the birefringent plate and that changes between 90° optical rotation and non-optical rotation according to the drive signal. the solid-state image sensor section includes a first and a second solid-state image sensor, the first solid-state image sensor is disposed at an imaging position of the transmitted light of the polarizing half mirror, 2. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is disposed at a position where the reflected light of the polarizing half mirror is imaged. (4) The active optical element section has a first state in which the incident light is separated into two light beams separated by a certain distance in the polarization direction, an ordinary light and an extraordinary light, according to a drive signal, and a first state in which all polarization components are the same as the ordinary light. comprising first and second electro-optical elements that are switched to a second state in which the light is transmitted through the optical path; The distances are made equal to each other, and the control means is configured such that when the first electro-optical element is in the first state, the second electro-optical element is in the second state, and the first electro-optical element is in the second state. 2. The solid-state imaging device according to claim 1, wherein the drive signal is switched and outputted so that the second electro-optical element is in the first state when the second electro-optical element is in the first state. (5) The active optical element section includes a birefringent plate that separates the incident light from the optical system into two light beams separated by a first distance in a first direction of ordinary light and extraordinary light; a first state in which the incident light is separated into two beams of ordinary light and extraordinary light separated by a distance twice the first distance in the same or opposite direction to the first direction; 2. The solid-state imaging device according to claim 1, further comprising an electro-optical element that can be switched to a second state in which all components are transmitted through the optical path of ordinary light in the first state.