JPS6027279A - Picture reading method - Google Patents

Abstract

PURPOSE:To simplify the constitution and reduce noise components by providing a focus deflecting element in an optical system in the picture reading method of a solid-state image pickup element. CONSTITUTION:An image pickup part 2 consists of an optical system 6 provided in the front end part of a lens barrel 4 and a CCD 8 arranged in the focusing surface of the optical system 6, and the optical system 6 consists of a taking lens 10, which focuses an object, and a transparent parallel plane plate 12 which deflects the focus position. This parallel plane plate 12 is rotated interruptedly, and the image focused on the CCD 8 is rotated by an eccentric quantity of about a half of the picture element pitch, and the image is read when the CCD 8 comes to upper, lower, left, and right parts, thereby obtaining the number of sampling picture element equivalent to a high-density zigzag arrangement.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an image reading method, and more particularly to an image reading method of a solid-state image pickup device in which photosensitive portions are arranged at intervals.

Background technology Solid-state imaging devices such as MO8 type image sensors and CCDs are
A large number of photosensitive parts (photodiodes, etc.) corresponding to one pixel are arranged in a grid or staggered pattern (referred to as "pixel shifting" or "honeycomb"). Between the photosensitive parts,
A non-photosensitive part such as a channel stopper 9 to prevent carriers in the photodiode from leaking to neighboring areas, a signal line for readout, or a vertical transfer CCD (V-CCD) is provided. A CCD requires approximately the same width as the photosensitive section, and therefore, the effective pixel area is about 40 to 70% of the pixel area seen at one pitch interval. Therefore, if this solid-state image sensor is used as is, each part of the image can only be read intermittently, and there is a limit to the resolution.

Comparing lattice-like and staggered pixel arrays, even if the number of pixels is the same, the zigzag arrangement has a higher resolution in the horizontal direction, and conversely, the resolution in the diagonal direction has a higher resolution in the lattice arrangement. Considering the visual characteristics of humans, it can be said that the resolution of the staggered arrangement is superior overall. However, the staggered arrangement requires more advanced technology in manufacturing the de-guises, and is likely to result in higher costs.

Therefore, conventional methods have been considered in which pixels are arranged in a grid pattern at high density and as much of the image as possible is read as information. However, increasing the pixel density means making the mask and turns of the IC much smaller in manufacturing the image sensor, which is technically difficult and reduces the yield. Therefore, the cost has to be high.

A method has been proposed in which the image formed by an optical system is read while moving relative to a solid-state image sensor, and the image density is increased isometrically. This method is performed, for example, by inserting a mirror into the optical system, vibrating the mirror to deflect the optical path, or mechanically moving the solid-state image sensor or the optical system back and forth or in the XY directions. ing. However, this method uses mechanical vibrations to perform relative motion, so the device is complicated and large.
This method has the disadvantage that mechanical play is likely to occur and the resolution deteriorates over time.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an image reading method that eliminates the drawbacks of the above-mentioned prior art, can read images at high resolution with a simple configuration, and has few noise components.

DISCLOSURE OF THE INVENTION According to the present invention, an image formed through an optical system is separated into pixels and read by a solid-state image sensor comprising a large number of photosensitive parts arranged vertically and horizontally at intervals. In the reading method, an imaging deflection element is provided in the optical system, and this imaging deflection element is rotated to cause the image on the solid-state image sensor to move circularly with an eccentricity amount of about A of the pixel pitch. This involves reading the image using a solid-state image sensor when it appears on the top, bottom, left, or right.

Next, embodiments of the image reading method according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an example of an imaging section and circuit blocks of a television camera configured based on the image reading method according to the present invention. In the figure, the imaging section 2 is comprised of a CCD 8 placed on the imaging plane of an optical system 6 provided at the front end inside the lens barrel 4. The optical system 6 is composed of a taking lens io which forms an image of a subject (see FIG. 3) 28, and a transparent parallel plane plate 12 which shifts the position of the image. The taking lens 10 is fitted into a ring 14 that is rotatably screwed onto the tip of the lens barrel 4. By rotating the ring 14 and moving it forward and backward, the taking lens 10 can focus on the CCD 8. It has become. The parallel plane plate 12 is inserted obliquely to the optical axis C between the taking lens IO and the CCD 8. This parallel plane plate can be rotated about the optical axis C by the operation of the rotation mechanism 16. This rotation mechanism 1G includes a cylinder 20 that grips a parallel plane plate 12 and is rotatably supported in the lens barrel 4 by a bearing 18, and a stepping motor 24 that rotationally drives the cylinder 20 via a belt 22. It consists of This stepping motor 24c rotates intermittently at a constant speed to intermittently rotate the parallel plane plate 12 about the optical axis.
It has a function of circularly moving the image formed on the CCD S by a predetermined amount of eccentricity.

Here, to explain in detail the action of the parallel plane plate 12, as shown in FIG. d(x--!-) where d: Thickness of the semi-linear plane plate n: Has the function of shifting the refractive index of the parallel plane plate to the rear point P2. As shown in FIG. 3, when the optical system is composed of only the taking lens lO and there is no parallel plane plate 12, the light emitted from the object AB passes through the path shown by the two-dot chain line and reaches the plane Ll A'B' Assuming that the parallel plane plate 12 is to be imaged as the taking lens 1
When inserted behind 0 with the normal direction inclined by θ with respect to the optical axis C, the light emitted from the object AB passes through the path shown by the solid line from the image A'B' in the normal direction of the parallel plane plate 12. An image A″B″ is formed at the point where the object moves a distance of . Image plane L2
By arranging the CCD 8, it becomes possible to read the image. The amount of deviation e in the direction perpendicular to the optical axis C of A//B'' with respect to A/B/ is determined by referring to Fig. 4. becomes. The eccentricity e is determined by the CCD8 as shown by diagonal lines in FIG.
Photosensitive sections 30A and 30B are arranged in a grid pattern vertically and horizontally.
, . . , 32 A, 32 B, . for example,
Refractive index n = 1.5, thickness d = 2na of the parallel plane plate 12
, θ-1°, e = 12 fim, which is about half the pixel pitch of a normal solid-state image sensor.

When the rotation mechanism 16 is operated in this state and the parallel plane plate 12 is rotated around the optical axis C, the direction of deviation of the image A''B'' changes on the facing surface 2, and e is increased by the amount of eccentricity. The parallel plane plate 12 is intermittently rotated in a clockwise direction every 1/4 rotation when the image is vertically and horizontally moved on the CCD B. For example, the photosensitive section shown in FIG. The partial image 44B that was on 32B is 44B → 44B → 44B →
It moves intermittently in a circular motion with an eccentricity of 44B0 and the pixel pitch. In addition, to simplify the diagram, the pixels of the image are shown as circles.

For ease of understanding, if we fix the image and move the CCD 8 intermittently in a circular motion, when the CCD 8 is relatively upward, the partial pixels 4OA, 40B, 4 of the odd line
0C,..., 44A, 44B.

44C2...Photosensitive sections 30A and 30B at each stage above.

30C1..., 32A, 32B, 32C,... are located (see diagram (1) in FIG. 6). When the image is rotated by 1/4 and the CCD 8 is located relatively to the left, even-numbered line partial pixels 42B, 42C, . . . , 46B.

46 C, ... photosensitive parts 30 A, 30 B on top
, . . . , 32A, 32B, . . . are located (see diagram (2) in FIG. 6). The image rotates 1/4 again COD
8 is relatively lower, partial pixels 44A, 44B, . . . , 48A of odd-numbered lines below the third line.

48B, . . . on top of the photosensitive sections 30A, 30B, . . .
32A, 32B, etc. are located (see diagram (3) in FIG. 6). When the CCD 8 is located relatively to the left after a further 1/4 rotation, the partial pixel 42A of the even line.

42B, ..., 46A, 46B, ... photosensitive section 3 on top
0 A, 30 B, -..., 32 A, 32
B, ... is located (see diagram (4) in Figure 6),
When the image is further rotated by 1/4, the above-mentioned figure 6 (1)
Return to state.

Therefore, if you read an image when the CCD 8 moves up, down, left, or right, the lines will be shifted every 1/4 rotation and the partial image will be scanned one line at a time. The number of pixels for horizontal and vertical sampling can be made equivalent to a staggered arrangement, and the number of pixels for horizontal and vertical sampling can be made equivalent to a staggered arrangement. Interlace scanning can be performed. For example, in the case of an NTSC television, the number of scanning lines corresponding to the actual screen in the vertical direction is approximately 480. Considering interlace, the number of vertical pixels of CCD 8 may be half, 240, and in the horizontal direction. The same applies to

Also, for example, if we pay attention to the third line, when the CCD 8 is located at the top and bottom, the photosensitive portions 32A respectively.

32B, . . . and 3OA, 30B, . . . alternately inject partial images 44A, 44B, . will be reduced by 3 dB.

A motor drive control circuit 50 is connected to the stepping motor 24 of the rotation mechanism 16 . This motor drive control circuit 50 rotates the stepping motor 24 in synchronization with a vertical synchronization signal sent from a synchronization signal generator (SSG) 52 for double interlace scanning of the television camera, and rotates the stepping motor 24 every one field period of the television. The parallel plane plate 12 is intermittently rotated by 1/4 rotation. In the NTSC system, one frame consists of two fields and the frame frequency is 30 Hz, so the parallel plane plate 12 has a frequency of 15
It is sufficient to rotate intermittently at a speed of rps. On the other hand, CCD8
A clock generator 54 for reading is connected to. This clock generator 54 reads out each pixel information of the CCD 8 field by field in synchronization with the vertical and horizontal synchronizing signals sent from the synchronizing signal generator 52.

To explain in more detail, when the CCD 8 is of an interline transfer type, for example, each photosensitive section 30A, 30 is
B,..., 32A, 32B.

. . , all the pixel information accumulated in the V
- Move to COD and perform vertical transfer and horizontal transfer according to the clock pulse sent from the clock generator 54,
A signal is taken out in series from the output section 55. At this time, the 6th
Assuming that figures (1) to (4) in the figure are the first to fourth fields, respectively, in the second field (fourth field), the A pixel pitch rear approach (
The readout from COD 8 is delayed (advanced) by the bar pixel pitch in order to capture the partial pixels (front), and in the third field, the readout from COD 8 is delayed (advanced) by the bar pixel pitch to capture the partial pixels two rows below.
By delaying the readout of the image by one horizontal scanning period (IH), the image corresponding to the subject 28 is transferred to the CRT of the television.
It can be displayed on the screen. In the NTSC system, for example, if the vertical and horizontal pixels of a solid-state image sensor are the same number of pixels, and the vertical effective pixel count is 243 pixels, the horizontal effective pixel count is 4/3 times the vertical pixel, or 243 x 4 h = 324 pixels. . Furthermore, the number of pixels corresponding to the entire horizontal scanning period considering the horizontal retrace period is 32410.83 = 390390 pixels. Therefore, 39 OfH=6, 14 MHz, the time for the A pixel pitch is about 80 ns, and one horizontal scanning period is 635 μS. However, the vertical and horizontal pixel pitches of the solid-state image sensing device do not necessarily have to be the same pitch, and it is sufficient that the vertical and horizontal pitches have relatively close values.

A preamplifier 56 is connected to the output side of the CCD 8, and the preamplifier 56 amplifies the image signal to a predetermined level. The amplified image signal is serialized on the time axis by a sample/hold circuit (S/) I) 58 based on a sample signal synchronized with the readout clock of the CCD 8, and then passed through a low-pass filter (LPF). ) 60, and is further synthesized with vertical and horizontal synchronizing signals sent from the synchronizing signal generator 5z in a synchronizing synthesis circuit 62, and output as a composite video signal to an external monitor television 64, etc. ing.

The rotation of the parallel plane plate 12 is keyed to keep it out of synchronization with the vertical synchronization signal.
Since the carriers accumulated in B, . . . are used as pixel information, rotation unevenness (wow and flutter) can be ignored.

In the above embodiment, a case where a parallel plane plate as an imaging deflection element is inserted at the rear side of the taking lens is explained, but it may also be inserted at the front side. , as shown in FIG. 7, taking lens IOA
It is also possible to perform both the imaging action and the circular movement action of the image by rotating the lens itself once around a rotation axis eccentric by a distance g from the optical axis C. Subject ABO image A'B' when assuming that the optical axis of the taking lens IOA is located along the rotation axis (refer to the optical path indicated by the two-dot chain line in Fig. 7)
and the image A//B when the optical axis is located at a distance g from the rotational axis position (see the optical path indicated by the solid line in the same figure)
Letting the amount of deviation between ΔAOD' and ΔA A//A
From the similarity with /, tonashi, for a normal television camera, a) b, so it becomes X kg. Therefore, by rotating the taking lens IOA at a position A pixel pitch away from the optical axis as the rotation axis D, the image can be rotated by an eccentric amount of A pixel pitch. When the taking lens IOA is configured with multiple ratios, all or only some of the lenses may be rotated.

Further, when the present invention is applied to a single-panel color television camera, for example, a so-called payer array color filter is provided, and the photosensitive portion 30B in FIG. 5 is R (red), 32
When B is G (green), R and G are sampled alternately in the partial image 44B, so that a false color signal (
(cross color) is reduced.

Further, in the embodiment described above, the image is moved intermittently in a circular motion, but it may be moved in a circular motion continuously in synchronization with the field frequency. At this time, an aperture corresponding to the area of the photosensitive section scans the image, resulting in spatially weighted sampling. As a result, the spatial frequency characteristics (MTF) decrease in both the vertical and horizontal directions, making it equivalent to applying a two-dimensional optical low-pass filter (OLPF) such as a crystal filter. Therefore, an optical low-pass filter is used to prevent input of high spatial frequency components that would cause false signals (moiré) that do not correspond to the image of the subject, which is required in the discrete sampling method used in solid-state image sensors. have the same effect. Further, by providing a rotating shutter synchronized with this circular motion, exposure conditions equivalent to intermittent motion can be achieved. In this case, it is possible to select an appropriate action between intermittent motion and continuous motion depending on the opening angle of the shutter.

In other words, in this way, improvement of resolution and removal of false signals, which have contradictory properties, can be achieved by adjusting the spatial frequency characteristics (MT
F) can be appropriately selected and optimized.

Effects With the image reading method according to the present invention, it is possible to obtain the number of sampling pixels equivalent to a high-density staggered array with a simple configuration, and the resolution is significantly improved, reducing the burden on the device and reducing noise components. It becomes possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment in which the image reading method according to the present invention is applied to a television camera; FIGS. 2 to 4 are explanatory diagrams showing the action of a parallel plane plate inserted in the optical system; The figure is an explanatory diagram showing the movement of an image on a solid-state image sensor. Figures (1) to (4) in Figure 6 are explanatory diagrams showing the relative positional relationship between the image and the solid-state image sensor when the parallel plane plate rotates by 1/4 rotation, and Figure 7 is another embodiment of the present invention. It is a block diagram which shows an example. Description of symbols of main parts 6...Optical system 8...CCD 10, IOA...Taking lens 12...Parallel plane plate 16...Rotation mechanism BOA, BOB,..., 32A, 32B ,...
... Photosensitive section procedural amendment August 2, 1980 4 □￥ Fraud Office Commissioner Kazuo Wakasugi 2 Name of the invention Image reading method 3 Person making the amendment 4 Agent address 1 Toranomon, Minato-ku, Tokyo 105 -13-4 Toranomon Hoju Kaikan, 7th floor, 6, Contents of the amendment (1) Specification wS page 4, lines 6 to 7, r-backlash is likely to occur'' has been changed to ``vibration is likely to occur due to backlash, which further causes backlash. I'll make it bigger, so I'll edit it to J.

Claims (1)

[Claims] 1. An image formed through an optical system is separated into pixels by a solid-state imaging device comprising a large number of photosensitive parts arranged at intervals in the vertical and horizontal directions of an imaging screen. In the image reading method, the image on the solid-state image sensor is moved circularly by an eccentricity of about the pitch of the photosensitive part by rotating an imaging deflection element provided in the optical system, and this circular movement 1. An image reading method characterized in that the image is read by the solid-state image sensor when the image comes to any one of the top, bottom, left, and right positions. 2. The method according to claim 1, wherein the rotational speed of the imaging deflection element is substantially equal to 1/4 of the field frequency of the rask scan video signal, and An image reading method characterized in that an image is read.