JPH0777442B2 - Solid-state imaging device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a solid-state imaging device equipped with a CCD solid-state imaging device.

(B) Conventional Technology In the CCD solid-state image pickup device used in the solid-state image pickup device, the method of the image pickup device is considered at the design stage, and the number of pixels and the pixel pitch are set according to the image pickup method. This imaging method standardizes the number of scanning lines and scanning period of one screen to unify the video signals, and the NTSC method and the PAL method are widely adopted.

In the case of the NTSC system, the number of horizontal scanning lines in one frame is 525, and the effective number of scanning lines is 485, so
The condition for the number of pixels P _{V in} the vertical direction is 485 <P _V <525 (1). In addition, one horizontal scanning period (1H) is the reference clock
CK is 910 cycles of (frequency f _N = 14.31818 MHz), since the effective period of this is 756 cycles, the conditions of horizontal pixel number P _H is _{756 · f NT / f N <} P H < 910 ・ f _NT / f _N …… (2) Where f _NT is the frequency of the horizontal transfer signal. Then, in order to make the aspect ratio of the screen 3/4, the pixel pitch S _V , S _H in the vertical direction and the horizontal direction is 485 · f _N · S _V from the number of effective scanning lines and the effective period of the horizontal scanning lines. / 756 · f _NT · S _H = 3/4 …… (3) is required to be satisfied. That is, CC compatible with NTSC system
In D, if the above equations (1) and (2) are not satisfied, the playback screen is chipped or the signal is folded, and if equation (3) is not satisfied, the screen is distorted.
The number of pixels of D and the pixel pitch are set so as to satisfy all of the expressions (1) to (3).

FIG. 2 is a block diagram showing a main clock generator of the NTSC type image pickup apparatus.

The reference clock oscillator (1) includes a crystal oscillator and generates a reference clock CK. This reference clock CK
Is divided into 1/4, 1/910 and 1/2 by frequency dividers (2), (3) and (4), respectively, and becomes a subcarrier signal SC, a horizontal synchronizing signal HD and a horizontal transfer signal HT. The horizontal synchronizing signal HD determines the scanning timing of the horizontal scanning line, and is actually used by changing the duty ratio after dividing the reference clock CK by the frequency divider (3). The horizontal transfer signal HT determines the horizontal transfer frequency, and a multi-phase horizontal transfer clock is created from this horizontal transfer signal HT. The subcarrier signal SC is a signal for modulating the video signal on the imaging device side and demodulating it on the reproducing side, and includes a horizontal synchronization signal HD and a horizontal transfer signal.
It is synchronized with HT and set to a frequency of 1 / n times or n times (n is an integer) the horizontal transfer signal.

On the other hand, in the PAL system, the number of horizontal scanning lines in one frame is 6
The number of effective scanning lines is 575, and the number of pixels P _{V in} the vertical direction is 575 <P _V <625 (4). In addition, one horizontal scanning period (1H) is the reference clock
A 908 cycles of CK _H (frequency f _P2 = 14.1875MHz), since the effective period of this is 739 cycles, and the frequency of the horizontal transfer signal and f _PT horizontal pixel number P _H Condition Is 739 · f _PT / f _P2 <P _H <908 · f _PT / f _P2 (5). Then, the pixel pitches S _V and S _{H in} the vertical and horizontal directions
Needs to satisfy 575 · f _P2 · S _V / 739 · f _PT · S _H = 3/4 (6) in order to set the screen aspect ratio to 3/4. Therefore, CCD compatible with PAL system,
Similar to the case of the NTSC system, the number of pixels and the pixel pitch are set so as to satisfy all the above expressions (4) to (6).

FIG. 3 is a block diagram showing a main clock generator of the PAL type image pickup apparatus.

The first and second reference clock oscillators (11) and (12) have different frequencies (f _P1 = 17.734375MHz, f _P2 = 14.1875MH).
z) Reference signals CK _S and CK _H are generated. The reference signal CK _H is divided into 1/908 and 1/2 by the frequency dividers (13) and (14), respectively, and becomes a horizontal synchronizing signal HD and a horizontal transfer signal HT. Further, the reference clock CK _S becomes the subcarrier signal SC whose frequency is divided into 1/4 by the frequency divider (15). By the way, since the subcarrier signal SC needs to be synchronized with the horizontal synchronization signal HD and the horizontal transfer signal HT, the reference clock CK _S is divided by the frequency divider (16) to 1/1135 to obtain the horizontal synchronization signal HD. A phase comparison (17) and a PL for operating the first reference clock oscillator (11) based on this comparison
L circuit is configured. Therefore, the horizontal synchronization signal HD and the horizontal transfer signal HT, and the subcarrier signal synchronized with them
SC is obtained.

(C) Problems to be Solved by the Invention In a general image pickup apparatus, a CCD is pulse-driven according to a horizontal synchronizing signal HD and a horizontal transfer signal HT obtained from the configurations shown in FIGS. The video signal obtained from is modulated with the subcarrier signal SC. Therefore, the circuit for generating each of these signals SC, HD, HT is made into a frequency divider IC, and a crystal oscillator etc. is externally attached to this IC to form a CCD.
Along with this, it is mounted on the imaging device.

However, since the CCD and circuit configurations differ depending on the imaging method, the NTSC method and PAL method cannot be handled by the same CCD and IC, and the CCD and IC are compatible with each imaging method.
It is necessary to configure each of the ICs. CCDs and ICs configured exclusively for each imaging method have a narrow range of use, and thus increase costs.

(D) Means for Solving the Problems The present invention has been made to solve the above problems, and a CCD solid-state imaging device in which a plurality of light receiving pixels are arranged in a matrix in the horizontal and vertical directions is used for predetermined imaging. In a solid-state image pickup device which obtains a video signal of one screen unit by scanning in horizontal and vertical directions according to the method, means for generating a first reference clock having a frequency corresponding to the first image pickup method; Means for generating a second reference clock having a frequency corresponding to the imaging method, means for dividing the first or second reference clock to obtain a subcarrier signal, and 1 / n times or n times the means. A means for obtaining a horizontal transfer signal by dividing the first or second reference clock at a frequency division ratio twice, and a first frequency division ratio for the first reference clock, Set to the second division ratio for the reference clock of 2. And a means for obtaining a horizontal synchronizing signal by dividing each reference clock. The selecting means selects the first or the second reference clock and associates the dividing rate for obtaining the horizontal synchronizing signal with each reference clock. It is characterized in that the imaging method is set according to the above.

(E) Operation According to the present invention, in the image pickup device configured for the NTSC system, the PAL system is changed by changing the reference clock and the dividing ratio for creating the horizontal synchronization signal. A horizontal synchronization signal corresponding to PAL is generated, and a common reference clock is further divided by two frequency dividers having a division ratio of an integer to generate a subcarrier signal corresponding to the PAL system and a horizontal transfer signal. Created. Therefore, both the NTSC system and the PAL system can be supported without changing the circuit configuration.

(F) Embodiment An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a main part of the system of the present invention. The first reference clock oscillator (20) generates a reference clock CK ₁ (f _N = 14.31818MHz) corresponding to the NTSC system,
The second reference clock oscillator (30) generates a reference clock CK ₂ (f _P1 = 17.734375 MHz) corresponding to the PAL system.
The reference clocks CK ₁ and CK ₂ from these reference clock oscillators (20) (30) are divided into 1/4 by the frequency divider (21) to become subcarrier signals SC, and the frequency divider (22) Is divided by 2 and becomes a horizontal transfer signal HT. This horizontal transfer signal HT is
It is used to create the horizontal transfer clock of the CCD, and its frequency f _HT is set to 1 / n times or n times (n is an integer) times the frequency f _SC of the subcarrier signal SC. Where f _HT
= 2f _SC and the frequency division ratio of the frequency divider (22) that obtains the horizontal transfer signal HT is set to 1/2.

Further, the reference clocks CK ₁ and CK ₂ are frequency-divided by a frequency divider (23) at a predetermined frequency division ratio to become a horizontal synchronization signal HD. The frequency division ratio of the frequency divider (23) is set according to the imaging method setting signal MS, and is set to 1/910 in the NTSC method and 1/1135 in the PAL method.

That is, in the case of the NTSC system, the frequency division ratio of the frequency divider (23) is 1/910
, The first reference clock oscillator (20) is selected, and the first reference clock is supplied to each of the frequency dividers (21) (22) (23).
CK ₁ is input. Then, in the case of the PAL system, the second reference clock oscillator (30) is selected instead of the first reference clock oscillator (20), and the frequency division ratio of the frequency divider (23) is set to 1/1135. It is set and the second reference clock CK ₂ is input to each of the frequency dividers (21) (22) (23).

Therefore, when each frequency divider (21) (22) (23) is integrated into an IC,
By selecting the oscillator provided externally to the IC according to the imaging method, and corresponding the dividing ratio of the frequency divider (23) to the imaging method according to the imaging method setting signal MS, NTSC method and PAL method And can be realized with the same circuit configuration.

The CCD used here is the number of pixels corresponding to the NTSC system,
The pixel pitch is set, and it does not support the original PAL system. However, even if the number of pixels does not match the condition, if the pixel pitch satisfies the condition, a screen without distortion can be obtained. That is, a CCD compatible with the NTSC system
When applied to the AL system, even if the conditions of the above formulas (4) and (5) are not satisfied, if the formula (6) is satisfied, the screen will be cut off due to the small number of horizontal scanning lines. No screen is obtained. Therefore, when the aspect ratio is calculated from the equation (6) using the condition of the equation (3), f _N = 14.318
Since it is 18MHz, f _P1 = 17.734375MHz, f _P2 = 14.1875MHz, it becomes 575 ・ f _P2・ S _V / 739 ・ f _PT・ S _H = 0.97 ・ 3/4 (7). Therefore, the distortion of the screen becomes about 3%, which practically causes no problem, and the common CCD can be applied to both the NTSC system and the PAL system.

Such an image pickup device is unsuitable when video is required for the entire area of the effective screen, but when the image is not necessarily required for the entire area of the effective screen such as an endoscope or a security camera. It can be used effectively.

(G) Effect of the Invention According to the present invention, it is possible to realize an image pickup apparatus that can support both the NTSC system and the PAL system without significantly increasing the circuit configuration, and prevent an increase in the circuit scale. Cost reduction can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a solid-state imaging device according to the present invention,
2 and 3 are block diagrams showing a main part of a conventional solid-state image pickup device, showing an NTSC system and a PAL system, respectively. (1) (11) (12) (20) (30) …… Reference clock oscillator, (2) (3) (4) (13) (14) (15) (16) (2
1) (22) (23) ... divider.

Claims (2)

[Claims] 1. A solid-state imaging device for obtaining a video signal for each screen by scanning a CCD solid-state imaging device in which a plurality of light receiving pixels are arranged in a matrix in the horizontal and vertical directions in the horizontal and vertical directions according to a predetermined imaging method. A means for generating a first reference clock having a frequency corresponding to the first imaging method, a means for generating a second reference clock having a frequency corresponding to the second imaging method; A means for obtaining a subcarrier signal by dividing the second reference clock, and dividing the first or second reference clock by a dividing ratio of 1 / n or n times (n is an integer) of this means. Means for obtaining a horizontal transfer signal, and a first division ratio is set for the first reference clock, and a second division ratio is set for the second reference clock. A means for dividing each reference clock to obtain a horizontal synchronization signal The provided solid-state imaging device, characterized in that for setting the imaging scheme the division ratio to obtain the horizontal synchronizing signal corresponding to each reference clock as well as selecting the first or the second reference clock. 2. The solid-state image pickup device according to claim 1, wherein the first and second image pickup systems are NTSC system and PAL, respectively.
The first reference clock is divided into 1/910 to obtain a horizontal sync signal compatible with the NTSC system, and the second reference clock is divided into 1/1135 and compatible with the PAL system. A solid-state imaging device, which obtains a horizontal synchronization signal that