JPH0614752B2 - Imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image pickup apparatus for forming a frame image using a single solid-state image pickup element.

[Prior art]

A television receiver is generally used as a video signal reproducing apparatus currently in use. As signals input to this television receiver, for example, the PAL system and N
There are video signals based on the TSC system and the like, and the interlace system is adopted for these.

Therefore, as the image pickup apparatus, it is necessary to form a video signal adopting an interlace system, that is, an odd field signal and an even field signal in order to enable input to a television receiver. Therefore, most of the image pickup devices used in the image pickup apparatus are for frame images except those for simple field photography.

As the image pickup device for picking up the frame image, there is one in which image pickup cells for odd fields and even fields are alternately arranged. Further, this image pickup device cannot secure a sufficient number of horizontal image pickup cells due to problems in the current LSI technology, and therefore it is necessary to use the vertical correlation of the image to increase the resolution. Furthermore, it is required to be adaptable to the purpose of both moving image capturing and still image capturing.

However, considering the above-mentioned frame countermeasures and vertical correlation, it is said that the current image pickup device is a system for reading out the charges accumulated by photoexcitation to the outside, so that it is sufficient for obtaining good image quality. Is hard to say.

For example, conventional IL-CCD or XY address type MOS
As described above, when image pickup is performed using an image pickup device in which image pickup cells for odd fields and even fields are alternately arranged and vertical correlation processing is performed, a circuit configuration becomes complicated because a delay line or the like needs to be provided, Moreover, there is a problem that a false signal is likely to be generated due to a long vertical correlation distance.

Further, as a solid-state image pickup device for solving the above-mentioned problem relating to the correlation distance, an XY disclosed in Japanese Patent Laid-Open No. 59-50684.
Although there is an address type MOS, this requires one more signal processing system, and since a still image recording head capable of writing both odd and even fields simultaneously is required, there is a problem in terms of circuit and cost.

〔Purpose〕

The present invention solves the above problems, provides a predetermined color separation filter and a simple circuit configuration, and provides an imaging device capable of forming a high-quality color frame image with high resolution without generating a false signal. The purpose is to do.

〔Example〕

First, prior to the description of the invention, reference figures related to the invention will be described. A first reference example will be described with reference to FIGS. 1 to 4.

FIG. 1 is a diagram showing an arrangement example of the color separation filter 1,
₁ , ₂ , _3, ... Represent each horizontal line, and the number thereof is about 490 in the NTSC system, for example. The odd numbered horizontal lines ₁ , ₃ , _5, ... Have a green light transmission filter g for transmitting green light and a red light transmission filter r for transmitting red light, and an even numbered horizontal line ₂ ,.
_4, 6 are _...... Yes by arranging repeatedly alternately blue transmission filter b that transmits green light transmitting filter g and the blue light, the number of pixels of one horizontal line has a 570 pixel.
Due to the different color lights obtained through the color separation filter 1, electric charge as a color signal is accumulated in each pixel of the non-destructive readable image sensor. In this reference example, a color signal is read from a non-destructive readable image pickup device (hereinafter referred to as SIT) by a two horizontal line simultaneous read method. In the figure, n ₁ H, n ₂ H, n ₃ H, ... Are horizontal lines read simultaneously when forming odd fields.
The combination of ₁ , ₂ , _3, ... Is m ₁ H, m ₂ H, m
₃ H ... Represents a combination of horizontal lines ₁ , ₂ , _3, ... Simultaneously read when forming an even field. That is, horizontal lines ₁ and ₂ in n ₁ H and horizontal line _{3 in} n ₂ H in odd fields.
_The adjacent horizontal lines are sequentially read out at the same time, such as 4. In the next even field, in order to interpolate the image signal of the odd field, the combination n ₁ H, n
Reading is performed from _{2 H} ... in combination shifted one horizontal line. That is, in m ₁ H, horizontal lines ₂ and ₃ ,
In the case of m ₂ H, two horizontal lines are read at the same time in the combination of horizontal lines ₄ and ₅ which are shifted by one horizontal line from the case of the odd field. Thereafter, the color signals read out in the above combination are subjected to the signal processing described below using the vertical correlation.

FIG. 2 is a schematic diagram showing the signal reading means 2a from the SIT2. In this reference example, two G signals (green signals), R signals (red signals) and B signals for every two horizontal lines are used.
The 4-wire output system allows signals (blue signals) to be read independently. By using this method, the sample hold for color separation, which is usually required in the signal processing described later, is unnecessary. Each horizontal line ₁ ,
_2, 3 _...... is selected by the vertical switch 2a _1, each pixel signal is selected by the horizontal transfer switch (not shown). The reset of each pixel accumulated charge is performed by the vertical Riseto switch 2a _2. The vertical reset switch 2a _2, the timing of the operation in the still image shooting and moving image shooting is different. When a still image is picked up, the unnecessary charges accumulated in all the image pickup cells of SIT2 are simultaneously reset, and the shutter is closed after a predetermined time to control the charge accumulation time. After this, SIT2 with accumulated charge
, N ₁ H, n ₂ H ... Are sequentially read to form image signals in odd fields, and m ₁ H, m ₂ H ...
Are sequentially read to form an even-numbered field image signal. As a result, a 1-frame image signal is obtained.

Further, in moving image capturing, resetting is performed after the signal is read out, and the charge accumulation time is determined by the timing at which the signal is next read out. In this case, in the two-horizontal line simultaneous reading method, since the odd field and the even field have different combinations, it is desirable to perform reset in consideration of this point. For example, in FIG. 1, n ₂ of an odd field
After H signal readout end of the horizontal line ₂ at m _{1 H} when reading by performing the two reset horizontal lines ₂ and ₃ for the reading of m _{1 H} even field, ₃
Have the same storage time, and these two horizontal lines ₂
The level difference of the signals read from ₃ disappears. This effect is one of the features of this reference example. It should be noted that the charges are reset so that the accumulation times are the same for each nH in the other odd fields and each mH in the even fields.

In the above description, the case where the horizontal lines are simultaneously reset has been described. However, if the reset is performed for each pixel, the accumulation times of the pixels can be made completely equal.

FIG. 3 is a block diagram showing the signal processing means S ₁ for the color signals read from the SIT 2.

In the figure, the R. G. The B signal is an amplifier 3 having almost the same delay time,
After being input to the white balance amplifiers 4 and 5 for white balance, it is input to the subsequent process circuit 6. The process circuit 6 performs clamping, γ correction, and the like. B. Since the R signals are input to the circuits having the same configurations, the G.R. B. The R signal becomes a signal delayed by almost the same time. The R.M. output from this process circuit 6 is output. The B signals are added by 1/2 by the adder 7, and then input to the switch synthesizing circuit 8 together with the G signals. Switch synthesis circuit 8
Then, G signal (G ₁ + G ₂ ) and R signal + B signal (R ₁ + B
₂ ) and are switch-synthesized with a phase of 180 ° based on the spatial arrangement. As a result, the sampling aliasing component is canceled by the carrier frequency of each color component as shown in FIG.
It is possible to resolve the band shown in the shaded area in FIG. The signal output from the switch synthesis circuit 8 is about 4.2.
After passing through the low-pass filter 9 of MHZ, the outline is emphasized by the APC circuit 10 and input to the adder 11. Further, the Y _L matrix circuit 12 uses NT signals based on the input RGB signals.
Luminance signal Y _N R = 0.3R + 0.59G + based on SC method
0.11B is formed. The luminance signal Y _N is input to the subtracter 13 where it is subtracted from the output from the switch synthesizing circuit 8 and then further reduced by about 1 MHz.
After passing 4, the low-frequency luminance signal Y _L is obtained. In addition, the signal Y (4.2 MHz) output from the APC circuit 10 and the low-pass filter 9
The high frequency luminance signal Y _H can be obtained by adding Y _L (1 MHz) obtained through the above in the adder 11. That signal _{Y '=} Y L + Y _H is obtained from the adder 11.
The output Y'from the adder 11 is the encoder 1
Input to 5.

On the other hand, in the color difference forming circuit 16, the R. G. The B signals, the color difference signals _(R-Y L), is formed _{(B-Y L),} this is input to the encoder 15 via the low pass filter 17 and 18, respectively. The encoder 15 forms and outputs an NTSC signal based on the color difference signals ( _RYL ) and ( _BYL ) and the signal Y'from the adder 1.

Further, in the case of still image pickup, the signal Y ′ output from the adder circuit 11 is FM-modulated by the FM modulator circuit 20 after the synchronizing signal SYNC is added by the adder 19, and the low-pass filter is used. The color difference signals (R−Y _L ) and (B−Y _L ) output from the output terminals 17 and 18 are line switch circuits 21.
After being converted to a line-sequential signal by the
The signal is modulated and further added to the FM-modulated signal Y ′ by the amplifier 23, and recorded on the magnetic recording medium by the magnetic head 24.

FIG. 5 is a block diagram showing a second reference example. This reference example is the same as the first reference example except that the average value of the G signal and the R.V. B
The switch combination with the signal is performed after the process processing, whereas the switch combination is performed before the process processing. According to this, the first
In the reference example, it is possible to relax the required circuit accuracy as compared with the case where the circuit up to the switch combination requires a high accuracy in the high frequency characteristics and the delay characteristics between the channels. The folding strain in this case is as shown in FIG.

7 and 8 are diagrams showing the reference example of FIG. This third reference example is the same as the first reference example and the second reference example.
While the horizontal lines are read at the same time, the three horizontal lines are read at the same time as shown in FIG. 7 to further improve the image quality. In this case, as the image information reading means, the same one as shown in FIG. 2 can be used by changing the selection of the horizontal line by the vertical switch 2a ₁ . For example, odd field n ₁
When reading H, the vertical switch 2a ₁ causes the horizontal lines on both sides of the _three horizontal lines ₁ , ₂ and _{3 to be} read.
₁ and ₃ are selected so that they are added on the same signal line, and the central horizontal line ₂ is read out to another signal line.

FIG. 8 is a block diagram showing the main part of the signal processing means S ₃ of the third reference example. In this reference example, four color signals are output from SIT2. For example, in the case of reading n ₁ H, color signals (hereinafter referred to as main signals) G ₂ and B on the central horizontal line _2
2 , G signals (G ₁ + G ₃ ) and R signals (R ₁ + R · ₃ ) obtained by adding the color signals (hereinafter referred to as sub-signals) of the horizontal lines ₁ and ₃ on both sides are output. In this case, since the signal level of the added sub signal is 6 dB higher than that of the main signal, the attenuator 2 is provided between the process circuit 6 and the amplifiers 3a and 3b and the white balance amplifiers 4 and 5.
5, 26, 27 and 28 are inserted and the R.V. G. The signal levels of the B signal are matched.
This makes it possible to correct the false signal, and this effect is one of the features of the third reference example. Also, the amplifiers 3a and 3b
The color signals output from the wide balance amplifiers 4 and 5 are output while switching to the main signal and the sub signal for each field. Therefore, the switches SW1, S
Attenuator 2 by switching W2, SW3 and SW4
5, 26, 27 and 28 are selectively used. This simplifies the circuit configuration and has the third effect.
This is one of the features of the reference example. This switch SW1, SW
2, SW3 and SW4 are switched according to the field switching signal FS, and the switches SW1 and SW3 are attenuator 2
When connected to 5 and 27 (for example, in the case of an odd field), the other switches SW2 and SW4 are connected to the amplifier 3
b and the output of the white balance amplifier 5 are directly connected, and the switches SW2 and SW4 are attenuators 26 and 2
When connected to 8 (for example, even field), the switches SW1 and SW3 are directly connected to the outputs of the amplifier 3a and the white balance amplifier 4. Then, for example, when reading out n ₁ H, the color signal (G ₁ + G ₃ ) output from the process circuit 6 and G 2 are added by the adder 29, and the color signal (also output from the process circuit 6 ( R ₁ + R ₃ ) and B ₂ are added by the adder 30. After that, the color signals output from the adders 29 and 30 are switch-synthesized by the switch synthesizing circuit 8. In addition to the color signals (R ₁ + R ₃ ) and B ₂ , only the main signal (G _{2 in} this case) is input to the color difference forming circuit 16 as a G signal. The input of only the main signal (G ₂ ) is performed by the switch SW5 which is switched by the field switching signal. After that, the color difference forming circuit 16 forms the low-frequency luminance signal Y _L using these color signals, so that a good vertical resolution can be obtained. Further, the high-frequency luminance signal can be obtained by performing the same signal processing as that shown in FIG. 3 using the signal from the switch synthesizing circuit 8 and the low-frequency luminance signal Y _{L. In} this case, 3 as mentioned above
Since the signals of the horizontal lines ₁ , ₂ and ₃ of the book are combined, the effect of canceling the aliasing distortion is further improved as shown in FIG. This is one of the features of the third reference example. Also, 3
1, 32 are color difference subtraction circuits for white balance,
Here, based on the color signals of the same horizontal line, (RG) (B
-G) Since the signal can be formed, the white balance effect by the white balance circuit 33 in the subsequent stage is also improved.

FIG. 10 is a block diagram showing an essential part of the signal processing means S ₄ in the fourth reference example. In the fourth reference example, the switch synthesis in the third reference example is performed before the process processing. Therefore, as in the case of the second reference example, the required circuit accuracy can be relaxed.

Next, an embodiment of the present invention will be described.

FIG. 11 to FIG. 14 are views showing the present invention, in which the color separation filter 1b having the arrangement as shown in FIG. 11 is used in simultaneous reading of three horizontal lines, and the arrangement is any horizontal column and vertical. Even in a row, if any three adjacent color transmission filters are specified, r, g, b
It is an array that can be a combination of. By using this color separation filter 1b, R, G, B signals are always obtained from the main signal, and if a low-frequency luminance signal is formed from this signal, vertical correlation will contribute only to the high-frequency luminance signal. There is no fear that the vertical resolution will decrease. Further, in the formation of the luminance signal, R.
G. Since there is a B signal, switch to switch composition processing,
The effect is that it is sufficient to simply perform addition processing.

Then, for reading N2H after reading N1H, 1
Two horizontal lines ₃ are overlapped and horizontal lines ₃ , ₄ ,
₅ is being read. Here, a non-destructive element is used as the image pickup element, and the bias potential of the collector of this transistor is modulated by the photocharges accumulated in the base of the bipolar transistor, and the element is read out from the emitter by the emitter follower operation. Unless the photocharge generated by one exposure is reset, the signal component modulated by the photocharge can be read from the same non-destructive element a plurality of times. Further, the image signal reading means 2b is of a two-line output system as shown in FIG. 12, which simplifies manufacturing. In the same figure, by changing the selection of the horizontal line by the vertical switch 2b ₁ , it is possible to read three horizontal lines at a time, or in a combination in which the odd field is shifted by one horizontal line in the even field. For example, when reading n1H in an odd field, the vertical switch 2b
_{1 so that} the horizontal lines ₁ and ₃ on both sides of the _three horizontal lines ₁ , ₂ and ₃ are added on the same signal line, and the horizontal line _{2 at} the center is read to another signal line. To do. FIG. 13 is a block diagram showing an essential part of S ₅ of the signal processing means of the present invention.
Three color signals are output from a1 and A2. For example, in the case of reading n2H, the central horizontal line of A2
₂ color signals _{G 2,} is output as R 2, _{B 2,} color signals obtained by adding the color signals on either side horizontal line _{1, 3} A1 _{(R 1}
+ B ₃ ), (G ₁ + G ₃ ), and (G ₁ + B ₃ ) are output.

FIG. 13 is a block diagram showing the signal processing means S ₅ in the present invention. In the figure, the two color signals A ₁ and A ₂ output from SIT2 are respectively added as they are by an adder 34 to become a luminance signal Y. At this time, in an ideal state when an achromatic image is captured, aliasing distortion occurs at 10.7 MHz as shown in FIG. Therefore, the filter characteristics can be designed quite easily. Further, the switch SW6 is switched for each field in response to the field switching signal and is always adapted to take out the main signal. The color signal taken out through the switch SW6 is supplied to the R.R. G. The signal is color-separated into the B signal, and the process circuit 6 receives the R signal from the G signal and the white balance amplifiers 4 and 5.
B signal is input. In this case, as the sample hold command pulse SC, the R. G. It is necessary to shift the B signal.

〔effect〕

As described above, according to the present invention, RGB is always included in the 3n rows read at the same time.
Since the luminance signal can be obtained for each horizontal pitch, and the band of the luminance signal can be expanded thereby, the resolution can be significantly improved, and in order to generate the luminance signal from the read signal, simply It is only necessary to add the outputs of the elements, which facilitates signal processing and allows a simple circuit configuration.

Further, by reading out 3n rows at the same time and overlapping each 3n row with each other, it is possible to bring the sensitivity centroids of the horizontal scanning lines closer to each other as compared with the case where the 3n rows are not overlapped as shown in FIG. As a result, it is possible to prevent the generation of moire in the vertical direction and improve the vertical resolution.

Furthermore, since the amount of information per horizontal scanning line increases,
It is possible to increase the degree of freedom of signal processing in the subsequent stage.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an arrangement example of a color separation filter used in a first reference example related to the present invention, FIG. 2 is an explanatory diagram showing a signal reading means of the first reference example, and FIG. 3 is a first reference example. FIG. 4 is a block diagram showing the signal processing means in the example, FIG. 4 is a diagram showing the aliasing distortion in the one shown in FIG. 3, FIG. 5 is a block diagram showing the signal processing means of the second reference example, and FIG. FIG. 5 is a diagram showing aliasing distortion in what is shown in FIG. 5, FIG. 7 is an explanatory diagram showing an arrangement example of color separation filters used in the third reference example, and FIG. 8 is a block diagram showing signal processing means of the third reference example. FIG. 9 is a diagram showing the aliasing distortion in the one shown in FIG. 8, FIG. 10 is a block diagram showing the essential parts of the signal processing means of the fourth reference example, and FIG. 11 is a color separation filter used in the present invention. 12 is an explanatory view showing an example of the arrangement of FIG. Illustration showing, FIG. 13 is a block diagram showing a signal processing section in accordance with the present invention, the first 14 illustrates the aliasing in those shown in FIG. 13. 1: color separation filter 2: nondestructive readable image sensor 2a: image information reading means _{S 1, S 2, S 3} , S 4, S 5: the signal processing means g1, g2, g3 ......: green light filter b1 , B2, b3 ...: Blue light filter r1, r2, r3 ...: Red light filter

Continuation of the front page (56) Reference JP-A-58-9478 (JP, A) JP-A-51-56123 (JP, A) JP-A-56-149187 (JP, A) JP-A-61-157093 (JP , A) JP 61-157092 (JP, A) JP 58-119286 (JP, A) JP 55-20012 (JP, A)

Claims (1)

[Claims] 1. A red filter, a green filter, and a blue filter are arranged in each row, and color filters of these three colors are included in three consecutive rows in a vertical direction, and these are arranged in a row direction and a column direction. Color separation filters arranged repeatedly, image pickup means having a plurality of nondestructive read-out image pickup cells arranged in horizontal and vertical directions, and signals of three rows vertically adjacent to each other for one horizontal scanning line image Simultaneously read as information and continue 1
At least one of the three rows that are simultaneously read in each horizontal scanning period is overlapped with each other, and the signals from the central row and the addition signals of the upper and lower two rows of the signals of the three rows are read to different output lines. An image pickup apparatus comprising: an image information reading unit; and a signal processing unit that obtains an image signal for one image from the read image information.