JPS61269481A - Color image pickup device - Google Patents

Abstract

PURPOSE:To obtain superior color reproducibility without deteriorating the SN ratios of chrominance signals by allotting the photodetection time or the quantity of light irradiation of an object image for every primary color according to spectral sensitivity characteristics of an image pickup element. CONSTITUTION:Illumination light irradiated by a xenon discharge tube 8 controlled with pulses from a pulse generator 9 is color-separated to illuminate an object through a light guide 2 and a lens 3 for illumination. The rotational frequency of a rotary disk 7 is provided with an offset one-third as large as (n+1/3)ff. The object is irradiated with only blue light twice continuously and a blue light image is photodetected by an stored in a CCD image pickup element 5 twice continuously, so levels of blue signals G, R, and B obtained in surface sequence are equalized without any deterioration in SN ratio, thereby obtaining an image of good quality having superior color reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to a surface-sequential solid-state color imaging device suitable for constructing an endoscope device or the like.

[Technical Background of the Invention] A color imaging device that obtains three primary color signals in a frame-sequential manner, which is used in an endoscope or the like, has the advantage that it can be converted into a simultaneous color camera and is simple in structure and easy to manufacture. In order to obtain the three primary color signals of the object image sequentially, a method is used in which the light source that illuminates the object is sequentially separated into colors, or a method in which the object image illuminated by a white light source is color separated using three primary color filters. ing.

"Problems in the background art" By the way, the above-mentioned surface sequential type color Oka imaging device has the following problems. Figure 6 shows a solid-state 1Iiii image element, which is a type of image sensor, for example. This figure shows the spectral characteristics of a charge-coupled image element (referred to as a 1-segment COD range image element).As can be seen from this figure, the sensitivity of the COD image element decreases as the wavelength becomes shorter. Therefore, the sensitivity of blue (hereinafter referred to as B) is higher than that of green (hereinafter referred to as G).
) and red (hereinafter referred to as R).
This is the B signal among the three primary color signals that are sent frame-by-frame when imaging a white subject (the level is lower than the G and R signals. Therefore, in order to obtain accurate color reproducibility, the B signal is The white balance is achieved by adjusting the level with an amplifier, but there is a problem in that the S and /N of the B signal deteriorates and the image quality is not adversely affected. B for subtle color reproduction of the following + (referred to as C1) colors
The signal has a large influence, and the above-mentioned drawbacks have been a significant factor limiting diagnostic accuracy.

[Object of the Invention] In view of the above-mentioned drawbacks, the object of the present invention is to provide color imaging that can obtain excellent color reproduction '1-in-1' without degrading the S/N of the color signal! Our aim is to provide A1 Koi.

"IW Essentials of the Invention" The present invention appropriately allocates the light reception time or light exposure time of the subject image to the image sensor for each primary color according to the spectral sensitivity of the imaging element. The above object is achieved by making the signals of the three primary color signals obtained from the imaging probe substantially equal.

``Embodiment of the Invention'' An embodiment of the present invention will be explained below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a direct-viewing endoscope apparatus to which the color history imaging device of the present invention is applied. Case 1
A lie 1 to a guide 2 are inserted into the inside of the case 1, and an illumination lens 3 is placed in the portion of the case 1 facing the tip of the lie 1 to the kite 2. Lens 3 in case 1
An imaging lens 4 is located in the vicinity of the
An image sensor 5 is disposed inside the case 1 facing the lens 4. A signal line connected to the image sensor 5 is led out to the outside through a duplex 6.

On the other hand, a three-primary color rotary plate 7 is provided at a position facing the exposed end of the itonoid 2, and behind this rotary plate 7 is provided a xenon discharge tube 8 which is a flash light source. The Kirenon discharge tube 8 is lit by a pulse output from a pulse generator 9. Further, the output pulses of the pulse generator 9 are supplied to a drive motor for the rotary plate 7 and a drive circuit 10 that drives the image pickup device 5. The drive circuit 10 is a CCDWL
A drive signal group 100 is supplied to all image elements 5. On the other hand, the output signal 200 of the image element 5 is input to the preamplifier 11 via a signal line. The field sequential (field sequential) primary color signals amplified to a predetermined level by the amplifier 11 are inputted via the switch circuit 12 to process circuits 13G and 14R 115B corresponding to each of the three primary color signals G, R, and B. The respective primary color signals subjected to various processing by the process circuits 13G, 14R, and 15B are manually converted into digital signals by A/D (analog-digital) converters 16G, 17R, and 118B.

The output digital signal of A/D converter 16G is input to either field memory 22Q or 23G via switch circuit 19G. The output digital signal of the A/D converter 17R is input to either the field memory 24R or 25R by the switch circuit 2OR. The output digital signal of the A/D converter 183 is sent to the switch circuit 211'3.
The data is then input to either refield memory 26B or 27B. The digital green signal read from the field memory 22G or 23G is input to the D/Δ (digital-analog) converter 31G via the switch circuit 28G. The digital red signal read from the field memory 24R or 25R is sent to D via the switch circuit 29R.
/A converter 32R. field memory 26
The digital blue signal read from B or 27B is sent to the digital/analog converter 33 via the switch circuit 303.
3 will be done manually. D/Δ converter 31G, 32R, 33B
Green signal G and red signal R converted into analog signals by
1 blue signal B is input to the color encoder 34, where it is encoded and then the final color video signal 300 is extracted. In addition, switch circuits 12.19G, 20
A pulse signal from the pulse generator 9 is supplied to R121B, 28G, 29R, and 30B.
(Then, each switch circuit is switched at a predetermined timing.

Next, the operation of this embodiment will be explained. First, the illumination light emitted from the chilenon discharge tube 8 is color-separated by the three primary color rotary plate 7 under pulse control from the pulse generator 9.
Light 1 is irradiated onto the subject through a guide 2 and an illumination lens 3. The reflected light from the object forms an optical image on the CCD @ image element 5 via the imaging lens 4,
Drive signal group 10 (
) photoelectrically converts the optical image written in Oi2 and outputs a field-sequential primary color signal 200.

Here, the CCDIfa image element 5 has a type element of 5250 pixels and 100 pixels arranged in the horizontal direction, and as shown in FIG. 2, one unit pixel 51 is composed of one light receiving element 52 and one stage of vertical transfer CCD 53. . The signal charge read out from the light receiving element 52 to the vertical transfer CCD 53 during the vertical blanking period is either a four-phase pulse from the drive circuit 10 or the electrode 54.
By tanning the data, the data are sequentially transferred in the vertical direction using the horizontal blanking period. The signal charge thus sent to the horizontal transfer CCD 5B is transferred to the drive circuit 10.
The three primary color signals 20 are transferred horizontally at high speed by two-phase pulses applied to the terminal 55 from
().

The field sequential primary color signal 20 obtained in this way
After 0 is I-widthed to a predetermined level by the preamplifier 11, it is output to the G, R, and B signals by the switch circuit 12 for each field (process circuits 13G and 14, respectively).
R,153. Each wrestling circuit 13G, 14
R and 158 perform processing such as clamping, gamma correction, and white balance adjustment on the G, R, and B signals, and the processed primary color signals are sent to A/D converters 16G and 17R1, respectively.
3, which is input to 18B and converted into a digital primary color signal.
The conversion pitch number of these A/D converters 16G, 17R, and 18B is, for example, 8 pitches. Each of the primary color signals digitized in this way is sent to a switch circuit 19Q,
A pair of field memories 22G by 20R1213
, 23G and 24R, 125R and 263.27B. That is, field memories 22G, 23G
is the G signal, 24R, 25R is the R signal, 26B,
B signals are respectively inputted and outputted to 27B. Next, field memories 22G, 23G, 24R, 25R and 26
The respective G, R, and B signals read from B and 27B are synchronized by switching the switch circuits 28G and 29R1303 at appropriate timings. The synchronized digital primary color signals GD, RD, and BD are converted back to analog primary color values SG, R, and B by D/converters 31G, 32R, and 33B, respectively, and then converted to analog primary color values SG, R, and B by the color encoder 3.
4 and processed, the final color video signal 3
00 is retrieved from color encoder 34.

Next, the S/N improvement operation of the sequential three primary color signals, especially the B signal, will be described in detail in the following field.

As shown in FIG. 3, the three primary color rotary plate 7 shown in FIG. 1 is divided into three areas of equal area, namely a green area 71, a red area 72, and a blue area 73.
It is designed to only allow light in wavelength bands corresponding to red and blue to pass through. The rotary plate 7 having such a configuration has a field frequency of -rt (=59.941-
(7) (n+1/3) times (n is an integer) frequency, e.g. 1.22 to +-17 (n=20>), and the drive motor is Therefore, the time for one revolution of the rotary plate 7 is 820 μsec.

FIG. 4 shows charts 1 to 4 showing the timing of lighting the xenon discharge tube 8 while the rotating plate 7 is rotating as described above. In this FIG.
(D> represents a field shift l-pulse for transferring charge from the optical element 52 of the image element 5 to the vertical transfer CCD 53, and a pulse for lighting the xenon discharge tube 8 emitted by the flash light source, respectively. First, at time 1.1, as shown in FIG. 4(C), when field shift 1 to pulses are obtained, unnecessary charges accumulated in the light receiving element 52 due to dark current are sent to the vertical transfer CCD 53.

After that, from time 1Th2 to t3, the vertical transfer CCD5
3 is driven at a high speed, for example, 1M+-17, unnecessary charges are discharged to the outside. When there are 250 stages of vertical transfer CCDs 53 and the opening frequency is 1 MH7, this opening period (13-12>) is 250 μsec.

Next, at time 1:4, the xenon discharge tube 8 is turned on momentarily.

At this time, if the rotation frequency of the rotary plate 8 is 1.22 or +-17, the lighting time should be set to 820 ÷ to prevent color mixture.
It takes 273 microseconds for three strokes. When the green area 71 of the rotary plate 7 is in front of the xenon discharge tube 8, the colored light irradiated onto the subject through the light kite 2 is green. When it returns 4. At rl t 5, the field shift 1 pulse is applied again, and the green signal charge is read out from the light receiving element 52, sequentially transferred vertically and horizontally, and outputted from the terminal 58 as a G signal to the outside. In the next field, a field shift pulse is applied at time 1X6 and the same operation as above is repeated.

However, the rotation frequency of the rotating plate 70 is (n+1/3 > ff
]/3 A-fuse; to l) Ringing I Kome, 11) Time 1
] At 7, the A-senon discharge tube 8 was lit +tl ■ The area of the rotary plate 7 in front of the light source (j, red area and 4'f,
An R signal is output from the CCD 1frj image sensor 5.

Next, in the third field, at times 1-8 to 110, the operation is the same as that of the above two fields until the unnecessary charge is discharged.Then, at time ↑11, the xenon discharge tube ε3 is instantaneously activated. When the light is turned on, the blue area 1 or 73 of the rotating plate 7 is in front of the discharge tube 8.
” From 11 to 82 (time 111 seconds later, when the Kirenon discharge tube 8 is turned on again at 2, 820 microseconds corresponds to one period of the rotary plate 7, so the rotary plate 7 is again turned on in front of the discharge tube 8. In other words, in this 3Mth field, blue light passes through the lights 1 to 2 and illuminates the subject twice at an interval of 820 μs. Finally, at time t13, field shift 1~pulse is applied, and a B signal is output from the CCDfffl image element 5.In the end, the object image using blue light is COD twice.
By receiving and accumulating light in the optical image element 5, the lack of color sensitivity of the COD image element 5 is corrected by -l'I-. Thereafter, three field operations are repeated.

Next, the synchronization of each primary color signal taken out in field sequence from the image sensor 5 will be described with reference to the timing chart shown in FIG. Image signals are G1 and R1
, B1, G2, R2, B2... and so on.
obtained from the ffi image element 5. Therefore, the switch 12 is switched to the process circuit 13G side, 14R side, 15B side, 13G side, etc., and each primary color signal is sent to each process circuit.

On the other hand, the switch circuit 19G on the input side of the field memory
, 20R121B are switched completely synchronously at a frequency of ff/3 as shown in FIG. That is, for example, the switch circuit 19G connects the field memory 2 between the first three fields.
It switches to the 2G side, and then switches to the field memory 23G side for the next three fields.

The same is true for the switch circuit of 1. On the other hand, switch circuits 28G and 29R13 on the output side of the field memory
0[3 similarly switches at a frequency of ff/3, but the switching timings are out of phase with each other. Therefore, field meter 22G, 23G, 24R, 25R
Each primary color signal is written into and read out from 126B and 27B at the timing shown in FIG. That is, when focusing on one field memory, writing and reading of primary color signals are repeated at the following timings: ] field time write, followed by 3 field time read, followed by 2 field time pause. Therefore, focusing on the fourth field in FIG. 5, since the field memories 22G and 2/1R 126B are read out at the same time, the image values @G1, R1, and B1 are read out at the same time. The same goes for the others, and each of the synchronized primary color signals is (
G1, R1, 81), (G2, R1, B1), (G2,
R2, Bl), converted into an analog signal δ, and manually inputted to the color encoder 34.

According to this embodiment, only blue light is irradiated onto the subject twice in succession (), and the blue light image is received and accumulated in the CCDm image element 5 (52 degrees consecutively), so that the blue value is 1q in the field sequential manner. @
The levels of G, R, and B can be made equal without deterioration of the S/N ratio, and a high-quality image with color reproduction of t[Omega] can be obtained. Therefore, when used in an endoscope or the like, it is possible to reproduce the delicate pink color inside the body, thereby improving the accuracy of diagnosis. In addition, since it is a field sequential type, it is possible to make maximum use of the limited number of pixels of the solid-state gravity element from the viewpoint of image quality resolution and moiré, and the improvement in image quality is noticeable when handling still images or images close to this. .

In the above embodiment, the number of flashes of the xenon discharge tube 8 is set to B.
Although a method has been described in which flashing is performed once for each red color and twice for blue, the method is not limited to this, and an appropriate number of flashes can be adopted depending on the spectral sensitivity of the CCD II image element 50.

However, in this case, the frequency of the rotating plate 7 is 1. It is necessary to change it according to the change in the number of J1 flashes. Further, in the above embodiment, a method of continuously rotating the rotary plate 7 has been described, but it may also be rotated intermittently by a pulse motor. In addition, although the xenon discharge tube 8 has been described as a flash light source, it is also assumed that the xenon discharge tube 8 is used as a continuous light source in areas 71, 72, .
A method may be adopted in which the light receiving time or the light irradiation period to the image carrier element 5 is adjusted by changing the area ratio of the image carrier 73. Furthermore, in the above embodiment, the interline transfer type CCD K image element shown in FIG. 2 was used as the solid-state image sensor 5, but in addition to this, other imaging elements such as an MO3 type imaging specific gravity or an eye tube may be used. It's okay. Furthermore, the number of pixels of the solid-state 1 most imaging element is not limited to 250 vertically and 400 horizontally. It is possible to increase the vertical ff'i' image quality. Furthermore,
The basic repetition unit time for processing 1q of each primary color signal in a field-sequential manner is not limited to 1 field time, that is, 1/60 second, but may be faster, for example, 1/180 seconds, which is three times faster.
You can also set it to seconds.

In this case, the repetition time for combining the three primary color signals into one is one field time, and the image quality is greatly improved in terms of afterimages and dynamic resolution. Further, the color dance image device of the present invention can be applied to devices that handle still images, such as electronic still cameras, in addition to the above-mentioned endoscope devices, and similar effects can be obtained. .

"Effects of the Invention" As described above, according to the color imaging device of the present invention,
According to the spectral sensitivity characteristics of the image sensor, the light reception time or the amount of light illumination of the subject image to the image carrier is appropriately distributed for each primary color, and the level of the three primary color signals obtained from the image carrier is roughly calculated. By making them equal, there is an effect that excellent color reproducibility can be obtained without deteriorating the S/N of the color signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an endoscope apparatus to which the color eye imaging device of the present invention is applied, and FIG. 2 is a block diagram showing a detailed configuration example of the CCDR image element shown in FIG. 1. , Fig. 3 is a diagram showing a detailed example of the three primary color rotary plate shown in Fig. 1, and Fig. 4 is a diagram showing the lighting and C of the xenon discharge tube shown in Fig. 1.
FIG. 5 is a timing chart showing the driving element timing of the CDHti image element. FIG. 5 is a timing chart showing the timing of synchronizing the three primary color signals obtained from the image carrier 5 in a field-sequential manner as shown in FIG. 1. FIG. 1 is a diagram showing an example of spectral characteristics of a general CCV) image carrier element. 2... Light guide 3... Illumination lens 4
...Specific gravity lens 5...Imaging element 6...Tube 7...3 primary color rotating plate 8...Xenon discharge tube? ...Pulse generator 10...Drive circuit 12.19G, 20R, 21B, 28G, 29R, 30
B...Switch circuit 22G, 23G, 24R, 25R, 26B, 27B...
・Field memory agent Patent attorney Kensuke Chika (and 1 other person) Figure 6 Exhibitor (ヮ7)

Claims (1)

[Scope of Claims] 1) A light projecting means for irradiating a subject with light, a color separation means for successively color-separating the light irradiated from the light projecting means or light reflected from the subject, and an electrical system for generating an optical image of the subject. The image sensor includes an image sensor that converts into a signal, and a control means that controls the timing of light irradiation of the light projecting means, and the image sensor sequentially receives the three primary color images of the object, and generates the three primary color signals from the image sensor in a field sequential manner. In a color imaging device for obtaining a color image, a means is provided for adjusting the light irradiation time to the subject or the light irradiation to the subject, which adjusts the light reception time of the image sensor for each primary color or the distribution of the light irradiation amount to the subject. Characteristic color imaging device. 2) The means for adjusting the light irradiation time on the subject or the light irradiation on the subject performs an operation of changing the number of times the subject is irradiated for each of the three primary colors. The color imaging device described. 3), comprising a storage means for storing field-sequential three primary color signals obtained from the image pickup device, and by once writing the obtained three primary color signals in the storage means and then reading them out, the three primary color signals are synchronized and output. A color imaging device according to claim 1 or 2.