JP2002345747A - Ccd drive unit for electronic endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regularly obtain a satisfactory image in an endoscope using a single phase-driven PCCD. SOLUTION: Signal charges accumulated in M-stages of horizontal lines parallel to the horizontal transfer part of the CCD are successively transferred to the horizontal transfer side every stage at a time by a vertical drive pulse ϕp, and the charge of the stage adjacent to the horizontal transfer part is transferred to the horizontal transfer part. Horizontal drive pulses ϕs of the number sufficient to output the signal charges transferred to the horizontal transfer part is outputted until the next vertical drive pulse ϕp. In order to output the signal charged accumulated in each horizontal line in a transfer period provided within a light shielding period, M-pieces of vertical drive pulses ϕp and a vertical drive pulse ϕp (pulse SE) for outputting the residual charges are outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus and a driving method for a CCD mounted on an electronic endoscope.

[0002]

2. Description of the Related Art Recently, a CC mounted on an electronic endoscope has been developed.
Although an interline method and a frame transfer method are often used as D, an electronic endoscope which requires a small and thin insertion portion requires a single-phase drive requiring a small number of electrodes and signal lines. VPCCD (virtual phase charged coup
It is desirable to use a led device).

[0003]

However, charge accumulation in a clocked phase part where electrodes are provided and a virtual phase part where no electrodes are provided due to variations in processing conditions in the manufacturing process, etc. The capacity of the well varies. If the capacity of the charge storage well is not well-balanced between the clock phase section and the virtual phase section, the excess charge overflowing from the horizontal line farthest from the horizontal transfer section if the amount of received light is large and excess charge is generated. However, after the output of one image is completed, it is left as a residual charge on a horizontal line adjacent to the horizontal transfer unit. The remaining residual charge mixes with the signal charge of the captured image in the next exposure period, causing an image defect.

[0004] The present invention has been made in view of the above problems, and has as its object to always obtain good images in an electronic endoscope using a VPCCD.

[0005]

According to the present invention, a C for an electronic endoscope is provided.
The CD driving device includes a light receiving unit having M stages of horizontal lines in which a plurality of pixels are arranged in a row, and a light receiving unit that is adjacent to and parallel to one of the outermost horizontal lines among the M stages of horizontal lines. And a horizontal transfer unit that outputs the signal charges accumulated in the plurality of pixels in units of horizontal lines. The signal charge stored in each pixel of each horizontal line is sequentially transferred one stage at a time in the horizontal transfer unit direction on a horizontal line basis, and the signal charge held in the horizontal line adjacent to the horizontal transfer unit is horizontally transferred. Vertical transfer means for transferring the signal charges of one horizontal line transferred to the horizontal transfer unit by the vertical transfer means before the next horizontal line is transferred by the vertical transfer means. And a horizontal transfer means for outputting to the CD of an external, vertical transfer means, CCD is characterized by the transfer of at least (M + 1) stages or more horizontal lines in the light-shielding period not exposed.

The vertical transfer means is preferably driven by a vertical drive pulse, and the number of vertical drive pulses corresponds to the number of stages of the horizontal line to be transferred. Further, the vertical transfer means can minimize the transfer period when performing (M + 1) -stage transfer during the light-shielding period.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing a circuit configuration of an electronic endoscope system according to one embodiment of the present invention.

The electronic endoscope system according to the present embodiment includes an electronic endoscope (electronic scope) 10, a video signal processing device 27,
It is roughly composed of a TV monitor 28. The electronic endoscope 10 is detachably connected to a video signal processing device (hereinafter referred to as a processor) 27, and the TV monitor 28 is connected to a video output terminal of the processor 27 via a video signal cable. In this embodiment, the TV monitor 2 is used as a peripheral device.
8, only a video printer or VC
Peripheral devices such as R and a computer may be connected at the same time.

The electronic endoscope 10 is connected to an elongated and flexible insertion portion 11, an operation portion 12 for operating the electronic endoscope, a flexible connecting portion 13, and a processor 27. And a connector section 20 for performing the operation. A single-phase driven VPCCD 14 is provided at the tip of the insertion section 11.
The VPCCD 14 is connected to the CC provided in the connector unit 20.
The driving is controlled by a CCD driving pulse output from the D driver 24, and the CCD driver 24 is driven based on a clock pulse output from the timing control circuit 25.

The electronic endoscope 10 picks up images by, for example, a frame sequential method, and outputs R (red), G
The (green) and B (blue) illumination lights are sequentially and intermittently emitted in a time series. The CCD 14 detects a monochrome image corresponding to each color of RGB as an analog image signal in accordance with the emitted RGB illumination light. This image signal is sent to the connector section 20 of the electronic endoscope 10 via a signal cable and is input to the pre-processing circuit 21. The pre-processing circuit 21 amplifies the image signal from the CCD 14 to an appropriate signal level, performs signal processing such as sample hold, blanking, clamping, white balance, and gamma correction, and converts the image signal into a digital image signal. You. The digital image signals are output to the image memories 22r, 22g, and 22b, respectively, as monochrome images for each of RGB, and are sequentially stored temporarily. Image memory 22r, 2
When one set of RGB images is provided in 2g and 22b, these are synchronized and output to the post-processing circuit 23. In the post-processing circuit 23, the digital image signal is converted into an analog signal, subjected to amplification, clamping, and blanking processing, and is converted into, for example, a luminance signal Y and a color signal C. The luminance signal / color signal Y / C is output to the TV monitor 28 via the processor 27. The first-stage processing circuit 21, the field memories 22r, 22g, 22b, and the second-stage processing circuit 23
It is controlled by the system control circuit 26 based on the pulse signal from the timing control circuit 25.
The drive of the timing control circuit 25 is controlled by the system control circuit 26.

The RGB light emitted from the distal end of the insertion portion 11 passes through a light guide (not shown) formed of a bundle of ultra-fine optical fibers provided in the electronic endoscope 10.
Although supplied from a lamp (not shown) provided in the processor 27, the lamp provided in the processor 27 and the light guide provided in the electronic endoscope 10 are omitted in this figure. The lamp is a white light source such as a xenon lamp or a halogen lamp. The lamp is separated into R light, G light, and B light by a conventionally known rotating disk-shaped color separation filter.
The light is radiated sequentially in a time-series manner from the distal end of the insertion portion 11 as GB illumination light. Note that there is a light-blocking period during which illumination light is not irradiated for a predetermined period of time during which the illumination light changes from R to G, G to B, and B to R. Irradiation.

A video signal output from the post-processing circuit 23 of the electronic endoscope 10 and input to the processor 27 is subjected to conventionally known video signal processing. The video signal that has been subjected to various signal processing in the processor 27 is output to the TV monitor 28 together with a synchronization signal as a luminance signal Y and a color signal C.

FIG. 2 is a diagram schematically showing a planar structure of the single-phase drive VPCCD 14 used in the present embodiment.

The light receiving section 30 of the VPCCD 14 is composed of a number of pixels 30p arranged in a two-dimensional lattice (for example, M rows in the vertical direction and N columns in the horizontal direction). The horizontal transfer unit 31 is provided adjacent to the horizontal transfer unit 31 (a pixel group of one stage of the pixels 30p arranged substantially parallel to the horizontal transfer unit 31 in the light receiving unit 30 is a horizontal line, and the pixel group substantially vertical to the horizontal transfer unit 31). A pixel group for one column of the pixels 30p arranged in a row is hereinafter referred to as a vertical line.) Since the light receiving unit 30 also serves as a vertical transfer unit, each pixel 3 of the light receiving unit 30 is exposed during the exposure period.
The signal charges generated and accumulated at 0p are sequentially transferred one horizontal line at a time by the vertical drive pulse φp to the horizontal transfer unit 31 side during the light blocking period, and are transferred to the horizontal transfer unit 31 and the FDA (floating diffusion amplifier) 32 via the horizontal transfer unit 31.
It is output to the outside of the VPCCD 14 for each horizontal line. The transfer operation of the signal charges in the horizontal direction (left side in the figure) in the horizontal transfer unit 31 is performed by a horizontal drive pulse φs.

FIGS. 3A and 3B show vertical drive pulses φp
FIG. 4 is a block diagram showing an example of a portion related to the output of the vertical drive pulse φp and the horizontal drive pulse φs in the timing control circuit 25 shown in FIG. 3 and 4
The basic output operation of the vertical drive pulse φp and the horizontal drive pulse φs in the present embodiment will be described with reference to FIG. FIG. 3B is an enlarged view of the section AB in FIG. 3A.

As shown in FIG. 3A, the horizontal drive pulse φs is always output at a predetermined timing shown in FIG. 3B. On the other hand, the vertical drive pulse φp
Is output only during the transfer period and not during the accumulation period. During the accumulation period, the VPCCD 14 is exposed, and each pixel 3
0p is a period in which signal charges corresponding to the amount of received light are accumulated, and is equal to the exposure period. The transfer period is a period between two accumulation periods (exposure periods).
4 includes a light-blocking period in which no light is received. The signal charge corresponding to the subject image accumulated in each pixel of the light receiving unit 30 is vertically and horizontally transferred during one transfer period and is
It is output to the outside of the CCD 14. During the transfer period, the vertical drive pulse φp is output every time the horizontal drive pulse φs is output a predetermined number of times (N times) as shown in FIG. This number N corresponds to the number of pixels 30p arranged in the light receiving section 30.
Is equal to the number N of vertical lines of the horizontal transfer unit 31.
All signal charges for one horizontal line transferred to FDA3
2 is output. For example, when the vertical drive pulse S1 is output, the signal charges held in each horizontal line of the light receiving unit 30 are shifted downward by one horizontal line, and the signal charges at the bottom are transferred to the horizontal transfer unit 31. Thereafter, the horizontal drive pulse φs is output N times, and the signal charges for one horizontal line held in the horizontal transfer unit 31 are sequentially output to the outside of the VPCCD 14 via the FDA 32. When the output of the horizontal drive pulse φs for N times is completed, the vertical drive pulse S2 is output, and the signal charges held in each horizontal line of the light receiving unit 30 are shifted downward by one horizontal line again. At this time, the signal charges held in the lowermost horizontal line are transferred to the horizontal transfer unit 31. This transfer operation is repeatedly performed during the transfer period in which the light receiving unit 30 is shielded from light, and the light receiving unit 3
The signal charges accumulated in each of the 0 pixels 30p are all output to the outside of the VPCCD 14 in units of horizontal lines.

Vertical drive pulse φp, horizontal drive pulse φs
Is output from the CCD driver 24, and the output timing is controlled based on the vertical transfer clock φkp and the horizontal transfer clock φks from the timing control circuit 25. The vertical transfer clock φkp and the horizontal transfer clock φks are a clock signal CLK, a horizontal synchronization signal HD,
Based on the vertical synchronizing signal VD, it is generated in the φp timing generation circuit 35 and the φs timing generation circuit 36, respectively. Note that the clock signal CLK and the horizontal synchronization signal H
D and the vertical synchronizing signal VD are generated in the timing control circuit 25, for example.

FIGS. 5A, 5B and 5C show the light receiving section 3
It is a figure which shows notionally a part of cross section along the 0 vertical line. The vertical transfer operation in the single-phase driven VPCCD 14 will be described with reference to FIGS.

The VPCCD 14 is composed of a clocked phase section Ac provided with a single-phase electrode (for example, a transparent electrode) 41 and a virtual phase section Av provided with no electrodes. Part A
cw and Avw. In each part of the substrate 40, ions are implanted such that the barrier portion Acb forms a stepped potential barrier with respect to the well portion Acw, and the barrier portion Avb forms a stepped potential barrier with respect to the well portion Avw. For example, during the accumulation period (exposure period), a potential is formed on the substrate as shown by the solid line L0 in FIG. That is, when an L (low) level signal voltage is applied to the vertical drive pulse φp in the accumulation period, potentials are formed in the well portions Acw and Avw, respectively, and the generated electric charges are generated by these potentials. Wells, out of which accumulate

During the transfer period, the vertical drive pulse φp includes H
The (high) level signal voltage and the L (low) level signal voltage are alternately applied. That is, the potential level represented by the broken line L1 and the potential level represented by the broken line L2 are alternately formed in the clocked phase section Ac during the transfer period. By repeating this, the signal charges accumulated in the potential well are transferred in the right-hand direction (the horizontal transfer unit 31 side) in the figure.

For example, as shown in FIG. 5B, when an H level signal voltage is applied to the electrode 41 as the vertical drive pulse φp, the potential level of the vertical drive pulse φp changes to a broken line L1.
In order to lower the level, deeper wells are formed, and the signal charges stored in the wells in FIG. 5A move to the wells formed in the clocked phase section Ac on the right side, respectively. . Similarly, the signal charge accumulated in the well moves to a deeper well formed in the clocked phase section Ac on the right side, and the signal charge from the well section Avw of the virtual phase section Av on the left side in the well ′. I will move. Next, as shown in FIG.
As the vertical transfer pulse φp, an L-level signal voltage is applied to the electrode 4
When the voltage is applied to 1, the potential levels of the wells 'and' rise to the level of the broken line L2, so that the signal charges transferred and accumulated in the wells 'and' in FIG. Well, move to each.
As described above, by performing the timing control of repeatedly applying the H and L level signal voltages to the electrodes 41, the signal charges accumulated in each pixel are sequentially transferred to the right hand direction (the horizontal transfer unit 31 side) in the figure. You. In the above description, the principle of the vertical transfer operation has been described by taking one vertical line as an example, but the same timing control is performed simultaneously on all the vertical lines of the light receiving unit 30. That is, the signal charges accumulated on one horizontal line are sequentially transferred to the horizontal transfer unit 31 while maintaining the same horizontal line. Here, one pixel 30p is composed of a pair of adjacent clocked phase parts Ac and virtual phase parts Av. In FIG. 5, for example, the signal charges accumulated in the well are the same as the signal charges of one pixel 30p. Become.

In the vertical transfer operation described above, only one horizontal line (M stages) of the light receiving section 30 is conventionally performed during one transfer period. That is, in the conventional vertical transfer operation, when the signal charges accumulated in the uppermost horizontal line in FIG. 2 are transferred to the horizontal transfer unit 31 during the accumulation period, the vertical transfer operation ends. However, when such a vertical transfer operation is performed in an electronic endoscope system using a single-phase driven VPCCD, the following FIG.
(A), (b), (c), image defects as described with reference to FIGS. 7 and 8 may occur.

FIGS. 6A, 6B and 6C are views conceptually showing a part of the cross section of the substrate 40 along the vertical line, similarly to FIG. However, FIG. 6 shows a portion including the uppermost horizontal line (the left end in the drawing) of the light receiving unit 30. FIG. 6A shows that the signal charges (shaded portions E2 and E4) of the well portion Avw (corresponding to the hatched portions E21 and E41) and the barrier portion A of the virtual phase portion Av are stored in the accumulation period.
vb (corresponding to hatched portions E22 and E42) is shown. Thus, the virtual phase unit Av
The state where signal charges are accumulated not only in the well portion Avw but also in the barrier portion Avb occurs when the amount of received light in the upper portion of the light receiving portion 30 is large, for example.

Next, when an H-level signal voltage is applied to the electrode 41 to shift to the transfer period and reach the potential state shown in FIG. 6C, it is held in the virtual phase section Av in FIG. 6A. Most of the signal charges shown by hatched portions E2 and E4 are in the clocked phase portion Ac on the right.
(Shown by oblique lines E3 'and E5'). However, as shown in FIG. 6B showing one aspect of the process of shifting from the state of FIG. 6A to the state of FIG. 6C, in the transfer process, the signal indicated by the hatched portion E22 'is shown. Part of the electric charge moves to the clock phase section Ac on the left (shaded area Er) and becomes residual electric charge. The residual charge indicated by the hatched portion Er is sequentially moved to the left (toward the horizontal transfer portion) by the subsequent vertical transfer operation. Will be held. Therefore, in the accumulation period following the vertical transfer operation, in the pixels of the lowermost horizontal line in the light receiving unit 30, the above-described residual charges are mixed with the signal charges generated by the light reception. That is, when such a residual charge (Er) occurs when performing video shooting using a single-phase driven VPCCD, the image corresponding to the lowermost horizontal line of the light receiving unit 30 is displayed at the uppermost position of the previous screen. The images corresponding to the horizontal lines are overlapped and displayed.

Next, with reference to FIGS. 7 and 8, the effect of the above-described residual charge Er on the image display of the TV monitor will be described. FIG. 7 shows a case where an image shot by a normal video camera is displayed on a TV monitor.
Shows a case where an image captured by the electronic endoscope is displayed on a TV monitor.

7 and 8, a rectangle 50 represents an image display area on a TV monitor, and rectangles 51 and 52 are imaged by a CCD of a normal video camera and a CCD (VPCCD) of an electronic endoscope, respectively. Represents the effective area of the image to be displayed. That is, a CCD mounted on a normal video camera detects an image in an area indicated by a rectangle 51, but a part of the detected image (rectangle 50) is displayed in an image display area (rectangle 50) of the TV monitor. Only the area surrounded by the rectangle 50) is displayed. On the other hand, since the CCD of the electronic endoscope is smaller and has a smaller number of pixels than an ordinary video camera, the image of the area indicated by the rectangle 52 detected by the CCD of the electronic endoscope is entirely a TV monitor. Is displayed in the image display area (rectangle 50). Note that, for example, a black level video signal is output to an area outside the rectangle 52 in the image display area (rectangle 50) of the TV monitor.

The shaded areas 51a and 52a of the rectangles 51 and 52 shown in FIGS. 7 and 8 indicate areas where the luminance is relatively low and dark on the screen, and the unshaded areas 51b and 52b. Reference numeral 52b denotes a bright area on the screen where the luminance is relatively high. Regions 51c and 52c that are not shaded are rectangles 51 and 52, respectively.
The area corresponding to the uppermost horizontal line in the images indicated by 1, 52 is shown. Since the orientation of the image displayed on the TV monitor is opposite to the orientation of the image on the imaging surface of the CCD, the images displayed in the areas 51c and 52c are shown in FIG.
Corresponds to the image detected by the lowermost horizontal line of the light receiving section 30 shown in FIG. As described with reference to FIGS. 6A, 6B, and 6C, when the amount of light received by the pixels above the light receiving unit 30 is large and the signal charge overflows, the lowermost horizontal line Is mixed with residual charges (Er) due to excessive signal charges detected in the uppermost horizontal line of the previous screen. That is, the residual charge (E
Under the condition that r) occurs, the image of the lowermost horizontal line in the image detected by the CCD and indicated by the rectangles 51 and 52 becomes the image of the uppermost horizontal line in the next image. Superimposed.

As shown in FIGS.
If the upper region of the image shown in FIG. 2 is dark as in the hatched regions 51a and 52a, the image of the top horizontal line is discontinuously bright because of the residual charge (Er). Become. In the case of a normal video camera, the area 51c is not displayed in the image display area (rectangle 50) as shown in FIG. 7, so there is no problem.
As shown in the figure, the area 52c is also an image display area (rectangle 50).
, This area appears as a discontinuous bright line and causes an image defect.

Next, with reference to FIG. 9, a description will be given of the residual charge sweeping operation performed to prevent the defective image in the present embodiment. FIG. 9 is a timing chart showing output timings of the horizontal drive pulse φs and the vertical drive pulse φp in the present embodiment.

FIG. 9 is an enlarged view of the section CD in FIG. 3A. However, the timing of the horizontal drive pulse φs relative to the vertical drive pulse φp is conceptual and not accurate. That is, the vertical drive pulses S1 and S2 in FIG. 3B correspond to, for example, S1 and S2 shown in FIG. 9, and N horizontal drive pulses are provided between them as shown in FIG. There is a pulse φs. VPCCD1
When there are M stages of horizontal lines in the four light receiving units 30, it is sufficient to output M pulses as the vertical drive pulse φp in order to output all the horizontal lines from the VPCCD 14. Therefore, the vertical drive pulse φp is
Were output only for the number of horizontal lines (M times). However, in such a method, an image defect as described above occurs. In this embodiment, after outputting M pulses as the vertical drive pulse φp, the pulse SE is further transferred as the vertical transfer pulse φp in the transfer period. Output within. Thus, the residual charges (Er) held on the lowermost horizontal line of the light receiving unit 30 are transferred to the horizontal transfer unit 31. The residual charge (Er) transferred to the horizontal transfer unit 31 is converted into the VPCCD 14 by the constantly output horizontal drive pulse φs.
Is output to the outside of. The pulse SE is generated by the vertical transfer clock φ output from the φp timing generation circuit 35.
This is performed by setting the number of pulses of kp to M + 1. Further, in the present embodiment, the pulse SE output for sweeping out the residual charges is one time, but may be output any number of times within the light shielding period (transfer period).

The present invention is not limited to the above-mentioned practical example, but is also effective for an electronic endoscope of a simultaneous imaging system using a color filter for a CCD, and is not limited to a CCD transfer system. .

[0032]

As described above, according to the present invention, the VPC
In an electronic endoscope using a CD, a good image is always obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating a circuit configuration of an electronic endoscope system according to an embodiment of the present invention.

FIG. 2 shows a conventionally known VPCCD used in the present embodiment.
3 is a plan view schematically showing the structure of FIG.

FIG. 3 is a timing chart showing output timings of a vertical drive pulse and a horizontal drive pulse for driving a VPCCD.

FIG. 4 is a block diagram illustrating a part of a configuration of a timing control circuit related to output of a vertical drive pulse and a horizontal drive pulse.

FIG. 5 is a diagram for explaining the vertical transfer principle of a single-phase driven VPCCD.

FIG. 6 is a diagram illustrating the cause of signal charges overflowing from the uppermost horizontal line remaining during vertical transfer in a single-phase driven VPCCD.

FIG. 7 is a diagram illustrating a relationship between a detected image and a display image when an image captured by a normal video camera is displayed on a TV monitor.

FIG. 8 is a diagram illustrating a relationship between a detected image and a display image when an image captured by an electronic endoscope is displayed on a TV monitor.

FIG. 9 is an enlarged view of a section CD in FIG. 3A, and is a timing chart of a vertical drive pulse φp in the present embodiment.

[Explanation of symbols]

 14 VPCCD 24 CCD driver 25 Timing control circuit 30 Light receiving unit 30p Pixel 31 Horizontal transfer unit

Continued on the front page F term (reference) 4C061 CC06 NN01 SS04 5C022 AA08 AB37 AC42 AC69 5C024 BX02 CX17 GY01 GZ10 JX44 5C054 AA01 AA04 CC02 EA01 EJ05 HA12 5C065 AA04 BB18 BB23 DD03 HH01

Claims (3)

[Claims] 1. A light receiving unit having M stages of horizontal lines in which a plurality of pixels are arranged in a row, and a light receiving unit adjacent to one of the outermost horizontal lines of the M stages of horizontal lines An electronic endoscope using a single-phase driven virtual phase CCD as an imaging device, comprising: a horizontal transfer unit that is provided in parallel and outputs signal charges accumulated in the plurality of pixels in units of the horizontal lines. The signal charge stored in each pixel of each horizontal line is sequentially transferred one stage at a time in the direction of the horizontal transfer unit in units of the horizontal line, and the signal charge held in a horizontal line adjacent to the horizontal transfer unit is transferred. Vertical transfer means for transferring to the horizontal transfer unit, and 1 transferred to the horizontal transfer unit by the vertical transfer means.
Horizontal transfer means for outputting signal charges for horizontal lines to the outside of the CCD before the next horizontal line is transferred by the vertical transfer means, wherein the vertical transfer means does not expose the CCD A CCD driving device for an electronic endoscope, wherein at least (M + 1) or more horizontal lines are transferred during a light shielding period. 2. The electronic device according to claim 1, wherein the vertical transfer unit is driven by a vertical drive pulse, and the number of pulses of the vertical drive pulse corresponds to the number of stages of the horizontal line to be transferred. CCD drive device for endoscope. 3. The CCD driving apparatus for an electronic endoscope according to claim 1, wherein the vertical transfer means performs at least (M + 1) -stage transfer during the light-shielding period.