Electronic endoscope apparatus

Details Electronic endoscope apparatus Electronic endoscope apparatus

1999-01-04

2002-12-03

Lee, Richard (Department: 2613)

Television

Special applications

With endoscope

Reexamination Certificate

active

06489987

ABSTRACT:

BACKGROUND OF THE INVENTION
This application claims the priority of Japanese Patent Application No. 10-14980 filed on Jan. 9, 1998, Nos. 10-33776 and 10-33777 filed on Jan. 30, 1998, Nos. 10-38170 and 10-38171 filed on Feb. 4, 1998 and No. 10-54421 filed on Feb. 18, 1998 which are incorporated herein by reference.
The present invention relates to an electronic endoscope apparatus, and more particularly to structure of an electronic endoscope apparatus for forming a still image through the use of an all-pixel reading system which reads out all pixels accumulated on an image-pickup device.
DESCRIPTION OF THE PRIOR ART
In an electronic endoscope apparatus, for example, CCD (Charge Coupled Device) is used as a solid image-pickup device, and this CCD is structured so as to obtain an image signal (video signal) by reading out charge accumulated in units of pixels by a photoelectric conversion device. In, for example, a simultaneous type electronic endoscope apparatus, color filters are arranged in units of pixels on the top surface of the foregoing CCD to thereby obtain a color image.
FIG. 16
shows an arrangement state for the foregoing color filters, and Mg (magenta) and Cy (cyan) pixels are arranged on, for example, an even line, and G (green) and Ye (yellow) pixels are arranged on an odd line on a picked-up surface of CCD
1
as shown. In this CCD
1
, accumulated charge (pixel signal) in units of pixels is to be obtained through these color filters.
According to a conventional color difference line sequential mix reading (pixel mix reading) system, accumulated charges of pixels on the upper and lower lines are added and mixed to be read out. For example, during first exposure, video signals of such Odd field as a mixed signal of
0
-line and
1
-line, a mixed signal of
2
-line and
3
-line, . . . are read out, and during the second exposure, video signals of such even field as a mixed signal of
1
-line and
2
-line, a mixed signal of
3
-line and
4
-line, . . . are read out. Therefore, two lines of mixed signals of CCD
1
become one line of signals of field image, and one odd or even field of data are to be obtained by one exposure.
FIG. 17
shows an operation of signals read out from the foregoing CCD
1
, and in an electronic endoscope apparatus, an odd field and an even field are formed on the basis of the O (Odd)/E (Even) signal (field signal) for each {fraction (1/60)} second (vertical synchronizing period) as shown in FIG.
17
(A). Therefore, as shown in FIG.
17
(B), signals are accumulated in accumulation (exposure) time T of an electronic shutter during the foregoing period of {fraction (1/60)} second, and the accumulation mixed signal is read out during the next {fraction (1/60)} second period. As a result, as shown in FIG.
17
(C), an odd field signal, and an even field signal are to be obtained, and for example, the (n−1)th odd field signal becomes mixed signals of (
0
+
1
)line, (
2
+
3
)line, (
4
+
5
)line . . . which are shown on the left of
FIG. 16
, and the n-th even field signal becomes mixed signals of (
1
+
2
)line, (
3
+
4
)line, . . . which are shown on the right of FIG.
16
.
These odd field signals and even field signals are interlace scanned to be formed as an one-frame image, and this image is displayed as a moving image on a monitor. Also, in the endoscope apparatus, a freeze switch is arranged in the operating unit, and when this freeze switch is depressed, a still image at the time is formed and displayed.
BRIEF SUMMARY OF THE INVENTION
In the foregoing simultaneous type electronic endoscope apparatus, however, there is a time lag of {fraction (1/60)} second between those odd field image and even field image which are used to form the one-frame image as shown in the foregoing FIG.
17
(C), and if there is a shake of the endoscope itself, a movement of the object to be observed or the like during this period of time, there is the problem that the image quality (resolution, color shift, etc.) will be deteriorated when the still image is displayed. In other words, in the case of a moving image, it is often better to faithfully reproduce the movement and the like of the subject conversely by the foregoing mix reading system in the CCD
1
, but in the case of a still image, the resolution will be deteriorated.
Also, in the electronic endoscope apparatus, an electronic shutter function for changing the accumulation time of a signal is frequently adopted, and by the use of the electronic shutter, it is possible to improve the image quality if the accumulation time is made shorter in a light place at a short distance or the like. As shown in
FIG. 17
, however, there is a time lag of {fraction (1/60)} second between two accumulation (exposure) for forming an one-frame image, and in a still image, there is the inconvenience that the effect of shortened accumulation time is not sufficiently exhibited.
The present invention has been achieved in the light of the foregoing problems, and is aimed to supply an electronic endoscope apparatus capable of forming a still image with high image quality by reading out all pixels obtained through an image-pickup device by one exposure, and faithfully reproducing the movement concerning a moving image.
Another object is to prevent, in the foregoing electronic endoscope apparatus, any incomplete image from being displayed or the screen from being blurred when switching from a moving image to a still image.
Still another object is to stabilize, in the foregoing electronic endoscope apparatus, black level clamping treatment when a still image is selected, and to prevent the image quality from being deteriorated.
SUMMARY OF THE INVENTION
In order to achieve the foregoing object, an electronic endoscope apparatus according to a first invention comprises: an image-pickup device having a plurality of color filters arranged in units of pixels; light shielding means for intercepting illumination light so that pixel signals for a predetermined period of time are not accumulated on this image-pickup device; and switching means for switching driving control for both a pixel mix reading system, which mixes pixels accumulated on the foregoing image-pickup device between upper and lower horizontal lines to output from the image-pickup device, and a all-pixel reading system, which reads out signals of all pixels accumulated on the foregoing image-pickup device by one exposure through the use of a light shielding period set by the foregoing light shielding means.
In the foregoing, there can be provided control means for forming a moving image using the foregoing pixel mix reading system and a still image using the foregoing all-pixel reading system while controlling the foregoing switching means.
Also, the foregoing first invention is preferably structured by including: an image-pickup device driving circuit for controlling so as to read out, concerning all pixel signals accumulated on the foregoing image-pickup device by one exposure, image signals on either an odd line or an even line first, and next to read out image signals on the remaining line; a memory for storing, at the execution of the foregoing all-pixel reading system, image signals on the foregoing odd line obtained from the image-pickup device and image signals on the foregoing even line; a phase adjustment memory for adjusting phase, at the execution of the foregoing all-pixel reading system, between image signals on a predetermined line previously stored in the foregoing memory and image signals on the other line; a mixing circuit for forming a still image signal by mixing pixel signals of the foregoing odd line and the foregoing even line during the same exposure which have been read out from the foregoing each memory; and an image switching circuit for directly inputting a moving image signal of the pixel mix reading system outputted from the foregoing image-pickup device to switch either this moving image signal or the still image signal outputted from the foregoing mixing circuit on the basis of the operation of a freeze switch.
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