Surgery – Endoscope – With camera or solid state imager
Reexamination Certificate
1999-02-05
2001-05-22
Leubecker, John P. (Department: 3739)
Surgery
Endoscope
With camera or solid state imager
C600S160000, C348S076000
Reexamination Certificate
active
06234957
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of Japanese Patent Application No. 10-42837 filed on Feb. 9, 1998 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electronic endoscope system, and more specifically to an electronic endoscope system which is configured as a whole so as to be capable of ensuring a predetermined brightness with a halogen lamp in particular used as a light source.
2. Description of the Prior Art
An electronic endoscope system supplies rays from a light source such as a xenon lamp or a halogen lamp to a tip of an electronic endoscope through a light guide and captures an internal image of an object to be observed with an image pickup device, for example, a CCD (charge coupled device) by projecting the rays from the tip into the object to be observed. Video signals which are to be used, for example, as odd field data and even field data are sequentially read from the CCD, subjected to processing such as amplification, white balance and gamma compensation, and are stored in a memory. The video signals are then read out of the memory to display an internal image of the object to be observed on a monitor or the like.
FIG. 5
shows a condition for reading out field signals from the CCD mentioned above. Accumulated electric charges (corresponding to picture elements) are read out from the CCD generally at intervals of a vertical synchronous period (field period) of {fraction (1/60)} second. Odd field signals and even field signals are read out alternately, for example, as shown in FIG.
5
: an odd field signal (data) for a period of n+1 ({fraction (1/60)} second), an even field signal for a period of n+2, an odd field signal for a period of n+3 and an even field signal for a period of n+4.
Though electric charges on odd lines and even field lines of the CCD can be read out as odd field signals and even field signals respectively, the color-difference line sequential mixture readout system adds electric charges accumulated on an upper line to those accumulated on a lower line, thereby reading out mixture signals of (0+1) line, (2+3) line, . . . , for example, as odd field signals and mixture signals of (1+2) line, (3+4) line, . . . as even field signals.
The field signals of the periods n+1 and n+2 are used to form an n+first frame, whereas the field signals of the periods n+3 and n+4 are used to form an n+second frame, whereby an internal image of an object to be observed is displayed on the monitor by interlace scanning of these field signals.
BRIEF SUMMARY OF THE INVENTION
Though the electronic endoscope system described above uses a xenon lamp or a halogen lamp as a light source, the halogen lamp emits rays in an amount as small as ⅛ of that of rays emitted from the xenon lamp. When a halogen lamp is to be used as a light source, it is therefore necessary to configure an electronic endoscope system as a whole so as to maintain the brightness of the image at a predetermined level.
When the electronic endoscope system is to be used for observing an object which is located a relatively short distance from the tip of an electronic endoscope, the halogen lamp poses no problem, but when the electronic endoscope system is to be used for observing an object which is deep and far away, the amount of rays emitted from the halogen lamp is often insufficient, thereby obliging the use of a compensation measure.
The present invention has been made in view of the problem described above and has a primary object of providing an electronic endoscope system which is capable of forming, even with a halogen lamp, an image as bright as one which is formed with a xenon lamp.
SUMMARY OF THE INVENTION
To accomplish the object described above, the electronic endoscope system according to the present invention is characterized in that it comprises a light source unit that uses a halogen lamp as a light source and that leads rays emitted from the halogen lamp to the tip of an electronic endoscope through a light guide, an image pickup device that picks up an internal image of an object to be observed by way of an objective optical system while irradiating the object with illuminating rays from the light source unit, and a signal processing means that adds video signals at one and the same picture element location read out sequentially from the image pickup device in different periods and processes an addition signal as a single video signal.
Another electronic endoscope system according to the present invention is characterized in that it comprises a light source unit that uses a halogen lamp as a light source and that leads rays emitted from the halogen lamp to the tip of an electronic endoscope through a light guide, an image pickup device that picks up an internal image of an object to be observed by way of an objective optical system while irradiating the object with illuminating rays from the light source, an image pickup device driving circuit that reads out one and the same field signal successively at least twice from the image pickup device, a luminance enhancement circuit consisting of a delay circuit that delays a field signal read out from the image pickup device for a predetermined time and an adder which adds a field signal output from the delay circuit to the same field signal read out from the image pickup device, and a signal processing means that processes an output from the luminance enhancement circuit as a single field signal.
Furthermore, the electronic endoscope system according to the present invention may include a switching control means that selects whether or not the luminance enhancement circuit is to be used so that the image pickup device driving circuit can drive the image pickup device to read out one and the same field signal successively when the luminance enhancement circuit is used selectively or to read out an odd field signal and an even field signal alternately when the luminance enhancement circuit is not used selectively.
Furthermore, the electronic endoscope system according to the present invention may include a function of an electronic shutter that controls the exposure time of the image pickup device so that the signal processing means selectively uses an output from the luminance enhancement circuit as a video signal for a slow scan mode in which a shutter speed is slower than the minimum speed of the electronic shutter.
The electronic endoscope system that has the configuration described above is capable of reading out each of the signals of an odd field signal and an even field signal twice from the image pickup device, and adding two data sets for one and the same field (for the odd field and the even field) with the delay circuit and the adder. As a result, the electronic endoscope system is capable of providing a luminance signal multiplied to a level (brightness) twice as high.
Even if the slowest shutter speed is set at {fraction (1/60)} second, for example, while brightness is being controlled with the function of the electronic shutter, the electronic endoscope system is capable of providing an exposure which is the same as that at a shutter speed of {fraction (1/30)} second (in the slow scan mode), since it is capable of providing a luminance signal twice as high by executing luminance enhancement processing at a shutter speed of {fraction (1/60)} second.
REFERENCES:
patent: 5010413 (1991-04-01), Bahr
patent: 5929900 (1999-07-01), Yamanaka et al.
patent: 6100920 (2000-08-01), Miller et al.
patent: 55-43684 (1980-03-01), None
Fuji Photo Optical Co., Ltd.
Leubecker John P.
Snider Ronald R.
Snider & Associates
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