Television – Special applications – With endoscope
Reexamination Certificate
1998-11-24
2002-09-24
Diep, Nhon (Department: 2613)
Television
Special applications
With endoscope
C600S101000
Reexamination Certificate
active
06456317
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an endoscopic apparatus which makes it possible to expand a dynamic range thereof to obtain an image signal more efficiently.
2. Description of the Related Art
For observing the interior of a body cavity, medical-purpose endoscopes are employed. Since the interior of a body cavity is dark, lighting equipment is needed. In an electronic endoscope or an endoscopic apparatus employing an endoscope mountable camera, if the illumination is too bright, a halation effect occurs. On the if other hand the illumination is too dark, it is difficult to observe the image. These effects are attributable to the dynamic range of a solid-state imaging device such as a CCD.
In general, an effective luminance range available for imaging by an imaging apparatus such as a TV camera is defined uniquely by the photoelectric conversion characteristic of an imaging device, for example, a solid-state imaging device. In other words, the lower limit of the voltage levels of the outputs of the imaging device is restricted by a noise level. On the other hand, the upper limit thereof is restricted by a saturation value. A usable operating range of voltage levels is thus defined. Moreover, a characteristic curve indicating the voltage levels of the outputs of the solid-state imaging device has a slope retained at a certain value. The effective luminance range available for imaging by the solid-state imaging device is therefore defined uniquely.
For example, Japanese Unexamined Patent Publication No. 57-39673 has proposed an imaging apparatus that synthesizes image signals produced with an object set to two different brightness levels so as to expand the dynamic range of a solid-state imaging device for an image signal.
However, when an endoscope is used for imaging, illumination is needed to observe the interior of a body cavity. The interior of a body cavity contains moistened surfaces having numerous irregularities. For this reason, if the dynamic range is to narrow, a halation effect occurs in imaging an object located at a near point because of too bright illumination. Moreover, an object located at a far point cannot be imaged. As disclosed in the prior art, therefore, an apparatus for synthesizing image signals produced with an object set to two different brightness levels so as to expand the dynamic range of a solid-state imaging device for an image signal is employed. Even when this apparatus is employed in an electronic endoscope or an endoscopic apparatus including an endoscope mountable camera, the apparatus of the prior art does not take into account the effect of the lighting equipment used for illuminating the object. Even if the dynamic range were expanded, there would arise a problem in that an object located at a far point cannot be imaged because of an insufficient amount of light.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an endoscopic apparatus which makes it possible to view an endoscopic image which depicts the interior of a body cavity while keeping the interior at a given brightness level at all points ranging from a near point to a far point in the body cavity, but bringing about neither a halation effect when the imaged point in the body cavity is located at a near point nor an insufficient amount of light when the imaged point is located at a far point.
Moreover, another object of the present invention is to provide an endoscopic apparatus which makes it possible to expand a dynamic range thereof and successfully view an object image which depicts the interior of a body cavity at all points ranging from a near point in to a far point the body cavity.
Still another object of the present invention is to provide an endoscopic apparatus capable of preventing occurrence of an insufficient amount of light especially when an object is located at a far point, while making it possible to expand the dynamic range, and to successfully observe the object located at the far point.
An endoscopic apparatus includes an endoscope, a light source unit, a signal processing unit, a light adjustment signal producing unit, and an amount-of-light control unit. The endoscope is inserted into a body cavity and has an imaging device, which images an object in the body cavity, incorporated therein or mounted thereon. The light source unit supplies illumination light to the endoscope. The signal processing unit processes an image signal sent from the imaging device of the endoscope, and synthesizes images projected during different exposure times so as to expand the dynamic range of the imaging device. The light adjustment signal producing unit produces a light adjustment signal. When the signal processing unit expands the dynamic range of the imaging device, the light adjustment signal causes an amount of light emanating from the light source unit and falling on the imaging device to increase compared with an amount of light employed in a normal state. The amount-of-light control unit controls an amount of illumination light emanating from the light source unit according to the light adjustment signal sent from the light adjustment signal producing unit.
Moreover, the endoscopic apparatus of the present invention may include an endoscope, a light source unit, and a signal processing unit. The endoscope is inserted into a body cavity and has an imaging device, which images an object in the body cavity, incorporated therein or mounted thereon. The light source unit supplies illumination light to the endoscope whereby an amount of illumination light to be supplied to the endoscope is controlled according to a light adjustment signal. The signal processing unit processes an image signal sent from the imaging device in the endoscope. Moreover, the signal processing unit synthesizes images projected during two different exposure times to thus expand the dynamic range of the imaging device. The signal processing unit produces a light adjustment signal that causes an amount of light falling on the imaging device to increase when the dynamic range is expanded as compared with an amount of light falling thereon in a normal state.
REFERENCES:
patent: 4704520 (1987-11-01), Kanno et al.
patent: 4945366 (1990-07-01), Hisamichi et al.
patent: 5408263 (1995-04-01), Kikuchi et al.
patent: 5517242 (1996-05-01), Yamada et al.
patent: 5638119 (1997-06-01), Cornuejols
patent: 6278490 (2001-08-01), Fukuda et al.
patent: 3436057 (1985-05-01), None
patent: 57-39673 (1982-03-01), None
patent: 4-196776 (1992-07-01), None
patent: 5-153473 (1993-06-01), None
patent: 6-141229 (1994-05-01), None
Kami Kuniaki
Kusamura Noboru
Matsumoto Kanichi
Mochida Akihiko
Ogasawara Kotaro
Diep Nhon
Olympus Optical Co,. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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