Electronic endoscope

• US 6,473,116 B1
• Filed: 12/23/1999
• Issued: 10/29/2002
• Est. Priority Date: 12/28/1998
• Status: Expired due to Term

• Current Assignee: Hoya Corporation
• Original Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Inventors: Takahashi, Tadashi
• Primary Examiner(s): LEE, RICHARD J
• Application Number:
  US09/471,368
• Time in Patent Office: 1,041 Days
• Field of Search: H01/N.718, 348/65, 348/68-72, 348/625, 600/101, 600/109, 600/112, 600/180, 600/181
• US Class Current: 348/65
• CPC Class Codes: A61B 1/0655 Control therefor
• CPC Class Codes: A61B 1/0669 at proximal end of an endoscope
• CPC Class Codes: H04N 23/555 for picking-up images in sites, inaccessible due to their dimensions or hazardous conditions, e.g. endoscopes or borescopes
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 7/183 for receiving images from a single remote source

Abstract

Electronic endoscope includes a video-scope, video-processor, a light source, a luminance value calculator, a stop, a motor, a drive-amount setter, a stop-controller, and a drive-amount determiner. The luminance value calculator successively calculates a luminance value indicating brightness of the object image, on the basis of image-pixel signals. The drive-amount setter sets a target drive-amount of the stop, to make the brightness of the object image constant, on the basis of the luminance value. The stop-controller adjusts the quantity of light radiating from the distal end of the video-scope by controlling the stop in accordance with the target drive-amount at regular time-intervals, whereby the stop opens and closes such that the brightness of the object image at constant level. The drive-amount determiner determines whether the target drive-amount exceeds a tolerable drive-amount. When the target drive-amount exceeds a tolerable drive-amount, the stop-controller at least suspends a drive of the stop at the next adjustment of the quantity of light.

Claims

1. An electronic endoscope comprising:

a video-scope that has an image sensor provided at a distal end of said video-scope, on which an object image is formed, and a light guide provided throughout said video-scope, to guide light from a proximal end of said video-scope to the distal end of said video-scope;

a video-processor, to which said proximal end of said video-scope and a monitor for displaying said object image are respectively connected, adapted to process image-pixel signals corresponding to said object image, successively read from said image sensor;

a light source provided in said video-processor such that light, emitted from said light source, is guided through said light guide and radiates from the distal end of said video-scope;

a luminance value calculator adapted to successively calculate a luminance value indicating brightness of said object image on the basis of said image-pixel signals;

a stop provided between said light source and said proximal end of said video-scope, adapted to regulate a quantity of light radiating from the distal end of said video-scope;

a motor adapted to drive said stop, said stop being connected to said motor such that said stop is driven in accordance with a motion of said motor;

a drive-amount setter adapted to set a target drive-amount of said stop, to make brightness of said object image constant, on the basis of said luminance value;

a stop-controller adapted to adjust the quantity of light radiating from the distal end of said video-scope by controlling said stop in accordance with said target drive-amount at regular time-intervals, wherein said stop opens and closes such that the brightness of said object image displayed on said monitor is maintained at constant level; and

a drive-amount determiner adapted to determine whether said target drive-amount exceeds a tolerable drive-amount, said stop-controller adapted to at least suspend a drive of said stop at the next adjustment of the quantity of light when said target drive-amount exceeds said tolerable drive-amount;

wherein when a drive-time of said stop, depending on the target drive-amount, exceeds the time-interval for performing the adjustment of the quantity of light, said stop-controller suspends the drive of said stop for at least the next adjustment of the quantity of light and substantially prevents hunting.

2. The electronic endoscope of claim 1, wherein said tolerable drive-amount is under a maximum drive-amount of a series of drive-amounts, said tolerable drive amount substantially preventing hunting.

3. The electronic endoscope of claim 1, wherein said motor is a stepping motor adapted to rotate in accordance with a pulse number of pulse signals, said stop-controller adapted to one of open and close said stop by rotating said stepping motor by a target pulse number corresponding to said target drive-amount, whereby said stop is adapted to be driven by said target pulse number.

4. The electronic endoscope of claim 3, wherein said stop-controller is adapted to adjust the quantity of light radiating from the distal end of said video-scope on the basis of a difference between said luminance value and a reference value indicating a proper brightness of said object image at regular-time-intervals.

5. The electronic endoscope of claim 4, wherein said drive-amount setter is adapted to set a target pulse number corresponding to said target drive-amount, on the basis of a reference table, in which a correspondence relationship between the difference of said luminance value and said reference value, and said target pulse number is indicated, said stop-controller adapted to one of open and close said stop by rotating said stepping motor by said target pulse number.

6. The electronic endoscope of claim 4, wherein said reference value is a middle value of a range of luminance values.

7. The electronic endoscope of claim 3, wherein said stop comprises:

a cover member adapted to cover light radiating from said light source toward said proximal end of said video-scope; and

a support arm extended from said cover member, which is rotatably connected to said stepping motor, said stop adapted to pivot on said support arm such that the quantity of light radiating from the distal end of said video-scope is changed in accordance with a position of said cover member.

8. The electronic endoscope of claim 7, wherein said stop is pivotable between from an angle of approximately 0 degrees where said cover member covers all of light radiating from said light source and an angle of approximately 30 degrees where all of light radiating from said light source passes through said stop.

9. The electronic endoscope of claim 8, wherein said drive-amount determiner is adapted to determine whether said target pulse number exceeds a tolerable pulse number corresponding to a shifting-angle of 4 degrees of said stop.

10. The electronic endoscope of claim 1, wherein said luminance value is an average luminance value, which is an average value of one frame worth of luminance values.

11. The electronic endoscope of claim 1, further comprising a histogram-data generator adapted to successively generate a histogram-data on the basis of said image-pixel signals, said luminance value calculator adapted to read said histogram-data and then calculate an average luminance value, which is an average value of one frame worth of luminance values, on the basis of said histogram-data.

12. The electronic endoscope of claim 1, further comprising a single said stop.

13. The electronic endoscope of claim 1, wherein the luminance value is renewed every time said stop-controller adjusts the quantity of light.

14. The electronic endoscope of claim 1, wherein the regular time intervals correspond to a scanning time.

15. The electronic endoscope of claim 1, wherein when the drive-time of said stop, depending on the target drive-amount, exceeds the regular time-intervals for the adjustment of the light amount, said stop controller does not set the target drive amount and does not feed a drive signal to said stop for at least the next adjustment of the quantity of light.

16. A video-processor of an electronic endoscope, to which a proximal end of a video-scope and a monitor for displaying an object image are respectively connected, said video-scope having an image sensor provided at a distal end of said video-scope, on which an object image is formed, and a light guide provided throughout said video-scope, to guide light from the proximal end of said video-scope to the distal end of said video-scope, said video-processor processing image-pixel signals corresponding to said object image, read from said image sensor successively, so as to generate video signals and feed said video-signals to said monitor, said video processor comprising:

a light source provided in said video-processor such that light, emitted from said light source, is guided through said light guide and radiates from the distal end of said video-scope;

a luminance value calculator adapted to successively calculate a luminance value indicating brightness of said object image on the basis of said image-pixel signals;

a stop provided between said light source and the proximal end of said video-scope, adapted to regulate a quantity of light radiating from the distal end of said video-scope;

a motor adapted to drive said stop, said stop being connected to said motor such that said stop is driven in accordance with a motion of said motor;

a drive-amount setter adapted to set a target drive-amount of said stop, to make brightness of said object image constant, on the basis of said luminance value;

a stop-controller adapted to adjust the quantity of light radiating from the distal end of said video-scope by controlling said stop in accordance with said target drive-amount at regular time-intervals, wherein said stop opens and closes such that the brightness of said object image displayed on said monitor is maintained at constant level; and

a drive-amount determiner adapted to determine whether said target drive-amount exceeds a tolerable drive-amount, said stop-controller adapted to at least suspend a drive of said stop at the next adjustment of the quantity of light when said target drive-amount exceeds said tolerable drive-amount;

wherein when a drive-time of said stop, depending on the target drive-amount, exceeds the time-interval for performing the adjustment of the quantity of light, said stop-controller suspends the drive of said stop for at least the next adjustment of the quantity of light and substantially prevents hunting.