Autofocusing endoscopic system

• US 20030040659A1
• Filed: 08/23/2001
• Published: 02/27/2003
• Est. Priority Date: 08/23/2001
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation), Smith & Nephew Incorporated (Smith & Nephew PLC)
• Original Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Inventors: Kazakevich, Yuri
• Granted Patent: US 6,749,561 B2
• Time in Patent Office: Days
• US Class Current: 600/167
• CPC Class Codes: A61B 1/00188 with focusing or zooming features
• CPC Class Codes: G02B 23/2407 Optical details
• 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 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: Y10S 600/921 Manipulating image characteristics

Abstract

An endoscopic apparatus and method allow for robust autofocusing operation regardless of contrast characteristics of the environment. The endoscopic apparatus and method can focus on a field stop edge and store default information of the apparatus focused on the edge. Later, if the endoscope fails to focus on an internal target object during the course of normal operation, the endoscope recalls the default information from memory to focus the lens on the edge of the field stop. Thus, internal structural objects in front of the endoscopic apparatus are brought into reasonable focus for visualization.

Claims

1. A method for maintaining a focused image viewed by an autofocusing endoscopic apparatus having an optical system, the method comprising:

determining an transition between an imaging area and a non-imaging area;

focusing the optical system on the transition; and

storing in a memory a position of the optical system focused on the edge.

2. The method according to claim 1 further comprising:

selecting at least a portion of the imaging area for focusing;

determining a contrast value of at least the portion of the imaging area;

comparing the contrast value of at least the portion of the imaging area with a preset value; and

moving the optical system to the position of the optical system stored in the memory to focus on the edge if the contrast value is below the preset value.

3. The method according to claim 2, further comprising:

determining and comparing the contrast value at a predetermined frequency.

4. The method according to claim 1 further comprising:

selecting at least a portion of the imaging area for focusing;

determining a contrast value of at least the portion of the imaging area;

comparing the contrast value of at least the portion of the imaging area with a preset value; and

focusing the optical system on at least the portion of the imaging area if the contrast value is above the preset value.

5. The method according to claim 4 further comprising:

determining and comparing the contrast value at a predetermined frequency.

6. An method maintaining a focused image viewed by an autofocusing endoscopic apparatus having an optical system, the method comprising:

determining an transition between an imaging area and a non-imaging area;

focusing the optical system on the transition; and

storing in a memory a position of the optical system focused on the edge;

selecting at least a portion of the imaging area for focusing;

determining a contrast value of at least the portion of the imaging area;

comparing the contrast value of at least the portion of the imaging area with a preset value;

moving the optical system to the position of the optical system stored in the memory to focus on the edge if the contrast value is below the preset value; and

focusing the optical system on at least the portion of the imaging area if the contrast value is above the preset value.

7. An article comprising a machine-readable medium that stores machine-executable instructions for causing an endoscopic apparatus to:

determine an transition between an imaging area and a non-imaging area;

focus the optical system on the transition; and

store in a memory a position of the optical system focused on the edge.

8. The article according to claim 7 further including instruction for causing the edoscopic apparatus to:

select at least a portion of the imaging area for focusing;

determine a contrast value of at least the portion of the imaging area;

compare the contrast value of at least the portion of the imaging area with a preset value; and

move the optical system to the position of the optical system stored in the memory to focus on the edge if the contrast value is below the preset value.

9. The article according to claim 8 further including instruction for causing the apparatus to determine and compare the contrast value at a predetermined frequency.

10. The article according to claim 7 further including instruction for causing the apparatus to:

select at least a portion of the imaging area for focusing;

determine a contrast value of at least the portion of the imaging area;

compare the contrast value of at least the portion of the imaging area with a preset value; and

focus the optical system on at least the portion of the imaging area if the contrast value is above the preset value.

11. The article according to claim 10 further including instruction for causing the apparatus to determine and compare the contrast value at a predetermined frequency.

12. An endoscopic apparatus comprising:

an optical system;

an autofocusing module for focusing the optical system on a selected focusing zone;

the selected focusing zone including a zone around an edge between an imaging area and a non-imaging area and;

a memory for storing a position of the optical system focused on the edge.

13. The endoscopic apparatus according to claim 12 wherein the autofocusing module comprises:

an image size detector to find the edge between the imaging area and the non-imaging area;

a zone selector to select the focusing zone including the zone around the edge; and

an edge detector to focus the optical system on the edge.

14. The endoscopic apparatus according to claim 12 further comprising:

a driver for moving focusing elements of the optical system; and

a focus controller for controlling the driver;

wherein the focus controller interacts with the autofocusing module to focus the optical system on the edge.

15. The endoscopic apparatus according to claim 12 further comprising:

a photosensitive device for converting an image transmitted from the optical system into video signals, wherein the video signals are transmitted to the autofocusing module for signal processing.

16. The endoscopic apparatus according to claim 14, wherein the focusing elements comprise movable lens.