Image recording apparatus and rearview CRT therefor

• US 5,389,985 A
• Filed: 11/15/1993
• Issued: 02/14/1995
• Est. Priority Date: 11/15/1993
• Status: Expired due to Fees

• Current Assignee: Electronics For Imaging Incorporated
• Original Assignee: Management Graphics, Inc. (Electronics For Imaging Incorporated)
• Inventors: Olson, Thor A., Keeney, Richard A.
• Primary Examiner(s): BLANKENSHIP, HOWARD BENNETT
• Application Number:
  US08/153,230
• Time in Patent Office: 456 Days
• Field of Search: 354/75, 354/76, 355/20, 313/473, 313/477 R
• US Class Current: 396/429
• CPC Class Codes: G03B 15/003 Apparatus for photographing CRT-screens
• CPC Class Codes: H01J 31/12 with luminescent screen
• CPC Class Codes: H04N 1/1004 using two-dimensional electrical scanning, e.g. cathode-ray tubes using two-dimensional arrays H04N1/195
• CPC Class Codes: H04N 2201/0404 Scanning transparent media, e.g. photographic film

Abstract

An imaging system such as an image recorder or scanner is provided with a rearview cathode ray tube. A transparent viewport of optical quality is provided along an optical axis of the CRT which is perpendicular to the CRT faceplate and generally centered with respect to the image area. The electron beam used for scanning the images is placed off-axis with respect to the CRT screen. A deflection control system compensates for spherical distortion and for the keystone effect that results from the off-axis placement of the electron gun. The structure of the present invention eliminates halation, thereby improving the dynamic range and contrast achievable for imaging and/or scanning purposes. The phosphor layer used in the CRT is made substantially thicker than in conventional CRTs, thereby reducing blemishes and improving uniformity, resolution and light output. The partial sharing of electron beam and optical paths enables more compact imaging and scanning systems to be provided.

Claims

1. Apparatus for recording an image on a substrate such as photographic film, comprising:

a rearview cathode ray vacuum tube having a faceplate;

a layer of phosphor deposited on said faceplate in the interior of said vacuum tube;

an optical viewport in said vacuum tube for viewing an image on an image area of said phosphor inside said vacuum tube, said optical viewport disposed along an optical axis generally perpendicular to said faceplate and generally centered with respect to said image area;

means mounted in said vacuum tube offset from said optical axis, for generating an electron beam at an acute angle with respect to said optical axis to write said image on the image area of said phosphor; and

a camera mounted to view said image through said optical viewport for recordal of the image.

2. Apparatus in accordance with claim 1 further comprising:

means for controlling said electron beam generating means to compensate for keystone distortions caused by the offset mounting thereof as said image is written onto said phosphor.

3. Apparatus in accordance with claim 1 wherein said phosphor has a transmissivity of ≦

10%.

4. Apparatus in accordance with claim 1 wherein said faceplate is opaque.

5. Apparatus in accordance with claim 1 wherein said faceplate includes an opaque anode layer underneath said phosphor layer.

6. Apparatus in accordance with claim 1 wherein said faceplate comprises an interior substrate having said phosphor deposited thereon and mounted between said viewing port and an exterior face of said vacuum tube.

7. Apparatus in accordance with claim 6 wherein said faceplate is flat.

8. Apparatus in accordance with claim 1 wherein said faceplate comprises an exterior face of said vacuum tube.

9. Apparatus for scanning an image comprising:

a rearview cathode ray vacuum tube having a faceplate;

a layer of phosphor deposited on said faceplate in the interior of said vacuum tube;

an optical viewport in said vacuum tube for viewing a scanning window on said phosphor inside said vacuum tube, said optical viewport disposed along an optical axis generally perpendicular to said faceplate and generally centered with respect to said scanning window;

means mounted in said vacuum tube offset from said optical axis, for generating an electron beam at an acute angle with respect to said optical axis;

means for controlling said electron beam generating means to produce a scanning spot within the scanning window of said phosphor;

optical means including an image carrier mounted along said optical axis, said image carrier adapted to carry an image to be scanned by said scanning spot exiting said optical viewport; and

sensor means for sensing said scanning spot as it scans an image carried on said image carrier.

10. Apparatus in accordance with claim 9 further comprising:

means for controlling said electron beam generating means to compensate for keystone distortions caused by the offset mounting thereof as said image is written onto said phosphor.

11. Apparatus in accordance with claim 9 wherein said phosphor has a transmissivity of ≦

10%.

12. Apparatus in accordance with claim 9 wherein said faceplate is opaque.

13. Apparatus in accordance with claim 9 wherein said faceplate includes an opaque anode layer underneath said phosphor layer.

14. Apparatus in accordance with claim 9 wherein said faceplate comprises an interior substrate having said phosphor deposited thereon and mounted between said viewing port and an exterior face of said vacuum tube.

15. Apparatus in accordance with claim 14 wherein said faceplate is flat.

16. Apparatus in accordance with claim wherein said faceplate comprises an exterior face of said vacuum tube.