Image recorder having automatic alignment method and apparatus

• US 4,754,334 A
• Filed: 01/08/1987
• Issued: 06/28/1988
• Est. Priority Date: 01/08/1987
• Status: Expired

• Current Assignee: Electronics For Imaging Incorporated
• Original Assignee: Management Graphics, Inc. (Electronics For Imaging Incorporated)
• Inventors: Olson, Thor A., Glass, William H., Kriz, J. Stanley
• Primary Examiner(s): ADAMS JR, RUSSELL E
• Application Number:
  US07/001,456
• Time in Patent Office: 537 Days
• Field of Search: 354/75, 354/76, 358/244, 358/244.1, 358/345, 364/521, 364/525
• US Class Current: 386/230
• CPC Class Codes: G03B 27/72 Controlling or varying light intensity, spectral composition, or exposure time in photographic printing apparatus
• CPC Class Codes: H04N 1/047 Detection, control or error compensation of scanning velocity or position H04N1/0402 and H04N1/17 take precedence
• 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 2201/02425 Self-adjusting arrangements, e.g. compensating for temperature fluctuations
• CPC Class Codes: H04N 2201/03162 Original guide plate
• CPC Class Codes: H04N 2201/0471 using dedicated detectors
• CPC Class Codes: H04N 2201/04717 on the scanned sheet, e.g. a reference sheet
• CPC Class Codes: H04N 2201/04729 in the main-scan direction
• CPC Class Codes: H04N 2201/04731 in the sub-scan direction
• CPC Class Codes: H04N 2201/04787 by changing or controlling the addresses or values of pixels, e.g. in an array, in a memory, by interpolation
• CPC Class Codes: H04N 2201/04789 in the main-scan direction
• CPC Class Codes: H04N 2201/04791 in the sub-scan direction
• CPC Class Codes: H04N 2201/04793 using stored control or compensation data, e.g. previously measured data

Abstract

An image recorder for providing a CRT image and apparatus to store the image on a film disposed on a film plane. The relative position, intensity and focus parameters of the image are measured during an initial startup of the image recorder, wherein the position, intensity and focus parameters of the CRT and the image thereon are automatically aligned to assure enhanced performance. The apparatus according to the present invention provides an alignment mask disposed in the CRT plane, and the CRT parameters are measured by observation of the light collected through the alignment mask from the CRT and processing the corresponding light intensity signals. The light sensing device provides a signal which is processed typically by a microprocessor controlled geometry engine to derive a set of correction data which is based on a prototype array of initialized data values. The correction data provide signals which are combined with uncorrected CRT deflection signals to provide a corrected signal. The parameters corrected by the apparatus and method according to the present invention include x and y position, focus and relative picture intensity over the surface of the screen (vignette). The above-listed parameters are used alone and in combination to provide image centering, image scaling and pincushion correction, correction for non-orthogonality between the x and y deflection coils, image rotation and correction for nonlinear second and third order effects. The set of data can also be deliberately distorted to provide image precompensation such as keystone (trapezoid) and spherical corrections as well as vignette compensation such that, when the final image is projected or displayed, a true (nondistorted) image results.

Claims

1. An image recorder providing a photographic copy of a CRT image at an image plane onto a photographic film disposed on a film plane in spatial relationship apart from said image plane, comprising:

lens means for transforming said image from said image plane to said photographic film;

an alignment mask having a target image thereon overlaying said image at said image plane;

means to selectively illuminate the CRT according to at least one of a deflection signal and an intensity signal;

photodetector means responsive to said target image selectively illuminated by said CRT and producing a target signal therefrom; and

means for adjusting at least one of said deflection signals and said intensity signal according to said target signal in response to said target signal, wherein correction for at least one of image position, rotation, orthogonality, pincushion and size are provided.

2. The image recorder of claim 1, wherein said alignment mask comprises a clear plate at least one opaque target thereon.

3. The image recorder of claim 2, further including focus adjustment means responsive to said target signal to provide a focused image on said photographic film.

4. The image recorder of claim 3, wherein said focus adjustment means comprises means for adjusting the focus of said CRT image.

5. The image recorder of claim 4, wherein said CRT image comprises a spot, and said target signal corresponds to the intensity of the CRT image and said means for adjusting the focus of said CRT provides a minimum target signal.

6. The image recorder of claim 5, wherein

said alignment mask includes a plurality of said opaque targets distributed over said image plane,

said means for adjusting provides said corrections at said targets, and further includes

interpolation means for providing said corrections adjacent to said targets.

7. The image recorder of claim 6, wherein said means for adjusting includes:

means for detecting an edge of said opaque target; and

means for determining the position of said CRT image according to the detected edge of said target.

8. The image recorder of claim 7, wherein

said means for selectively illuminating includes means to provide a movable illuminated focused spot, and wherein

said means for adjusting further includes

means for determining the intensity profile of said spot;

and

means for adjusting the focus of said spot according to said intensity profile.

9. The image recorder of claim 8, wherein said means for adjusting includes a prototype mesh for providing preliminary correction.

10. The image recorder of claim 9, wherein said means for adjusting further includes a mesh correction processor responsive to said prototype mesh and said sampled target signal, and providing a corrected mesh signal.

11. The image recorder of claim 10, wherein said means for adjusting includes at least one of:

means for sampling the target signal;

multiplication means for providing scaling correction to at least one image characteristics including image position, rotation, orthogonality, pincushion, size and vignette according to the sampled target signal; and

addition means for providing a offset correction to at least one image characteristic including image position, rotation, orthogonality, pincushion, size and vignette according to the sampled target signal.

12. The image recorder of claim 11, wherein said means for adjusting further includes a random access memory for storing said corrected mesh signal.

13. The image recorder of claim 12, wherein said means for adjusting further includes a geometry engine providing control signals to the CRT including at least one of deflection, focus and vignette signals.

14. An image recorder providing a photographic copy of a CRT image at an image plane on a photographic film disposed on a film plane in spatial relationship apart from said image plane, comprising:

lens means for transforming said image from said image plane to said photographic film;

an alignment mask disposed at said film plane having a target image thereon;

means to selectively illuminate the CRT according to at least one of a deflection signal and an intensity signal;

photodetector positive means to receive said target image selectively illuminated by said CRT and producing a target signal therefrom; and

means for adjusting at least one of said deflection signals and said intensity signal according to said target signal in response to said target signal, wherein correction for at least one of image position, rotation, orthogonality, pincushion and size are provided.

15. The image recorder of claim 14 wherein

said photographic film is contained within a first removable module, and

said alignment mask is contained within a second removable module, wherein

said first and second removable modules are selectively interchangeable.

16. The image recorder of claim 15, wherein

said photographic film is displaced from said film plane and

said alignment mark is substituted in the place of the film during adjustment by said means for adjusting.

17. An image recorder providing a photographic copy of a CRT image at a CRT plane on a photographic film, comprising:

a film holder including

an aperture plate having an aperture therein corresponding to a selected film format and also having means for providing an encoded signal corresponding to said selected format;

encoded signal sense means providing a format signal according to said aperture plate recess;

a CRT display providing said CRT image in response to a video signal and an adjustment signal; and

image adjustment means providing said adjustment signal in response to format size signals for adjusting the CRT image size and position according to said format signals.

18. The image recorder of claim 17, wherein

said mechanical encoded signal is provided by recesses in said aperture plate,

said encoded signal sense means comprises mechanical switches operative according to the presence of said recesses.

19. An image recorder providing a photograhic copy of a CRT image at a CRT plane on a photographic film disposed on a film plane in spatial relationship in an optical path apart from said CRT plane, comprising:

lens means for transforming said CRT image from said CRT plane to said photograhic film;

an alignment mask interposed in said optical path between said film plane and said CRT plane having a target image thereon;

means for selectively illuminating the CRT according to at least one of a deflection signal and an intensity signal;

photodetector means positioned to receive said target image selectively illuminated by said CRT and producing a target signal therefrom; and

means for adjusting at least one of said deflection signals and said intensity signal according to said target signal in response to said target signal, wherein correction for at least one of image position, rotation, orthogonality, pincushion and size are provided.

20. The image recorder of claim 19, wherein said target image comprises one of an opaque, a transparent and a reflective target image.

21. The image recorder of claim 19, wherein said optical path includes a mirror.

22. An image recorder providing a photographic copy of a CRT image at a CRT plane on a photographic film disposed on a film plane in spatial relationship apart from said CRT plane, comprising:

lens means for transforming said CRT image from said CRT plane to said photographic film;

an alignment mask overlaying said CRT image at a focal point of said lens means, and having a target image thereon;

means for selectively illuminating the CRT according to at least one of a deflection signal and an intensity signal;

photodetector means positioned to receive said target image selectively illuminated by said CRT and producing a target signal therefrom; and

means for adjusting at least one of said deflection signals and said intensity signal according to said target signal in response to said target signal, wherein correction for at least one of image position, rotation, orthogonality, pincushion and size are provided.

23. An image recorded, comprising:

CRT display means selectively providing a two-dimensional CRT image according to one of a plurality of image spatial density of pixels including a higher and a lower pixel density image, wherein each said image pixel density comprises a particular two-dimensional array of pixels; and

camera means for recording said CRT image on photographic film, wherein

said CRT display means includes means for replicating pixels of said lower pixel density image at said two-dimensional array corresponding to said higher image resolution to permit color matching on film.

24. The image recorder of claim 23, wherein

said means for replicating provides even multiple replications of the lower resolution image pixels in the two dimensions of the CRT display.

25. A method of alignment of a image recorder having a CRT and a photographic film disposed on a film plane, comprising the steps of:

providing an alignment target;

generating a deflection signal according to expected X and Y positions;

selectively illuminating said alignment target with a point light source from said CRT according to said deflection signal, wherein said alignment target partially obscures said selective illumination;

detecting the selectively obscured illumination;

calculating the intensity profile of said point light source; and

adjusting the focus of said point light source according to said intensity profile.

26. The method of claim 25, further including the steps of:

calculating the position of said point light source;

comparing the calculated position of said point light source to a specified position and providing an error signal therefrom; and

adjusting said expected position signal according to said error signal.

27. The method of claim 26, further including the step of:

adjusting said expected position signal to provide correction for at least one of image position, image rotation, coordinate nonorthogonality, pincushion distortion and size distortion.

28. The method of claim 27, wherein said step of adjusting said expected position signal includes the step of generating a prototype position.

29. A method of aligning a CRT display, comprising the steps of:

providing a prototype mesh having preliminary display parameters therein;

correcting said prototype mesh by mask measurements of a predetermined image;

storing corrected mesh parameters;

generating display parameters;

correcting display parameters by said corrected mesh parameters; and

displaying image with corrected display parameters.