Image quality control in an imaging system

• US 20070036453A1
• Filed: 08/09/2005
• Published: 02/15/2007
• Est. Priority Date: 08/09/2005
• Status: Abandoned Application

• Current Assignee: CareStream Health Incorporated
• Original Assignee: Eastman Kodak Company
• Inventors: Preska, William, Lindquist, Thomas
• Application Number:
  US11/200,363
• Publication Number:
  US 20070036453A1
• Time in Patent Office: Days
• US Class Current: 382/254
• CPC Class Codes: H04N 1/407 Control or modification of tonal gradation or of extreme levels, e.g. background level

Abstract

A method of and system for controlling image quality in a digital image printing system, such as a medical image printing system, is provided a digital medical image including a set of pixels, each of which has a pixel value, is acquired from a medical image source. A medical image printer prints the medical image on media to produce a medical image print. A device measures the density of at least a subset of the set of pixels on said medical image print to produce a measured density image. There is calculated for at least the subset of the set of pixels of the digital medical image a predicted density image. The measured density image and the predicted density image are compared to produce density corrections, if any; and any density corrections are used in printing subsequent digital medical images to improve image quality thereof.

Claims

1. A method of controlling image quality in a digital image printing system, comprising:

acquiring a digital image including a set of pixels, each of which has a pixel value;

printing said digital image on media to produce a digital image print;

measuring the density of at least a subset of said set of pixels on said digital image print to produce a measured density image;

calculating for said subset of said set of pixels of said digital image a predicted density image;

comparing said measured density image and said predicted density image to produce density corrections, if any; and

using any said density corrections to modify software used in printing subsequent digital images to improve the image quality thereof.

2. A method of controlling image quality in a medical image printing system, comprising:

acquiring a digital medical image including a set of pixels, each of which has a pixel value;

printing said medical image on media to produce a medical image print;

measuring the density of at least said set of pixels on said medical image print to produce a measured density image;

calculating for at least said set of pixels of said digital medical image a predicted density image;

comparing said measured density image and said predicted density image to produce density corrections, if any; and

using any said density corrections to modify software used in printing subsequent digital medical images to improve the image quality thereof.

3. The method of claim 2 wherein said digital medical image is acquired from one of the following medical image sources, among others, a medical film digitizer, a diagnostic imaging modality, a computed radiography system, a direct digital radiography system, an archive of digital medical images.

4. The method of claim 2 wherein said printing is carried out by means of one of a medical laser printer which produces medical image prints on thermally processable photothermographic media, an electrophotographic printer, an ink jet printer, a direct thermal printer, a thermal dye transfer printer.

5. The method of claim 3 wherein said acquired digital medical image is digitally processed by means of a media model lookup table which converts said set of pixels into calibrated exposure values which are used by said medical laser printer to produce said medical image print.

6. The method of claim 2 wherein said density measuring is carried out by one of a spot densitometer, a 1-D line receptor, and a 2-D area receptor.

7. The method of claim 2 wherein said density measuring is carried out by means of a spot densitometer having a measuring aperture of predetermined size, wherein said acquired digital medical image includes an array of pixels each of which has a pixel value, and wherein said calculating includes:

using a provided lookup table for mapping pixel value to theoretical printed densities;

calculating from the acquired digital medical image, an image of theoretical transmittance values at full printer resolution;

calculating, by summing transmittances in small neighborhoods, a reduced resolution transmittance image, which is smaller than the predetermined size of said densitometer aperture;

convolving the reduced resolution transmittance image with an aperture mask equivalent to the densitometer'"'"'s aperture; and

converting the convolved transmittances to optical densities to produce said predicted density image.

8. The method of claim 2 wherein said comparing includes:

using an edge detection algorithm, finding the indices corresponding to media edges in said measured density image;

using known media border thicknesses adjusting the edge indices of said measured density image to correspond to image edges in said measured density image;

for a range of hypothetical small translational offsets and skew, calculating an associated densitometer trace line array, consisting of values extracted from the predicted density image along each hypothetical line;

selecting the hypothetical trace line which gives the greatest consistency along the trace line;

sorting all density differences, between said measured density image and said predicted density image along the chosen trace line, into density bins, and, for bins with a sufficient number of counts, taking the average density difference in that bin as an error estimate of the difference between measured and predicted density, in that density interval; and

modifying the media printing software as a function of this array of density errors to control the image quality of subsequent medical image prints.

9. A system for controlling image quality in a digital image printing system, comprising:

a digital image printer for printing an acquired digital image including a set of pixels, each of which has a pixel value, on media to produce a medical image print;

a device for measuring the density of at least a subset of said set of pixels on said digital image print to produce a measured density image; and

an image processor and printer control,

which calculates for at least said subset of said set of pixels of said acquired digital image a predicted density image;

which compares said measured density image and said predicted density image to produce density corrections, if any; and

which uses any said density corrections to modify software used in printing subsequent digital images to improve the image quality thereof.

10. A system for controlling image quality in a medical image printing system, comprising:

a medical image printer for printing an acquired digital medical image including a set of pixels, each of which has a pixel value on media to produce a medical image print;

a device for measuring the density of at least said set of pixels on said medical image print to produce a measured density image; and

an image processor and printer control,

which calculates for at least said set of pixels of said acquired digital medical image a predicted density image;

which compares said measured density image and said predicted density image to produce density corrections, if any; and

which uses any said density corrections to modify software used in printing subsequent digital medical images to improve the image quality thereof.

11. The system of claim 10 wherein said digital medical image is acquired from one of the following medical image sources, among others, a medical film digitizer, a diagnostic imaging modality, a computed radiography system, a direct digital radiography system, an archive of digital medical images.

12. The system of claim 10 wherein said medical image printer is one of a medical laser printer which produces medical image prints on thermally processable photothermographic media, an electrophotographic printer, a direct thermal printer, an inkjet printer, a thermal dye transfer printer.

13. The system of claim 12 wherein said image processor and printer control processes said acquired digital medical image by means of a media model lookup table which converts said set of pixels into calibrated exposure values which are used by said medical laser printer to produce said medical image print.

14. The system of claim 10 wherein said density measuring device is one of a spot densitometer, a 1-D line receptor, and a 2-D area receptor.

15. The system of claim 10 wherein said density measuring device is a spot densitometer having a measuring aperture of predetermined size, wherein said acquired digital medical image includes an array of pixels each of which has a pixel value, and wherein said calculating of said image processor and printer control includes:

using a provided lookup table for mapping pixel value to theoretical printed densities;

calculating from the acquired digital medical image, an image of theoretical transmittance values at full printer resolution;

calculating by summing transmittances in small neighborhoods a reduced resolution transmittance image, which is smaller than the predetermined size of said densitometer aperture;

convolving the reduced resolution transmittance image with an aperture mask equivalent to the densitometer'"'"'s aperture; and

converting the convolved transmittances to optical densities to produce said predicted density image.

16. The system of claim 10 wherein said comparing of said image processor and printer control includes:

using an edge detection algorithm, finding the indices corresponding to media edges in said measured density image;

using known media border thicknesses adjusting the edge indices of said measured density image to correspond to image edges in said measured density image;

for a range of hypothetical small translational offsets and skew, calculating an associated densitometer trace line array, consisting of values extracted from the predicted density image along each hypothetical line;

selecting the hypothetical trace line which gives the greatest consistency along the trace line;

sorting all density differences, between said measured density image and said predicted density image along the chosen trace line, into density bins, and, for bins with a sufficient number of counts, take the average density difference in that bin as an error estimate of the difference between measured and predicted density, in that density interval; and

modifying the media printing software as a function of this array of density errors to control the image quality of subsequent medical image prints.