Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/14—Picture signal circuitry for video frequency region
  • H04N5/20—Circuitry for controlling amplitude response
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/30—Transforming light or analogous information into electric information
  • H04N5/32—Transforming X-rays

Definitions

• the invention relates to a method for reproducing images comprising an area made up of pixels and having a brightness value for each pixel, which method comprises varying the brightness values of the pixels according to a function which is dependent on and not constant with time.
• the invention also relates to a method for reproducing images comprising an area made up of pixels and having a brightness value for each pixel, wherein each pixel may be composed per se of at least two different colours and wherein the intensity for at least one and at most all with the exception of one of the colours may also permanently be zero.
• Radiography The obtaining of medical X-ray images is referred to as radiography. Radiography is nowadays performed both by an analog procedure and by a digital procedure.
• analog radiography procedure a photographic film is exposed to the X-ray image to be reproduced, developed and subsequently reproduced by placing the developed film in a generally somewhat darkened room in front of a light box and then viewing it.
• digital manner of radiography the image is obtained electronically. It can then be reproduced on a viewing screen.
• viewing screens have the following contrast-reducing properties: light scattering between the phosphor layer and the glass window; reflection of the ambient light at the outer surface of the glass window.
• the contrast sensitivity of an observer in relation to an observed image depends on the depth of modulation with which said image is presented to an observer image by image.
• the contrast sensitivity can be increased by changing the image brightness from image to image, for instance by modulating the image brightness with a frequency between 5 and 50 Hz.
• the brightness of the reproduced image could also be increased, but that is not possible to an adequate extent due to technical limitations, such as maximum electron current and saturation of the phosphor.
• the light scattering in the thin film is also less than in the thick glass window of the viewing screen.
• the object of the invention is to improve the contrast observation of an image comprising an area made up of pixels, such as, for example, a medical X-ray image on a viewing screen.
• Patent Application 84.01605 a television image projected on a screen, a video monitor, a film for a screen, on which screen a television image is projected, an LCD monitor.
• the method according to the invention which method comprises varying the brightness value of the pixels is characterized in that the function is also dependent on the initial brightness with which at least the respective pixel would be reproduced if the function were not used and in that, for higher initial brightnesses, the ratio between the highest and the lowest value of the function is at least just as close or closer to one than for lower initial brightnesses.
• each pixel may be made up of at least two different colours
• the colour coordinates of each pixel are varied according to a function which is not constant with time and which is dependent on the initial brightness with which at least the respective pixel would be reproduced if the function were not used and in that, for higher initial brightnesses, the variation in colour coordinates is at most just as great or is smaller than for lower initial brightnesses.
• the image comprises an area made up of pixels and having a brightness value for each pixel.
• Viewing screen devices to which the invention can be applied often comprise, specifically, a so-called "look-up" table which determines the relationship between a signal presented to the viewing screen device and the signal which controls the image brightness on the screen, for example the intensity of the electron beam.
• a device in which the invention is used in this simple way is therefore characterized by at least two non-identical tables and means for changing from the one to the other "look-up" table during a picture return.
• a method according to the invention is characterized in that at least two different, spatially filtered variants of the original image are alternated.
• the reproduction system should therefore have at its disposal a larger memory from which the various filtered images can be retrieved.
• the increase in the contrast sensitivity depends both on the frequency and the depth of modulation of the modulated signal and is associated with the brightness to be reproduced.
• the first is the function which specifies the processing for the signal which determines or reproduces the brightness and/or the colour of the image on the viewing screen.
• the second is the function which specifies the order in which the images are reproduced which have not been processed or have been processed using the first function. Examples of the second function are: processed - not processed - processed - not processed etc., also to be described as yes/no/yes/no/yes/no... yes/no/no/yes/no/no/yes/no/no... yes/no/no/no/yes/no/no/no processed according to function 1/not processed/not processed according to function
• the function which specifies the processing can be, according to the above: another brightness, another colour, another spatial filtering.
• the depth of modulation can be made to increase with decreasing brightness and/or the modulation frequency can be chosen closer to that for optimum contrast observation.
• the second function it is advantageous to choose the period time as a whole multiple of the image interval, as in the examples reproduced above.
• image repetition frequency of 70 Hz which is standard per se, 35, 23.3, 17.5, 14, 11.6, 10, 9.1, 8.3 Hz etc. are then obtained as possible frequencies.

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Publications (1)

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Citations (10)

Family Cites Families (3)

• 1997
  • 1997-06-27 NL NL1006420A patent/NL1006420C2/nl not_active IP Right Cessation
• 1998
  • 1998-06-29 EP EP98931146A patent/EP0992156A1/en not_active Withdrawn
  • 1998-06-29 WO PCT/NL1998/000375 patent/WO1999000975A1/nl not_active Application Discontinuation

Patent Citations (10)

Non-Patent Citations (2)

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