System of absolute measurement for radiological image luminance control
First Claim
1. For use with a CRT display device having a glass envelope jug and a display face carrying internally of the display face phosphors in a phosphor layer backed internally of the glass envelope jug by a reflective, partially light-transmissive mask, a system for automatically measuring the absolute luminance of the CRT display device and the ambient illuminance produced by illumination at the face of the CRT, variations in luminance performance of the CRT and ambient illumination tending to interfere with the fidelity or facility of displayed image interpretation of images displayed by the CRT, the system comprising in combination a photosensor carried invisibly to a viewer of the CRT face while presented in intimate relation to the CRT such that a reproducibly measurable illuminance proportion of light resulting from the ambient lighting on the CRT face will be received indirectly by the photosensor in addition to another reproducibly measurable luminance proportion of the light generated by said phosphors of the CRT, the photosensor being positioned on the jug of the CRT at a location rearward of the display face of the CRT for receiving light emitted backward through the mask from said phosphors of the CRT, and for receiving light indirectly from ambient light impinging on the CRT display face, and so positioned that the output of the photosensor is the sum of two components, one of which is proportional to the absolute luminance of excited phosphors from the face of the CRT as said luminance is measured by the photosensor through the mask and the other of which is proportional to the ambient illuminance as received at the CRT face, and means responsive to the photosensor for determining said absolute luminance and illuminance.
2 Assignments
0 Petitions
Accused Products
Abstract
An inconspicuous system is defined for measuring the absolute luminance of a CRT display and the actual effective luminance as would be measured from the viewer'"'"'s perspective due to additional reflected ambient illuminance in order to enable closed loop adjustment of the display device and to thereby enable luminance quality control, facilitate image perception, and ascertain fidelity of image presentation conveniently over time.
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Citations
13 Claims
- 1. For use with a CRT display device having a glass envelope jug and a display face carrying internally of the display face phosphors in a phosphor layer backed internally of the glass envelope jug by a reflective, partially light-transmissive mask, a system for automatically measuring the absolute luminance of the CRT display device and the ambient illuminance produced by illumination at the face of the CRT, variations in luminance performance of the CRT and ambient illumination tending to interfere with the fidelity or facility of displayed image interpretation of images displayed by the CRT, the system comprising in combination a photosensor carried invisibly to a viewer of the CRT face while presented in intimate relation to the CRT such that a reproducibly measurable illuminance proportion of light resulting from the ambient lighting on the CRT face will be received indirectly by the photosensor in addition to another reproducibly measurable luminance proportion of the light generated by said phosphors of the CRT, the photosensor being positioned on the jug of the CRT at a location rearward of the display face of the CRT for receiving light emitted backward through the mask from said phosphors of the CRT, and for receiving light indirectly from ambient light impinging on the CRT display face, and so positioned that the output of the photosensor is the sum of two components, one of which is proportional to the absolute luminance of excited phosphors from the face of the CRT as said luminance is measured by the photosensor through the mask and the other of which is proportional to the ambient illuminance as received at the CRT face, and means responsive to the photosensor for determining said absolute luminance and illuminance.
- 5. For use with a CRT display device having a glass envelope jug a and a display face carrying internally of the display face phosphors, a system for a automatically measuring the absolute luminance of a CRT display device having a CRT and the ambient illumination at the face of the CRT, variations in luminance performance of the CRT and ambient illumination tending to interfere with the fidelity or facility of displayed image interpretation of images displayed by the CRT, the system comprising in combination a photosensor carried invisibly to a viewer of the CRT face while presented in intimate relation to the CRT such that a reproducibly measurable illuminance proportion of light resulting from the ambient lighting on the CRT face will be received indirectly by the photosensor in addition to another reproducibly measurable luminance proportion of the light generated by phosphors of the CRT and means responsive to the photosensor for determining said absolute luminance and illuminance, wherein the photosensor-responsive means comprises a current to frequency converter interconnected and closely associated with the photosensor means for integrating and converting the analog output of the photosensor means to a buffered binary signal with a dynamic range of at least 5 decades, and a microprocessor control to interpret the resulting binary signal and to effect with certainty the absolute blanking of the CRT as by sufficient reduction of the positive voltage at the G2 element of the CRT electron gun.
Specification