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ppt (1.6 MB)

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ppt (1.6 MB)

  1. 1. R2-29 (2nd report) Characterization of Imaging Luminance Measurement Devices (ILMDs) Dr. Peter Blattner Swiss Federal Office of Metrology and Accreditation METAS video photometer, imaging photometer, CCD luminance meter
  2. 2. Conclusion of the 1st report <ul><li>from metrological point of view ILMDs are complex systems (traceability, software validation, etc) </li></ul><ul><li>the parameters defined by CIE 69-1987 are not sufficient to characterize ILMDs </li></ul><ul><li>there is some interest from industry to have some guidelines on how characterize ILMDs </li></ul>Prepare a Technical Report on methods for the characterization of imaging luminance measurement devices TR:
  3. 3. Progress since the last meeting Discussions with several users and manufacturers: <ul><li>more products/manufacturers on the market </li></ul><ul><li>increasing number of devices were sold </li></ul><ul><li>more quantities that are measured/deduced </li></ul>-> new applications <ul><li>some inconsistencies are found between different users in some specific cases </li></ul>
  4. 4. Quantities derived with ILMDs (1) <ul><li>Luminance distributions </li></ul>-> Display, lamps, filaments -> tunnel lightening © TechnoTeam GmbH
  5. 5. Quantities derived with ILMDs (2) <ul><li>geometrical parameters (angles,…) </li></ul><ul><li>“ partial” vertical illuminance </li></ul><ul><li>Physiological glare </li></ul>
  6. 6. Quantities derived with ILMDs (3) - >Analysis of complex sceneries © TechnoTeam GmbH <ul><li>Illuminance distributions </li></ul><ul><li>UGR </li></ul>
  7. 7. Quantities derived with ILMDs (4) <ul><li>luminance coefficients </li></ul>- > Analysis of non uniform surfaces <ul><li>angular dependant luminance distribution </li></ul><ul><li>> near field goniophotometry </li></ul><ul><li>(color coordinates) </li></ul>- > colorimetry
  8. 8. Discussions with users <ul><li>Some differences in measurements of the same sample were found between different users having different systems (differences up to 20% ) </li></ul>Explication: - Measurement task: measurement of luminance distribution of displays with LED backlights. This is inherit to ILDMs: partial filtering is not applicable and there is only a limited number of glass fiters available. © TechnoTeam GmbH One has to life/deal with that problem ! The situation is even worse when grayfilters have to be used <ul><li>Most users are „happy“ with the system they were using </li></ul>However: best possible f 1 ‘ that can be done on ILMDs is in the order of 2.5%
  9. 9. Discussions with manufacturers <ul><li>There is a limited interest from industry to have some internationally agreed guidelines on how to characterize ILMDs. </li></ul><ul><li>The characterization problems are solved mostly within the industry. </li></ul><ul><li>Some procedures are part of the “in-house” knockledge of the manufactures. </li></ul><ul><li>One manufacturer is strongly in favor for a CIE-TC (and would like to chair a possible TC). </li></ul>
  10. 10. How to go on? <ul><li>Close R2-29, new TC to generate a „User‘s guide“ </li></ul><ul><li>Close R2-29, new TC to generate guide for characterizing ILDMs </li></ul><ul><li>Close R2-29, no action (yet) </li></ul>Some of the problems are not specific to ILDMs but to LDMs Only a few number of manufacturers are concerned What to do with the parameters in CIE 69-1986 that are not applicable or missing?
  11. 11. properties of luminance meter as defined by CIE publication 69-1986 <ul><li>deviation of relative spectral responsivity from the V(l) function - > f 1 ‘ </li></ul><ul><li>UV response, IR response -> u, r </li></ul><ul><li>directional response -> f 2 (g) </li></ul><ul><li>effect from the surrounding field -> f 2 (u) </li></ul><ul><li>linearity error -> f 3 </li></ul><ul><li>error of display unit -> f 4 </li></ul><ul><li>temperature coefficient -> a </li></ul><ul><li>fatigue -> f 5 </li></ul><ul><li>modulated radiation -> f 7 </li></ul><ul><li>polarization -> f 8 </li></ul><ul><li>range change -> f 11 </li></ul><ul><li>error of focus -> f 12 </li></ul><ul><li>lower/upper frequency limit -> f l , f u </li></ul>
  12. 12. properties of video camera system <ul><li>number of pixels (total, effective, output) </li></ul><ul><li>cell size </li></ul><ul><li>frame rate </li></ul><ul><li>shutter speed </li></ul><ul><li>noise </li></ul><ul><li>dynamic range </li></ul><ul><li>photo response non-uniformity (PRNU) </li></ul><ul><li>dark signal non-uniformity (DSNU) </li></ul><ul><li>defective pixels </li></ul><ul><li>optical imaging parameter (MTF, distortion, etc) </li></ul>
  13. 13. CIE publication 69-1986: inconsistencies, missing parameters <ul><li>Examples: </li></ul><ul><li>measurement of the effect of the surrounding field </li></ul><ul><li>spatial homogeneity (shading: depends on aperture, focusing distance) </li></ul><ul><li>cross talk between neighbor pixels (blooming, smearing,data compression, etc) </li></ul>gloss trap measurement field
  14. 14. other problems associated with ILMDs <ul><li>timing problems (integration time : 0.01 msec - 1 sec) </li></ul><ul><li>dark current (resp. drift of dark current), depends on temperature, position </li></ul><ul><li>fixed aperture/ focus versus variable aperture/ focus </li></ul><ul><li>image compression </li></ul><ul><li>straylight </li></ul><ul><li>dynamic range </li></ul><ul><li>polarization </li></ul><ul><li>and finally </li></ul><ul><li>data acquisition, manipulation, and evaluation made by a computer. There is always a mathematical transformation between the luminance value and the pixel value, typically </li></ul>luminance(x,y,t) = (pxl (x,y,t) - dark(x,y) - dark(t)) * calibration * shading (x,y) * nonlinearity (pxl) luminance(x,y,t) = pxl (x,y,t) * calibration ideal: real:

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