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Deflectometric Measurement System QDec
Quality Control of the Shape of Solar Reflector Panels

QDec is an optical measurement system for control of the shape accuracy of solar reflector panels. It is used for industrial production quality control as well as in R&D environments. QDec provides high resolution and high precision measurement results of the shape deviations of curved or flat reflector panels of a wide range of geometries. It uses a non-contact optical measurement and digital image processing technique based on the deflectometric measurement principle (distortion of reflected patterns). This technique is particularly well suited to quantify the relevant geometric quality parameters for CSP reflector panels in production control and quality assurance. Initiated at the German Aerospace Center (DLR) and further developed by CSPS, QDec has become the standard tool in solar reflector panel measurements. It is in application in major industrial production lines and test and research centers such as the DLR QUARZ Center.

Exceptional system features are its easy operation, short measurement time, high spatial resolution, high measurement precision and a post-processing specially adapted to solar concentrator specifications. The system is equipped with an electrical control cabinet with touch panel and high-end components prepared for industrial working environments. The software features a graphical user interface that allows comfortable operation of the system, automatic data evaluation, display of the results and automated quality reports.

The QDec system can be flexibly adapted to a large variety of reflector panel geometries, measurement orientations and customer requirements. It is suited for in-line process monitoring in glass bending lines up to 100% control. The system can also be applied to control the shape quality of entire heliostats, dishes and parabolic trough modules. The software offers a variety of features specifically developed for CSP applications, such as calculation of focus deviation, ray-tracing simulation considering real sunshape, display of local intercept, display of flux distribution, reverse ray-tracing to detect and assess local panel deviations and more.

QDec System Features

  QDec Offline QDec Inline
Measurement time < 30 s < 5 s
Evaluation time < 40 s < 10 s
Number of measurement points
(standard / maximum)
˜250.000 / ˜1.000.000 ˜250.000 / ˜1.000.000
Measurement uncertainty
local spot / global value (RMS)
< 0.5 mrad / < 0.2 mrad < 0.5 mrad / < 0.2 mrad
Numerical output SDx, SDy, FDx, FDy, IC, ICsun, etc. SDx, SDy, FDx, FDy, IC, ICsun, etc.
Graphical output local slope deviation (x/y)
local focus deviation
local intercept factor
local height deviation
standard quality reports (pdf)
local focus deviation
Output database formats standard: .csv
optional: .xls/SQL
standard: .csv
optional: .xls/SQL
Optional output
(with increase of evaluation time)
matrix data in ASCII file (.csv) graphical output of
- local slope deviation (x/y)
- local focus deviation
- local intercept factor
- local height deviation
standard report (pdf)
matrix data in ASCII file (.csv)

Example Pictures

Measurement image of regular stripe pattern on target

Measurement image with distorted reflection of stripe pattern
QDec measurement summary example