ing at the problem of high magnitude target simulation in the lab, a weak-light single star simulator (WLSSS) consisting of light source, adjustable diaphragm, integrating sphere, photoelectric detector and collimator is developed to measure the magnitude detecting ability of detecting cameras and star sensors. The relationship between the readings of photoelectric detector, the spectral radiance in the outlet of integrating sphere and tunable obscuration ratio is deduced. Combining the magnitude definition formula and the image illuminance equation formula, the operation principle of weak-light single star simulator is introduced, and the calibration challenge of high magnitude target is solved. The magnitude simulation range and precision of WLSSS are theoretically analyzed, and results show that the highest simulating magnitude is 19.5 Mv, and the precision is 11.6%. When the simulation magnitude is lower than 15 Mv, its precision is better than 8%. Experiment results show that in the lab, the maximum relative error between simulated magnitudes and KLL-04 wide-range illuminator tested magnitudes is 7.09%. The relative error of measured magnitude detecting ability between laboratory and astro-observation detecting cameras is 1.9% in 6.5 Mv, and 2.6% in 15.2 Mv. The designed WLSSS can effectively simulate high magnitude targets.
.ing at the problem of repeated calibration in the traditional mobile screen deflectometry, a deflectometry measurement method of single-camera monitoring is proposed based on the principle of the phase measurement deflectometry. The two positions of a LCD screen were monitored by an auxiliary camera, and the position of the LCD screen relative to the main camera was determined by the PnP method and the coordinate system transformation. The incident light was determined by the absolute phase tracking of the homonymy phase points at two positions of the LCD screen for the same pixel. Accordingly, the normal line and gradient information were determined and the mirror surface was reconstructed accurately through the radial basis function interpolation. The two cameras with different fields of view were calibrated by the mirror calibration method. The calibration was implemented only once without the repetitive error. The results of the simulation and experiments verify the feasibility of the proposed method and show the method has a relatively high detection accuracy.
.ing at the problem of inconvenient placement of a target in the measuring plane and the difficulty of making a large-scale target in wide-area monocular plane measurement system, a method of calibrating with small-size plane targets laid on a parallel plane is proposed. A parallel plane is selected as a calibration plane, a single small-size plane target is placed reasonably in a plurality of positions on the calibration plane for shooting, and a large-scale plane target is constructed by combining the photos and the nonlinear optimization method is used to complete the optimization of the internal and external parameters of the camera. Combining with the parallel constraint and the distance parameter, the homography matrix between the measuring plane and the image plane is obtained and then the wide-area plane measurement is realized. The precision model of plane measurement is established, and the distribution of precision in the measuring area and the factors influencing measurement precision such as the internal parameters, the installation angle and height of the camera are analyzed theoretically and experimentally. The experimental results show that the proposed method can effectively guarantee the overall measurement precision. In the calibration in a trapezoidal visual field with an upper line of 920 mm, a lower line of 1360 mm and height of 920 mm, the measurement error is lower than 0.6% in the measuring plane away from the calibration plane 200 mm. The distribution of errors in the measuring area is consistent with that of the precision model. This method is fully applicable to the wide-area plane measurement.
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