Subaperture stitching （SAS） provides us with an attractive way of extending the effective aperture and dynamic range of phase measuring interferometers. Accuracy of stitching algorithm becomes the key factor in the ...Subaperture stitching （SAS） provides us with an attractive way of extending the effective aperture and dynamic range of phase measuring interferometers. Accuracy of stitching algorithm becomes the key factor in the SAS technology. In this paper, the basic principle of SAS was introduced and four modes of SAS were discussed. The stitching experiments were done through the SSI-300 workstation designed and developed indepen- dently. There were several comparisons between the four different stitching methods and the measurement of full aperture. The results suggest that the global error averaging mode with reference of subaperture near optic axis is of high precision.展开更多
This paper proposes a calibrated method for quasi-broadside side-looking mode SAR imaging with small squint angle and an improved method named as phase alignment algorithm of subaperture reference signal. The calibrat...This paper proposes a calibrated method for quasi-broadside side-looking mode SAR imaging with small squint angle and an improved method named as phase alignment algorithm of subaperture reference signal. The calibrated method adopts subaperture spotlighting algorithm of broadside mode to image the real data of quasi-broadside mode SAR, then based on the obtained image the small squint angle is estimated and the calibrated subaperture spotlighting algorithm of squint mode is employed to obtain the final image. The calibrated method can calibrate the abnormal region and obtain the correct image. The phase alignment algorithm of subaperture reference signal adjusts phases of respective subaperture reference signals in order to make them be in phase and constructs a new spotlighting window function for SAR imaging. Theoretical analysis shows that with the same sample data, the improved method can increase SAR imaging area in azimuth dimension. The methods are verified by the results of computer simulation.展开更多
In-situ testing is an ideal technology for improv- ing the precision and efficiency of fabrication. We developed an in-situ subaperture stitching interferometric test system for large piano optics in the workshop envi...In-situ testing is an ideal technology for improv- ing the precision and efficiency of fabrication. We developed an in-situ subaperture stitching interferometric test system for large piano optics in the workshop environment with high precision and satisfactory repeatability. In this paper, we provide a brief account of this system and the principle ofin- situ subaperture stitching measurement. Several validation tests are presented, which demonstrate that the developed system is capable of realizing in-situ testing. The size of optical flats can be measured is up to 420 mm×780 mm, and repeatability is smaller than 0.03λ. The paper also dis- cusses the necessary requirements for a suitable workshop environment for ensuring that the tests are stable and reliable.展开更多
In this paper, the principle of subaperture stitching interferometry was introduced. A testing stage with five degrees of freedom for stitching interferometry was built. A model based on least-squares method and error...In this paper, the principle of subaperture stitching interferometry was introduced. A testing stage with five degrees of freedom for stitching interferometry was built. A model based on least-squares method and error averaging method for data processing was estab- lished, which could reduce error accumulation and improve the precision. A 100ram plane mirror was measured with a 50mm aperture interferometer by means of stitching interferometry. Compared with the results by a 100 mm interferometer, peak to valley （PV） and root mean square （RMS） of the phase distribution residual are 0.00382 and 0.00042, respectively. It proved that the model and method are helpful for large optical measurement.展开更多
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 60978043, 61128012, 610611 60503, and 61222506）.
文摘Subaperture stitching （SAS） provides us with an attractive way of extending the effective aperture and dynamic range of phase measuring interferometers. Accuracy of stitching algorithm becomes the key factor in the SAS technology. In this paper, the basic principle of SAS was introduced and four modes of SAS were discussed. The stitching experiments were done through the SSI-300 workstation designed and developed indepen- dently. There were several comparisons between the four different stitching methods and the measurement of full aperture. The results suggest that the global error averaging mode with reference of subaperture near optic axis is of high precision.
文摘This paper proposes a calibrated method for quasi-broadside side-looking mode SAR imaging with small squint angle and an improved method named as phase alignment algorithm of subaperture reference signal. The calibrated method adopts subaperture spotlighting algorithm of broadside mode to image the real data of quasi-broadside mode SAR, then based on the obtained image the small squint angle is estimated and the calibrated subaperture spotlighting algorithm of squint mode is employed to obtain the final image. The calibrated method can calibrate the abnormal region and obtain the correct image. The phase alignment algorithm of subaperture reference signal adjusts phases of respective subaperture reference signals in order to make them be in phase and constructs a new spotlighting window function for SAR imaging. Theoretical analysis shows that with the same sample data, the improved method can increase SAR imaging area in azimuth dimension. The methods are verified by the results of computer simulation.
文摘In-situ testing is an ideal technology for improv- ing the precision and efficiency of fabrication. We developed an in-situ subaperture stitching interferometric test system for large piano optics in the workshop environment with high precision and satisfactory repeatability. In this paper, we provide a brief account of this system and the principle ofin- situ subaperture stitching measurement. Several validation tests are presented, which demonstrate that the developed system is capable of realizing in-situ testing. The size of optical flats can be measured is up to 420 mm×780 mm, and repeatability is smaller than 0.03λ. The paper also dis- cusses the necessary requirements for a suitable workshop environment for ensuring that the tests are stable and reliable.
基金This work was supported by the National Natural Science Foundation of China （Grant No. 61128012） and the Research Grants Council of the Hong Kong Special Administrative Region （No. 9041577）.
文摘In this paper, the principle of subaperture stitching interferometry was introduced. A testing stage with five degrees of freedom for stitching interferometry was built. A model based on least-squares method and error averaging method for data processing was estab- lished, which could reduce error accumulation and improve the precision. A 100ram plane mirror was measured with a 50mm aperture interferometer by means of stitching interferometry. Compared with the results by a 100 mm interferometer, peak to valley （PV） and root mean square （RMS） of the phase distribution residual are 0.00382 and 0.00042, respectively. It proved that the model and method are helpful for large optical measurement.
