| dc.description.abstract | With the progress of technology, the application of lenses has become more extensive, and the quality requirements for optical modules have gradually increased. However, in the process of manufacturing, inferior products are inevitably induced, causing errors such as eccentricity or tilting of the lens, or Other unnecessary aberrations. Therefore, quality control of lens is very important to achieve perfect imaging. And this paper shows that we can calculate the modulation transfer function (MTF) by measuring the wavefront, to compare the lenses in good or bad from the information of wavefront and MTF. In this paper, the four-wave transverse shear interferometer (QWLSI) wavefront detector is combined with the calculation of MTF for detection, because QWLSI has high resolution and measurement accuracy, large dynamic range, fast detection, simple structure and easy operation. As a result, the technique is used as a basis to detect wavefront aberrations and to reconstruct MTF using wavefront aberrations to evaluate the optical imaging quality of the object under test.
For the measurement method of QWLSI, firstly, QWLSI must select the range of diverging light to place after the sample to be tested for measurement, so that the calculation process of the restored wavefront can completely collect information, and then using to find the placement of the better contrast of the interference point to determine the CCD measurement position and to match the automatic axis to control it. Next, the paper analyzes the importance of the frame selection mask. It introduces an automatic circle finding algorithm to select the center of the interferogram automatically, and then tests the algorithm to find the center of the circle repeatedly. The standard deviation of position and radius is below 0.5 pixel. The algorithm can avoid artificial error. Therefore, the final measurement can be combined with the automatic axis control CCD measurement position and automatic circle finding to achieve automatic detection. After testing, QWLSI is tested the stability of the wavefront measurement to 1/449 waves (RMS), the accuracy of it to 1/246 waves (RMS), the dynamic range measurement of at least 160 μm, and an error of less than 1.3% compared with the commercial measurement machine of MTF (Trioptics).
Therefore, by combining the QWLSI measurement technology with advantages and the calculation of MTF as the lens detection technology, it is possible to effectively judge the quality of the lens, and it is with the automation technology, the future trend has the opportunity to become an online inspection product.
| en_US |