基于计算全息元件的大口径非球面透镜透射波前检测方法

Measurement of the Transmission Wavefront of a Large-Aperture Aspheric Lens Based on Computer-Generated Hologram

针对大口径非球面透镜透射波前检测,提出了采用计算全息元件(CGH)作为光路相位补偿元件进行检测的方法。大口径非球面透镜透射波前通常采用球面干涉仪进行检测,为了达到零位检测的目的,在光路中往往需要加入相位补偿元件以补偿高阶像差(HOA)。传统的折射式相位补偿元件的精度溯源比较困难,导致检测数据缺乏可信度。将CGH作为相位补偿元件可达到零位检测的目的。针对大口径非球面透镜的透射波前检测,设计并加工了相应的CGH作为相位补偿元件,并与传统的折射式补偿元件进行了对比测试。测试结果表明:两种相位补偿方法的测试数据具有良好的一致性,峰谷(PV)值的差值为0.034λ(λ为检测光的波长),均方根(RMS)值的差值为0.006λ,因此CGH作为相位补偿元件具有相当高的测试精度。

To measure the transmission wavefront of a large-aperture aspheric lens,we propose a method by using a computer-generated hologram(CGH)as a phase compensation element.The transmission wavefront of a largeaperture aspheric lens is typically tested by a sphere interferometer.To conduct a null test,phase compensation is required to compensate for high-order aberrations(HOAs).However,validating the accuracy of conventional refractive-phase compensation elements is difficult,and they therefore generate unreliable measurement results.An alternative type of phase compensation employs a CGH,which is a diffraction element that can also be used to conduct a null test.To conduct a null test for the transmission wavefront of a large-aperture aspheric lens,we design and manufacture a CGH.A contrast test is implemented with two different phase compensation elements,which results in two measured data those are very similar to one another,between which the peak valley(PV)difference is 0.034λ(λis the wavelength of the detect light),and the root mean square(RMS)difference is 0.006λ.Therefore,the null-test method using a CGH proposed in this study displays a high degree of accuracy.