菱体型相位延迟器是高度消色差的λ/4相位延迟器。由于材料折射率色散的影响,在可见光范围内,仍存在2°的延迟偏差。为满足精确应用和测量的需求,从相位延迟的全反射相变理论出发,阐述了斜入射相位延迟原理,以菲涅耳菱体为例,分析了菱体型相位延迟器相位延迟随其入射角变化的规律性,结果表明:当光线非严格准直时,光的入射角对相位延迟量有明显的影响,延迟量不但对入射角变化敏感,而且还与入射光线的入射方位密切相关,呈不对称形式。当入射光的波长改变时,只需改变菱体延迟器的方位,让光线在菱体的前端面上斜入射,适当选取入射角,就可以补偿相位延迟的色散偏差,使同一菱体达到对不同波长都满足λ/4相位延迟。当角度调整精度Δi=±0.01°时,引入的延迟偏差不超过±0.009°,这一精度是其它石英波片或云母波片所不能比的。

Rhomb-type retarder is a high-precision achromatic λ/4 phase retarder. Because of material dispersion of the refractive index, there is still 2° deviation of the delay in the visible range. In order to meet the demand of precise measurement and applications, the principle of phase retardation with oblique incident angle is expounded, based on the total-reflection phase transformation theory of the phase retardation. By means of Fresnel rhomb, the variation law of the phase retardation for rhomb-type retarder with the incident angle is analyzed. The result indicates that incident angle has obvious influence over the phase retardation.The phase retardation is sensitive to the incident angle, and also has close correlation to incident position of the incident ray, which is asymmetrical to the incident position of the incident ray. So when the wavelength of the incident light changes, only the position of rhomb-type retarder need to be changed to allow the light to represent oblique incidence in the front of rhomb, and then selecting suitable incident angle can compensate the dispersion phase deviation, and make the same rhomb possess standard λ/4 phase retarder under all different wavelengths. Deviation of the delay is less than ±0.009° when the precision of angle adjustment is ±0.01°. The precision cannot be obtained for quartz wave plate or mica wave plate.