Dual Rotating Retarder Polarimeter Research Articles

Simple polarization measurement of a depolarizing retarder with diattenuation

A method is proposed to measure the polarimetric parameters of a depolarizing retarder with diattenuation (DRD). The retardance is expressed as a tangent function that recovers its correct sign as opposed to the usual calculation of the retardance through a cosine function. The depolarizing parameters of a pure depolarizer, normally retrieved with the Lu-Chipman decomposition method, can be calculated directly, through the Fourier transform of three different measured irradiances. This method needs the measurement of one of the axes of the DRD. Assuming the retardance between zero and π, the proposed method can then distinguish if this axis is the fast or slow axis without any additional measurements, as is required in other characterization methods. As a result the correct Mueller matrix of the DRD is always recovered. Two examples are presented and validated using a dual rotating retarder polarimeter (DRR) calibrated with the eigenvalue calibration method (ECM).

Polarimetric measurement of non-depolarizing optical systems

The use of polarization measurements has become more common in recent years, as it gives more information than pure intensity measurements. Polarimetric components such as fixed or variable retarders and polarizers must be included in optical systems to obtain the polarization parameters required, and in many cases the optical system also includes other components such as relay and/or imaging optical systems. In this work we present a simple and robust method for the polarimetric characterization of non-depolarizing polarization components and other optical elements in the system, which does not require a full polarimeter. Since there is no depolarization, we represent the components as pure retarders with diattenuation and find their parameters (transmittance for the polarization components, angle of orientation of the fast axis, and retardance), from which we can retrieve their Mueller matrix. Our results show that the proposed method is accurate when compared with results obtained with a Mueller matrix dual-rotating retarder polarimeter calibrated using the eigenvalue calibration method, considered in this work as the gold standard, and is comparatively easier than the latter to implement, particularly for imaging polarimeters.

Error analysis and compensation for a discrete dual rotating retarder Mueller matrix polarimeter.

In this work, the error sources that affect a dual rotating retarder polarimeter working in a discrete rotation scheme are studied. Moreover, those errors not sufficiently analyzed in the literature are addressed in detail. To this end, the equations necessary for characterizing its components, performing its calibration, and carrying out measurements are deduced. We also discuss strategies to perform the experimental implementation, correct the existing errors, and estimate the margin of uncertainty associated with those errors that cannot be corrected. The study developed in this work allows us to generate a polarimeter with an error margin of 0.2%, almost an order of magnitude below recently reported values.

Accuracy enhancement of dual rotating mueller matrix imaging polarimeter by diattenuation and retardance error calibration approach

We present a new calibration method to minimize the errors due to non-ideal retarders of a dual rotating Mueller matrix polarimeter. To increase the accuracy of the dual rotating retarder polarimeter, it is necessary to compensate the errors caused by the inaccuracy of retarders. Although calibration method for retardance already exists, limitations on the accuracy have been obtained by considering only the retardance errors. In the proposed model we added the calibration of diattenuation error of the retarder along with retardance error on the standard model. An enhancement in the accuracy of the system is obtained. The proposed model is described with equations and supporting experimental results are presented.

Effects of a measurement floor on Mueller matrix measurements in a dual rotating retarder polarimeter bidirectional scatter distribution function system.

Since a measurement of the bidirectional scatter distribution function (BSDF) of a material is proportional to the intensity of the scattered light, a BSDF measurement system with the addition of a dual rotating retarder polarimeter can be used to calculate the Mueller matrix of a scatterer. One advantage of a BSDF system using a laser source is its large dynamic range, which allows the measurement of scattered light both near to and away from the specular region. As BSDF measurements move away from the specular region and into a more diffuse-scatter region, the measured signal decreases and may approach the system's measurement floor. Therefore, BSDF and Mueller-matrix measurements are dependent not only on the scatter from the sample but also on the noise floor of the system. By analyzing numerically created bidirectional reflectance distribution function data, we show that since the noise floor of a system is typically constant, the Mueller-matrix measurement at the noise floor appears to be that of a perfect depolarizer. Therefore, as the BSDF measurement space moves away from the high-signal region and the noise floor is approached, the Mueller matrix assigned to the sample artificially approaches that of a perfect depolarizer. The rate and location in scatter-angle space of this shift is dependent on the BSDF of the material and on the signal-to-noise ratio in the system. Therefore, caution must be taken when drawing conclusions about measured Mueller matrices for scattered light, particularly in measurement regions where the measured signal approaches the system floor.

All polarization properties of PLZT ferroelectric ceramics observed in two dimensional distributions under applied voltage by the Mueller matrix

This paper describes spatial distributions of all polarization properties of anti-ferroelectric PLZT-8.9/65/35 (lead lanthanum zirconate titanate) ceramics as a function of the applied voltage. The application of PLZT in optical devices requires an understanding of the distributions of its optical characteristics. However, birefringence measurement, which is a general method for observing the distribution of optical characteristics, is not useful for the evaluation of other polarization properties. For the quantitative measurement of all of the polarization properties, therefore, we focused on the Mueller matrix, which describes all of the polarization properties. Initially, in order to evaluate the optical characteristics of PLZT for optical devices that are not based on the spatial distributions of the polarization properties, all of the integral polarization properties, which are the averages of each polarization property, were measured using a dual-rotating retarder polarimeter. These results were then used to valuate the significance of the polarization property distributions measured using the polarimeter combined with a microscope, which enabled detection of the spatial distributions of the Mueller matrix. We have observed that birefringence indicates the distributions that depend on the grain structure. With increasing voltage, the birefringence is oriented by the external electric field. Thus, a reduction of the variation in the birefringence can be achieved by maintaining direction of the electrical polarization, and this reduction causes a decrease in the depolarization. These measurements are useful for revealing the optical behavior of ferroelectric ceramics, and provide helpful information for the development of optical devices.

Polarization properties of PLZT under applied voltage measured by dual-rotating retarder polarimeter.

PLZT is a transparent piezoelectric polycrystal usually used for controlling the polarization of a light by an applied voltage. However, PLZT has some disadvantages that it is difficult to obtain polarization properties in detail. The reason for the problem is that when a polarized light induced into PLZT, there are depolarization by scattering in the crystal grain boundary. To evaluate optical properties of PLZT, we have measured its Mueller matrices under applied voltages by using the dual-rotating retarder polarimeter proposed by Azzam. For analysis of detailed polarization properties, we have decomposed its Mueller matrices by the decomposition algorithm given by Chipman. Birefringence and depolarization of PLZT depend on applied voltage. And depolarization ratio rapidly decrease when applied voltage is in the specific range.

Optimization of Mueller matrix polarimeters in the presence of error sources

Methods are presented for optimizing the design of Mueller matrix polarimeters and and in particular selecting the retardances and orientation angles of polarization components to ensure accurate reconstruction of a sample's Mueller matrix in the presence of error sources. Metrics related to the condition number and to the singular value decomposition are used to guide the design process for Mueller matrix polarimeters with the goal of specifying polarization elements, comparing polarimeter configurations, estimating polarimeter errors, and compensating for known error sources. The use of these metrics is illustrated with analyses of two example polarimeters: a dual rotating retarder polarimeter, and a dual variable retarder polarimeter.