Development of a compact broadband circular dichroism spectropolarimeter for circular polarizer applications

•A compact, low-cost, and broadband liquid crystal polarization grating (LCPG)-based circular dichroism (CD) apparatus is demonstrated.•The CD measurement error can be reduced by one order of magnitude for whole spectrum by subtracting the residual spectra of the LCPG.•The measurement accuracy of our system is determined to be around 0.3°.•The proposed CD apparatus is applied to test a circular polarizer and is able to detect the change of the ambient reflectance around 0.03%.