Re hlahisa likhalase tse khahlang tsa square optical tse etselitsoeng ho hotetsa mokhoa oa hau oa ho tseba.Likhalase tsena tse entsoeng ka foreimi ea boleng bo holimo ea acetate, li ithorisa ka 'mala o hlakileng le o hlakileng o kopanyang mebala e ntšo, e tala le paterone e sootho.