optical reader optical reading optical receiver optical recognition optical recording optical reflector optical relay optical resolution optical response optical rotation optical rotations optical satellite optical scanner optical scanning optical science optical security optical sensing optical sensor optical sensor system optical sensors optical shop optical sight optical signal optical signals optical sorting optical source optical spectroscopy optical spectrum optical splitter optical storage optical structure optical structures optical surface optical surfaces optical switch optical switches optical switching optical system optical systems optical techniques optical technologies optical technology optical telecommunications optical telegraph optical telescope optical telescopes optical test optical thickness optical tomography optical tracking optical transceiver optical transceivers optical transducer optical transmission optical transmission system optical transmitter optical transparency optical transport optical tweezers optical type optical unit optical units optical viewfinder optical wave optical waveguide optical waveguides optical wavelength optical window optical windows optical zone optical zoom optically active optically active compound optically active compounds optically clear optically coupled optically pure optically readable optically transmissive optically transparent optically variable opticals optician opticians opticks optics optics and photonics optics can optics system optics technology optik optim optima optimal optimal absorption optimal activity optimal adaptation optimal air optimal alignment