3. Relating to the science of optics; as, optical works. Optic angle (Opt.), the angle included between the optic axes of the two eyes when directed to the same point; — sometimes called binocular parallax. — Optic axis. (Opt.) (a) A line drawn through the center of the eye perpendicular to its anterior and posterior surfaces. In a normal eye it is in the direction of the optic axis that objects are most distinctly seen. (b) The line in a doubly refracting crystal, in the direction of which no double refraction occurs. A uniaxial crystal has one such line, a biaxial crystal has two. — Optical circle (Opt.), a graduated circle used for the measurement of angles in optical experiments. — Optical square, a surveyor's instrument with reflectors for laying off right angles.
OPTICALLY
Op"tic*al*ly, adv.
Defn: By optics or sight; with reference to optics. Optically active, Optically inactive (Chem. Physics), terms used of certain metameric substances which, while identical with each other in other respects, differ in this, viz., that they do or do not produce right-handed or left-handed circular polarization of light. — Optically positive, Optically negative. See under Refraction.
OPTICIAN
Op*ti"cian, n. Etym: [Cf. F. opticien. See Optic, a.]
1. One skilled in optics. [R.] A. Smith.
2. One who deals in optical glasses and instruments.
OPTICS
Op"tics, n. Etym: [Cf. F. optique, L. optice, Gr. Optic.]
Defn: That branch of physical science which treats of the nature and properties of light, the laws of its modification by opaque and transparent bodies, and the phenomena of vision.
OPTIGRAPH
Op"ti*graph, n. Etym: [Optic + -graph: cf. F. opticographe. See
Optic, a. ]
Defn: A telescope with a diagonal eyepiece, suspended vertically in gimbals by the object end beneath a fixed diagonal plane mirror. It is used for delineating landscapes, by means of a pencil at the eye end which leaves the delineation on paper.