parfocaladj.

1886 Microsc. Bull. & Sci. News Aug. 31/1 Referring to the article in the April issue..on ‘changing eye-pieces without altering focus, etc.’, we announce that we are prepared to furnish eye-pieces, as there described... We have named these eye-pieces parfocal, meaning ‘of equal focus’.

1926 Science 20 Aug. (front matter) (advt.) It contains 3 pairs of objectives of different powers held in parfocal position.

1944 C. P. Shillaber Photomicrogr. iii. 234 The objectives are said to be parfocal with each other when one setting of the microscope will serve to focus all four objectives.

1955 Sci. Amer. Feb. 122/2 This is called ‘parfocal’ mounting, and it saves a lot of time when, for example, you are searching your collection for a specific type of crystal, surface texture or color to match an unknown mineral.

1970 R. P. Loveland Photomicrogr. I. iii. 114 The rotating objective holder is the most convenient in use when the objectives are parfocal.

1991 Lancet 9 Mar. 625/2 This fluorescent objective screws into the turret of any light microscope, and with an adaptor it becomes parfocal with the other objectives on the microscope.

1974 Physics Bull. May 197/2 For optical measurements the instrument has a high pressure xenon arc lamp and six pairs of matched condenser and objective lenses mounted parfocally in turrets.

1995 Proc. National Acad. Sci. U.S.A. 92 9708/1 Average fast elongation rates were measured for 10 different experiments using available parfocally measured distances.