| 释义 |
preˈfocus, a. and v.
[f. pre- A. 1.]
A. adj. Of a bulb: constructed so that the lamp is automatically focused upon fitting of the bulb; also applied to parts of such bulbs, esp. the cap, which make possible the necessary accurate positioning of the filament during manufacture.
1944(title) Dimensions of prefocus lamp-caps and lampholders (British Standards Institution). 1950Young & Griffiths Automobile Electr. Equipment (ed. 4) vi. 181 Fine adjustment for the filament position is..essential in order to take care of slight manufacturing discrepancies in the filament distance from the bulb cap unless, of course, the bulb is of the pre-focus type now prevalent in British-made headlamps. 1967L. Holmes Odhams New Motor Man. x. 238/1 For Continental towing, British cars must have their headlamps converted to dip to the right instead of to the left, and for this purpose special pre-focus bulbs can be obtained. 1970A.A. Bk. of Car 162/4 The cut-away in the flange of a pre-focus bulb ensures that it is correctly located and focused. 1972Gloss. Electrotechnical, Power Terms (B.S.I.) iv. iii. 17 Prefocus cap, cap..which enables the luminous element to be brought into a specified position relative to the cap during the manufacture of the lamp.
B. v. trans. To make or adjust so that a lamp will be automatically focused when a bulb is fitted. So preˈfocused ppl. a., preˈfocusing vbl. n.
1951Philips Technical Rev. XII. 309/1 It is of great importance that when a new bulb is fitted into a headlight its filament comes to lie exactly in the right position. This is ensured by a pre-focusing of the filament in the factory with the aid of a special adjusting device. Ibid. 312 (caption) On the base can be seen two of the three studs with which the lamp is focused: they ensure that the axis of the lamp coincides with that of the reflector, the filament being ‘prefocused’ with respect to the studs. 1954A. W. Judge Automobile Electr. Maintenance (ed. 3) viii. 209 In the case of recent American-type headlamps, ‘sealed-beam’ units are employed. These consist of a lens, bulb, and reflector unit built into one water- and dust⁓proof pre-focused unit. 1970A.A. Bk. of Car 162/4 Quartz-halogen bulbs. These are obtainable for fitting into pre-focused units in place of ordinary bulbs. 1977Nature 6 Jan. 92/1 The built-in lamp turret keeps four prefocussed lamps aligned, powered and ready to work. |