Microfiche reader

Optics: image projectors – Selective data retrieval – Plural picture rows on single microcard

Patent

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Details

353 25, G03B 2114

Patent

active

056476540

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a microfiche reader intended, by means of a suitable optical arrangement, to project a light beam emitted by a light source onto a selected field of a microfiche in order to visualize it on a projection surface or screen, comprising a microfiche holder which can be moved in translation relative to a projection lens, the microfiche being inserted between two transparent glass plates, it being possible to move one of the plates away from the other, for example by pivoting, in order to allow it to be fitted or withdrawn.
The light source of this apparatus usually consists of a dichroic-reflector halogen lamp with low voltage and high luminous power. However, this arrangement requires a voltage transformation electric circuit in order to supply the lamp using the electric mains current, and the significant heating of the lamp additionally makes it necessary for it to be arranged in a suitable case which is relatively far from the microfiche holder and is suitably ventilated.
The object of the invention is to overcome these drawbacks by providing a microfiche reader, of the aforementioned type, characterized in that it includes a light source consisting of a set of high-luminosity light-emitting diodes arranged on a support surface capable of focusing the light flux emitted by the diodes onto the elements of the optical arrangement of the apparatus.
The light-emitting diodes are advantageously juxtaposed over the extent of the support surface, but they may, of course, be arranged in any other shape configuration, for example in concentric rings on the support surface.
Said support surface may be planar or curved, and preferably concave so as itself to focus the light emission as much as possible.
The light-emitting diodes of the reader thus together ensure a sufficient luminous power, their number and their installation area being determined to this end. They are supplied directly by the mains current and with much less overall heating than a conventional halogen lamp, with an equivalent luminous power. Similarly, the power consumption is significantly reduced. In addition, they are inexpensive, even in large numbers, and their service life is significantly longer (approximately 10,000 hours as compared to 2,000 for a halogen lamp).
The reader according to the invention does not require an expensive electrical conversion circuit for the current or a system for cooling the lamp (generally a cooling system with ventilation fins on conventional readers). Moreover, the light source can be installed closer to the microfiche holder, which reduces the overall bulk of the apparatus.
The invention is illustrated hereafter with the aid of an illustrated embodiment and with reference to the appended drawings, in which:
FIG. 1 is a schematic view, with cutaway, of the light-source device of a microfiche reader according to the invention,
FIG. 2 is an enlarged sectional view of the optical device of this reader, and
FIGS. 3 and 4 show alternative embodiments.
As represented in FIG. 1, the microfiche reader according to the invention comprises a lower base 1, an upper visualization screen 3 fixed on the base and a central microfiche holding device 5 mounted on the upper planar surface of the base. The lens 7 for focusing the image onto the screen is arranged just above the microfiche holder 5. This holder, of the type with conventional transparent glass plates 9, is mounted so that it can be moved in the plane of the lens so as to make it possible to select as desired the fields of the microfiche 11 visualized.
The lower base 1 houses the light source 13, which emits a light beam 14, a mirror 15 for reflecting the emitted light flux and a condenser lens 17 arranged vertically in line with the mirror 15. This condenser lens converges the light beam onto the lens 7 through the selected field of the microfiche. The resultant image beam is again reflected on a second reflecting mirror 19 (accommodated at the lower part of the screen) then on a third mirror 21, arranged at the rear part of the scr

REFERENCES:
patent: 3733121 (1973-05-01), Smitzer
patent: 3944350 (1976-03-01), Yerick
patent: 4143953 (1979-03-01), Rauffer
patent: 4339183 (1982-07-01), Yamada et al.
patent: 4727289 (1988-02-01), Uchida
patent: 4805087 (1989-02-01), Frankel et al.

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