Light box

• US 4,418,378 A
• Filed: 03/05/1981
• Issued: 11/29/1983
• Est. Priority Date: 03/05/1981
• Status: Expired due to Fees

• Current Assignee: Plan Hold Corporation
• Original Assignee: Plan Hold Corporation
• Inventors: Johnson, Sigurd A.
• Primary Examiner(s): Walsh, Donald P.
• Application Number:
  US06/240,851
• Time in Patent Office: 999 Days
• Field of Search: 362/97, 362/217, 362/223, 362/248, 362/290, 362/291, 362/293, 362/311, 362/317, 362/342, 362/343, 362/354, 362/355
• US Class Current: 362/217.08
• CPC Class Codes: F21V 11/14 with many small apertures
• CPC Class Codes: F21V 17/04 the fastening being onto or by the light source
• CPC Class Codes: F21V 9/08 for producing coloured light, e.g. monochromatic; for reducing intensity of light with provision for controlling the colour F21V9/40
• CPC Class Codes: G09F 13/0409 Arrangements for homogeneous illumination of the display surface, e.g. using a layer having a non-uniform transparency arrangements of reflectors G09F13/14
• CPC Class Codes: G09F 13/0454 Slidable panels or parts

Abstract

A light box having one or more fluorescent light source tubes provided with light diffusing and mixing members of tubular form for modifying the light emitted by the fluorescent light tubes to provide a substantially uniformly illuminated backlighted work surface for use in tracing, stripping art work, and viewing color slides, photo negatives, and X-rays. The light box includes internal coated reflective surfaces on bottom and side walls. The light diffusing and mixing member includes light reflective interior and exterior coatings, shaped end portions and in one example perforations providing light transmitting openings. A light diffusing and mixing member of selected light translucent material having shaped end portions and arranged in accordance with the intensity of light emanating from the tubular fluorescent light source.

Claims

1. A light intensity modifying means for an elongated tubular light emitting source comprising:

a tubular cylindrical member of sheet material having means for transmitting selected amounts of light therethrough along its length, having a central portion of substantially cylindrical shape transmitting a selected amount of light and adapted to be sleeved over the central cylindrical portion of said tubular light source, said light transmitting means providing progressively increased amounts of light to the ends of the tubular member with respect to the amount of light transmitted at the central portion of said tubular member, and whereby the amount of light emitted by said source and transmitted by said tubular member is reduced at said central portion and the amount of light transmitted at said end portions is progressively increased with respect to the reduced amount of light at said central portion to provide substantially uniform illumination.

2. A light means as stated in claim 1 wherein

said sheet material is opaque,

said means for transmitting light includes light transmitting openings of selected area throughout the length of the tubular member to compensate for variations in intensity of light emitted by said light source.

3. A light means as stated in claim 1 wherein

said end portions are of truncated form and are at an angle to the axis, of said tubular member for transmitting light in proportion with the loss of light intensity at ends of the tubular light emitting source.

4. A light means as stated in claim 2 wherein

said surfaces of sheet material facing said light source have a light reflective coating.

5. A light means as stated in claim 1 wherein

said sheet material is translucent.

6. A light means as stated in claim 5 wherein

said translucent sheet material is provided with varying pigmentation in its composition to provide a predetermined light transmission therethrough when sleeved over an elongated light emitting source.

7. A light means as stated in claim 1 including

sixty to thirty-five percent of the total surface area of said tubular light emitting source is covered by said tubular member of sheet material.

8. In a light box having one or more flourescent light source tubes of selected length and provided with light reflecting internal surfaces and a light transmitting wall providing a working surface to be illuminated, the provision of:

a light diffusing and mixing member of hollow tubular cylindrical form having a central cylindrical portion and having end sections of truncated shape;

said light mixing member having means along its length for transmitting selected amounts of light from said light source tube;

each truncated end section being formed by a plane disposed at an angle to the axis of the cylindrical member of about 10 to 20 degrees,

each end section terminating in spaced relation to the adjacent end of the light source tube;

said cylindrical light mixing member being positionable on said light source tube with said truncated end sections covering the surface of the light source tube nearest the light transmitting wall and internal faces of said end sections facing the reflecting surfaces of said box opposite said light transmitting wall, whereby light emitted along the length of the light source tube is transmitted by said central portion in reduced amount and said light transmitted at said end sections is partially reduced in accordance with variations of light intensity along the length of said light source tube to provide mixed reflected light for substantially uniform illumination of said light transmitting wall and said working surface.

9. In a light box as stated in claim 8 wherein

said light mixing member is of opaque sheet material;

and said means for transmitting light includes thru openings of selected area in said opaque material.

10. In a light box as stated in claim 8 wherein

said means for transmitting light in said light mixing member includes means for varying light transmitting characteristics of said sheet material.