Light guide and lateral illuminator

Details Light guide and lateral illuminator Light guide and lateral illuminator

2002-10-03

2004-12-28

Wells, Nikita (Department: 2881)

Optical waveguides

Noncyclindrical or nonplanar shaped waveguide

C385S125000, C385S133000, C385S901000, C385S902000, C362S551000, C362S559000, C362S562000, C362S578000

Reexamination Certificate

active

06836611

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
The field of the invention is lighting systems and more specifically a light guide that provides essentially uniform illumination from a bent surface of the guide.
Ever since development of the first light generating electrical filament, there has been a desire to control light to provide various lighting affects. One light control mechanism is a light guide or pipe. A light guide generally comprises an elongated transparent or translucent member having external surfaces. As well known in the art, when a light ray is directed within a light guide and subtends a surface of the guide, if the incident angle formed by the light ray and the surface is less than a critical angle, the light is reflected back into the guide along a trajectory that defines a reflected angle equal to the incident angle and toward another surface of the guide. Thus, if a guide is designed properly and light rays directed into a guide end are directed along suitable trajectories, in theory, the guide should facilitate total internal reflection (TIR) of the light and hence pass all of the light to an opposite end of the guide.
If the incident angles formed by light rays that subtend a guide surface are greater than the critical angle, the light is emitted through the guide surface and illuminates the area adjacent the emitting surface.
It is also known that deformities can be formed in a guide surface or within the guide itself to control the amount of light emitted from different sections of a light guide within limits. Exemplary U.S. Pat. No. 6,185,356 (hereinafter “the '356 patent”) which is entitled “Protective Cover for a Lighting Device” and which issued on Feb. 6, 2001 teaches various types of illuminators that are integrally formed with surgical instruments (e.g., retractors, forceps, etc.) to provide light at desirable locations proximate the surgical implements.
In general, the '356 patent teaches that guide surface deformities such as textured surfaces, particles within the guide, etc., scatter or “randomize” light rays within a guide. Thus, guides can be constructed to both deliver right rays and to then disperse the light rays at desired locations along the guide length. To deliver light, a guide section can be designed to facilitate TIR. To disperse light rays and provide light at specific locations, deformities are formed in the guide that alter light ray trajectories and thereby cause at least a portion of the rays passing through the guide to travel along trajectories forming incident angles with guide surfaces that are greater than the critical angle—hence causing the rays to be emitted from the guide surface.
The '356 patent also generally recognizes that a uniform lighting effect can be provided by varying the deformity pattern along a guide surface. For instance, assume that an elongated light guide includes a first segment adjacent a light source and a second segment adjacent the first segment, that the lengths of the first and second segments are identical and that a light source directs 10 units of light into a distal end of the first segment opposite the second segment. Also assume that deformities along the first segment cause three units (e.g., 30% of the total light from the source) of the light to refract out of the guide surface so that only seven units of light are passed on to the second guide segment. Here, if the second segment includes deformities having light refracting properties similar to the first segment, approximately 30% of light entering the second segment (i.e., approximately 2.3 units) is refracted out the surface along the second segment length and, therefore, the intensity of light emitted along the second segment is less than along the first segment.
However, if deformities are provided in the second segment surface that cause approximately 43% of the light entering the second segment to be emitted along the second segment length, approximately three units of the seven units entering the second segment are emitted along the second segment surface and hence similar quantities of light are emitted from the first and second guide segments. This principle of non-uniform deformities can be applied to a large number of small adjacent guide segments to provide a substantially uniform lighting affect.
In the case of a textured surface, the randomizing texture can be formed on either or both of an emitting guide surface (i.e., a surface from which light is intended to be emitted) and a primarily reflecting surface opposite or at least substantially opposed to the emitting surface. In the case of a textured emitting surface, the texture alters the angle of the surface subtended by the light rays so that the incident angle with the small subtended surface is greater than the critical angle and light is emitted. In the case of the textured reflecting surface, the texture causes reflected light rays to travel toward the emitting surface along trajectories that form incident angles with the emitting surface that are greater than the critical angle and hence, similarly, cause light ray emission.
The '356 patent also recognizes that a textured surface can be formed by molecularly bonding some type of coating material to a guide surface. The molecular bonding process, in effect, causes small hills and valleys (i.e., texture) on the bonded guide surface. The bonding and texturing process may include a painting or spraying procedure followed by a curing period, other material deposit type processes, forming of a guide about a thin reflective member (e.g., a plastic member), etc.
In addition, the '356 patent recognizes that the coating material bonded to a guide may be light opaque so that light rays are not emitted from the coated surface of the guide but rather are redirected back into the guide. Here, where the coating material has a specific color, the color will affect the appearance of the light emitted from the emitting surface. For instance, a white paint coat on a reflecting surface affects the appearance of the emitting surface.
While the '356 patent teaches some useful concepts, the '356 patent has some shortcomings when used to provide certain effects. First, while deformity variance along a guide length can be provided to cause essentially uniform illumination from each guide segment, where the deformity variance is too great, the visual effect of the different guide segments will often be very different. Thus, for instance, one guide segment having ten times the deformities as another segment may cause a similar quantum of light to escape the guide along a similar length but the deformities may cause a different light pattern. This variable appearance problem is particularly acute in the case of long illuminating surfaces where distal guide segments are a relatively long distance from a light source than are other segments and the degree of deformity necessary to facilitate a uniform appearance is excessive.
Second, the '356 patent fails to teach a configuration having a uniformly appearing emitting surface that has both a linear and a curved component. In this regard, when a light source directs light through a linear guide section and then into a curved guide section adjacent the linear section, and a reflecting coating is provided on a guide surface opposite an emitting surface, often “shadows” or “dark spots” will appear when the emitting surface of the curved section is viewed. This “spotting” phenomenon occurs because light exiting the linear section of the guide is generally along trajectories parallel to the guide length and hence the rays shoot past the beginning and middle part of the curved section, subtend the ending part of the curved section and non-uniformly illuminate the curved section. The '356 patent fails to recognize this phenomenon as a problem, and instead, teaches guide configurations that either geometrically do not have the spotting

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