Optical coupling of light pipes

[0002] This invention relates generally to optical coupling of light sources and light pipes; and more particularly concerns endwise optical coupling of LEDs to fiber optics light pipes in a simple and effective manner to maintain their coaxial relationship during light transmission from the LED to the light pipe, as will appear.

[0003] There is need for improvements in apparatus, and methods, to overcome difficulties in optical coupling as between light sources and light pipes; and there is need to improve light transmission between and by these elements.

[0004] It is a major object of the invention to provide improvements in such optical coupling, as will meet the referenced need.

[0005] Basically, a light transmission device that will meet such need comprises, in combination:

[0006] a) a longitudinally axially extending light pipe having opposite ends,

[0007] b) one of said ends defining a recess for reception of light source structure that transmits light into the light pipe.

[0008] As will appear, the recess may typically be dished, and define a concavely curved inner wall via which light is transmitted into the light pipe. Further, the light source may typically have a portion thereof received into the recess whereby the recess defines a perimeter extending about the light source. The light source may be attached, as by surface mounting, to a printed circuit board, and the light pipe end recess typically defines a perimeter that projects toward said board, sidewardly of the light source which comprises an LED.

[0009] It is another object of the invention to provide light transmitting and diverging facets at the opposite end of the light pipe. The facets may extend in substantially circular arcs.

[0010] A further object includes provision of a support panel carrying the light pipe, in spaced relation to said recess. The faceted opposite end of the light pipe typically terminates proximate the panel, and a pipe flange engages one side of the panel. A grip ring may be provided for gripping the light pipe and engaging the opposite side of the panel.

[0011] The method of positioning a light pipe and light source, in accordance with the invention, includes the steps

[0012] a) providing a panel,

[0013] b) assembling the light pipe to the panel to project through an opening in the panel,

[0014] c) and assembling the light pipe and light source so that the light source projects into an end portion of the light pipe in spaced relation to the panel.

[0015] A recess is typically provided at an end of the light pipe, and the method includes assembling the light pipe and light source to receive a portion of the light source into said recess. That recess is typically formed to provide a concave inner wall that engages and centers the light source, such as an LED, in optically coupled relation to the light pipe.

[0016] These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which:

[0017] FIG. 1 is an elevation taken in section to show positioning of the light pipe relative to a light source such as an LED, and with a panel supporting the light pipe;

[0018] FIG. 2 is a perspective view showing one end of the light pipe;

[0019] FIG. 3 is a perspective view showing the opposite end of the light pipe;

[0020] FIG. 4 is an enlarged section showing a light pipe incorporating the invention;

[0021] FIG. 5 is an end view taken on lines 5—5 of FIG. 4;

[0022] FIG. 6 is an enlarged axial section taken through a grip ring employed to retain the light pipe to a mounting panel;

[0023] FIG. 7 is an end view taken on lines 7—7 of FIG. 6; and

[0024] FIG. 8 is an axially exploded view showing elements as also seen in FIG. 1;

[0025] FIGS. 1-6 show a light pipe or fiber optics cable 10 of relatively short axial length between its opposite ends 11 and 12. End 11 defines a recess 13 for reception of light source structure that transmits light endwise into the light pipe.

[0026] In the example, the recess may typically and advantageously define a dished inner wall 14 which may be concavely curved. That wall positions the light source 15 shown as an LED, and having an end portion 15areceived into the recess, with light pipe perimeter 10aextending about the LED. Dished wall 14 may also axially mutually center the light pipe and the light source, as seen in FIG. 1. The LED 15 also shown as surface mounted at 16 on the printed circuit board 17, which also typically carries other circuitry, shown at 18, for example. Light rays from the LED pass into the light pipe and travel generally axially, as indicated at 19-21. The light pipe perimeter 10aprojects toward the circuit board.

[0027] The opposite end 12 of the cylindrical light pipe may advantageously define light transmitting facets shown as extending in circular arcs at 12a, in FIG. 5. Light is transmitted by the facets as indicated by rays 23-27, within a cone. Cone angularity α may advantageously be about 120°.

[0028] FIG. 1 shows a support panel 30 carrying the forward end extent 10bof the light pipe in endwise spaced relation to recess 13. End extent 10btypically projects through an opening 31 in that panel, with pipe faceted end 12 located proximate the panel side 30a. A cylindrical flange 32 may be formed by or on the light pipe to engage panel side 30a, to accurately endwise position the light pipe relative to the panel.

[0029] Further positioning of the light pipe is afforded by an annular grip ring 35 extending closely about the light pipe to grip its outer surface at 10c. The grip ring is axially adjusted to cause the forward end 35aof the ring to engage the panel rearward side 30b, whereby the panel is retained between the ring and the flange 32. This also serves to axially space the panel relative to the circuit board, in a simple, predetermined, and effective manner. The grip ring may have serrations 38 at its bore, to frictionally engage the light pipe outer surface 10d, and block axial movement of the grip ring axially rightwardly relative to the light pipe, in FIG. 1.

[0030] The method of positioning a light pipe and light source, includes the steps:

[0031] a) providing a panel,

[0032] b) assembling the light pipe to the panel to project through an opening in the panel,

[0033] c) and assembling the light pipe and light source so that the light source projects into an end portion of the light pipe in spaced relation to the panel.

[0034] That end portion of the light pipe may define the concave recess 13, as referred to, to engage and optically axially align the light pipe and LED.

[0035] The method may also include providing grip structure gripping the light pipe, and providing a flange on the light pipe, and locating the panel to extend between said grip structure and flange, to be engaged thereby, for positioning the panel relative to a circuit board that carries the LED, as by surface mounting.