Miniaturized linear light source sub-module for various format main modules

A miniaturized linear light source sub-module comprising a symmetrical lens array, a light guide bar with dual reflecting surfaces, at least one light emitting diode light source, and a sub-module housing is disclosed. The symmetrical lens array comprises two identical covers, two identical lens sections, and a middle holder. Each lens section comprises a plurality of lenses disposed on the top and bottom of the lens section. The dual reflecting surface light guide comprises a light emitting surface, a v-shaped light reflecting surface, an asymmetrical saw-toothed light reflecting surface, an apex cut-off surface, and a bottom cut-off surface. At least one light emitting diode light source is connected to an end of the dual reflecting surface light guide. The sub-module housing holds the lens array assembly, the dual reflecting surface light guide, and the at least one light emitting diode light source to form the miniaturized linear light source sub-module.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optics. More specifically, the present invention discloses a miniaturized linear light source sub-module comprising a highly efficient light guide with a first reflecting surface to maximize light reflection and a second reflecting surface to enhance the uniformity of the emitted light, at least one light emitting diode light source, an array of lenses for high-resolution imaging of a surface, and a sub-module housing.

2. Description of the Prior Art

Linear light sources emit light in a different direction from the direction the light originated from. For example, a light is produced by a light emitting diode at an angle of zero degrees. By affecting the direction of the light beam the linear light source can emit the light at various angles such as 90 degrees.

Refer toFIG. 1A, which is a drawing illustrating a light source of the prior art. As shown inFIG. 1A, the conventional light source comprises a light emitting diode110and a transparent light rod120. Both ends of the transparent light rod120are flat surfaces. When power is applied to the light emitting diode110the light emitting diode110emits light. Some of the light enters the transparent light rod120. However, since the end of the transparent light rod120is flat, much of the light is reflected back and is lost. This lowers the efficiency and intensity of the light source.

The light that enters the transparent light rod120exits the side surface of the transparent light rod120. Unfortunately, some of the light exits the transparent light rod120in directions not intended. This results in an additional loss of light. To overcome this disadvantage a reflective housing must be used in order to try to reflect the escaping light back into the transparent light rod120. This increases the cost of the light source.

Additionally, since only one light emitting diode110is utilized in the conventional light source the emitted light is brighter closer to the light emitting diode110and dimmer at the far end of the transparent light rod120. As a result the conventional light source's emitted light is not uniform.

Therefore, there is need for an improved light guide for a linear light source that is highly efficient and provides an emitted light that is uniform in intensity.

Traditionally, the lens for a one to one imaging optical scanner is a rod lens array. Please refer toFIG. 1B, a perspective drawing of a prior-art rod lens array130. The rod lens array130is constructed from a plurality of fiber optic rod lenses131. Each individual fiber optic rod lens131is cut from a fiber optic glass strand, and its ends must be polished. The plurality of fiber optic rod lenses131are then arranged side by side, in a row or multiple rows with their optical axes in parallel, in a frame132and held in place by an adhesive layer133. The fiber optic rod lenses131are typically made from GRIN (graduated index) fibers, with the refractive index of the glass carefully controlled during manufacture to have a graduated refractive index that decreases radially from the central axis to the edge.

However, this type of lens is expensive to manufacture. GRIN type fiber optic glass strands are expensive in and of themselves; cutting and polishing the strands to precise lengths to form fiber optic rod lenses131, assembling them so that their axes are precisely parallel in the frame132, and gluing the fiber optic rod lenses131are all precision steps for which entire technologies have had to be developed in order to satisfy requirements.

In addition, a major disadvantage of this type of lens is that because of the number of lenses and the difficulty in orienting them, it is not practical to shape the ends of the lenses so that they can magnify the surface that they are imaging; flat ends are used. In order to increase the imaging resolution, it is necessary to use larger numbers of smaller-diameter rod lenses131, limiting the maximum resolution and driving up the costs as the desired resolution increases. Furthermore, suppliers for the necessary GRIN fiber optic strands are limited, and thus the base materials themselves are expensive.

Additional, the glass used in the conventional rod lens contains lead which is not environmentally friendly.

Therefore there is need for an improved lens array for which materials are substantially cheaper and which is simpler to manufacture, and which can have increased resolution without substantially increasing costs.

SUMMARY OF THE INVENTION

To achieve these and other advantages and in order to overcome the disadvantages of the conventional method in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides a miniaturized linear light source sub-module comprising a highly efficient light guide with a first reflecting surface to maximize light reflection and a second reflecting surface to enhance the uniformity of the emitted light, at least one light emitting diode light source, an array of lenses for high-resolution imaging of a surface, and a sub-module housing.

The highly efficient light guide of the miniaturized linear light source sub-module maximizes light reflection, prevents light loss at the entry point, and provides a uniform emitted light.

The light guide for a miniaturized linear light source sub-module of the present invention is comprised of transparent or semi-transparent material. The light guide bar is solid, semi-hollow or hollow.

The light guide of the present invention comprises a light emitting surface, a v-shaped light reflecting surface, an asymmetrical saw-toothed light reflecting surface, a bottom surface, a top surface, a light entry end surface, a light entry opposite end surface, an apex cut-off surface, and a bottom cut-off surface.

The light emitting surface is a surface of the light guide where light exits the light guide.

The v-shaped light reflecting surface is disposed on a surface of the light guide opposite the light emitting surface. The v-shaped light reflecting surface comprises two light reflecting surfaces at 90° apart. The center of the v-shaped light reflecting surface where the two light reflecting surfaces meet is the apex of the v-shaped light reflecting surface. The v-shaped light reflecting surface maximizes light output.

The top surface is disposed between the light emitting surface and the v-shaped light reflecting surface. The bottom surface is disposed opposite the top surface next to the bottom of the v-shaped light reflecting surface.

The asymmetrical saw-toothed light reflecting surface is disposed between the bottom surface and the light emitting surface. The asymmetrical saw-toothed light reflecting surface comprises a plurality of notches and ridges with increasing gradient from the light entry end to the end surface opposite the light entry end. The asymmetrical saw-toothed light reflecting surface enhances the uniformity of the emitted light.

Light emitted by a light source enters the light guide through the light entry end surface. The light exits the light guide on the light emitting surface. The asymmetrical saw-toothed light reflecting surface makes the emitted light more uniform in intensity thereby enhancing the quality of the linear light source.

The asymmetrical saw-toothed light reflecting surface comprises a plurality of notches and ridges. The depth of the notches is deepest on the light guide furthest away from the LED light source. The farther away from the LED light source the depth of the notches of the asymmetrical saw-toothed light reflecting surface gradually increases. In this way the asymmetrical saw-toothed light reflecting surface affects the light more gently where the light intensity is strongest (closer to the LED light source).

The light guide further comprises an apex cut-off surface and a bottom cut-off surface at the light entry end of the light guide to prevent light loss at the light entry point further enhancing the light channeling performance.

Additionally, the light travels through the light guide at various angles and is reflected by the v-shaped light reflecting surface thereby maximizing light output.

The lens array of the miniaturized linear light source sub-module comprises a plurality of lens faces molded into surfaces of polymer bars, thus simplifying manufacturing, using inexpensive materials, and aligning the lenses without requiring significant manufacturing infrastructure.

The present invention further provides a lens array where the lens faces are configurable at the time of design to support increased resolution.

The lens array of the present invention comprises two identical covers, two identical lens sections, and a middle holder. Each lens section comprises a plurality of lenses disposed on the top and bottom of the lens section. The lens array is assembled with the middle holder positioned between the two lens sections. The two covers are positioned one cover on the top of the upper lens section and one cover positioned on the bottom of the lower lens section. The two covers hold the lens array assembly together.

Since each lens section is identical and each cover is identical the same lens section tooling is used for all lens sections and the same cover tooling is used for all covers. As a result, manufacturing cost is reduced and assembly is simplified.

A plurality of first lenses gathers and focuses light reflected from an object so that the light travels in a divergent beam through the first lens section to a second plurality of lens surfaces. The light is generated by an external source. The middle holder blocks and absorbs scattered light, while a plurality of holes allow desired, focused light to reach the third plurality of lens surfaces. The light then transits the second lens section and exits through a fourth plurality of lens surfaces, which focuses the light onto a sensor or sensors.

The linear light source sub-module of the present invention further comprises a sub-module housing for holding the lens array assembly, the dual reflecting surface light guide, and the at least one light emitting diode light source to form the miniaturized linear light source sub-module.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refer toFIG. 2, which is a three dimensional drawing illustrating a light guide with an asymmetrical saw-toothed light reflecting surface according to an embodiment of the present invention, toFIG. 3, which is a perspective view of a light guide with a circular light emitting surface according to an embodiment of the present invention, and toFIG. 4, which is a perspective view of a light guide with a polygonal light emitting surface according to an embodiment of the present invention.

The light guide200of the present invention comprises a light emitting surface210, a v-shaped light reflecting surface220, an asymmetrical saw-toothed light reflecting surface250, a bottom surface240, a top surface230, a light entry end surface260, and a light entry opposite end surface270.

The light emitting surface210is a surface of the light guide200where light exits the light guide200. In the embodiment illustrated inFIG. 3the light emitting surface is a circular or arc-shaped surface. In the embodiment illustrated inFIG. 4the light emitting surface is a polygonal-shaped surface.

The v-shaped light reflecting surface220is disposed on a surface of the light guide200opposite the light emitting surface210. The v-shaped light reflecting surface220comprises two light reflecting surfaces, a top light reflecting surface220A and a bottom light reflecting surface220B, at 90° apart. The center of the v-shaped light reflecting surface220where the two light reflecting surfaces meet is the apex221of the v-shaped light reflecting surface220. The v-shaped light reflecting surface220maximizes light output.

The top surface230is disposed between the light emitting surface210and the v-shaped light reflecting surface220. The bottom surface240is disposed opposite the top surface230next to the bottom light reflecting surface220B of the v-shaped light reflecting surface220.

The asymmetrical saw-toothed light reflecting surface250is disposed between the bottom surface240and the light emitting surface210. The asymmetrical saw-toothed light reflecting surface250comprises a plurality of notches and ridges with increasing gradient from the light entry end surface260to the light entry opposite end270which is the end surface of the light guide200opposite the light entry end surface260. The asymmetrical saw-toothed light reflecting surface250enhances the uniformity of the emitted light.

Refer toFIG. 5, which is a drawing illustrating an asymmetrical saw-tooth pattern of the asymmetrical saw-toothed light reflecting surface according to an embodiment of the present invention.

As shown inFIG. 5, the asymmetrical saw-toothed light reflecting surface250comprises an asymmetrical saw-tooth pattern of ridges251and notches252. The asymmetrical saw-tooth pattern gradually increases in gradient from the light entry end surface260to the end opposite the light entry surface270. The asymmetrical saw-tooth pattern has a constant saw-tooth angle and a constant pitch. In this embodiment of the present invention the constant saw-tooth angle is 75°. In other embodiments of the present invention the constant saw-tooth angle is greater or less than 75°. Also, in this embodiment the constant pitch is 1.0 mm. In other embodiments of the present invention the constant pitch is greater or less than 1.0 mm.

The saw-tooth height of the asymmetrical saw-tooth pattern gradually increases in height as the pattern moves away from the light entry end surface260and towards the opposite end270of the light guide200. As shown in the lower left side ofFIG. 5at the end270of the light guide200the greatest distance from the light entry end surface260the ridges251and notches252are clearly defined to produce the asymmetrical pattern. At this end270the saw-tooth height or depth is greatest.

As shown in the lower right side ofFIG. 5at the end of the light guide200closest to the light entry end surface260the ridges251are clearly defined but the notches252are shallow valleys with flat surfaces. Again, as the pattern moves from the light entry end surface260towards the opposite end270of the light guide200the shallow valleys of the notches252gradually increase in depth until the notches251are clearly defined to produce a distinct saw-tooth.

In the embodiment illustrated inFIG. 5the asymmetrical saw-tooth pattern begins with a saw-tooth height of 0.3 mm at the light entry end and rises to a saw-tooth height of 0.5 mm at the opposite end of the light guide. In other embodiments of the present invention other saw-tooth heights are utilized.

Refer toFIGS. 6A and 6B, which are drawings illustrating an apex cut-off surface of the light guide according to an embodiment of the present invention.

In the embodiment illustrated inFIGS. 6A and 6Bthe light guide200further comprises an apex cut-off surface280. The apex cut-off surface280is at the light entry end surface260of the light guide200. The apex cut-off surface280is at an angle from the apex221of the v-shaped light reflecting surface. The apex cut-off surface280prevents light loss at the light entry point further enhancing the light channeling performance on the light entry end. Light emitted by a light source265enters the light guide200via the light entry end surface260. Light that might normally exit the light guide200near the light entry end surface260is reflected or channeled by the apex cut-off surface280. In the embodiment illustrated in FIGS.6A and6B the angle from the apex221is 15°. In other embodiments of the present invention the angle is greater or less than 15°.

Refer toFIG. 7, which is a drawing illustrating a bottom cut-off surface of the light guide according to an embodiment of the present invention.

In the embodiment illustrated inFIG. 7the light guide200further comprises a bottom cut-off surface290. The bottom cut-off surface290is at the light entry end surface260of the light guide200. The bottom cut-off surface290is at an angle from the bottom surface240of the light guide200. The bottom cut-off surface290prevents light loss at the light entry point further enhancing the light channeling performance on the light entry end. Light emitted by a light source265enters the light guide200via the light entry end surface260. Light that might normally exit the light guide200near the light entry end surface260is reflected or channeled by the bottom cut-off surface290. In the embodiment illustrated inFIG. 7the angle from the bottom surface240is 15°. In other embodiments of the present invention the angle is greater or less than 15°.

As described above the light guide of the present invention comprises dual light reflecting surfaces, a v-shaped light reflecting surface for maximizing light output and an asymmetrical saw-toothed light reflecting surface for enhancing the uniformity of emitted light. The v-shaped light reflecting surface comprises two light reflecting surfaces at 90°. The asymmetrical saw-toothed light reflecting surface comprises notches and ridges with increasing gradient from the light entry end of the light guide to the opposite end. The asymmetrical saw-tooth has a constant pitch and constant saw-tooth angle. The light guide further comprises an apex cut-off surface and a bottom cut-off surface at the light entry end of the light guide to prevent light loss at the light entry point further enhancing the light channeling performance.

Please refer toFIG. 8, which shows an exploded perspective drawing of a lens array of a miniaturized linear light source sub-module of the present invention. The lens array1200of this embodiment consists of a first cover1210A, a second cover1210B, a first lens section1220A, a second lens section1220B, and a middle holder1230. Each component is discussed in further detail below. The first cover1210A and the second cover1210B enclose the perimeter of the assembled lens array1200, providing support, mounting, and protection, as well as blocking out external light.

The middle holder1230and the covers1210A,1210B comprise a plurality of holes organized such that the centers of the holes form a line down the center of the middle holder1230and the covers1210A,1210B. The holes are spaced apart equally by the inter-axis distance. The holes are circular, oval, cylindrical, or conical.

Refer toFIG. 9, which is a cross-sectional view of a lens array of a miniaturized linear light source sub-module according to an embodiment of the present invention.

Each lens section1220A,1220B comprises a plurality of lenses disposed on the top and bottom of the lens section1220A,1220B. The lens array1200is assembled with the middle holder1230positioned between the two lens sections1220A,1220B. The two covers1210A,1210B are positioned one cover1210A on the top of the upper lens section1220A and one cover1210B positioned on the bottom of the lower lens section1220B. The two covers1210A,1210B hold the lens array assembly1200together. Each of the components of the lens array1200has mating elements that allow the components to attach and be held together. The mating elements also assist during assembly.

Refer toFIG. 10A, which is a top view of a lens section of a lens array according to an embodiment of the present invention,FIG. 10B, which is a side view of a lens section of a lens array according to an embodiment of the present invention, andFIG. 10C, which is a bottom view of a lens section of a lens array according to an embodiment of the present invention.

The lens section1220comprises a first surface1221and a first plurality of lenses1223are formed with their optical axes in line, spaced apart equally by one inter-axis distance. The line of the centers of the first plurality of lenses1223in this example embodiment is along the center line of the lens section1220. A surface of the cover fits snugly against the lens first surface1221so that the plurality of holes of the cover are lined up with their centers on the optical axes of the first plurality of lenses1223.

The second surface1222of the lens section1220has a second plurality of lenses1224formed with their optical axes in line, spaced apart equally by one inter-axis distance. The line of the centers of the first plurality of lenses1223in this example embodiment is along the center line of the lens section1220. A surface of the cover fits snugly against the second surface1222so that the plurality of holes in the cover is lined up with their centers on the optical axes of the second plurality of lenses1224.

The lens section1220further comprises at least one mating element1225to mate with mating elements of the middle holder to assist in assembly and hold the lens section and the middle holder together.

The lenses of the lens section on both surfaces have identical diameters and optical radii.

The plurality of optical axes of the first plurality of lenses1223are inline with the plurality of optical axes of the second plurality of lenses1224. Please note that the optical axes of the second plurality of lenses1224are aligned with the optical axes of the first plurality of lenses1223and that the number of lenses in the first plurality of lenses1223is the same as the number of lenses in the second plurality of lenses1224.

Refer toFIG. 11A, which is a top view of a cover of a lens array according to an embodiment of the present invention,FIG. 11B, which is a side view of a cover of a lens array according to an embodiment of the present invention, andFIG. 11C, which is a bottom view of a cover of a lens array according to an embodiment of the present invention.

The cover1210comprises a plurality of holes1213that are sized and spaced according to the size and spacing of the lenses on the lens section. In an embodiment of the present invention the holes1213are smaller in diameter than the diameter of the lenses.

The cover1210also comprises a plurality of mating elements1215that mate with mating elements on the middle holder in order to attach and hold the lens array assembly together. In an embodiment of the present invention the mating elements1215are male elements, for example posts, tabs, or risers and the mating elements on the middle holder are female elements, for example holes, slots, indentations, or channels. In another embodiment the genders of the mating elements are switched.

Refer toFIG. 12A, which is a top view of a middle holder of a lens array according to an embodiment of the present invention,FIG. 12B, which is a side view of a middle holder of a lens array according to an embodiment of the present invention, andFIG. 12C, which is a bottom view of a middle holder of a lens array according to an embodiment of the present invention.

The middle holder1230comprises a plurality of holes1233. The size and spacing of the holes1233are related to the size and spacing of the lenses of the lens sections. A plurality of mating elements1235is disposed on the top surface1231and the bottom surface1232of the middle holder1230. These mating elements1235mate with the mating elements of the cover holder in order to attach and hold the lens array assembly together.

Refer toFIG. 13A, which is a diagram illustrating an assembled lens array of a miniaturized linear light source sub-module according to an embodiment of the present invention, andFIG. 13B, which is a diagram illustrating an exploded view of a lens array according to an embodiment of the present invention.

The lens array1200of the present invention comprises a top cover1210A, a bottom cover1210B, a top lens section1220A, a bottom lens section1220B, and a middle holder1230.

To assemble the lens array1200of the present invention mating elements of the top lens section1220A mate with mating elements of the top surface of the middle holder1230and mating elements of the bottom lens section1220B mate with mating elements of the bottom surface of the middle holder1230. Additionally, mating elements of the top cover1210A mate with mating elements of the top surface of the middle holder1230and mating elements of the bottom cover1210B mate with mating elements of the bottom surface of the middle holder1230. The mating elements of the covers, lens sections, and the middle holder cooperate to attach and hold the lens array assembly together.

Refer toFIG. 14, which is a diagram illustrating imaging through lens sections of a lens array according to an embodiment of the present invention.

In application, an object is positioned at a location that offers proper focus above the lens sections1220of the lens array. Light illuminates areas of the object. For example purposes these areas are designated A and A′. As the light illuminates the object's A and A′ and the light enters the top lens section1220A via the lenses1223A. The light travels through the top lens section1220A and exits through the lenses1224A. The light continues through the space between the two lens sections and enters the bottom lens section1220B via lenses1224B. The light travels through the bottom lens section1220B and exits through the lenses1223B. The lenses direct the light so that an image of the object's A and A′ is focused and a suitable image of the object is obtained. For example, the light is directed towards an array of sensors which detect and store the image data.

Refer toFIG. 15A, which is a diagram illustrating imaging through lens sections of a lens array with an object in focus according to an embodiment of the present invention,FIG. 15B, which is a diagram illustrating imaging through lens sections of a lens array with an object 1 mm above the focus plane according to an embodiment of the present invention, andFIG. 16, which is a graph illustrating through-focus performance of a lens array according to an embodiment of the present invention.

As shown inFIGS. 15A,15B, and16the lens array of the present invention provides superior performance. Even with the object 1 mm out of the ideal focus position an acceptable image is obtainable. The lens array of the present invention provides improved depth of field. Additionally the lens array has enhanced image uniformity and brightness.

In an embodiment, the first lens section and second lens section are made of a refractive, substantially transparent polymer and the cover and middle holder are made of an opaque polymer, for example black, to absorb and/or block undesirable scattered or external light.

When the lens array assembly is used in an image scanner, it is very important that image light does not pass from one lens into another lens that is not perpendicular to it. When this light progresses into an adjacent lens, the resultant image that the sensor captures is a ghost image of the adjacent lens. This is called cross-talk and is undesirable.

An advantage of the present invention is that due to the wall thickness of the middle holder extend to the edges of the individual lenses, cross-talk is prevented.

If the lens array assembly doesn't have a suitable lens housing, light can pass between lenses and result in ghosting. However, in the present invention if light passes from one lens into the hole of the middle holder, the light is absorbed by the wall of the middle holder thus preventing the undesirable light from entering the adjacent lens. As a result, cross-talk is eliminated and ghosting is prevented.

The dots per inch (DPI) resolution of the lens array is adjustable at design time by changing the optical radii, conic constant, or aspherical coefficients of the four lens groups. In contrast with the prior art rod lenses, the lens array can be designed to magnify the surface being imaged.

The lens array thus provides a substantial improvement over the prior art by reducing manufacturing complexity and materials costs. Furthermore, the lens array makes it substantially easier to increase the resolution of a device using the lens array compared to the prior art.

Refer toFIG. 17, which is an exploded view drawing illustrating a miniaturized linear light source sub-module according to an embodiment of the present invention and toFIG. 18, which is a drawing illustrating an assembled miniaturized linear light source sub-module according to an embodiment of the present invention.

As shown inFIG. 17andFIG. 18, the miniaturized linear light source sub-module1700of the present invention comprises an LED linear light source1710comprising a highly efficient light guide with a first reflecting surface to maximize light reflection and a second reflecting surface to enhance the uniformity of the emitted light and at least one light emitting diode light source1712, a symmetrical lens array1720comprising an array of lenses for high-resolution imaging of a surface, and a sub-module housing1730. The sub-module housing1730holds the lens array assembly1720, the LED linear light source1710with dual reflecting surface light guide and the at least one light emitting diode light source to form the miniaturized linear light source sub-module1700.

The LED linear light source1720further comprises LED electrical contacts1711on the LED light source package1720. The LED electrical contacts1711couple with sub-module electrical contacts1740on the sub-module housing. Power supplied from a main module to the sub-module electrical contacts1740reaches the LED light source package1712via the LED electrical contacts1711.

The assembled miniaturized linear light source sub-module provides a highly integrated, standardized, and miniaturized linear light source sub-module that can be installed in main modules of various formats. Utilizing the sub-module of the present invention simplifies manufacturing and production processes by providing a complete linear light source assembly.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the invention and its equivalent.