ABBE prism lens with improved focus and reduced flair

An Abbe prism lens and lens array are disclosed. The lens comprises front lenses disposed on a front surface of the Abbe prism, rear lenses disposed on a rear surface of the Abbe prism, a front bottom reflecting surface, a rear bottom reflecting surface, a left top reflecting surface, and a right top reflecting surface. An aperture cover is positioned over the front surface of the Abbe prism lens and a field cover is positioned over the rear surface of the Abbe prism lens. The aperture cover comprises aperture holes encircling the aspherical front lenses. The field cover comprises field holes encircling the aspherical rear lenses. Light enters the Abbe prism lens and reflects off the front bottom reflecting surface, reflects off the left top reflecting surface and the right top reflecting surface, reflects off the rear bottom reflecting surface, and exits the rear lens of the Abbe prism lens.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optics. More specifically, the present invention discloses an Abbe prism lens and a lens array assembly comprising a plurality of Abbe prism lenses for high-resolution imaging of a surface.

2. Description of the Prior Art

Traditionally, the lens for a one to one imaging optical scanner is a rod lens array. Please refer toFIG. 1, a perspective drawing of a prior-art rod lens array100. The rod lens array100is constructed from a plurality of fiber optic rod lenses110. Each individual fiber optic rod lens110is cut from a fiber optic glass strand, and its ends must be polished. The plurality of fiber optic rod lenses110are then arranged side by side, in a row or multiple rows with their optical axes in parallel, in a frame120and held in place by an adhesive layer130. The fiber optic rod lenses110are 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 lenses110, assembling them so that their axes are precisely parallel in the frame120, and gluing the fiber optic rod lenses110are 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 lenses110, 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.

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 superior imaging properties 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 an Abbe prism lens and a lens array assembly comprising a plurality of Abbe prism lenses.

The present invention also provides a lens array where a plurality of lens faces are 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 Abbe prism lens of the present invention comprises an aspherical front lens disposed on a front surface of the Abbe prism, an aspherical rear lens disposed on a rear surface of the Abbe prism, a front bottom reflecting surface, a rear bottom reflecting surface, a left top reflecting surface, a right top reflecting surface, a front slope surface, and a rear slope surface comprising an upper rear slope surface and a lower rear slope surface.

The front slope surface is positioned between the left top reflecting surface and the right top reflecting surface and the front surface. The rear slope surface is positioned between the left top reflecting surface and the right top reflecting surface and the rear surface. The front bottom reflecting surface is positioned between the front surface and the rear bottom reflecting surface and the rear bottom reflecting surface is positioned between the front bottom reflecting surface and the rear surface. The left top reflecting surface and the right top reflecting surface form a roof on the Abbe prism lens.

Light is reflected off an object and enters the aspherical front lens of the Abbe prism lens. This light then reflects off the front bottom reflecting surface, reflects off the left top reflecting surface and the right top reflecting surface, reflects off the rear bottom reflecting surface, and exits the aspherical rear lens of the Abbe prism lens.

After the light reflects off the front bottom reflecting surface a portion of the light takes a path that reflects firstly off the left top reflecting surface and then secondly off the right top reflecting surface before reflecting off the rear bottom reflecting surface. The other portion of the light takes a path that reflects firstly off the right top reflecting surface and then secondly off the left top reflecting surface before reflecting off the rear bottom reflecting surface.

Light entering the Abbe prism lens of the present invention is reflected a total of four times before exiting. As a result, the corresponding image of the object is in up-right orientation and not upside-down.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refer toFIG. 2A, which is a side view drawing illustrating an Abbe prism lens according to an embodiment of the present invention, toFIG. 2B, which is a perspective front view drawing illustrating an Abbe prism lens according to an embodiment of the present invention, toFIG. 2C, which is a rear view drawing illustrating an Abbe prism lens according to an embodiment of the present invention, and toFIG. 2D, which is a perspective rear view drawing illustrating an Abbe prism lens according to an embodiment of the present invention.

As shown inFIGS. 2A-2D, the Abbe prism lens200of the present invention comprises an aspherical front lens220disposed on a front surface210of the Abbe prism200, an aspherical rear lens280disposed on a rear surface270of the Abbe prism200, a front bottom reflecting surface230, a rear bottom reflecting surface260, a left top reflecting surface250, a right top reflecting surface240, a front slope surface215, and a rear slope surface218comprising an upper rear slope surface217and a lower rear slope surface216.

The front slope surface215is positioned between the left top reflecting surface250and the right top reflecting surface240and the front surface210. The rear slope surface218is positioned between the left top reflecting surface250and the right top reflecting surface240and the rear surface270. The front bottom reflecting surface230is positioned between the front surface210and the rear bottom reflecting surface260and the rear bottom reflecting surface260is positioned between the front bottom reflecting surface230and the rear surface270.

The left top reflecting surface250and the right top reflecting surface240form a roof on the Abbe prism lens200.

Refer toFIG. 3A, which is a side view drawing illustrating an Abbe prism lens according to an embodiment of the present invention and toFIG. 3B, which is a rear view drawing illustrating an Abbe prism lens according to an embodiment of the present invention.

As shown inFIG. 3A, the angle range between the front bottom reflecting surface230and the rear bottom reflecting surface260is between 1 and 179 degrees.

As shown inFIG. 3B, the angle range between the left top reflecting surface250and the right top reflecting surface240is between 1 and 90 degrees.

Refer toFIG. 4, which is a cross-sectional side view drawing illustrating an Abbe prism lens assembly according to an embodiment of the present invention, toFIG. 5A, which is an assembled view drawing illustrating an Abbe prism lens assembly according to an embodiment of the present invention, and toFIG. 5B, which is an exploded view drawing illustrating an Abbe prism lens assembly according to an embodiment of the present invention.

In the embodiment illustrated inFIGS. 4,5A, and5B the present invention provides an Abbe prism lens assembly700which further comprises an aperture cover300positioned over the front surface210of the Abbe prism lens200and a field cover400positioned over the rear surface270of the Abbe prism lens200. The aperture cover300comprises an aperture hole310encircling the aspherical front lens220. The field cover400comprises a field hole410encircling the aspherical rear lens280.

Refer toFIGS. 6A-6Dwhich are drawings illustrating light paths through an Abbe prism lens according to an embodiment of the present invention.

As shown inFIGS. 6A-6Dan object such as a document is placed on a transparent surface600such as a glass platen of a flatbed scanner. Light is reflected off the object and enters the aspherical front lens220of the Abbe prism lens200. This light then reflects off the front bottom reflecting surface230, reflects off the left top reflecting surface250and the right top reflecting surface240, reflects off the rear bottom reflecting surface260, and exits the aspherical rear lens280of the Abbe prism lens.

After the light reflects off the front bottom reflecting surface230a portion of the light takes a path that reflects firstly off the left top reflecting surface250and then secondly off the right top reflecting surface240before reflecting off the rear bottom reflecting surface260. The other portion of the light takes a path that reflects firstly off the right top reflecting surface240and then secondly off the left top reflecting surface250before reflecting off the rear bottom reflecting surface260.

Light entering the Abbe prism lens of the present invention is reflected a total of four times before exiting. As a result, the corresponding image of the object is in up-right orientation and not upside-down.

Refer toFIG. 7A, which is a front view drawing illustrating an Abbe prism lens array according to an embodiment of the present invention, toFIG. 7B, which is a rear view drawing illustrating an Abbe prism lens array according to an embodiment of the present invention, toFIG. 7C, which is a top view drawing illustrating an Abbe prism lens array according to an embodiment of the present invention, toFIG. 7D, which is a bottom view drawing illustrating an Abbe prism lens array according to an embodiment of the present invention, and toFIG. 7Ewhich is a perspective view drawing illustrating an Abbe prism lens array according to an embodiment of the present invention.

In the embodiment illustrated inFIGS. 7A-7Ethe present invention comprises a plurality of Abbe prism lenses connect together to form an Abbe prism lens array200A. The Abbe prism lens array200A is formed by, for example, injection molding of transparent material. Utilizing the Abbe prism lens array200A allows for reproducing or capturing a greater linear area of an image.

Refer toFIG. 8A, which is an exploded view drawing illustrating an Abbe prism lens array assembly according to an embodiment of the present invention and toFIG. 8B, which is an assembled view drawing illustrating an Abbe prism lens array assembly according to an embodiment of the present invention.

In the embodiment illustrated inFIGS. 8A and 8Bthe present invention provides an Abbe prism lens array assembly700A which further comprises an aperture cover300A positioned over the front surface210of the Abbe prism lens array200A and a field cover400A positioned over the rear surface270of the Abbe prism lens array200A. The aperture cover300A comprises a plurality of aperture cover holes310encircling the aspherical front lenses220. The field cover400A comprises a plurality of field holes410A encircling the aspherical rear lenses.

Refer toFIG. 9A, which is a drawing illustrating a lens simulation for the Abbe prism lens array according to an embodiment of the present invention and toFIG. 9B, which is a drawing illustrating a lens simulation for a convention lens array of the prior art.

FIGS. 9A and 9Bshow a spot size comparison between the Abbe prism lens array of the present invention and a conventional lens array when an image is positioned 1 mm away from the optimal focal point. On the left hand side ofFIG. 9Athe spot size is 36.11 μm and on the right hand side the spot size is 36.23 μm. On the left hand side ofFIG. 9Bthe spot size is 121 μm and on the right hand side the spot size is 127 μm.

By comparing the two results it is easily seen that the Abbe prism lens array of the present invention provides an improved image quality when an image is not positioned in the optimal position for best focus. For example, if a document is warped and portions of the document don't contact the platen glass, the Abbe prism lens array will still allow for a high quality image capture. The Abbe prism lens array of the present invention is more tolerant or forgiving when compared to the conventional lens array. With the conventional lens array any portions of a document or object that are positioned outside the optimal focal point are reproduced poorly. Devices utilizing the Abbe prism lens array of the present invention offer superior quality image reproduction or capture and have a higher focal point tolerance.

Refer toFIG. 10A, which is a drawing illustrating a lens simulation for the Abbe prism lens array according to an embodiment of the present invention and toFIG. 10B, which is a drawing illustrating a lens simulation for a conventional lens array of the prior art.

Again with a defocus of 1 mm the image comparison between the Abbe prism lens array of the present invention and the conventional lens array clearly shows that the resultant image is far more focused and superior for the Abbe prism lens array.

Since the Abbe prism lens and Abbe prism lens array are formed in one piece injection-molding, issues associated with assembly stack-up tolerances are minimized.

By altering the thickness of the front of the aperture cover, flair can be reduced. In other words, by increasing or decreasing the length of the aperture hole (increasing or decreasing the thickness between the front face of the aperture cover and the rear face of the aperture cover) flair can be reduced.

Additionally, by altering the diameter of the aperture hole image intensity can be controlled.

By altering the diameter of the field cover hole, flare can be reduced and linear image range or size of captured image is controlled.

In an embodiment of the present the diameter of the aperture cover hole and the diameter of the field cover hole are different. In an embodiment of the present the diameter of the aperture cover hole and the diameter of the field cover hole are the same.

In an embodiment of the present the curvature of the front lens and the curvature of the rear lens are different. In an embodiment of the present the curvature of the front lens and the curvature of the rear lens are the same.

In some embodiments of the present invention the aperture cover and the field cover have a plurality of holes organized such that the centers of the holes form a line down the center of the cover. The plurality of holes are spaced apart equally by the inter-axis distance. The plurality of holes are circular, oval, cylindrical, or conical.

In some embodiments of the present invention the aperture cover and the field cover are made of 1 piece, 2 pieces, 3 pieces, or more pieces. For example, in an embodiment the one piece aperture cover is made of semi-flexible material and clamps over the Abbe prism lens or Abbe prism lens array. While the embodiments illustrated in the figures the aperture cover and the field cover are shown covering the front and rear of the Abbe prism lens, in other embodiments the aperture cover and the field cover cover the top and bottom or other orientations. In these embodiments the aperture cover and the field cover still provide aperture holes and field holes encircling the front and rear lenses.

In embodiments of the present invention the aperture cover and the field cover further comprise mating elements to attach and hold the lens assembly together. For example, along the edges of the field cover a plurality of notches is positioned to mate with a plurality of ears on the aperture cover.

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 aperture cover and the field cover and the aperture and field holes extend to the edges of the individual lenses, cross-talk 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 lenses. In contrast with the prior art rod lenses, the lens array can be designed to magnify the surface being imaged.

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

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.