Adjustable imaging lens assembly in imaging reader

Abstract

An adjustable imaging lens assembly focuses light from indicia along an optical path onto a solid-state imager of an imaging reader. The lens assembly includes a plurality of lenses and an aperture stop spaced apart along the optical path, at least one of lenses being mounted with multiple freedoms of movement relative to the optical path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a point-of-transaction workstation operative for capturing light from symbol-bearing targets in accordance with this invention;

FIG. 2 is a perspective view of an electro-optical reader operative in either a hand-held mode, or a workstation mode, for capturing light from symbol-bearing targets in accordance with this invention;

FIG. 3 is a block diagram of various components of the workstation of FIG. 1;

FIG. 4 is an exploded view of an adjustable imaging lens assembly for focusing light onto an imager in accordance with this invention;

FIG. 5 is an end view of the adjustable assembled imaging lens assembly of FIG. 4; and

FIG. 6 is an assembled sectional view of the adjustable imaging lens assembly taken on line 6-6 of FIG. 5, with representative light rays being captured by an imager.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference numeral 10 in FIG. 1 generally identifies a workstation for processing transactions and specifically a checkout counter at a retail site at which products such as a can 12 or a box 14, each bearing a target symbol, are processed for purchase. The counter includes a countertop 16 across which the products are slid at a swipe speed past a vertical window (i.e., presentation area) 18 of a box-shaped vertical slot reader 20 mounted on the countertop 16. A checkout clerk or operator 22 is located at one side of the countertop, and the reader 20 is located at the opposite side. A cash/credit register 24 is located within easy reach of the operator.

Reference numeral 30 in FIG. 2 generally identifies another reader having a different configuration from that of reader 20. Reader 30 also has a generally vertical window (i.e., presentation area) 26 and a gun-shaped housing 28 supported by a base 32 for supporting the reader 30 on a countertop. The reader 30 can thus be used as a stationary workstation in which products are slid or swiped past the vertical window 26, or can be picked up off the countertop and held in the operator's hand and used as a handheld reader in which a trigger 34 is manually depressed to initiate reading of the symbol.

As described so far, the readers 20, 30 are conventional. As schematically shown in FIG. 3, an imager 40 and an imaging lens assembly 41 are mounted in an enclosure 43 in either reader, such as the reader 20. The imager 40 is a solid-state device, for example, a CCD or a CMOS imager and has an array of addressable image sensors operative for capturing light through the window 18 from a target, for example, a one- or two-dimensional symbol, over a field of view and located in a working range of distances between a close-in working distance (WD1) and a far-out working distance (WD2). In a preferred embodiment, WD1 is about two inches from the imager array 40 and generally coincides with the window 18, and WD2 is about eight inches from the window 18. An illuminator is also mounted in the reader and preferably includes a plurality of light sources, e.g., light emitting diodes (LEDs) 42, arranged at opposite sides of the imager 40 to uniformly illuminate the target.

As shown in FIG. 3, the imager 40 and the illuminator LEDs 42 are operatively connected to a controller or microprocessor 36 operative for controlling the operation of these components. Preferably, the microprocessor is the same as the one used for decoding light scattered from the indicia and for processing the captured target images.

In operation, the microprocessor 36 sends a command signal to pulse the illuminator LEDs 42 for a short time period, say 500 microseconds or less, and energizes the imager 40 to collect light from a target symbol only during said time period. A typical array needs about 33 milliseconds to read the entire target image and operates at a frame rate of about 30 frames per second. The array may have on the order of one million addressable image sensors.

Although the aforementioned imaging lens assembly 41 is depicted as a single lens, this was done to simplify the drawing. In practice, the lens assembly 41 includes a plurality of optical lenses arranged along an optical path to focus the illumination light from the indicia onto the imager. In the prior art, each of these lenses had very high opto-mechanical tolerances, and optical consistency among the known imaging lens assemblies was low.

In accordance with the invention, as depicted in FIGS. 4-6, the lens assembly includes a tubular holder 50 having an oversized open-ended cavity 52 in which a movable lens 54 is mounted with multiple freedoms of movement as described below, another open-ended large cavity 56 in which lenses 58, 60 are mounted, an intermediate small cavity 62 in which another lens 64 is mounted, and an aperture stop 66 mounted in the cavity 56 in abutment with a shoulder 68 formed between the large and small cavities 56, 62.

The movable lens 54 is mounted with mechanical clearance in the oversized cavity 52 for movement relative to an optical path 70. The movable lens 54 has multiple freedoms of movement, for example, a turning movement can be in either circumferential direction about the optical path 70, or a back-and-forth movement can be in either linear direction along the optical path 70, or a radial movement can be in either linear direction radially of the optical path 70, or a tilting movement can be in opposite angular directions about a tilt axis orthogonal to the optical path 70, or a composite movement comprised of a combination of one or more of these movements can be performed. The movable lens 54 is moved to an adjusted position in which it optically compensates for any misalignment or tolerance build-ups of the other lenses 58, 60, 64 and the aperture stop 66 of the assembly, and is then secured in place, preferably by an optically transparent, quick-setting adhesive.

In the preferred embodiment, the movable lens 54 is furthest away from the imager 40 and has a relatively low optical power, either positive or negative. The other lenses 58, 60, 64 have relatively higher optical powers. The aperture stop 66 is positioned between lenses 60, 64 of the assembly. The resulting assembly is optically balanced, compact, easy to adjust and is usefully employed in portable and mobile applications where size and weight are at a premium.

It will be understood that each of the elements described above or two or more together, also may find a useful application in other types of constructions differing from the types described above. Thus, readers having different configurations can be used.

While the invention has been illustrated and described as an adjustable imaging lens assembly for focusing light onto an imager in an imaging reader, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

Claims

1. A reader for electro-optically reading indicia, comprising: a) a housing having a presentation area; b) a solid-state imager in the housing and including an array of image sensors for capturing light through the presentation area from the indicia over a field of view during reading; andc) an imaging lens assembly for focusing the light from the indicia along an optical path onto the sensors, including a plurality of lenses and an aperture stop spaced apart along the optical path, at least one of the lenses being mounted for movement relative to the optical path.

2. The reader of claim 1, wherein the at least one lens has multiple freedoms of movement, including at least one of a turning movement in either circumferential direction about the optical path, a back-and-forth movement in either linear direction along the optical path, a radial movement in either linear direction radially of the optical path, a tilting movement in opposite angular directions about a tilt axis orthogonal to the optical path, and a composite movement comprised of a combination of at least one of said movements.

3. The reader of claim 1, wherein the lens assembly includes a tubular holder having open-ended cavities in which the lenses are mounted.

4. The reader of claim 3, wherein the at least one lens is mounted with mechanical clearance in one of the cavities.

5. The reader of claim 3, wherein the holder includes a shoulder between two of the cavities, and wherein the aperture stop is in contact with the shoulder.

6. The reader of claim 1, and an illuminator in the housing for illuminating the indicia during reading with illumination light directed from an illuminating light source through the presentation area, and wherein the imaging lens assembly is operative for focusing the illumination light captured from the indicia onto the sensors.

7. The reader of claim 1, wherein the housing has a handle for handheld operation.

8. The reader of claim 1, wherein the housing has a base for supporting the housing on a support surface for workstation operation.

9. A reader for electro-optically reading indicia, comprising: a) housing means having a presentation area;b) imaging means in the housing means including a solid-state imager having an array of image sensors for capturing light through the presentation area from the indicia over a field of view during reading; andc) imaging lens means for focusing the light from the indicia along an optical path onto the sensors, including a plurality of lenses and an aperture stop spaced apart along the optical path, at least one of the lenses being mounted for movement relative to the optical path.

10. An imaging lens assembly for focusing light from indicia along an optical path onto a solid-state imager, comprising: a) a tubular holder having open-ended cavities; andb) a plurality of lenses and an aperture stop spaced apart along the optical path and supported by the holder, at least one of the lenses being mounted in one of the cavities with mechanical clearance for movement relative to the optical path.

11. The lens assembly of claim 10, wherein the at least one lens has multiple freedoms of movement, including at least one of a turning movement in either circumferential direction about the optical path, a back-and-forth movement in either linear direction along the optical path, a radial movement in either linear direction radially of the optical path, a tilting movement in opposite angular directions about a tilt axis orthogonal to the optical path, and a composite movement comprised of a combination of at least one of said movements.

12. The reader of claim 10, wherein the holder includes a shoulder between two of the cavities, and wherein the aperture stop is in contact with the shoulder.

13. A method of electro-optically reading indicia, comprising the steps of: a) capturing light through a presentation area of a reader from the indicia over a field of view during reading by an array of image sensors of a solid-state imager; andb) focusing the light from the indicia along an optical path onto the sensors, including spacing a plurality of lenses and an aperture stop apart along the optical path, and mounting at least one of the lenses for movement relative to the optical path.

14. The method of claim 13, wherein the mounting step is performed by providing the at least one lens with multiple freedoms of movement, including at least one of a turning movement in either circumferential direction about the optical path, a back-and-forth movement in either linear direction along the optical path, a radial movement in either linear direction radially of the optical path, a tilting movement in opposite angular directions about a tilt axis orthogonal to the optical path, and a composite movement comprised of a combination of at least one of said movements.

15. The method of claim 13, and mounting the lenses in cavities of a tubular holder.

16. The method of claim 15, wherein the mounting step is performed by mounting the at least one lens with mechanical clearance in one of the cavities.

17. The method of claim 15, and forming a shoulder between two of the cavities, and positioning the aperture stop in contact with the shoulder.

18. The method of claim 13, and illuminating the indicia during reading with illumination light directed from an illuminating light source through the presentation area, and wherein the focusing step is performed by focusing the illumination light captured from the indicia onto the sensors.

19. The method of claim 13, and the step of holding the reader by a handle for handheld operation.

20. The method of claim 13, and the step of supporting the reader on a support surface for workstation operation.