Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2002-12-26
2004-04-06
Le, Thien M. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S454000, C235S455000
Reexamination Certificate
active
06715683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Art
This invention relates to an optical data code reader which is particularly suitable for use in reading printed data code patterns, for example, for reading bar code labels or the like.
2. Prior Art
As for example of optical data reader for optically reading a printed data code pattern, for example, there have been widely in use the so-called bar code readers for scanning and reading encoded information on bar code labels. The bar code readers of this sort are generally constituted by a light projection means and a reflected light sensor means to read information which is printed on bar code labels in the form of a variable density pattern. The light projection means includes at least a light source and a converging lens to project and converge a light beam toward a bar code label. Further, the reflected light sensor means includes at least a capture lens and a photosensitive element. Reflected light rays from a bar code label are picked up by the capture lens and thereby projected on the photosensitive element to detect variations in density of the printed data code pattern as variations in received light intensity. Therefore, the photosensitive element functions as a photoelectric converter, and output signals of the photosensitive element are fed to a signal processor and processed by known signal processing operations to read and translate the data code pattern.
For reading a printed data code pattern which has a certain length like a bar code, it becomes necessary to scan the data code pattern. For this purpose, it has been the conventional practice to use a line sensor as a photosensitive device, in combination with a light source which is arranged to project light rays over the entire length of a printed data code pattern area by the use of light emitting elements which are arranged in a linear form or by projecting light rays through a slit of a predetermined length. In this connection, it has also been known in the art to employ a movable reflector mirror, for example, a polygon mirror or a galvanomirror for scanning a light beam which is projected from a light source.
Adoption of the above-mentioned arrangements however inevitably results in an optical data code reader which is objectionably large in size and weight. Therefore, compact and light-weight hand scanner type data code readers have been introduced and put into use to replace large and heavy apparatus. The hand scanner type data code readers are adapted to be manually moved along a surface of a printed data code pattern, for example, along a surface of a bar code label.
A hand scanner type optical data reader is disclosed, for example, in Laid-Open Japanese Patent Application H11-39425. This prior art data code reader has, within a pen type casing, a light projection means consisting of a light source and a projected light guide member, along with a reflected light sensor means consisting of a photosensitive element and a reflected light guide member. A ball lens is fitted in a distal end portion of the pen type casing. A light beam which is projected from the light source is converged toward the bar code label, and reflections of the projected light are picked up by the ball lens and shed on the photosensitive element through the reflected light guide member. Therefore, both of projected and reflected light rays are passed through the ball lens. In this instance, the reflected light guide member is constituted by fiber optics, and the light source is constituted by a plural number of light emitting elements which are arranged annularly around a bundle of fiber optics of the reflected light guide member. Further, the projection light guide member is constituted by a collimating lens and a converging lens which has a function of holding fiber optics. A mirror-finish lens tube is located between the converging lens and the ball lens.
The ball lens which is provided at the distal end of the pen type casing is dragged across a bar code label in contact with the surface of the bar code label or in a suitably spaced relation with the latter to scan the bar code, that is to say, to read the data code pattern. For this purpose, the light beam which is projected on the surface of the bar code label needs to be converged to a beam spot of a small diameter at a predetermined position on the bar code label surface. On the other hand, reflected light rays from the bar code label, the light signals indicative of variations in density of the data code pattern, should be securely captured into the optical fibers of the reflection light guide member and transferred to the photosensitive element without losses. Since both projected and reflected light rays are passed through the one and same ball lens, it becomes necessary to provide two separate light paths through the ball lens, i.e., a first light path provided through the center of the ball lens for passage of reflected light and a second annular light path provided around the first light path for passage of projected light. Accordingly, a light flux from the light source as well as a light flux coming out of the projected light guide member is in the form of an annular beam, which is fed to the ball lens as a forwardly converging light flux.
The projected light flux incident on the ball lens is converged to an extremely narrow solid beam pattern at a near point where a bar code label is located. In so doing, it is necessary to prevent the projection light from forming an annular or blurred beam spot on the bar code label surface. In this regard, the mirror-finish tube of the projected light guide member on the side of the light source functions to scatter those light components which would not contribute to converge appropriately on the bar code label.
In the case of the above-mentioned conventional pen type bar code reader in the shape of a hand-operated scanner, both of projected light rays toward a bar code label and reflected light rays from the bar code label are passed through the same ball lens despite extremely large light losses. Namely, in converging an annular light flux, which is projected toward the ball lens, into an extremely narrow solid beam pattern toward the surface of a bar code label, it is necessary to scatter away all of those light components which cannot be converged toward a predetermined position, at the cost of a large amount of light loss. Therefore, there has to be employed a high output type light source, in combination with a photosensitive element of a larger size. Besides, in order to project an annular light flux from a light source and to converge the light flux from the light source to one point, the projected light guide member needs to include a collimating lens and a converging lens between the light source and the ball lens and a space which is enshrouded in a tube, resulting in a projection system which is extremely complicate in construction and large in size to contain a long light path.
On the other hand, on the side of the light receiving system which is so located as to utilize a center portion of the ball lens, it is necessary to position the photosensitive element at least on the rear side of the collimating lens, more specifically, on the rear side of light emitting elements, and to provide a guide means to transfer signal light from a bar code label as far as the photosensitive element. This is the reason why fiber optics are used as a reflected light guide. In such a case, transfer losses are inevitable since the fiber optics have an intrinsic numerical aperture (NA). In addition, noise components are increased by scattered light occurring on the side of the light source as a result of reflections off the tube and ball lens and getting into the fiber optics by reflections. Therefore, in order to prevent these noise component from entering the fiber optics, attempts have been made to limit the maximum acceptance angle by providing a convex surface at a light receiving end of the fiber optics thereby to inhibit entrance of scattered light as much as possible. However, even
Aizawa Hidekuni
Komiya Keiji
Le Thien M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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