Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2001-08-07
2003-10-14
Lee, Diane I. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462420
Reexamination Certificate
active
06631846
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an apparatus and a method for reading an optical code. More particularly, the invention relates to an apparatus and a method for reading an optical code within a preset distance range.
As is known, optical codes can be read by means of either stationary or portable reading apparatus. In either cases, the apparatus include a casing with a reading window through which a means of illuminating a code to be read, and a means of reading the image of the code being read by detecting light scattered therefrom and converting it to electric signals, are both arranged to act. The detection means for converting the light signal to an electric signal may be of different types; in general, a so-called CCD (Charge-Coupled Device) is used which comprises an array of a very large number of light-sensitive elements.
Reading apparatus of the above-described type have a drawback in that they can only provide a correct reading of the optical codes within a limited distance range; this restricts substantially their applicability.
A problem to be solved in code reading as effected by a human operator and in automatic object sorting and handling systems, is that of identifying and classifying with a single apparatus objects wherein the distance between the reading apparatus and the optical code can considerably vary. In this situation, the use of an apparatus as above described is disadvantageous, since the apparatus is not always capable of correctly focusing on the object codes to be identificated.
The underlying technical problem of this invention is that of enabling proper reading of optical codes placed at varying distances within a broad range of distances, using an apparatus of simple and low-cost construction.
SUMMARY OF THE INVENTION
Thus, the present invention provides, according to a first aspect thereof, an optical code reading apparatus which comprises:
a casing;
a reading window open into the casing;
an illuminating means, housed within the casing, and arranged to act on an optical code to be read through the reading window;
a detection means, housed within the casing and responsive to light scattered from the illuminated optical code into the casing through the reading window;
an objective lens having an optical axis, the objective lens being housed within the casing between the reading window and the detection means, and being located to pick up light scattered from the illuminated optical code and project the picked-up light onto the detection means, wherein the detection means comprises a plurality of light-sensitive elements capable of converting said light to electric signals representing the light image, characterized in that the illuminating means comprises a first array of light sources which are active in a first illumination configuration, and at least a second array of light sources which are active in at least a second illumination configuration different from the first.
Thus, an apparatus for reading remotely placed optical codes is provided which is capable of reading a code from a fixed position as well as within a broad range of distances.
For this purpose, the apparatus of the invention has a field depth which is considerably greater than that of conventional reading apparatus, and is therefore particularly suitable for reading optical codes within a broad range of distances. The improved field depth is achieved by providing the reading apparatus with a plurality of arrays of light sources which can be selectively activated to define a plurality of different illumination configurations, such that the optical code can be illuminated and focused in an optimum manner at any values of the distance of the code from the reading apparatus.
Advantageously, the first array of light sources comprises a plurality of light source pairs, each pair in turn comprising respective light sources symmetrically arranged with respect to the optical axis of the objective lens and aligned along a substantially perpendicular direction to said optical axis, said light sources lying in a first emission lay intersecting the optical axis and the light-sensitive elements of the detection means. This allows each portion of an optical code being illuminated by the first array of light sources to be projected through the objective lens onto the light-sensitive elements, regardless of the distance between the optical code and the reading apparatus, thereby to detect the light scattered from the code and convert it to electric signals.
Advantageously, the plurality of light source pairs comprises a pair of outward sources disposed in an offset position from the optical axis of the objective lens by an angle &agr;, and a pair of inward sources disposed in an offset position from the optical axis of the objective lens by an angle &bgr;, smaller than the angle &agr;. Even more advantageously, the angle &agr; is in the range of about 15° to about 18°, and the angle &bgr; is in the range of about 30 ° to about 6°. In this way, the whole optical code can be suitably illuminated along its extension, even when placed at a considerable distance away from the reading apparatus.
In a specially advantageous embodiment, the apparatus of the invention further comprises a means for confining the light beam from the first array of light sources within a predetermined reading area. Preferably, this means comprises a ring-shaped masking element associated with the casing at the location of the reading window and having a substantially straight inward edge, set at an angle substantially equal to &agr; with respect to the optical axis of the objective lens. As such, a confined light beam can be obtained which has a well defined shape and an extension substantially equal to that of the vision field of the detection means; this contributes to ensuring optimum illumination of the whole optical code at any values of distance between code and reading apparatus, thereby increasing the reading reliability.
The aforementioned advantages are also achieved by the provision, in the reading apparatus, of a holder element for the plurality of light source pairs which is formed with respective seats for said light sources, said seats having respective side walls shaped to confine the light beam from each source within the predetermined reading area. Advantageously, said side walls also function to screen off the detection means, thereby preventing any spurious rays issued from one of the light sources or reflected from a protective glass pane covering the reading window in the casing, from interfering with the scattered light from the code and therefore affecting the reading.
According to one embodiment of the invention, the detection means comprises a linear CCD. In this case, the responsive region of the detection means is represented by a line lying on the aforesaid first emission lay.
Advantageously, the apparatus of the invention further comprises a means for widening the emission angle of the light beam from the first array of light sources along the direction of alignment of said first array of light sources, and narrowing the emission angle of the light beam from the first array of light sources along the perpendicular direction to the first emission lay. Preferably, this means comprises a pair of converging lenses housed within the casing at symmetrical locations with respect to the optical axis of the objective lens between the first array of light sources and the reading window. Thus, these lenses will widen and flatten the light beam from the first array of light sources to give it a comparable shape to that of the responsive region of the detection means, thereby improving the reading reliability.
Advantageously, the second array of light sources comprises a plurality of second light sources having a lower light intensity than the sources in the first array of light sources. These sources are intended for illuminating the optical code when the latter locates closer to the reading apparatus.
Advantageously, the second light sources are housed within the casing symmetric
Bianchi Maurizio
Piva Marco
Datalogic S.p.A.
Lee Diane I.
Sughrue & Mion, PLLC
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