Patent Application
20090272808
Solid-state imaging systems or imaging readers, as well as moving laser beam readers or laser scanners, have both been used to electro-optically read targets, such as one-dimensional bar code symbols, particularly of the Universal Product Code (UPC) type, each having a row of bars and spaces spaced apart along one direction, as well as two-dimensional symbols, such as Code 49, which introduced the concept of vertically stacking a plurality of rows of bar and space patterns in a single symbol. The structure of Code 49 is described in U.S. Pat. No. 4,794,239. Another two-dimensional code structure for increasing the amount of data that can be represented or stored on a given amount of surface area is known as PDF417 and is described in U.S. Pat. No. 5,304,786.
The imaging reader includes an imaging module having a solid-state imager with a sensor array of cells or photosensors, which correspond to image elements or pixels in a field of view of the imager, and an imaging lens assembly for capturing return light scattered and/or reflected from the symbol being imaged, and for projecting the return light onto the sensor array to initiate capture of an image of the symbol. Such an imager may include a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device and associated circuits for producing and processing electronic signals corresponding to a one- or two-dimensional array of pixel information over the field of view.
It is therefore known to use the imager for capturing a monochrome image of the symbol as, for example, disclosed in U.S. Pat. No. 5,703,349. It is also known to use the imager with multiple buried channels for capturing a full color image of the symbol as, for example, disclosed in U.S. Pat. No. 4,613,895. It is common to provide a two-dimensional CCD with a 640×480 resolution commonly found in VGA monitors, although other resolution sizes are possible.
In order to increase the amount of the return light captured by the imager, especially in dimly lit environments, the imaging module generally also includes an illuminating light assembly having a plurality of light sources, e.g., light emitting diodes (LEDs), and a plurality of illuminating elements, e.g., lenses, to uniformly illuminate the symbol with the illumination light for reflection and scattering therefrom.
Although generally satisfactory for its intended purpose, the use of an imaging reader is frustrated, because an operator cannot tell whether the imager, or the reader in which the imager is mounted, is aimed directly at the target symbol, which can be located anywhere within a range of working distances from the reader. The imager is a passive unit and provides no visual feedback to the operator to advise where the imager is aimed.
To alleviate such problems, the prior art proposed in U.S. Pat. No. 6,060,722 an aiming light assembly for an imaging reader. The known aiming light assembly utilizes an aiming light source, e.g., a laser, for generating an aiming laser beam, an aiming element, e.g., a lens, for collimating the laser beam, and a pattern-generating element, such as a diffractive optical element (DOE), a holographic element, or a Fresnel element, for optically modifying the collimated laser beam to generate a visible aiming light interference pattern on the symbol prior to reading, the pattern being useful for framing the field of view of the imager. It is also known to use non-interferometric optical elements to project an aiming line as described in U.S. Pat. No. 6,069,748, which disclosed the use of a toroidal lens to project a single aiming line to guide a cutting tool. U.S. Pat. No. 7,182,260 disclosed the use of a refractive optical element (ROE) having a plurality of refractive structures to generate an aiming light pattern on a symbol, also for framing the field of view of the imager.
As advantageous as an imaging reader has been in reading symbols, it has proven disadvantageous in that it is relatively expensive to manufacture and assemble due to its high number of discrete optical elements that must be separately made of different optical materials, such as glass or plastic, stocked, and optically aligned. Thus, the above-described plurality of illuminating lenses, aiming lens and pattern-shaping optical element comprise many parts that need to be individually manufactured, stocked and assembled in mutual optical alignment, and this represents not only added manufacturing and assembly costs to be minimized, but also, tolerance build-ups among stacked parts to be reduced. Also, these parts occupy non-negligible space in the imaging module and thus contribute to an oversized module that cannot readily fit in an arrangement requiring a more compact reader.
One feature of the present invention resides, briefly stated, in an imaging reader or module for, and a method of, imaging a target, such as one- or two-dimensional symbols. The reader or module includes an aiming assembly including an aiming laser, such as a laser diode, for generating an aiming laser beam, an aiming element, such as a lens, for collimating the laser beam, and a pattern-generating element, such as a DOE, a holographic element, a Fresnel element, or an ROE, for optically modifying the collimated laser beam to generate a visible aiming light pattern on the target.
The reader or module further includes an illuminating assembly including an illuminating light source, such as one LED or a plurality of LEDs, for generating illumination light, and an illuminating element, such as one illuminating lens or a plurality of illuminating lenses, for uniformly illuminating the target with the illumination light. A solid-state imager, such as a CCD or a CMOS, has an array of image sensors for capturing return illumination light from the target.
In accordance with one feature of this invention, the pattern-generating element is molded of a one-piece construction with at least one, if not all, of the aiming and illuminating elements or lenses. Also, if a carrier or holder for the pattern-generating element is provided, then the pattern-generating element may also be molded of a one-piece construction with the carrier. Further, if an aperture stop is provided for the collimated laser beam, then the pattern-generating element may also be molded of a one-piece construction with the aperture stop. Advantageously, the one-piece construction is molded of a synthetic plastic material.
The one-piece construction is advantageously a plate that is positioned to lie in a plane generally parallel to a printed circuit board on which the imager is mounted. The module includes a generally parallelepiped support for supporting the assemblies and the imager. The printed circuit board is mounted at a rear side of the support, and the plate is mounted at a front side of the support.
Due to the reduced number of discrete optical elements, it is no longer necessary to individually manufacture, stock and optically align a high number of optical elements. Manufacturing and assembly costs are reduced. Tolerance build-ups among stacked parts are decreased. Also, fewer parts occupy less space in the module and thus contribute to a compact design.
The method of imaging a target is advantageously performed by generating an aiming laser beam, collimating the aiming laser beam with an aiming element, optically modifying the collimated laser beam with a pattern-generating element to generate a visible aiming light pattern on the target, generating illumination light, uniformly illuminating the target with the illumination light with an illuminating element, capturing return illumination light from the target with a solid-state imager having an array of image sensors, and molding the pattern-generating element of a one-piece construction with at least one, if not all, of the aiming and illuminating elements.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Reference numeral 30 in
As schematically shown in
An illuminating assembly is also mounted in the imaging reader and preferably includes a plurality of illuminators or light sources 12, e.g., light emitting diodes (LEDs), and an illuminating lens assembly that includes a plurality of illuminating lenses 10, one for each LED 12, to uniformly illuminate the symbol 38. The illuminating assembly, as best seen in
An aiming assembly is also mounted in the imaging reader and preferably includes one aiming light source 18 or a plurality of aiming light sources or aiming lasers 18A, 18B (see
As shown in
In operation, the microprocessor 36 sends a command signal to energize the aiming light source 18 prior to reading, and also pulses the illuminator 12 for a short exposure time period, say 500 microseconds or less, and energizes and exposes the imager 24 to collect light, e.g., illumination light and/or ambient light, from a target symbol only during said exposure time period. A typical array needs about 33 milliseconds to acquire the entire target image and operates at a frame rate of about 30 frames per second.
In accordance with one feature of this invention, the pattern-generating elements 16C, 16D, the aiming elements 16A, 16B and the illuminating elements 10A, 10B, 10C, 10D are not manufactured as separate optical elements made of different glass or plastic materials, but instead, the pattern-generating elements 16C, 16D are molded of the same material, e.g., plastic, in a one-piece construction with at least one of the aiming elements 16A, 16B and the illuminating elements 10A, 10B, 10C, 10D, and preferably of all the aiming elements 16A, 16B and the illuminating elements 10A, 10B, 10C, 10D.
The one-piece construction is advantageously a plate 50 that is positioned to lie in a plane generally parallel to the plane of the printed circuit board 22 on which the imager 24 is mounted. An anti-reflective coating may be applied on the front surface of the plate 50 in all areas except where the pattern-generating elements 16C, 16D, the aiming elements 16A, 16B and the illuminating elements 10A, 10B, 10C, 10D are located. As previously mentioned, imaging readers having different housing configurations can be used. To that end, another feature of this invention resides in providing a compact imaging module of a form factor standardized to fit in diverse housings of different shapes. Thus, as shown in
Due to the reduced number of discrete optical elements, it is no longer necessary to individually manufacture, stock and optically align a high number of optical elements. Manufacturing and assembly costs are reduced. Tolerance build-ups among stacked parts are decreased. Also, fewer parts occupy less space in the module and thus contribute to a compact design.
Thus, as shown in
In
In
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, a single aiming assembly, rather than the two illustrated aiming assemblies may be employed. Also, two illuminating assemblies, rather than the four illustrated illuminating assemblies may be employed. The illustrated aiming pattern is merely exemplary, and many other aiming patterns may be projected.
While the invention has been illustrated and described as an imaging reader or module having some or all of its optical elements made of a one-piece construction, 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.
