Patent Application
20090218403
Direct part marking (DPM) allows workpieces to be directly marked, identified and traced to their origin, and its use is growing in the automotive, aerospace, electronics, medical equipment, tooling, and metalworking industries, among many others. Despite the ability to control very tight specifications on element size, width, spacing and so on, the lack of sharp contrast of machine-readable optical DPM codes directly marked on metal, plastic, leather, glass, etc., workpieces prevents traditional moving laser beam readers from electro-optically reading the DPM codes reliably. These moving beam readers emit a laser beam, which reflects off the highly reflective, typically non-planar, metal or glass, workpieces as bright light.
To counter a variety of problems, such as lack of contrast, difficulty of maintaining precise element specifications, limited available marking areas, and a large amount of data to be encoded, the art proposed the use of matrix codes, especially the DataMatrix code, which reduces the required marking element size, precision and area, as well as contrast so that markings are able to be directly made on parts with, for example, steel or aluminum surfaces, and also proposed the use of imaging readers, for example, as disclosed in U.S. Pat. No. 7,201,321, which use solid-state arrays or imagers similar to those used in digital cameras to capture an image of the marking. A microprocessor is used to analyze and decode the captured image of the matrix code.
Yet, the use of imaging readers, especially handheld readers, for reading DPM codes on workpieces has proven to be challenging. Contrast is still often less than desirable. Ambient lighting conditions are variable. Illumination from on-board illuminators or illumination light sources is directed at variable angles. Reflections from ambient light sources and illumination light sources often appear in the field of view of the reader as hot spots, glare, or specular reflections of intense, bright light that saturate the imagers, thereby degrading reading performance.
In addition, aiming the handheld imaging readers at the DPM codes, prior to reading the DPM codes, has proven to be difficult. Requiring an operator to aim the reader at the DPM codes makes the process of locating and decoding the DPM codes faster and easier. Unlike machine-readable codes printed in one color (for example, black) on paper of another color (for example, white), DPM codes are typically difficult for a human operator to even find on the workpieces, which often have complicated, i.e., non-planar, curved, reflective surfaces, to further complicate finding the DPM codes and aiming the reader directly at the DPM codes for reading.
Further complicating the aiming process is that the DPM codes are relatively small, e.g., less than 2 mm×2 mm. It is generally known to generate an aiming pattern frame to help target a machine-readable code, such as a bar code symbol, prior to reading, but, in the case of DPM codes, the aiming pattern frame is also correspondingly small. Trying to target a small DPM code with a small aiming pattern frame on a curved, reflective surface is a time-consuming, laborious, operator-unfriendly procedure. Also, if the reader is brought close to the code, then the line of sight to the code may be obstructed.
One feature of the present invention resides, briefly stated, in a method of, and an arrangement for, accurately aiming at indicia, especially direct part marking (DPM) codes on workpieces, prior to being imaged and electro-optically read. A light source, such as a laser, is operative for emitting an aiming light beam during aiming. An optical component is operative for optically modifying the aiming light beam during the aiming to generate an aiming light pattern having an outer bright region and an inner dim or dark region. The bright region is illuminated by the aiming light beam and is visible to an operator to enable the operator to manually position the bright region to entirely surround at least part, and preferably the entirety, of the DPM code. The dark region is not illuminated by the aiming light beam and is surrounded by the bright region. The dark region contains the part, and preferably the entirety, of the DPM code to be imaged and read after the aiming.
In a preferred embodiment, the bright region is circumferentially complete and symmetrical in all directions. Advantageously, the bright region is a circular annulus bounded by outer and inner concentric circles, and the dark region is an area contained within the inner circle. The DPM code occupies a predetermined area, e.g., less than 2 mm×2 mm, and the dark region has an area preferably greater than the predetermined area to contain the DPM code in its entirety.
In the preferred embodiment, the optical component may be a diffractive optical element (DOE), a refractive optical element (ROE), a holographic element, or a Fresnel element, which generates a light interference pattern. A non-interferometric optical component may also be used.
A handheld housing advantageously supports the light source and the optical component. A solid-state imager is also supported by the housing for capturing light over a field of view from the DPM code during subsequent imaging and reading. An illuminator may be used to illuminate the DPM code during the imaging and reading. A controller, e.g., a microprocessor, typically the same microprocessor used for decoding the DPM code, is operative for controlling that the aiming is not performed simultaneously with, and precedes, the imaging and the reading. The housing is aimed by the operator at a workpiece having the DPM code thereon.
Yet another feature of this invention resides in a method of accurately aiming at the direct part marking (DPM) code prior to being imaged and electro-optically read. The method is performed by emitting the aiming light beam during aiming; and by optically modifying the aiming light beam during the aiming to generate the aiming light pattern having the bright region illuminated by the aiming light beam and visible to an operator to enable the operator to manually position the bright region to entirely surround at least part, if not all, of the DPM code, and the dark region not illuminated by the aiming light beam and surrounded by the bright region, the dark region containing the part, if not all, of the DPM code to be imaged and read after the aiming.
Thus, the present invention proposes a large aiming pattern in which the outer bright region is highly visible to the operator. The annulus configuration is preferred, because it has no preference for orientation of the aiming pattern in any direction, e.g., up-and-down or side-to-side. The operator can easily and rapidly aim the bright region at, and position the bright region around, the DPM code and be reasonably assured that most, if not all, of the DPM code will be accurately located in the central dark region. The dark region is effectively a window for viewing the DPM code.
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.
a) is an enlarged view of an aiming light pattern generated in accordance with this invention on a DPM code of a small size;
b) is an enlarged view of the aiming light pattern of
c) is an enlarged view of the aiming light pattern of
Reference numeral 10 in
A manually actuatable trigger 20 is mounted in a moving relationship on the handle 14 in a forward facing region of the reader. The operator's forefinger is normally used to actuate the reader by depressing the trigger. For example, the trigger may be depressed once to initiate aiming, and depressed again to initiate image capture and reading. Alternatively, aiming may be a default condition, and the trigger may be depressed just once to discontinue or change the default condition and to initiate image capture and reading. A flexible electrical cable 22 may be provided to connect the reader to remote components of the code reading system. In alternative embodiments, the cable may also provide electrical power to the systems within the reader. In preferred embodiments, the cable 22 is connected to a host 24 that receives decoded data from the reader. In alternative embodiments, a decode module 26 may be provided exteriorly to the reader. In such an embodiment, decoded data from the decode module 26 may be transmitted to further host processing equipment and databases represented generally by box 28. If the cable 22 is not used, then a wireless link to transfer data may be provided between the reader 10 and the host 24, and an on-board battery, typically within the handle, can be used to supply electrical power.
An alternative embodiment incorporates a display and a keyboard, and optionally a wireless transceiver, preferably with an on-board decoder. The decoded data is then either transferred to a remote host computer in real time, or saved to an internal memory such that the stored data can be transferred to a host computer at a later time in batch mode, when the reader is physically connected to such a connected host computer.
A solid-state imager 32, as shown in
The lens assembly 38 has a fixed or variable focus and enables image capture over a range of working distances between a close-in distance and a far-out distance relative to the window 36. The imager and lens assembly are capable of acquiring a full image of the DPM code in lighting conditions from two lux to direct sunlight. Exposure time is about 15 milliseconds, and the imager is actuated, preferably once every 200-300 milliseconds. Resolution of the array can be of various sizes, although megapixel resolution is preferred.
An illuminator 34 is provided to provide an illumination field for the imager 32. The illuminator preferably constitutes a single illumination light source, or a plurality of illumination light sources, e.g., red light emitting diodes (LEDs), energized by power supply lines in the cable 22, or via the on-board battery. A diffuser 40 is operative for diffusing the illumination light en route to the DPM code. The diffuser 40 minimizes hot spots, glare and specular reflections and renders the illumination light more uniform across the DPM code. The diffuser 40, preferably a translucent or textured member, scatters the illumination light emitted by the illuminator 34.
In accordance with one feature of this invention, an aiming light source, such as a laser 42, is operative for emitting an aiming light beam, preferably in the red spectrum, during aiming. An optical component 44 is operative for optically modifying the aiming light beam during the aiming to generate an aiming light pattern having, as best seen in
In a preferred embodiment, the bright region 46 is circumferentially complete and symmetrical in all directions. Advantageously, the bright region 46 is a circular annulus bounded by outer 50 and inner 52 concentric circles, and the dark region 48 is an area contained within the inner circle 52. The DPM code occupies a predetermined area, e.g., less than 2 mm×2 mm. As shown in
In the preferred embodiment, the optical component 44 may be a diffractive optical element (DOE), a refractive optical element (ROE), a holographic element, or a Fresnel element, which generates a light interference pattern. A non-interferometric optical component may also be used.
In use, once the trigger 20 is depressed, a controller or microprocessor 54, preferably the same microprocessor used to decode and read the DPM code, actuates the aiming laser 42 to generate an aiming laser beam that diverges until it passes through an aperture stop (not illustrated), in which the beam is optically modified to have a predetermined cross-section. Alternatively, the aiming laser beam may be generated prior to depression of the trigger, and preferably pulsed, for example at a 50% duty cycle, whereupon, after the trigger 20 has been depressed, the controller 54 is operative to change the duty cycle. Thereupon, the aiming laser beam passes through the optical component 44, in which the beam is focused, collimated, and optically modified to generate the large aiming light pattern having the outer bright region 46 and the inner dark region 48, as described above.
The bright region 46 is highly visible to the operator. The annulus configuration is preferred, because it has no preference for orientation of the aiming pattern in any direction, e.g., up-and-down or side-to-side. The operator can easily and rapidly aim the bright region 46 at, and position the bright region 46 around, the DPM code and be reasonably assured that the DPM code will be accurately located in the central dark region 48. The dark region 48 is effectively a window for viewing the DPM code.
After aiming, the controller 54 deactuates the aiming laser and stops generating the aiming light pattern, and then actuates the illuminator 34 and the imager 32 to initiate imaging and reading of the DPM code. When the DPM code is entirely in the dark region 48, a successful read is more likely as compared to when only a part of the DPM code is located therein.
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. For example, other aiming light patterns, such as polygonal patterns, are contemplated. Also, it may be desired to generate a central aiming spot or mark as part of the aiming light pattern. In this case, the spot would advantageously be centered in the dark region 48 to indicate the center of the DPM code.
While the invention has been illustrated and described as embodied in an aiming arrangement and method used in an imaging reader for electro-optically reading DPM codes, 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. For example, to prevent the red illumination LEDs from washing out the red aiming light pattern, the imager is actuated infrequently, for example, once every 200-300 milliseconds as noted above, rather than having the imager be free-running.
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.
