US 20060131419 A1
An industrial reader is provided with an image formation system that is particularly adapted to read bar codes and two-dimensional symbols marked directly on objects. The image formation system includes illumination sources and illumination transmissive components that produce a combination of bright field and dark field illumination.
1. An industrial identification mark reader comprising:
an imaging module positioned within the housing to capture an image of a mark on an object placed before the reader;
an illuminator module comprising a plurality of selectively actuated illuminators, the illuminator mounted within the housing; and
an integrated optical transmitter mounted within the housing, the integrated optical transmitter having a dark field illuminator transmitter, the dark field illumination transmitter in optical cooperation with at least one of the plurality of selectively actuated illuminators to project dark field illumination on the object; and a bright field illumination transmitter, the bright field illumination transmitter in optical cooperation with at least one of the plurality of selectively actuated illuminators to project bright field illumination on the object.
2. The reader according to
3. The reader according to
4. The reader according to
5. A plastic molded optical transmitter for use in a direct part mark reader comprising:
a structural frame;
a dark field illumination transmitter integrated into the frame; and
at least one bright field illumination transmitter integrated into the frame, and adjacent to the dark field illumination transmitter.
6. The transmitter according to
7. The transmitter according to
8. The transmitter according to
9. The transmitter according to
10. A hand-held direct part mark reader comprising:
an imaging module having a field of view, the imaging module mounted within the housing for capturing an image of a mark on an object place in the field of view;
an illuminator module comprising a plurality of selectively actuated illuminators, the illuminator module mounted within the housing;
a dark field illumination transmitter, in optical cooperation with at least one of the plurality of selectively actuated illuminators in the illuminator module to project dark field illumination on the object, the dark field transmitter mounted within the housing; and
a viewing port through the housing to permit observation of the field of view.
1. Field of the Invention
This invention relates to the field of symbology readers used to read symbols marked directly on objects. Symbology readers of this type, commonly known as direct part mark readers, are an extension of hand-held and fixed-mount image-based symbology readers. A direct part mark reader requires a unique image formation system to produce an image of a symbol that can be successfully and consistently decoded.
2. Description of the Related Art
Two-dimensional symbols are used for most direct part marking applications because such symbols can encode a sufficient number of characters while maintaining a relatively compact size. Error correction schemes are typically included in most two-dimensional symbologies, to improve the readability. The two-dimensional symbols are marked directly on the part or component using various methods, depending upon the material composition, part application, and environmental conditions. Common methods include dot peening, laser, and electro-chemical etch.
Symbols marked directly on a part or component are often difficult to read in comparison to symbols printed on labels. An image of a dot-peened, or etched mark often exhibits very low contrast using illumination or image formation systems of most image-based symbology readers. When a symbol is printed on an adhesive label, and applied to a part or component, or the part packaging, a typical image-based symbology reader can provide sufficient read rate. Industry trends, however, suggest that applications of direct part marking are nevertheless increasing.
Illumination of a symbol or mark is a primary concern when acquiring an image of the symbol to be read and decoded by an image-based symbology reader. Where symbols are printed on labels, or when marked directly on a part with a flat surface, high-angle “bright field” illumination is the type of illumination often used. Bright field illumination is a term of art for a type of illumination that produces a dark object in a bright background. Under bright field illumination, high-angle illumination strikes the object nearly perpendicularly, or at an angle not greater than 45 degrees from perpendicular. This type of illumination results in substantial illumination reflecting back toward the reader.
When a symbol or mark is etched or peened onto the surface of part or component, and the surface is rough or irregular, high-angle bright field illumination may not be appropriate. The irregular surface of the mark features will scatter as much light back to the reader as the surface of the background, resulting in indistinguishable features in the image. Low angle, “dark field” illumination has been shown to be suitable for certain direct part marking applications.
Under dark field illumination, low-angle illumination strikes the object at a low angle from the surface of the object, i.e., at an angle between 45 degrees and 90 degrees from perpendicular. Dark field illumination reflects away from the reader, with only random, irregular features of the mark or symbol on the surface of the object reflecting a portion of the illumination back into the reader. Further, certain reading applications may yield higher successful read rates when a combination of bright field and dark field illumination is used.
Industrial symbology readers are typically designed to provide bright field illumination from lighting sources integrated into the reader. When these readers are adapted to read direct part mark symbols, the use of removable light pipes and other adapters are used to redirect bright field illumination into a dark field mode. Accordingly, hand held readers known in the art that are used for direct part mark reading applications are configured exclusively for either bright field mode or dark field mode.
Accordingly, there is a need for a direct part mark reader with integrated illumination that provides variable and controllable illumination in both bright field and dark field modes.
An illustrative embodiment of the present invention provides an industrial identification mark reader with integrated illumination for both bright field and dark field modes. The reader has a housing with an imaging module that captures an image of a mark on an object placed before the reader. Within the housing, an illumination module has an array of selectively actuated illuminators for illuminating the mark or object. An integrated optical transmitter, supported by the housing, is aligned with, i.e., in optical cooperation with, the selectively actuated illuminators. The integrated optical transmitter has a dark field transmitter for transmitting dark field illumination, and bright field transmitters, for transmitting bright field illumination.
The integrated optical transmitter has a transparent window to provide a path for reflected illumination into the imager module, and to provide protection from the elements to the imager module, the illuminator module, and other internal components of the reader.
In an alternate illustrative embodiment, the integrated optical transmitter has a light pipe for the dark field transmitter, with a base having the bright field transmitter positioned within the light pipe. The alternate illustrative embodiment can be a removable component of the reader to permit field replacement for maintenance and repair and/or to permit the use of alternate light pipe designs for further varied illumination properties.
A third illustrative embodiment of the reader has a viewing port through which a user can view the field of view to which is visible to the imager.
The invention description below refers to the accompanying drawings, of which:
The reader 100 shown in
The reader 100 provides illumination of the mark during the acquisition of an image of the mark through the emission of light from an illumination board 114 (shown in phantom). The reader 100 of the present invention includes an integrated optical transmitter 120, as shown in further detail in
The optical transmitter 120 also includes a dark field illumination transmitter 230 that transmits low angle dark field illumination from within the housing 106. The dark field illumination transmitter 230 consists of an extended barrel of light transmissive material terminating (in this embodiment) in an angled tip 235. As described further below, this tip is designed to cause internal reflection that projects a low-angle dark field illumination in the area directly in front of the reader 100. As noted above, such dark field illumination is typically provided at an angle greater than approximately 45 degrees from perpendicular.
The transmitter 120 also includes a window 240 that provides a transmission path for the reflected illumination into the housing 106 in the optical path of a field of view for the sensor module 112. The window 240 of the integrated optical transmitter 120 also provides physical protection from the elements for the several components of the reader that reside within the housing 106. Additionally, the window 240 can provide other optical functions, including filtering (for example, to reduce the effects of ambient illumination), and providing a telecentric view at the object by restricting the size of the opening.
The illumination board 114 has shown an array of dark field illuminators 330 that are generally aligned with the dark field transmitter 230. Each of the dark field illuminators 330 can be surface mounted LEDs that can be individually actuated by a processor controlling the illumination (not shown) to provide dark field illumination in a variety of modes concurrent to the acquisition of an image of a mark, if dark field illumination is desired during acquisition. For example, various modes of illumination can be provided by the array of dark field illuminators 330 that are actuated in quadrants, as disclosed in co-pending U.S. patent application Ser. No. 10/911,989 filed Aug. 5, 2004, herein incorporated by reference. Control of various modes of illumination, and the synchronization of illumination to a specific acquisition, can be performed by a processor module (not shown) within the reader 100.
The illumination board 114 of the illustrative embodiment has a hole 340 that is aligned with the window 240 and the imaging module 112 to permit the transmission of reflected illumination from the mark into the imaging module 112 during image acquisition. Note that the size and shape of the hole 340 is sufficiently sized to not obscure reflected illumination from entering the imaging module 112.
The imaging module 112 is positioned behind the illumination board 112 in the exemplary embodiment, to receive reflected illumination to produce an image of the mark or symbol. The imaging module 112 has an area sensitive imaging array and an imaging lens. The imaging array can be a charge coupled device (CCD) or a complimentary metal oxide semiconductor (CMOS) device, or other imaging sensor known in the art. The imaging module 112 can also include focus adjustment mechanism to optimize the focus of an image projected onto the imaging array. Additionally, the imaging module can also include illumination to project on-axis bright field illumination toward the field of view, and/or to project an aiming illumination beam onto the field of view to provide the user with guidance for positioning the reader 100 during acquisition.
Coupled to the imaging module 112 is a processor unit (not shown) for receiving an acquired image from the imager module 112 to process and ultimately decode the image of the mark or symbol presented to the reader 100. The imager 112 can receive configuration instructions from the processing unit to set acquisition parameters, such as exposure duration, gain, offset, etc., in a manner commonly known in the art. The processor unit is coupled to the trigger 104 to initiate the illumination and image acquisition process when the trigger is actuated by the user.
When bright field illumination is used to illuminate a mark or symbol, the illumination projected onto the field of view has a high angle of incidence, e.g., less than 45 degrees from normal, as depicted as bright field illumination rays 430 in
When dark field illumination is used to illuminate a mark or symbol, the illumination projected onto the field of view has a low angle of incidence, e.g., greater than 45 degrees from normal, as depicted as dark field illumination rays 420 in
Also shown in
The frame 570 receives the distal end member 575 of the optical transmitter 120 according to the alternate embodiment. A screw 590 can be used to secure the transmitter 120 into the frame 570. One skilled in the art will appreciate that various methods can be used to mechanically secure the described assembly in place to permit the operation of an industrial mark reader. The skilled artisan will also appreciate that a transmitter 120 described herein can be removable in the field by way of such methods of attachment.
The integrated optical transmitter 120 according to the illustrative embodiment is molded or fabricated with polymethyl methacrylate (PMMA) or polycarbonate. The optical properties of the transmitter 120 can be obtained through polished mold surfaces and/or post fabrication polishing of the transmitter 120.
The integrated optical transmitter 120 of the alternate embodiment can produce illumination in both bright field and dark field modes, as described above.
An inherent difficulty with dark field illumination in most industrial mark readers is that the it is difficult to ensure that the mark or symbol 410 is in the field of view. The reader body obscures the mark or symbol when it is in dark field mode 450 from the user's view, and therefore, aiming and alignment of the reader is difficult. In an alternate embodiment of the present invention, a low profile reader is provided that permits direct observation of the mark or symbol by the user in dark field mode.
The foregoing has been a detailed description of various embodiments of the invention. It is expressly contemplated that a wide range of modifications and additions can be made hereto without departing from the spirit and scope of this invention. For example, the number, position and relative placement of the bright field transmitters on the integrated optical transmitter is exemplary and a variety of such transmitters can be employed to perform bright field illumination on hand held image-based decoding methods herein. Further, additional functionality can be added to the optical transmitter 120, such as aiming optics to direct aiming illumination onto the field of view to provide guidance to a user during operation of the reader 100. Further still, sensor optics can be incorporated into the integrated transmitter 120 to permit the transmission and reception of electromagnetic signals to be used in conjunction with an auto-focus mechanism in the reader 100. Thus, improved or differing components can be employed within the teachings of this invention. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.