Abstract:
A barcode reading apparatus for reading a translucent barcode label or strip that has opaque indicia such as spaced black bars on a translucent background. The barcode reading apparatus includes a transmitter for projecting an incident light beam toward the label so that some of the light is returned back from the translucent background and some of the light passes through the translucent background to a light returning surface on the opposite side of the slide. The portion of the incident light beam that strikes the light returning surface is returned back through the slide toward a detector portion of the barcode reader. This portion of returned light produces a signal that is added to the signal produced by the portion of the incident light beam initially returned from the translucent background of the barcode label to produce a much stronger identifying signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     NOT APPLICABLE  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to a scanning mechanism and, more specifically, to a barcode reading mechanism for a DNA Microarray Scanner that identifies and quantifies genetic material.  
         [0003]     A microarray scanner includes a carousel that has radial slots. The carousel is rotatably mounted on a support that includes an annular wall surrounding the carousel. The annular wall has an access opening to the carousel. Each radial slot is adapted to receive a holder containing a transparent slide, e.g. a 1″ by 3″ glass slide. Each slide is located in a custom slide holder. A biological sample to be examined is located on one side of the slide. The sample is DNA or RNA material extracted from a biological sample. In a process known as Hybridization, the sample is allowed to bond with known DNA sequences or probes deposited in a two-dimensional array on the glass slide. A barcode that identifies the specimen to be examined is located on one side of the slide and spaced from the sample. The barcode is used to identify the sample on the slide in all phases of its processing, including hybridization, scanning and software analysis. A slide examination or scanning station is located outside of the carousel. An instrument at the slide examination station scans and produces a high-resolution image file of the array. A barcode reading mechanism is located between the examination station and the carousel just outside the access opening.  
         [0004]     During operation of the scanner, the carousel is selectively rotated so as to position a selected holder and contained slide at the access opening. A transfer mechanism grasps the selected holder and carries it through the barcode reading station to the slide examination station. The transfer mechanism is a robotic arm-like assembly used to transport the slide holder and slide out of the carousel before scanning, and back into the carousel after scanning. As the holder and the slide move through the barcode reading station, the barcode reader reads the barcode on the slide. The barcode on the slide is in the form of a label or strip that is applied to one of the surfaces of the slide. In the past, biological scanning mechanisms were set up so that a probe array containing a biological specimen was located on one side of the slide and a conventional barcode label or strip was located on the opposite side of the slide. A conventional barcode label or strip has black spaced bars on a white reflective background. The barcode label was read by a barcode reader located at the barcode reading station on the side of the station facing the side of the slide containing the barcode.  
         [0005]     For many sample scanning procedures, the barcode is required to be placed on the same side of the glass slide as the biological specimen sample or the “array” side of the slide. Since the barcode reader is located on the opposite side of the “array” side of the slide, a conventional barcode label cannot be read. In order to accommodate the above-described sample scanning procedures, a translucent barcode label was used. The translucent barcode label has black bars on a translucent background. An incident light beam from the barcode reader is projected through the transparent slide to the barcode label. A portion of the light beam is returned back toward the barcode reader to enable the barcode to be read by the barcode reader. Light from the barcode reader can be infrared, laser, or any state of the art light source. Since the background of the barcode label is translucent, a portion of the incident light beam passes through the barcode label so that the portion of the light beam returned back to the barcode reader is not as strong as the incident light beam. Normally, a series of incident light beams are directed toward the barcode as the slide passes through the barcode reading station to obtain several identifying signals for averaging to provide a consensus signal. In many cases the signals are not strong enough to provide an accurate identification of the barcode being read. This problem becomes more acute if there is any degradation of the label during treatment of the slide during the steps in pre and post hybridization operation, i.e. washings.  
         [0006]     The translucent barcode label must also be used in a microarray scanning mechanism in which the barcode reader is located on the “array” side of the slide but the barcode label is required to be placed on the opposite side of the slide. For example, the barcode label might need to be changed and applying it on the non-array side of the slide minimizes any contact with the array. Having the barcode label on the non-array side of the slide also minimizes any contact with wash chemicals during array processing.  
         [0007]     What is generally needed is a barcode reading apparatus that is able to read translucent barcode labels with high accuracy.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     In one aspect, the present invention provides a barcode reading apparatus for reading a translucent barcode label that has opaque indicia such as spaced black bars on a translucent background. The barcode reading apparatus includes a transmitter for projecting an incident light beam toward the label so that some of the light is returned back from the translucent background toward a detector portion of a barcode reader and some of the light passes through the translucent background to a light returning device on the opposite side of the slide, said light returning device bearing a light returning surface. The term “light returning device” is used herein to describe a device bearing a light returning surface. A light returning surface is a surface that is capable of receiving a beam of light from a source, and, in reaction to receiving the beam of light, radiates a return beam of light toward a light sensor associated with the source. The portion of the incident light beam that strikes the light returning surface is returned back through the slide toward the detector portion of the barcode reader. This portion of returned light produces a signal that is added to the signal produced by the portion of the incident light beam initially returned from the translucent background of the barcode label to produce a much stronger identifying signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention is described in the accompanying drawings in which:  
         [0010]      FIG. 1  is a fragmentary plan view of a biological scanning mechanism illustrating the barcode reading apparatus according to one aspect of the present invention;  
         [0011]      FIG. 2  is an isometric view of the light returning device portion of the barcode reading apparatus according to one aspect of the present invention;  
         [0012]      FIG. 3  is an isometric view of the holder for the slide according to one aspect of the present invention;  
         [0013]      FIG. 4  is a diagrammatic view showing the optical functions of the invention according to one aspect of the present invention; and  
         [0014]      FIG. 5  is an isometric view of the slide showing the barcode and probe array according to one aspect of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     Referring to  FIGS. 1 and 2 , the scanning mechanism of the present invention is generally indicated by the reference numeral  10  and includes a slide carousel, generally indicated by the reference numeral  12 , and a barcode reading apparatus, generally indicated by the reference numeral  14 . The slide carousel  12  includes a fixed base  16  and a slide tray  18  rotatably mounted on the base  16 . The base  16  has an annular outer wall  20  that includes a front opening  22 . The tray  18  has slots  25  for holding a plurality of slide holders  26 . Each slide holder  26  contains a slide  28 .  
         [0016]     Referring to  FIG. 3 , one of the slide holders  26  is shown without its slide. Slide holder  26  defines a cavity  23  for receiving the slide. The slide is held in place by a side wall  27  and tabs  29 . Side wall  27  can be pivoted to enable the slide to be inserted and then locked in place. Cavity  23  has a portion that extends beyond side wall  27  to form a window  31 . The barcode label on the slide is positioned at the window  31  when the slide is in the holder.  
         [0017]     Referring now to  FIG. 1 , the barcode reading apparatus  14  includes a barcode reader  30  and a light returning device, generally indicated by the reference numeral  36 . The barcode reader  30  has a transmitter portion  32  for transmitting a beam of light and a receiver portion  34  for receiving a beam of light, see  FIG. 4 . In an embodiment, the barcode reader was a Keyence Corporation BL600HA laser barcode reader. However, other commercially-available barcode readers can also be used. The light returning device  36  has a flat light returning surface  38  and is mounted adjacent the front opening  22  with light returning surface  38  facing the barcode reader  30 .  
         [0018]     Referring particularly to  FIG. 2 , the light returning device  36  is a composite structure made from three white channel pieces  40 ,  41  and  42 . Each channel piece has a flat base wall and a pair of side walls that extend away from the base wall at converging angles. The channel pieces  40  and  42  are arranged side by side with their bases in the same plane and forming the light returning surface  38 . The piece  41  is arranged with its base spaced from and parallel to the bases of pieces  40  and  42  and its side walls extending toward the bases of pieces  40  and  42 . The side walls of piece  41  straddle the adjacent side walls of pieces  40  and  41  and collectively form the inner side walls of the light returning device structure. The base of piece  40  engages the ends of the inner side walls of pieces  40  and  42 . The pieces  40 ,  41  and  42  are fixed by plastic welding or glue, e.g. a Loctite™ instant adhesive. When the light returning device  36  is assembled as shown in  FIG. 2 , a pair of slots  44  and  46  is formed on opposite sides of the piece  41 . Each slot  44  and  46  has an opening  48 . Referring to  FIG. 1 , the light returning device  36  is mounted at the opening  22  by inserting the free end of the wall  20  that is furthest from the barcode reader  30  into one of the slots  44  and  46 .  
         [0019]     During operation of the scanning mechanism  10 , the slide tray  18  is rotated until a selected holder and slide to be scanned and analyzed is aligned with the opening  22 . The selected holder  26   a  containing the selected slide is grasped by a transfer mechanism, not shown, and removed from its respective slot  25 . Slide holder  26   a  is transported through the barcode reading station, generally indicated by the reference numeral  50 , to the specimen scanning apparatus, not shown.  
         [0020]     Referring to  FIGS. 3-5 , one of the slide holders  26   a  is shown in  FIG. 3  without a slide.  FIG. 4  is a schematic view looking toward the opening  22  of the carousel and showing a selected slide  28   a  as it passes between the light returning device  36  and the barcode reader  30 . The holder containing the slide  28   a  is not shown for clarity of illustration. Slide  28   a  has a probe array  52  (as shown in  FIG. 5 ) and a translucent barcode label  54  on the side of the slide that faces the light returning device  36 . The portions of the barcode and probe array are shown in  FIG. 5 . The opposite side of the slide  28   a  faces the barcode reader  30 . Barcode label  54  has opaque areas  55  and translucent areas  56 .  
         [0021]     As the holder  26   a  and slide  28   a  pass through the barcode reading station  50 , between light returning device  36  and the barcode reader  30  as shown in  FIG. 4 , the barcode reader  30  transmits an incident light beam I 1 , through the slide to the barcode label  54 . Some of the light from the incident light beam I 1  is returned by the barcode label  54  toward the receiver portion of the barcode reader  30  as returned light R 1 . The remainder of the incident light beam I 1  passes through the barcode label to the light returning surface  38  of light returning device  36  as transmitted beam T 1 . Light returning surface  38  returns transmitted beam T 1  back toward the barcode label  54  as returned beam R 2 . Some of the light from returned beam R 2  is returned by the barcode label  54  as returned beam R 3 . The remaining portion of the returned beam R 2  is transmitted back to the barcode reader  30  as transmitted beam T 2 . The barcode reader  30  transmits a sequence of incident light beams to the barcode label  54  as the slide  28   a  passes through the barcode reading station  50 . The returned portions R 1  and T 2  of the incident light beam I 1  provide a print contrast signal. The print contrast signals from the several incident light beams I 1  are averaged by software associated with the barcode reader to produce a reading that identifies the barcode  54  and its associated probe array  52 . The slide  28   a,  within its holder  26   a,  continues to be transported to the specimen scanning station and then returned to its respective slot  25  in the slide tray  18 .  
         [0022]     A performance feature of a barcode reader is its Print Contrast Signal. Print Contrast Signal=(Reflectance of Space−Reflectance of bar)/Reflectance of Space. Reflectance is used herein to describe light returning capacity by any mechanism, not just by formal reflection. The term “space” refers to the space between the bars in the bar code. Print Contrast Signal measures the contrast between light returned from the bars and light returned by the spaces on the barcode label. The following is a comparison of readings of a translucent barcode with and without a light returning device such as light returning device  36 .  
         [0000]     Without Light Returning Device 
 
Reflectance of Space=R 1  
 
 With Light Returning Device 
 
Reflectance of Space= R   1   +T   2  
 
         [0023]     Now T 2 &gt;0. Therefore it follows that: 
 
Reflectance of Space with Light returning device&gt;Reflectance of Space without Light returning device 
 
         [0024]     Since the Reflectance of the bar is unchanged, it follows that:  
         [0000]     Without Light Returning Device 
 
Print Contrast Signal=1−Reflectance of Bar/Reflectance of Space=1−Reflectance of Bar/ R   1  
 
 With Light Returning Device 
 
Print Contrast Signal=−Reflectance of Bar/(R 1   +T   2 ) 
 
 Since, 
 
( R 1+ T 2)/Reflectance of Bar&gt; R 1/Reflectance of Bar, it follows that their negative reciprocals are related as, 
 
−Reflectance of Bar/( R 1+ T 2)&gt;−Reflectance of Bar/ R 1 and, 
 
1−Reflectance of Bar/( R 1+ T 2)&gt;1−Reflectance of Bar/R1 
 
         [0025]     Therefore, Print Contrast Signal (with light returning device)&gt;Print Contrast Signal (without Light returning device). This assumes that the reflectance (light returning efficiency) of the light returning device is 100%. However, it can be shown that any significant amount of return light from the light returning device improves the Print Contrast Signal.  
         [0026]     The present invention enables the translucent barcode label on the glass slide to be read by the barcode reader  3  with high efficiency. Barcode labels with barcodes printed on opaque white background or transparent background can also be used with the barcode reading apparatus of the present invention.  
         [0027]     Some styles of barcodes with imperfections in their printing can also be read. For instance: 
        1. Barcodes printed close to the right or left edge might have smaller quiet zones than needed. By returning light transmitted through the barcode back to the reader, the quiet zone size is increased, enabling clear readings on the start and end regions of the barcode.     2. Barcodes with faded bars on transparent or translucent backgrounds are especially hard to tread. Fading might occur when the barcode is bleached or wears with age. For example, microarray slides are often barcoded at the start of their processing. The slide is passed through processes where the slide is washed and comes in contact with solvent solutions. The invention increases the contrast ratio between bars and intermediary spaces, making these barcodes easier to read.        
 
         [0030]     By enabling the reading of transparent and translucent barcodes, the invention allows these styles of barcodes to be placed on either the front or the back surface of the slide. Prior to the present invention the barcode reader was required to have a fixed orientation relative to the slide, namely that it be positioned facing the front side of the glass. Physical space availability or accessibility restrictions might make this requirement difficult to implement in some processes. No such restrictions are needed when transparent or translucent barcodes are read by the barcode reading apparatus of the present invention.