 Diamonex® Products |
|
|
||||
|
|
|
|||
|
Abrasion-Resistant Qualities of Diamond-Like Carbon (DLC) - Coated AEGISGLASS® for Laser Barcode Scanner Window Applications Abstract Historically, plexiglass, float glass, and tin oxide-coated glass have been used in horizontal laser barcode scanners. Scratching and abrasion of these windows results from contact with bottles and cans being passed over the scanner window. This scratching and abrasion reduces the performance of the scanner from first pass read rates near 100% for a new scanner window to first pass read rates of less than 50% for windows which are typically considered worn out. Evaluations and experience has indicated that plexiglass windows have an economically useful life of approximately two weeks. Float glass should be replaced at approximately four-week intervals, and tin oxide-coated float glass may last eight weeks before scratching and haze results in significantly reduced performance. DIAMONEX AEGISGLASS® is a diamond-like carbon (DLC)-coated glass. Diamond-like carbon has properties similar to those of diamond. In-store testing suggests that the lifespan of AEGISGlass is in excess of nine years of continuous duty in a busy checkout lane. This paper addresses the reduced efficiency which results from scratched windows and the often hidden cost which results from reduced performance of scanning equipment. Introduction Interest in scanner efficiency by retail organizations has grown considerably in the last decade. Grocery stores and mass merchandisers are closely studying the efficiency of repetitive scanning, since it directly corresponds with front-end register throughput and checkout line delay. In this paper, test results (in-store and laboratory) on each type of scanner window will be presented to show the relationship between wear and abrasion and scanner efficiency. Experimental Actual in-store observations and documentations of plexiglass, tin oxide-coated glass, conventional glass,and AEGISGLASS® (DLC-coated tempered float glass) wear-resistant qualities were tested at retail outlets in Illinois, New York, and eastern Pennsylvania. Data on the performance of each type of scanner window in the retail environment was evaluated by scanner operators, and front-end managers were interviewed. Results and Discussion Windows in supermarket, drug store, and mass merchandiser laser barcode scanners are subject to abrasion from impact and dragging of objects, such as metal cans, glass bottles, and ceramic items. The amount of abrasion experienced by a window is directly related to the number of items scanned. Scratches on a window can scatter the outgoing laser light. This scattering can defocus the laser beam and cause spatial resolution loss. This spatial resolution loss will produce difficulty in reading the barcode due to the beam being larger than the barcode lines. Scattering can also significantly reduce the laser beam intensity, which results in reflected signals that are too weak to be processed. In this application, the window protects the scanning equipment from the abuse of the checkout lane. The purpose of an abrasion-resistant coating is to stop or reduce the formation of scratches which cause significant loss of spatial resolution or power of the laser beam[1]. REFERENCE: [1] B. Knapp and F. Kimock, "Abrasion-resistant Diamond-Like Carbon (DLC) Films for Optical Applications", Technical Publications, March 25, 1992. LABORATORY TESTING A scanner window's resistance to scratching directly correlates to the useful life of the window. AEGISGLASS® was developed for use as windows in laser barcode scanners. For this application, AEGISGLASS® was required to be highly transparent at 632 and 680nm, substantially more abrasion-resistant than uncoated glass or tin oxide-coated glass, and resistant to cleaning solutions. In addition, the application of the DLC coating could not appreciably reduce the strength of the tempered glass substrate. All AEGISGLASS® had sufficient transmission at 632 and 680 nm, so that the performance of the scanner was not degraded. All AEGISGLASS® passed the Steam/Thermal Shock test. The DLC coatings were shown to be resistant to cleaning solutions used in supermarkets. In a series of tests in which heavy items were dropped onto the windows, the coating did not affect the breaking strength of the tempered glass substrate. In abrasion testing, plexiglass, glass, and tin oxide-coated glass were rendered unusable after several passes of #600 diamond grit abrasive under 500gm load, while AEGISGLASS® was unaffected. Independent abrasion tests by major scanner manufacturers comparing samples of AEGISGLASS® to sapphire glass found AEGISGLASS® exhibited less haze than the sapphire glass after repeated exposure to a 500gm load on #600 diamond grit after 500 to 2000 abrasion strokes. IN-STORE TESTING During AEGISGLASS® development, in-store testing of various window materials was conducted over periods of several months to evaluate the performance of windows. The windows were installed in barcode scanners in 10 busy lanes in each of three grocery stores. The number of defects on each window was determined based on visual inspection of the number and length of scratches on the windows. Scratches which were obvious upon visual inspection were counted, since it was found that scratches which were not easily visible did not cause significant scattering of laser light. In a busy lane (50,000 items/week) of a grocery store, an uncoated float glass window typically has a lifetime of 2-4 weeks. Uncoated float glass accumulates approximately one defect per several hundred items scanned. A normal tin oxide wear-resistant coating can extend the life of float glass to 8-12 weeks. Plexiglass, being the softest material used for barcode scanner windows, only has a lifetime expectancy of 1-2 weeks. In the first grocery store test, the accumulation rate of defects on the AEGISGLASS® windows, relative to uncoated float glass, predicted an expected average lifetime greater than 9 years in a busy lane. In a second test, an in-store questionnaire was filled out by various store personnel concerning the plexiglass in their register scanning equipment. The cumulative results are demonstrated on the scanning glass questionnaire recap sheet (Table I.).
Further observations were made to determine the relationship between scratch defects and re-scanning. This was done by observing store checkout personnel during normal scanning procedures. The re-scan survey chart (Table II.) directly correlates the amount of scuffing/scratching to the number of re-scans per hour.
AVERAGE RE-SCANNING PER HOUR AT THE REGISTERS OBSERVED:
Based on an average time of three seconds to re-scan an item, Table III depicts the cost of
re-scanning at wages of $10 per hour (including benefits). With an average of six registers
open, and providing the condition of the plexiglass is equally divided among light, medium,
and heavy scuffing, a single store using the plexiglass windows observed could lose $3,420
per year from lost time due to re-scanning.
Similar observations were held by personnel at a store located in New York. In the endurance test, conventional glass, tin oxide-coated glass, and AEGISGLASS® were evaluated to determine the relative wear characteristics of each type of window under normal operating conditions. The goal of the evaluation was to quantify the superior performance of AEGISGLASS®. Table IV presents the extremely favorable results for AEGISGLASS®. During the test, both conventional glass and tin oxide-coated glass were scratched severely, and the AEGISGLASS® had virtually no signs of wear.
Conclusions Under normal retail store environments, plexiglass, tin oxide-coated glass, and conventional glass are but a short-term answer to the problem of abrasion, laser light scattering, and difficulty in barcode reading. AEGISGLASS® reduces re-scans, saves money, and has an expected life of eight to ten years of high quality, error-free scanner operation. Products |
About DIAMONEX Technology | News & Info |
Contact
Us | About Us | Home |
Sitemap A Division of Morgan
Advanced Ceramics
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
