WO 94115314 2 1 ~ 2 3 6 6 ~n~sg31l24sg .
PORTABLE OPTICAL READER SYSTEM FOR READING
OrTICALLY READABLE INFORMATION LOCATED
WITHIN A THREE DIMENSIONAL AREA
Technical Field 5The present i~1v~ ion is directed to optical information readers and more particularly to portable optical reader systems for illslalllalleously reading optical information within a substantial area.
Back~u_rld Art Manyindustriesdesignatetheirplvdu~lawithopticallyreadableinformation.
10 Optically readable information often takes the form of a bar code symbol cullaiaLillg of a series of lines and spaces of varying widths. Various bar code readers and laser scanning systems have been el..~,loyed to decode such symbol p~ s. One of the many PrOb1-~JIS encou,.tel~d in the bar code reader art, wherein a photos~llailive array is utilized, is to ~,.oduce an optical system capable of ~o.usi~g images of optically readable i. .fu, 1l lation where such information lies at varying ~;lialal IC~a from the reader.
Known to the art are readers which utilize lll~l.al.ical means to change the focal length of an optical system. Although such mechanical means may be e~ lvred to read optical information over a substantial range of diatal)ces, such means are often somewhat ~ b~laullle in design, ll:".pela,l,~l.tal, ~ ,.aive, and require the expenditure of additional battery energy. Thus, in the hand-held optical information reader art, where power corlaulll~Jlion~ weight, portability, convenience, range, and depth-of-field are of great concern, means fûr obviating and simplifying focusing l~uil~lllellts have long been sought.
Therefore, it is a principal object of the present invention to provide a method and apparatus for focusing an image of optical information over a WO 94/15314 A 221 523 6 6 PCr/USg3tl2459 substantial range of distances which requires no moving parts, is convenient, easy to use and simple in construction.
Another object of the present invention is to provide a method and apparatus for focusing an image of optical information within a substantial area and over a-5 substantial range of distances.
Diqt 1~ e of the ll.v~.Lon The present invention provides an aypalatLls capable of reading optically readable information located within a three-tl i . . ,. -. ~ciollal areâ. The present invention utilkes a two-dimensional phOlOs~llailive array which is o~æ.dted as a plurality of 10 linear arrays. Each linear array has a lens or series of lenses aaau.ial~d therewith for focusing the lelle~L~d light image of an object having a discrete set of coordainates within a three-di~ .aional space in front of the apparatus. In thisfashion, a user of the apparatus may simply direct the apparatus at a bar code or the like located within the coordinate range of the apparatus in order to read the bar 15 code or the like.
Brief De~ n of the Dl~ s FIG. 1 is a diaglal.u.,tic p~ ,a,ue live view of the a~tpalalus of the present invention illustrating the coordinate range of the apptaltal~ls;
FIG. 2 is a diagrammatic top plan of the multi-se~ t lens array of a 20 ~"er~ .Ic!d embodiment of the present invention;
FIG. 3 is a dia~rammatic ~e~a~e liv-e view of a portion of the mult-iseE;~ t lens array of a p.ef~ d embodiment of the present iulv~-lliu-l;
FIG. 4 is a diagrammatic side el~vational view of a portion of the multi-se~;ll,~nt lens array of a p.ere..ed embodiment of the present invention;
FIGS. 5, 6, and 7 illustrate the configuration of a pholua~llailive array and multi-se~;..,ellt lens array of a ~,rer~:"ed six target plane model of the present invention;
FIG. 8 is a diagrammatic side elevational view of a prer~.,ed six target plane model of the present invention illustrating the six target planes; and FIG. 9 is a diagrammahc ~la~e li~e view of of a ".~r~ d six target plane model of the present invention illustrating the six target planes.
Best Mode for Carryin~s Out the ll.~v~nl;on Typical resolution on a two-dimensional CCD imagin~ device might be around 512 by 512 pixels and some arbitrary gray-scale levels (16 or 256). Assume WO 94115314 2 1 5 2 3 6 6 PCTIUS93/124s9 the CCD device has been used to digitally capture a barcode image, for the sake of argument, a UPC code. Let us then assume that we wish to decode this barcode.
The Nyquist limit applied here dictates that we must be assured of having at least two pixels per vertical line. Since the lines on a UPC code are of varying widths, 5 we must i,.te.~ it to mean the thinnest vertical lines.
From looking at a sample UPC, the thickest lines are about 4 times the width of the lI,i"-,esl lines, and there are white lines as well as black lines. After counting the vertical bands and weighing the widths, a reasonable estimate is that it would require around 200 pixels across the length of the code in order to 10 accurately decode it. Thus, it is very illlpGI ldnt that the barcode occupy as large a portion of the sensing area as possill~ in order to be able to get the best resolution possible.
If one considers a similar CCD device, the portable ca."co~de., it may be obs~ ed that there is a lens array, with zoom and focus capabilities. The user (or 15 perhaps the camera with the aid of fuzzy logic) centers and zooms in and focuses the subject using a small viewscreen as fee~lhack. This apy.oacll has several problems for use in barcode del~lion:
Speed-Camcorder focusing and zooming systems are way too slow to keep up with the changing demands of a handheld sca.u,i..g device.
Moving Parts--Moving parts mean more oppullu~ for hilure, .an.e ~lob,le."s, need for calibration, and slow"~:.s.
Effort-The user must interact too much with such a device. They need su",el}""g that is as easy as point and shoot.
P,~ision--Mostpeoplecannotaimwiththeac~,lla.yleq~ dtokeep a distant target cl ~ ed. Again, point and shoot. Let the user do the general aiming and the device do the precision aiming.
Each single line of the CCD might have its own lens at a different magnification hctor and focal length. A lens could be consl, u~led that smoothly30 changed from one set of optical ~I~ara.tu.ialics to another, as you might find in a pair of bifocals, only on a grander scale.
In this fashion you could not only could you vary focal length and magnification, but the amount of lens prism ("prism" is the magnitude and direction wo g4/15314 2 1 ~ 2 ~ 6 6 ~uS93~l245g of linear translation (shifting) that a lens gives an image). This would allow a CCD
to have a wider field of view.
Bar codes have a great deal of vertical redundancy. There are an infinite number paths across a barcode that will allow it to be decoded, yet you need only one. Imagine a digitized barcode image, let us say 256 by 256 that has been c~:"le,t!d for proper decoding, every pixel along any horizontal line is desired, yet vertically the same image has been reproduced 255 times. For any barcode image scanned with a 2-D CCD, only 1/256 of the scanning area is really used. What if you could sac,ifice some of the vertical redundancy? Obviously you would gain more sensing area. If you gave up 50% of the vertical redundancy, you could possibly have two 128 x 256 CCD arrays, each sensing dif~ ,.t images. At the extreme, if you eliminated all redundancy, you might have 256 - 1 x 256 CCD
With four 1 x 256 CCD sensing arrays, you could look for the barcode in any one of 4 distinct sectors of the device's field of vision. If the four 1 x 256 CCD
sensing elem~:"ta could give us 4 adjacent sectors within the barcode, that is the first element senses the first 25%, etc., in effect we then have one 1 x 1024 CCD
array. We have suddenly quadrupled the resolution and by doing so, have quadrupled the range.
Illumination may utili7e fiber optics, holo~;,aphic plv~/~llies, or means to vibrate the lens in such a way that the signal may be s~ Jled several times fromslightly shifted pe,ape~lives. This invention uses a 2-vi,,~e,,aional imaging device which has a very large amount of redundancy in the vertical dimension. In this case, we have 700 x 500 or 350,000 or 2 orders of magnitude more pixels with redundancy. So spatially in the depth dimension you cover all the possible places that you have d~ "i"ed from a 11 illilllUlll to a maxi llul~ that you might need to be able to focus. Presumably, if you have the target somewhere in there then, one of those distances will give the best signal and that would be the one that you would then work with and the others would be degraded to the point that they don't have enough information to be ,~oE;"i~d by the recog,~ilion digital process.
It is a relatively small matter for each of those lensing el~ La to be tipped or tilted or swiveled if you would in space such that they cause by doing a reverse ray tracing process of all of the stack of these vertical lines to be moved out spatially, left to right, and top to bottom, as well as focus by focal length of the lens shape.
WO ~4!l5314 215 2 3 6 6'CTtUS93tl2459 A fly has a large array of discrete non-moving eyes each of which fan out and are optically disposed to read a certain or detect a certain area which would then reassemble back in the fly's brain to build it into a picture. We're suggesting a similar thing here where we have a piece of the bar code maybe detectable to one 5 of the optical paths and another piece detectable to another path and so on such that our .,u.,i...-~.:d resolution is built back log~ll.e, piece-wise. Fu~lh~ ùre, our plu~aSillg system can know what its optical paths are like so that by a fixed area it can have a pretty gûod idea of what it is lûûking at and know where the rest of it shûuld be found and assel..bla these things in sort of a mapping process. We 10 culltelllplate the facets being oblong in shape and rectangular so that they can be filled in solid in some material and then through some kind of a deterrnination that we have to make, d~t~...u..e how the image localic~ns both in X, Y, and Z map into a physical location on the image sensing array. The object here, is to rill the volume a truncated four-sided luylall idal volume in space with areas that are connected to 15 each other such that as you move from one roughly cubic volume to the next roughly cubic volume, there is continuily of image cdlJIulillg capability so that if you move from one to the next you jump from the point of focus of one to the focus of the next as it moves, say left to right, you cross-over such that maybe one area might be adjacent to one beside it so that you got part of the barcode in one area 20 and part in the next.
An alternate ~...bodi~..ent might utilize further optical paths that include variable maE;..ificalioll. And a further alternate ~...bc,di-,-enl might have certain porffons of the optical paths that are used for spotffng. For ~Aalllpla, some areas might have very low mag.-iri-alion and are used to idenfffy hrgets. And maybe even in conjull~lion with some addiffonal aiming or 'UUlllillg effect so it might be used as a ranging assistant.
Consider an area CCD scanner such as, for example, a black and white TV
camera device of, say 768 pixels horizontal x 492 lines vertical. For bar code only applications, this area sensor could be considered as 42 individual linear sensing arrays of 768 el~ llb each. Now, given this array of 492 individual linear arrays, consider an opffcal system with 492 sepa.dle optical paths to each linear array,where the target or image area may be located in a large variety of posiffons. (In fact, the variety of locations may vary in each of the X, Y, and Z pusilions and the image magnification as well.) In essence, a spaffal volume may be created anywhere WO 94115314 2 1 5 2 ~ 6 6 PCr/US93/12459 within which a target bar code may be located and read. For the total image sensing CCD array, only one line of 768 ele..,t:J,t, rnight have an acceptable sample of the bar code, while all others sense nothing, but that is sufficient. A single flashable li~ht source may illuminate the entire imaging volume, so an "electronlc 5 picture" of the imagable volume may be .aytuled. The multiple path optical system should be designed such that for any target location within the imaging volume, at least one yields an interpretable result.
As ~ tiùmed above, 768 hG.i ollldl pixels may not provide high enough resolution for most bar code reading luul ~uoçes. It would be feasible, however, to use 10 the multiple optical paths to project the target areas by section onto the imaging array for re-ass~J"bly of pieces of the target into the single bar code for ylelation A basic concept upon which all of this dis~llsaion is based is imrnediate transfer of the signals from the irnaging device to a ~u~uccil~lyul~-memory for signal yuucessillg and decoding.
FIG. 1 illushdtes the volume scannable region concept. The multiple discrete optical paths must be deaigned such that there are no "holes" big enough that a generally hc., i~o.)tally posilioned bar code of ordinary height such as 0.5 inch cannot be ~a~ulllled. The X, Y and Z di,.,e.,:,io.ls are delt: --u-,ed by the i~pl~ e~Ldlion of the optical system including a lens or ene lo/ of cc..--yû uld construction. A good 20 cu~ ylual example is a bifocal vision cGll~lillg lens, where multiple opticalch.,lc..lt:liali.s are included in a single sL u.lu.~ and are disyosed at di~ t locations of the sl,.l.lu~e. Our cc..,uou.,d lens :.hu.lure might have rectangular regions of various optical cha~a.l~ s to form the desired optical path for gdLh~.i lg; focusing and directing light from each of the plural potential target 25 yOsilic ns to generally linear sensing regions on the surface of the imaging device.
Consider the cG.."~olu,d lens which forms the plural optical paths. Such a lens might be best consl~u~led of i-.je_lion molded plastic of optical quality and might have oblon~ ;langular "hcets" as shown in FIGS. 2-7.
For practical conside.~li(..,s, 492 seydlelte~ single-line optical paths may not30 be realizable with available technology. Several dozen to say 100 paths may be practical. The larger number of discrete paths ant positions, the larger the ~f~live scanning volume. A major benefit of this concept is there are no moving parts whatsoever. Co--,ya-l-.ess and low power co.l~u...ylion also result.