CA1146261A - Scanning apparatus - Google Patents

Abstract

SCANNING APPARATUS
ABSTRACT OF THE DISCLOSURE
A line scanning apparatus employing a multiplicity of linear arrays, the linear extent of which is less than the length of the scan line. To permit an entire line to be covered, the arrays are offset from one another in the direction of scan with adjoining array ends overlapped. To correct for the misalignment and redundancy introduced, the image data from the arrays is buffered until a line is completed when readout, is initiated.
during readout, cross over from one array to the next is effected within the overlapped areas and the redundant data discarded.

Description

This invention relates to raster input scanners and, more particularly to, raster input scanners having multiple linear arrays.
~ canning technology has progressed rapidly in recent years and today arrays of fairly substantial linear extent are available for use in raster scanners. Indeed, the linear extent of new arrays are in some cases many times the linear extent of earlier array designs. However, the length of even these recent array designs is still not sufficient to enable a single array to span the entire width of the normal sized line, i.e. 8 1/2 inches. Furthe~, it appears improbable that arrays of sufficient length will be developed in the foreseeable future since fabrication of such arrays would appear to require a major breakthrough in semi-conductor fabrication technology.
As a result, raster input scanners are forced to rely on shorter arrays and must, therefore, employ a multiplicity of arrays if the entire line is to be scanned in one pass. This raises the question of how to place the arrays so as to cover the entire line yet provide data representative of the line which is free of aberrations at the array junctures. Recently, interest has been expressed in optically-butted arrays. However, optical and optical/
mechanical arrangements often experience difficulty in meeting and maintaining the tight tolerances necessary for aberration free scanning, particularly in operating machine environments.
It is, therefore, an object of an aspect of the present invention to provide a new and improved raster input scanner employing multiple arrays.
It is an object of an aspect of the ~resent invention to provide an improved single pass line scanner employing

-2-ultipl~ linear arrays.
It is an object of an aspect of the present inven tion to provide a system designed ~o accommodate misalignment of plural linear arrays.
It is an object of an aspect of the present inven-tion to provide, in a raster inpu~ scanner having multiple physically offset and overlapping linear arrays, means for removing offset and redundancy ~rom the data produced.
It is an object o an aspect of the present inven-tion to provide scanniny apparatus with plural relatively short linear arrays, having a composite leng~h at least equal to the scan width.
It is an object of an aspect of the present inven-tion to provide a line scanner incorporating plural over-lapping arrays whose composite leng~h equals the length of the scanned lines, with electronic means for switching from one array to the next without introducing noticeable aberrations and stigmatism.
It is an object of an aspect of the present inven-~0 tion to provide multiple linear arrays having overlapping v~ewing fields with data readout bridging between arrays in the overlapFing :i~lds thereof.
Various aspects of the invention are as follows:
In an apparatus for scanning an image line by line to produce data representative of the image scanned, the combination of: a movable carriage; at least two image reading arrays, said arrays being supported in side by side relationship on said carriage for scanning said image on scanning movement of said carriage; means for actuating said carriage and said arrays to scan said image; and control means to selectively delay actuation of said arrays individually to neutralize misalignment between said arrays.
In an apparatus for scanning an image bearing original line by line to produce data representative of the image scanned, the improvement comprising: at least two arrays, each of said arrays comprising a plurality of discrete photosensitive elements arranged in succession along the linear axis of said each array, means support-ing said arrays in position to scan said original with the linear axes of said arrays extending in a direction substantially parallel to the scanned dimension of said original, the length of the viewing area of said arrays along said linear axes being less than the scanned dimen-sion of the original; said arrays being supported so that said array viewing areas overlap whereby to provide a composite array viewing area having a length at least equal to the scanned dimension of the original; means providing relative movement between said arrays and said original; means for actuating said arrays to scan said image; and control means to selectively delay actuation o~ said arrays individually to neutraliz~ misalignment between said arrays.
Other objects and advantages will be apparent from the following description and drawings in which:
Figure 1 is an isometric view showing a raster input scanner incorporating the multiple array arrangement of the present invention;
Figure 2 is a schematic illustrating an exemplary array disposition;

3~ Figure 3 is a schematic view of the scanner operating control;

Figure 4 is a schematic representation of the memory buffer for temporarily storing image data;
Figure 5 is a schematic illustration of the data mapping arrangement to avoid bit shifting on readout from the temporary memory buffer of Figure 4;
Figure 6 is a schematic view showing the data readout system;
Figure 7 is a schematic illustration of the data readout with crossovar and removal of redundant data;
Figure 8 is a schematic view illustrating a modified array wherein the center-to-centex distances between the photo-sensitive elements of a portion of one array are changed to provide a vernier useful for aligning arrays;
Figure 9 is a schematic view of an alternate lS array configuration wherein a bridging array is employed to efect continuity between adjoining arrays; and -4a- ~

Figure 10 is a schematic view of another alte.rnative array configuration wherein a bridging array is combined with a standard array to form a unitary structure, the photosensitive elements of the bridging array being on different center-to-center distances to provlde a vernier.
Referring to Figure 1, an exemplary.raster input scan-ning apparatus 10 is thereshown. Scanning apparatus 10, as will appear more fully herein scans an original documen~ 12 line by line to produc~ a video signal represen~ative of ~he original document 12. The video signal 50 produced may be thereafter used to reproduce or duplicate the original 12, or stored in memory for later use, or transmitted to a remote source, etc.
Scanning apparatus 10 comprises a box-like frame or housing 14, the upper surface of which includes a. transparent platen section 16 on which the original document.12 to be scanned is disposed face down. A displaceable scanning mechanism desig-nated generally by the numeral 18, is supp~rted on frame 1~ below platen 16 for movement back and forth underneath ~he platen 16 and the original document 12 thereon in the Y direc~ion as sh~wr.
by the solid line arrow in Figure 1.
Scanning mechanism 18 includes a carriage 20 slidably supported up~n parallel rods 21, 22 through journals 23.. Rods 21, 22, which parallel the scanning direction along eaGh side of platen 16, are suitably supported up~n the frame 14.
Reciprocatory movement is imparted to carriage 20 by means of a screw type drive 24. Drive 24 includes a longitudin-ally extending threaded driving rod 25 rotatably journalled on frame 14 below carriage 20. Driving rod 25 is drivingly inter-connected with carriage 20 through a cooperating internally threaded carriage segment 26. Driving rod 25 is driven by means _5_ of a reversibLe motor 28.
A pluraLity o~ photosensitive linear arrays l, 2, 3, 4 are carried on plate-like portion 35 of carriage 20. Arrays l, 2, 3, 4 each comprise a series of individual pho~osensitlve picture elements or pixels 40 arranged in succession along the array longitudinal axis. The arrays scan the originaL document 12 on platen 14 as scanning mechanism 18 mov~s therepas~, scanning movement being in a directian tY) substantially perpendicular to the array longitudinal axis ~X). As bes-t se~n in Figure 2r the arrays l, 2, 3, 4 may, due to the difficuLty in accurately align-ing the arrays one with the oth~r, b~ offset from one another in the direction of scanning movement ( the Y direction) . To accom -modate the rela~ively short length o~ the individual arrays, th~
arrays overlap~ In tha exempIary illustration, the en~ portion of a~ray~ 2, l, 4 ove~lap the leading portion of the succeedins arrays l, 4, 3 when Looking from left to right in Figure 2 along the X direc~ion.
As will be understood, the length of th~'individual arrays l, 2, 3, 4 may vary with different types o arrays and from manu~acturer to manufacturer. As a result, the number of arr~ys re~uired to cover the entir~ width of the originaL document 12 may vàry f~om that illustrated herein.
Phatosensitive elemen s or pixels 40 of arrays l, 2, 3,

4 are normalLy siLicon with carrier detection by means of photo-transistors, photodiode-MOS amplifiers, or CCD detection cir-cuits. One suitable array is the fairchild CCD 121 - 1723 pixel 2-phase linear array manufactured by Fairchild Corporation. As described, arrays l, 2, 3, 4 are offset from one another in the scanning or sagittal direction (Y direction) but with an end p~r-tion of each array ove-rlapping the leading portion o~ the next succeèdinq array to form in effect a composite un~roken array~
To focus the image onto the arrays 1, 2, 3, 4 a le~s 43 is provided for each ar~ay~ Lenses 43 are supported on carriage 20 in operative disposition with the array 1, 2, 3, 4 associated therewith. Mirrors ~4, 45 on carriage 20 transmit the light images of the o~iginaL via lenses 43 to arrays 1, 2, 3,. 4. ~amp 48 is pro~ided for illuminating the original document 12, lamp 48 being 5uitably supported on ca~riage 20~ Re~lector 49 focuses the light emitted by lamp 48 onto the surface of platen 16 and the original document 12 restinq. thereon.
In operation, an original document 12 to be scanned is disposed on platen.16. The scanning mechanis~ 18 including motor 28 is actuated, motor 28 when energized operating driving mecha-nis~ 24 to move carriage 20 back and for~h below ~laten 16. Lamp 48 is energized du~ing th~ scanning cycle to illuminate the ori~
inal document 12.
To correlate movement o carriaqe 20 with opera.~ion.of arrays l, 2, 3, 4 an encoder 60 is provided. Encoder 60 gene.rates timing pulses proportional to the velocity o~ s~annin~ mechanism 18 in the Y direction. Encoder 60 includes a timing bar 61 having a ~uccession of spaced apertures 62 therethrough disposed along on~ side of the path of movement o carriage 20 in parallel with the direction of movement of carriage 20. A suitable signal generator in the form of a photocelL-lamp combination 64, 65 is provided on carriage 20 of scanning mechanism 18 with timing bar 61 disposed therebetween.
As carriage 20 of scanning mechanis~ 18 traverses back and forth to scan platen 16 and any document 12 thereon, photo-cell-lamp pair 64, 65 of encoder 60 moves therewith. Movement of the photocell-lamp pair 64, 65 past timing bar 61 generates a ~ 2~

pulse-like output signal in output lea~ 66 o~ photoceLl 64 directly ~roportional ta the velocity of~scann.ing mechanism L8.
As can be envlsioned by those skilled in the art, sup-port~ing arrays 1, 2, 3, 4 in exact linear or tangential alignment (along th~ X-axis) and maintaining such alignment th~oughout the opera~ing life of the scanning a~aratus is extremely difficult and somewhat impractic~le. To obvia~e this difficulty, a~ays 1, 2, 3, 4 are initially mounted o~ ca~riage 20 in substantial tangential alignment~ As can be seen in the exemplary showing Qf Figure 2, this nevertheless often results in tangen~ial array misalignment along the x-axis. I~ ~he disposition of the arrays 1, 2, 3, 4 is compared to a predetermined reference, such as ~he start o~ scan line 101 in Figure 2, it can be seen that each array 1, 2, 3, 4 is displaced or offset ~rom line I01 by some offset distance dl, d2, d3 t d4, respectively~ As wiLl appea~ more fully herein, the individuaL offset distances of each array 1, 2, 3, 4 is determined and the result programmed in an offset counter 120 (Figu~e 3) associated with each array. Offset counters 120 serve, at the start of the scanning cycle, to delay activa~ion of the array associated therewith until the interval dl, d2, d3, d4, thereor is ~aken up.
Reerring to Figure 3, tke pulse-like signal output o~
encoder 60 which is generated in response to movemen~ o~ carriage ~0 in the scanning direction (Y-direction), is inputted. to a phase locked frequency multipiier network 100~ Netw~rk 100, which is conventional, serves to multiply the relatively low fre-quency pulse-like signal input of encoder 60 to a high frequency clock signal in output lead 103. Feedback loop 104 of network L00 serves to phase lock the frequency of the signal in lead 103 with the frequency of the signal input rom encoder 60.

~ 6 As will be understood, changes in the rate o~ scan o~
carriage 20 produce a corresponding change in the frequency o the pulse-like signal generated by encoder 60~ The frequency of the clock signal produced by network 100 undergoes a correspond-ing change. This resuLts in a high frequency clock signaL i~
output lea~ 103 directly related ~o the scanning velocity o~ car-riage 20, and which accommodates va~iaticns in tha~ veLocity.
Th~ cIock signal in output lead 103 is~in~utted ~ pro-grammable multiplexer 106. The outpu~ of a second or aLternate clock signal source such as crys~tal con~rolled cloc~. 108 is input~ed via lead lO9 to muLtiplexer 1û6. ~ultiplexer 106 selects either network L00 or clock 108 a~ the clqck si~nal source in respons~ to control instruction~ (CLOC~ SELECT) from a suitable programmer (not shown). The selected clock signal appears in output lead IlL of multiplexer lQ6~
An o~?erating circuit lL4 is provide~ for each array 1, 2, 3, 4. Since the circuits L14 are the same for each array,. the circuit 114 for array l only is described in detail~ It is under-stood t}Iat the number. o circuits 114 is equaL to the number of arrays used~
Operating circuit 114 includes a line transfèr counter 115 for controlling the array imaging line shutter or sample time for each scan~ Counter 115 is driven by the clock signal in output lead 111 of multiplexer 105. It i5 understood that whera the signal input to countèr llS camprises the clock signal pro-duced by network 100, array sample size remains constant irres-pective of variations in the velocity of carriage 20. In other words, where carriage 20 slows down, array shu~ter time becomes longer. If carriage 20 speeds up, array shu~ter time becomes shorter.

_g_ Initial actuation of line transfer counter 115 is con-trolled by ~he offset counter 120 associated therewith. Offset counter 120, which is driven by the clock signal in output lead 111, is preset to toll a count representing the time interval required for array L to reach s~ar~ of soan line 10I ~ollowing start up of carriage 20. On tolling ~he preset count, o~fse~
counter 120 generates a signal in lead 122 enabling line transfer counter 115.
It will be understood that the offset counters 115 associated with the circ~ s 114 for the remaining-arrays 2, 3, 4 are similarly preset to a coun~ representing the distance d~, d3, d4, respectively by which arrays 2, 3, 4 are offset from start of scan line 101.
Re~erring particularly to Figure 2 each array 1, 2, 3, 4 scans a ~ortion of each line of the original documen~ 12~ ~h~
sum total of the data tless overlap as ~ill appear mor~ fully hèrein) produced by arrays 1, 2, 3 ~ 4 representing ~he entire line. Preferably, arrays 1, 2, 3, 4 are of the same size with the same number of pixels 40. As described, the line transfer counters 115 of circuits 114 control the array imaging line shut-ter time for each scan, counters 115 being pre~et. to activate the array associated therewith for a preselected period ~or thi5 pur-pose. Sc~nned data from the arrays 1, 2, 3, 4 is clocked ou~ by clock signals derived from a suitable pixel clock 118.
Sampled analog video data from the arrays 1, 2, 3, 4 is fed to a suitable video processor 148 which converts the video signals to a binary code representative of pixel image intensity.
The binary pixel data from processor 148 is mapped into segments or words by Pixel Data Bit Mapper 149 for storage in offset rela-tion in RAM 175 as will appear. Bit Mapper 149 is driven by clock signals from pixel clock 118.. Da~a from Bit Mapper l4g is pass~d via data bus 174 to RAM 175 where the data is temporarily stored pending receipt of data from the array which last views the line.
In the exem~lary arrangement illustrated, the last array would be array 4..
Multi~lexer 150 may be provided in data bus 174 to ~er-mit data from o~her sources (OT~E~ DATA) ~o be inputted to RAM
175 .
The binary da~a is stored in sequential addresses m RAM 175 (see Figure 4), the data being addressed into RAM 175 on a line by line basis by the R~ address poin~ers 165 through Address Bus 180. ~he clock signal output from pixel clock 118 is used to drive address pointers 165. Line scan counter 17û, which is driven by the output from line transfer counter 115, controls the number o ~ull scan lines that will be stored in RAM 175 before recycLing-. The output of counter 170 is fed to RAM Address pointer 165 via lead lL9o rt is unders~ood that line scan coun-ters 170 are individually preset tQ, reflect the degree of array offset in the Y-direction.
Ram 175 provides a buffer for scanned data from each array, RAM 175 buffering the data until a full line is completed ~ollowing which the data is read out. A suitable priority encoding system (not shown) may be used to multiplex the data input from arrays 1, 2, 3, 4 with the address associated there-with, Ram 175 has input and output ports for input and output of data thereto.
Since the degree of misalignment of arrays 1, 2, 3, 4 in the Y-direction may vary, the storage capacity of RAM 175 must be sufficient to accommodate the maximum misalignment antici~ated. A worst case misalignment is illustrated in Figure 4 wherein it is presumed that arrays 1, 2, 3, 4 are each mis-aligned by a full line. In that circums~ance and presuming scan~
ning of line 1 is completed, R~ 175 then stores ~he line data for lines 1, 11, 12, 13, 14 from array 1, lines 1, 11, 12, 13 from array 2, lines 1, 11, 12 ~rom array 3, and lines 1, 11 fro~ arra~
4. The blocks o binary data that comprise~ ~he completed line 1 are in condition to be read out o~ R~ 175. In the a~ove example, an extra line of data storage is ~rovided.
Li.ne scan counters L7~ a~e recycling counters which are individually preset for the number o~ lines o~ data to be s~ored for the array associated therewith. As a result, address pointers 165 operate in round robin fashion on a line by line basis. On reaching a preset count, the signal from counters 170 recycle the address pointer 165 associated therewith back to the first storage line to repea~ the procass. It is understood tbat prior thereto, that portion of RAM 175 has been cleared of data.
As described, data from video proce~sing hardware 14 i5 stored temporarily in RAM 175 pending comple~ion of the Line.
In placing the data in ~AM 175, the data is prefera~ly mapped in such a way as to avoid the need for eubsequent data bit shifting when ou~putting th~ data. Referring to ~igure 5, wherein mapping o~ pixel data from arrays 1, 2 is illustrated, data from an aarlier array (i.e~ array 1) is mapped by Pixel ~ata Bit Mapper L49 (Figure 3) into s~gments or words 180 before being stored in RAM 175. The first pixel (Pl - 1) of the array within the array overlap 181 is mapped into a known bit position within the seg-ment or word 180 at the point of overlap.
At the end of line transfer, the first pixel (Pl - 2) of the succeeding array (i.e. array 2) is clocked into the bit posi-tion (Pl - 1) of the first overlapped pixel of the previous array.

2~

This correlates the first overlapping pixel (P1 - 2) o~ tne succeeding array (i.e. array 2) with the first overLapped pixel (Pl - 1) o~ the preceding array (i.e. array 1). Crossover from one array to the succeeding array on data readout may then be effected without the need to shit bits.
Referring now to Figures 6 and 7, video data held in R~ 175 is read out to a user (not shown~ via RAM ou~Fut ~us 176, in both t~ngentially and spatially corrected form, line by line~
through output channel 20 0 . Data readout is controlled by a microprocessor, herein CP~ 204 in accordance with address program instructions in memory 206. CPU 204 may comprise any suitable commercially available processor such as a Model M680a manufac-tured by Motorola, ~nc.
The addr~ss program ins~ructions in memory 206 incLude a descriptor list 207. List 207 contains information identifying the number of bits to be read out (Nn)~ th~ addxess of the fi~st word ~A), and ot~er user in~ormation (U). The D~TA OUT address inormation is fed to address multiplexer 208 vla ~ddress bus.
209.
As described heretofore, exact tangen~ial alignment and end to end abutment of multiple arrays is difficult to achieve~
I~ the a~rangement shown, sagittal misalignme~t (in th~ ~
direction) among the arrays is accommodated by offset counters 12Q of the individual array operating. circuits 114. The need to accurately abut the arrays end to end is obviated by overlapping succeeding arrays.
As a result of the a~ove, the sequence in which video data i5 inputted to RAM 175 offsets sagittal misalignments between the s~veral arrays. By outputting the data from RAM 175 on a line by line basis, the lines are reconstructed without sagittal misalignment.
Due to the overlappiny disposition of arrays 1, 2, 3, 4, data within the overlapping portions o~ the arrays is redun-dant. To obviate this and provide a complete line of data without repeated or redundant portions, bit crossover on readout within the overlapping regions i5 used~
Refe~ring now to the embodiment shown in Figure 7, data bit c~ossover within the overlapping portions o arrays 1, 2, 3, 4 i~ effected by an algorithm which picks a predetermined last cell to be sampled within the overlapped region and au~omatically picks the next bit in the succeeding array. In the descriptor list ~7 iIlustrated in Figure 7, the total bit output from the ~irst array is Nl bytes ~ ~1 bits with the bit output rrom the second array N2 bytes - n~ bits. In the example shown in Figure 7, crossove~ from arra~ 2 to array 1 is`ef~ected between bi~ 4 and bit S.
I~ ~he arrangement described heretofore, the cente~-~o-center distance between successive photosensitive elements or pixels 40 is constant. Xeferring to Figure 8, wherein like numerals re~er to the like parts a pair of arrays 300, 301 are there shown with the end portions o~erlapped. The photosensitive elemen~s or pixels 4~ that comprise arrays 300, 301, excep~ ror the end ~Q8 o array 300, are on normal center-to~center ~is-~ances d. The photosensitive elements 4U' in the end 308 of array 300 are set on a slightLy reduced center-to-center distance d'.
The redùction in center-to-center distances between the photosen-sftive elements 40' in end 308 of array 300 provide in effect a vernier scale which normally provides at least one point where opposing arrays are in alignment irrespective of the degree o~
overlap between the arrays. In the exemplary arrangement shown, the end of photosensitive element 40 - 8 of array 301 is in sub-stantial alignment with the start of photoser.sitive element 40' -

5 of array 300, and crossover would be set at this point.
It will be understood that visual identification of the indi~idual photosensitive elements or pixels 40, 40' to determine the optimum crossover point may be made throush microscopic exam-ination of the arrays. It is further undeLstood that once the optimum crossover point is detenmined, the descriptor list of memory 206 (Figures 6, 7) is programmed to provide crossover from p}xels 4~ - 8 of array 301 to pixel 40' - 5 o~ array 300 o~
readout.
While the vernier scale is illustrated as being at one end 308 of array 300 only, it is understood that vernier scales may be provided a~ both ends of the array. In that event, in a scanning arran~ement employing four arrays suoh as shown in Figur~ 2, array 1 may have a vernie~ scale of the type desc~ihed at each end, array 3 a vernier scale at one end only, with remain-ing arrays 2, 4 conventional.
While th~ vernie~ scale described is es~ablished by reducing center-to-center distances between adjoining pixels, it is understood that a vernier scale may be created by increasing sligh~ly the center-to-center distances between adjoining array pi~els.
Referring to the embodiment shown in Figure 9, there a pair of relatively long linear arrays 350, 351 are disposed end to end. This may be effected optically as by means of lenses 43 in the scanning apparatus 10 of Figure 1 or mechanically through physical contact of the array ends with one another. To accom-modate any gaps between the array ends or misalignments along he ~ axis and to assure continuity of the composite array so formed, a relatively short bridging arra~ 360 is provided to overlap the adjoinin~ ends of each array 350, 351.
Bridging array 360 comprises a relatively short linear array, prefera~ly with the minimum quantity of pixels 40 needed to provide effective overlap of the adjoining arraysO Typic~lly, bridging array 360 may be comprised of ~he ordex of 100 pixels whereas arrays 350, 351 com~rise some 1700 pixels.
In user data from arrays 350, 3Sl, 360 may be. readout as described earLier, the data being stored temporarily in R~
175 (Figure 3) pending completion of the line. By choosing rela-t~vely short bridging arrays 360, the amount of da~a to be stored in RAM 175 and hence the size of R~l 175 may be substantially reduced. The data held in RAM 175 is, on completion of the line, read out from RA~ 175 into bus 176 (Figure 6), with crossover made rom array 350 to br.idging ar~ay 360 and thereafter from bridging àrray 360 to array 351 in ~he overlapping areas to assure contin-uity.
Referring to the embodiment shown in Figure 10, wher~
like numerals refer to like parts, an array structure 400 is thereshown. Array structure 400 includes relatively long and sh~rt arrays 40~, 404 respectively mounted upon a common sub-s~rate.or mask 4.06. Array 404 i5 disposed in paxallel with array 40~, with a portion 409 o~ array 404 overlapping one en~ 403 o~
array 402. The remainder of array 404 projects beyond end 403 of array 402 and is adapted to overlay the leading end o~ the next successive array structure 400' as seen in drawing Figure 10. To accommodate overlapping of successive array structures 400, sub-strate 406 is inset at 407. -To enhance alignment between the arrays and provideundistorted crossover between arrays, photosensitive elements or pixels 40' of array 404 are disposed on a center-to-center dis-tance d' different from the center-to-center dis~ance d of pixels 40 of array ~0~. This in ef~ect establishes a vernier scale which ena~les at least one pixel 40' of array 404 to be aligned with a corresponding pixel 40 of array 402. In the exemplary ar~ange-ment shown, pixel 40 - 5 of array 402 is in substantial alignment with pixel 40' - 4 of array 404 and crossover would be effected at this point.
Similarly, when associating the array structure 400 with the next succeeding array structure 400', crossover from array 404 to array 402' is selected at the polnt of closest ~ixel alignment. In the embodiment shown, crossover would be between oixel 40' - 7 of array 404 and pixel 40 - 3 of array 402.
While the-center-to-center distance d' betwee~ pixeLs 40' of array 404 is ill~strated as being less than ~he center-to-center distance d between the pixels 4~ of array 402, it is under-stood that dimension d' may be greater than ~imension While the invention has been described with reference to the structure disclosed, it is not confined to the details set ~orth, but is intended to cover such modifications or changes as may come within the scope of the following claims.
Attention is directed to the fact that the disclosure of t~is application describes an embodiment of an invention claimed in appli~ant's co-pending application Serial No. 302,305.

Claims (4)

WHAT IS CLAIMED IS:

1. In an apparatus for scanning an image line by line to produce data representative of the image scanned, the combination of: a movable carriage; at least two image reading arrays, said arrays being supported in side by side relationship on said carriage for scanning said image on scanning movement of said carriage; means for actuating said carriage and said arrays to scan said image; and control means to selectively delay actuation of said arrays individually to neutralize misalignment between said arrays.

2. An apparatus according to claim 1 in which said arrays are supported such that a portion of the viewing areas thereof overlap, data from said array overlapping portions being redundant, and means for removing said redundant data portions.

3. The apparatus according to claim 2 in which said last mentioned means includes: data storage means for temporarily storing data from each of said arrays including redundant data portions, readout means for reading data in said storage means from said arrays in succession, said readout means crossing over from one array to the next successive array during said redundant data portions.

4. In an apparatus for scanning an image bearing original line by line to produce data representative of the image scanned, the improvement comprising: at least two arrays, each of said arrays comprising a plurality of discrete photosensitive elements arranged in succession along the linear axis of said each array, means support-ing said arrays in position to scan said original with the linear axes of said arrays extending in a direction substantially parallel to the scanned dimension of said original, the length of the viewing area of said arrays along said linear axes being less than the scanned dimen-sion of the original; said arrays being supported so that said array viewing areas overlap whereby to provide a composite array viewing area having a length at least equal to the scanned dimension of the original; means providing relative movement between said arrays and said original; means for actuating said arrays to scan said image; and control means to selectively delay actuation of said arrays individually to neutralize misalignment between said arrays.