CA1132242A - Crossover arrangement for multiple scanning arrays - Google Patents

Abstract

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 buf-fered until a line is completed when readout, is initiated. Dur-ing readout, cross over from one array to the next is effected within the overlapped areas and the redundant data discarded.

Description

~3Z2~;~
This invention relates to raster input scanners and, more particularly to, raster input scanners having multiple linear arrays.
Scanning 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 same 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. Further, 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 multi-plicity 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 main-taining the tight tolerances necessary for aberration free sc~nning, particularly in operating machine environments.
It is, therefore, an object of an aspect of the present invention to provide a ne~ and improved raster input scanner employing multiple arrays.
It is an object of an aspect of the present invention to provide an improved single pass line scanner employing multiple linear arrays.

~l~3Z~2 It is an object of an aspect of the present invention to provide a system designed to accommodate mis-alignment of plural linear arrays.
It is an object of an aspec-t of the present invention to provide, in a raster input scanner having multiple physically offset and overlapping linear arrays, means for removing offse~ and redundancy from the data produced.
It is an object of an aspect of the present invention to provide scanning apparatus with plural relat-ively short linear arrays, having a composite length at least equal to the scan width.
It is an object of an aspect of the present invention to provide a line scanner incorporating plural lS overlapping arrays whose composite length e~uals 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 invention to provide multiple linear arrays having overlapping viewing fields with data readout bridging between arrays in the overlapping fields thereof.
Various aspects of the invention are as follows:
In an apparatus for scanning an image, the combination of:
a. a ~ovable scanning carriage;
b. at least two relatively long linear arrays on said carriage, said arrays being disposed in end to end relationship and extending in a direction substantially perpendicular to the direction of scanning movement of said carriage; and .

. . .

~L13~ 2 c. a relatively short linear bridging array on said carriage, said bridging array being disposed to overlap adjoining ends of said relatively long arrays whereby to form in cooperation with said relatively long arrays an uninterrupted composite array for scanning said image.
In a line scanning apparatus employing multiple arrays together forming a composite array having a length at least equal to the length of the line to be scanned, together with memory means to hold data from said arrays pending completion of a line, the improvement comprising:
a composite array consisting of relatively long linear arrays disposed in end-to-end relationship with a relatively short bridging array disposed to overlap the ends of said relatively long arrays, said relatively short bridging arrays reducing the amount of data to be stored by said memory means.
An array for use with scanning apparatus of the type having a plurality of overlapping arrays which cooperate to form a composite array of substantial length comprising:
a. an array support, b. means Lorming a first relatively long linear array on said support;
c. means forming a second relatively short linear array on said support, said second linear array being substantially parallel with said first array, said second linear array having a portion thereof overlaying one end of said first array with the remainder of said second linear array projecting beyond said first array one end.

-3a-~3~2~

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;
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 crossover and removal of redundant data;
Figure 8 is a schematic view illustrating a modified array wherein the center-to-center 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 array configuration wherein a bridging array is employed to effect continuity between adjoining arrays; and ~3~
~ igure 10 is a schem~tic view of another alternative array configuration wherein a bridging array is combi.~ed with a standard ~rray to rorm a unitary structure, the photosensi~ive elements of the bridging array being on di~erent center-to-center distances '~ provide a vernier.
Referring to Figure 1, an exemplary raster input scan-ning appara~us 10 is thereshown. Scanning ap~aratus 10, as will appear more fully herein scans an original document 12 line by line to produce a video signal representative of the original document 12. The video signal so 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 sup~orted on frame 14 belo~"
platen 16 for movement back and fortn underneath the platen 16 and the original document 12 thereon in the Y direction as sho~n by the solid line arrow in Figure 1.
Scanning mechanism 18 includes a carriàge 20 slidably supported upon parallel rods 21, 22 through journals 2~. Rods 21, 22, which parallel the scanning direction along each side of platen 16, are suitably supported upon the frame 14.
Reciprocatory movement is imparted to carriage ~0 by means of a screw type drive 24. Drive 2a 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 carri~ge segment 26. Driving rod 2S is driven by ~eans , _;_ ~3Z2 ~
of a reversiblQ motor 28.
A plurality of Dhotosensitive linear arrays 1, 2, 3, 4 are carried on plate-like portion 35 of carriage 20. Arrat~s 1, 2, 3, 4 each com~rise a series of individual photosensitive picture elements or pixels 40 arranged in succession along the array longitudinal zxis. The arra~s scan the original document 12 on platen 14 as scanning mechanism 18 moves therepast, scanning movement being in a direction (Y) substantially perpendicular to the array lon~itudinal axis (X). As best seen in Figure 2, the arrays 1, 2, 3, 4 may, due to the difficulty in accurately allgn-ing the arrays one with the other, be offset from one another in the direction of scanning movement (the Y direction). To accom-modate the relatively short length of the individual arrays, the arrays overlap. In ~the exemplary illustration, the end portion of arrays 2, 1, 4 overlap the leading portion of the succeeding arrays-l, 4, 3 when looking from left to right in Figure 2 along the X direction.
As will be understood, the length of the individual arrays 1, 2, 3, 4 may vary with different types of arrays and ~ro~
manufacturer to manufacturer. As a result~ tne number of arrays required to cover the entire width of the original document 12 may vary from that illustrated herein.
Photosensitive elements or pixels 40 of arrays 1, 2, ~, 4 are normally silicon with carrier detection by means of photo-transistors, photodiode-.~OS amplifiers, or CCD detection cir-cuits. One suiLable array is the fairchild CCD 121 - 1728 pixel

2-phase linear array manuractured by Fairchild Corporation. Aa described, arrays 1, 2, 3, 4 are offset from one another in the scanning or sagittal direction (Y direction) but with an end ~or-tion of each array overlapping the leading portion of the ne~t -~-~t ~ L~3~Z;24'~
succeeding array to form in efec~ a composite unbroken arr~.
To focus the image onto the arrays 1, 2, 3, 4 a lens }3 is provided for each array. Lenses 43 are supported on carriage 20 in operative dis~osition with the array 1, 2, 3, 4 associatQd therewith. .~irrors 44, 45 on carriage 20 transmit the lignt images of the original via lenses 43 to arra~s 1, 2, 3, 4. Lam?
48 is provided for illuminating the original document 1~ m~ ~8 being suitably supported on carriage 20. Re~lector 49 focuses the light emitted by lamp 48 onto the surface oE platen 16 and the original document 12 res~ing thereon.
In operation, an original document 12 to ~e scanned is disposed on platen 16. The scanning mechanism 18 includins motor 28 is actuated, motor 28 when energized operating driving mecha-nism 24 to move carriage 20 back and forth below platen 16. Lamp 48 is energized during the scanning cycle to illuminate the orig-inal document 12.
To correlate move.~ent of carriage 20 with operation of arrays 1, 2, 3, 4 an encoder 6a is provided. Encoder 60 generates timing pulses proportional to the velocity of scanning mechanism 18 in the Y direction. Encoder 60 ncludes a timing bar 61 having a succession of spaced apertures 62 therethrough disposed along one side of the path of movement of carriage 20 in parallel ~ith tbe direction of movement of carriage 20. A suitable signal generator in the form of a photocell-lamp com~ination 64, 65 is provided on carriage 20 o~ scanning mechanism 18 with timing bar 61 disposed therebetween.
As carri~ge 20 of scanning mechanism 18 traverses ~ac'c and forth to scan platen 16 and any document 12 thereon, photo-cell-lamp pair 64, 65 of encoder 60 moves therewith. ~ovement of the photocell-lamp pair 64, 65 past timing bar 61 generates a ~L3~
pulse-lice output sisnal in output lead 66 of photocell 6 directly propor~ion21 to the velocity of scanning mechanism 18.
As can be envisioned by those skilled in the art, su~-porting arrays 1, 2, 3, 4 in e~act linear or tangential align~ t (alons the X-axis) and maintaining such alignment throughout .he operating life or the scanning apparatus is extremely difriculL
and somewha~ impracticablQ. To obviate this difficulty, arrays 1, 2, 3, 4 are initially mounted on carriage 20 in substantial tangential alignment~ As can be seen in the exemplary showing of Figure 2, this nevertheless often resul~s in tangential array misalignment along the x-axis. If the disposition of the arrays 1, ~, 3, 4 is com~ared to a predetermined reference, such as the start of scan line 101 in Figure 2, it can be seen that each arrav 1, 2, 3, 4 is displaced or offset from line 101 by some ofrset dis~ance dl, d2, d3, d4, respectively. As will appear 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 (Figure 3) associated with each array. Offset counters 120 serve, at the start of the scanning cycle, to del~y activation of the array associated therewith until the interv~l dl, d~, ~3, d4, therefor is taken up.
Referring to Figure 3, the pulse-like signal output of encoder 60 which is generated in response to movement of carriage in the scanning direction (Y-direction), is inputted to a phas-e locked frequency multiplier network 100. Network 100, which ls conventional, serves to ~ultiply the relatively low fre-quency ~ulse-like signal input of encoder ~0 to a hish frequency clock sisnal in output lead 103. Feedback loop 104 of network 100 serves to phase lock the frequency of the signal in lead 103 with the frequency of the signal input from encoder 60.

~,

3~7l2 As will be understood, changes in th~ rate of scan o~
carriage 20 produce a corresponding ch.ange in the frequenc~ of the ~ulse-like signal generated by encoder 50. The frequency of the clock signal produced by network l00 undergoes a correspond-ing change. This results in a hish frequency clock signal in output lead 103 directly related to the scanning ~elocity of car-riage 20, and which accommodatès variations in that velocity .
The clock signal in out:put lead 103 is inputted to pro-grammable multiple~er 106. The output of a second or alternate clock signal source such as crystal controlled clock 108 7' S
inputted via lead 109 to multiplexer 106. Multiplexer l~o selects either network 100 or clock 108 as the cLock signal source in response to control instructions (CLOCX SELECT) from a suitable programmer (not shown). The selected clock signal appears in output lead 111 of multiplexer 106.
An operating circuit 114 is provided for each array 1, 2, 3, 4. Since the circuits 114 are the same for each arrav, the circuit 114 for array 1 only is described in detail. It is under-stood that the number of circuits 114 is equal to the number of arrays used.
Operating circuit 114 includes a line transfer 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 106. It is understood that where the signal nput to counter 115 comprises the clock signal pro-duced by network 100, array sample size remains constant irres-pective of va~iations in the velocity of carriage 20. In other words, where carriage 20 slows down, array shutter time beccmes longer~ If carriage 20 speeds up, array shutter time ~ecomes shorter.

`~F"`~' '' Initial actuation of line transfer counter 115 _s con-trolled by the orfset counter 120 associated therewit:n. ~ffset counter 120, which is driven by the clock signal in output load 111, is preset to toll a count representing ~he tim-e interia' required ror array 1 to reach start of scan line 101 follo~ing start up or carriage 20. On tolling the ~reset count, offset counter 120 generates a signal in lead 122 enabling line transfer counter 115.
It will be understooa tnat the ofrset counters 115 associated with the circuits 114 for the remaining arrays 2, 3, 4 are similarly preset to a co~nt representing the distance d2, d3, d4, respectively by which arrays 2, 3, 4 are ofrset from start of scan line 101.
Referring particularly to Figure 2 each array 1, 2, 3,

4 scans a portion of each line of the original document 12, the sum total of the data (less overlap as will appear more fully herein) produced by arrays 1, 2, 3, 4 represe~ting the entixe line. Preferably, arrays 1, ~, 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 preset to activate the array associated therewith ~or a preselected period for this pur-pose. Scanned data from the arrays 1, 2, 3, 4 is clocked out by cloc~ signals derlved 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 representati~e of pixel image intensity.
The binary pi~el data from processor 148 is mapped into segments or words by Pixel Data Bit Mapper 149 for s.orage in offset rela-tion in RAM 17S 25 will appear. Bit Mapper 149 is driven by clock t --10 --3z2~æ
signals from pixel clock 118. Data Erom Bit L~apper 1~9 is passed via data bus 174 to R~ 175 where the data is temporarily stored pending recei?t of data from the array which last views the line.
In the exemplary arransement illustrated, the last array ~ould be array ~.
Multiplexer 1;0 may be provided in data bus 17~ to per-mit data from other sources (OT~ER DATA) to be inputted to R~
175.
The binary data is stored in sequential addresses in RAM 175 (see Figure 4), the data being addressed into RAM ~7~ on a line by line basis by the R~ address pointers 1~5 through Address Bus 180. The clock sisnal output from pixel clock 118 is used to drive address pointers 165. Line scan ccunter 170, which is driven by the output from line transfer counter 115, controls the number of full scan lines that will be stored in R~ 175 before recycling. The output of counter 170 is fed to R~M Address pointer 165 via lead 119. It is understood that line scan cou~-ters 170 are individually preset to re1ect the degree of array offset in the Y-direction.
~ am 175 provides a ~uffer or scanned data from each array, RAM 175 buffering the data until a full line is completed following 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 oorts for input and output of data thereto.
Since the degree of ~isalignment of arrays 1, 2, 3, 4 in the Y-direction may vary, ~he storage capacity of R~ 175 must be sufficient to accommodate the maximum misalignment anticipated. A worst case misalignment is illustrated in ~igure ~.., ~3ZZ~;~
4 wherein it is pres~med that arrays 1, 2, 3, 4 are ea~ r~
aligned by a full llne. In that circumstance and 2resumir.s scan-ning of line 1 is completed, R~`~1 175 then stores the line da.a for lines 1, 11, 12, 13, 14 from array 1, lines 1, 11, 12, 13 from array 2, lines 1, 11, 12 from array 3, and lines 1, 11 from array 4. The bloc~s of binarv data that comprise the completed line 1 are in condition .o be read out or R~l 175. In the a~ove example, an extra line of data storage is provided.
Line scan counters 170 are recycling counters which are individually preset for the number of lines of data to be stored 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 si~nal from counters 17C
recycle the address pointer 165 associated therewith back to the first storage line to repeat the process. It is understood th~t prior thereto, that portion of RAM 175 has been cleared of data.
A~ described, data from video ~rocessing hardware 148 is stored temporarily in R~ 175 pending completion of the line.
In placing the data in R~M 175, the data is preferably mapped in such a way ~s to avoid the need for subsequent data bit snifting when outputting the data. Referring to Figure 5, wherein mapping of pixel data from arrays 1, 2 ls illustrated, data from an earlier array (i.e. array 1) is mapped by Pixel Data Bit Mapper 149 (Figure 3) into segments 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.

~F' '- ''~ ' ~L13Z2 ~Z
This correlates the first overlaoping pixel (Pl - 2) of tne succeeding array (i.e. arra~ 2j with the first overla~ed pi~el (Pl - l) or the ~receding array (i.e. arra~ 1). Crossover rrom one array to the succeeding ar~ay on data readout may then be effected without the need to snif~ bits.
Referring now to Figures 6 and 7, ~ideo data held in R~ 175 is read out to a user (not sho-~n) via R~ output bu. 17~, in both tangentially and spatia:Lly corrected form, line by line, through output channel 200. Data readout is controlled by a microprocessor, herein CPU 204 in accordance with address program instructions in memory 206. CPU 204 may com2rise anv suitable commercially available processor such as a Model M6800 manufac-tured by Motorola, Inc.
The address program instructions in memory 206 include a descriptor list 207. List 207 contains information identifying the number of bits to be read out (Nn), the address oE the first word (A) t and other user information (U). The DATA OUT address information is fed to address multiplexer 208 via address bus 209.
As described heretofore, e~act tangential alignment and end to end abutment of multiple arrays is difficult to achieve.
In the arrangement shown, sagittal misalignment (in the Y
direction) among the arrays is accommodated by offset counters 120 of the individual array o~erating ci~cuits ll4. The need to accurately a~ut the arrays end to end is obviated by overlapping succeeding arrays.
As a result of the above, the sequence iR ~lhich video data is inputted to P~ 175 offsets sagittal misalisnments between the several arrays. By out~utting the data from R~ 175 on a line by line basis~ the llnes are reconstructed w-thout .

.~

. . , sagitt~l misalignment.
Due to the overlap~ing disposition of arrays l, 2, 3, 4, data within the overlapping portions of the arrays is redun-dant. To obviate this and provide.a complete line of data without repeated or redundant portions, blt crossover on readout ~ithin the overlap~ing regions is used.
Referring now to the embodiment shown in Figure 7, data bit crossover within the overlapping por~ions of arrays l, 2, 3, 4 is ef~ected by an algorithm which pick5 a predetermined last cell to be sampled within the overlapped region and automaticall-y picks the next bit in the succeeding array. In the descriptor list 207 illustrated in Figure 7, the total bit output from the ~ s first array is Nl -byte_ ~ nl bits with the bit outp~t ~rom the second array N2 ~ ~ n2 bits. In the example shown in Figure 7, crossover from array 2 to array l is effected between bit 4 and bit 5.
In the arrangement described heretofore, tne center to-center dist~ance between successive photosens1tive elements or pixels 40 lS constant. Referring to Figure 8, wherein like numerals~refer to the like parts a pair of arrays 300, 301 are there shown with the end portions overlapped. The photosensitive elements or~ pixels 40~that comprise arrays 300, 30l, except for the end 308 of array 300, are on normal center-to-center dis-tances d. The~photosensitive elements 40' in the end 308 of arra~, 300 are set on~a slightly reduced center-to-center distance d'.
The reduction in center-to-cen~te~r distances between the photosen-sitive elements 40' iin end 3C8 or array 300 provide in e~fect a :;
~ vernier scale which normally~provides at least one polnt where :: , ~ . .
; ~ opposing arrays are in alisnment irrespective of the degree of :
overla~ between the arrays. In the exemplary a~rrangement shown, :
:
.:

~,~322 ~2 the end of photosensitive element 40 - 8 of array 301 is in sub~
stantial alisnment with the start of photosensitive element ~0' -

5 of array 300, and crossover ~ould be set at this poinL.
- It will be understood tha. visual identi~ica~ion o. t:~e individual ~hotosensitive elements or pixels 40, 40' to deter~ine the o~ti~lm crossover point may ~e made through microscopic e:~a.~-ination of the arrays. It is further understood tnat once the optimum crossover point is determined, the descriptor list o~
memory 206 (Figures 6, 7) is programmed to provide crossover from pixels 40 - 8 of array 301 to pixel 40' - 5 of array 300 on readout.
WhiLe the vernier scal~ is illustrated a~s being at one end 308 of array 300 only, it is understood that vernier scales may be provided at both ends of the array. In that event, in a scanning arrangement employing four arrays such as shown in Figure 2, array 1 may have a vernier scale of the type des~ribed at eac~ end, array 3 a vernier scale at one end only, with remain-.
.
~ ~ ing arrays 2, 4 conventional.
:
While the vernier scale described is established byreduclng~center-to-center dlstances~between adjoining ~pixels, it is understood that a ~ernier scale may be created by increasing sligh~tly~ the center-to-center distances betwaen adjoining arr~ay pixels. ~ ~
Re~ferri~s to the~e~bodi~ent shown in Fisure 9, there a 2air of relatively long linear arrays 350, 3;1 are disposed end to. end. This may be effected o~tically as by means of lenses ~3 in the scanning apparatus lO of FIsure 1 or mechanically through , physical contact of the array enda with one ~nother.~ To accom-modate any gaps between the array ends or misalignments along the :: :
X axis and to~assure continuitv of the composite array so ormed, ' ' :

~32Z42 a relativel~ short bridging array 360 is provided to overlap the adjoining ends of each arra~ 350, 351.
Bridging array 3~0 comprises a relatively short linear array, preferably with the minimum quantity of pixels 40 needed to provide effective overlap of the adjoining arrays. Typically, bridging array 360 may be comprised of the order of 100 pixels whereas arrays 350, 351 comprise some 1700 pi~els.
In use, data from arrays 350, 351, 360 may be readout as described earlier, the data being stored temporarily in R~M
175 (Pigure 3) pending completion of the line. By chQosing rela-tively short bridging arrays 360, the amount of data to be stored in RAM 175 and hence the size of R~M 17S ~ay be substantially reduced. The data held ln RAM 175 is, on completion of the line, read out from R~ 175 into bus 176 (Figure 6), with crossover made from array 350 to brldging array 3O0 and thereafter from bridging array 360 to~array 351 in the overlapping areas to assure contin-uity.
Referring to the embodiment shown in Figure 10, where e numerals refer to like parts, an array structure 400 is thereshown. Array structure 400 includes relatively lon~ and short~ arrays 402, 404~respectively mounted upon a common sub-.~ .
st~ate OE ~mas~ 406. Array 404 is disposed ln parallel w-l~h array 402, with~a~portion 409~of array 404 overlapplng one end 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 nex~t successive array structure 400' as seen in dr~awing Figure 10. To , ~
~ accommodate overlapping~of successive array~ strUctures 400, sub-; strate 406 is inset at 407.
:: . :

~ To enhance aligr.ment ~etween th~e ar~rays and provide :
undistorted cr~ossover between arrays, ~ho~tose~nsitive elements or .
. .

32.''2~2 pixels 40' of array 404 are disposed on a center-to-center distance d' different from the center-to-center distance d of pixels 40 of array 402. This in effect establishes a vernier scale which enables at least one pixel 40' of array 404 to be aligned with a corresponding pixel 40 of array 402. In the exemplary arrangement shown, pixel 40 - 5 of array 402 is in substantial align-ment 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 point of closest pixel alignment. In the embodiment shown, crossover would be between pixel 40-' - 7 of arxay 404 and pixel 40 ~ 3 of array 402.
While the center-to-center distance d' between pixels 40' of array 404 is illustrated as being less than thè center-to-center distance d between the pixels 40 of array 402, it is understood that dimension d' may zo be greater than`dimension d.
While the invention has been described with reference to the structure disclosed, it is not conined to the details set forth, but lS intended to cover such modifications or changes as may come wi-thin the scope of the following claims.
Reference is made to applicant's copending application SerLal ~o. 301,764 which claims an embodiment of an invention disclosed in the instant application.

~

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an apparatus for scanning an image, the combination of:
a. a movable scanning carriage;
b. at least two relatively long linear arrays on said carriage, said arrays being disposed in end to end relation-ship and extending in a direction substantially perpen-dicular to the direction of scanning movement of said carriage; and c. a relatively short linear bridging array on said carriage, said bridging array being disposed to overlap adjoining ends of said relatively long arrays whereby to form in cooperation with said relatively long arrays an uninter-rupted composite array for scanning said image.

2. The apparatus of claim 1 including memory means for storing data from said arrays pending readout, and data readout means for reading out data from said memory means, said data readout means on readout crossing from a first of said relatively long arrays to said bridging array and from said bridging array to the second of said relatively long arrays.

3. In a line scanning apparatus employing multiple arrays together forming a composite array having a length at least equal to the length of the line to be scanned, together with memory means to hold data from said arrays pending com-pletion of a line, the improvement comprising:
a composite array consisting of relatively long linear arrays disposed in end-to-end relationship with a relatively short bridging array disposed to overlap the ends of said relatively long arrays, said relatively short bridging arrays reducing the amount of data to be stored by said memory means.

4. An array for use with scanning apparatus of the type having a plurality of overlapping arrays which cooperate to form a composite array of substantial length, comprising .
a. an array support, b. means forming a first relatively long linear array on said support;
c. means forming a second relatively short linear array on said support, said second linear array being substan-tially parallel with said first array, said second linear array having a portion thereof overlaying one end of said first array with the remainder of said second linear array projecting beyond said first array one end.

5. The array according to claim 4 in which the center-to-center distance between photosensitive elements of said second array is different from the center-to-center distance between photosensitive elements of said first array whereby to facilitate crossover alignment of at least one photosensitive element in said second array with a photosensitive element in said first array.

6. The array according to claim 5 in which the center-to-center distance between photosensitive elements of said second array is less than the center-to-center distance between the photosensitive elements of said first array.

7. The array according to claim 5 in which the center-to-center distance between photosensitive elements of said second array is greater than the center-to-center distance between the photosensitive elements of said first array.