CA1044807A - Label sensor - Google Patents

Label sensor

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Publication number
CA1044807A
CA1044807A CA302,160A CA302160A CA1044807A CA 1044807 A CA1044807 A CA 1044807A CA 302160 A CA302160 A CA 302160A CA 1044807 A CA1044807 A CA 1044807A
Authority
CA
Canada
Prior art keywords
scan
information
camera
raster
output
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA302,160A
Other languages
French (fr)
Inventor
Ralph S. Cass
Vickram Sondhi
Anton R. Tyler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ferranti-Packard Ltd
Original Assignee
Ferranti-Packard Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US39355273 priority Critical patent/US3902047A/en
Priority to CA206,177A priority patent/CA1041666A/en
Application filed by Ferranti-Packard Ltd filed Critical Ferranti-Packard Ltd
Application granted granted Critical
Publication of CA1044807A publication Critical patent/CA1044807A/en
Application status is Expired legal-status Critical

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Abstract

A B S T R A C T
A surface containing encoded information bordered by bars where both the bars are the information contrast with a background is detected as to orientation and location and the information read by sampling the video scan output of a tele-vision camera which is designed to raster scan the image formed therein. The camera may be caused to scan with alternating rasters at an angle, preferably 90°, to one another while the orientation of the raster relative thereto is determined. The orientation of the raster scan may be rotated by electronic means, to provide the desired orientation of the raster relative to the information.

Description

~(J4~
This lnvention relates to means and a method for detecting by the use of a television camera, coded information on the surfaces of objects moving relative to the viewing axis of the television camera.
This application is a Divisional of Canadian Application Serial No. 206,177 filed August 2, 1974.
It is an objec'~ of this invention to provide means and a method utilizing a television camera to produce in the camera, an image of a surface carrying coded information, whose path is arranged to pass through the field of view of the camera, and to scan in a given direction the image of the object, to electronically rotate the scan to a more suitable angle, if necessary, and to analyze the video scan output signal resulting from such scan.
It is an object of this invention to provide means and a method utilizing a television camera to scan in a predetermined direction to detect coded information on a surface within its field of viewD wherein markings on said sur-face accompanying said coded information are detected to determine when the surface is within the field of view of said camera and to determine the orientation of the information relative to the scan direction.
It is an object of this invention to provide means and a method utilizing a television camera to detect said coded information on a ~urface within its field of view, wherein markings on said surface accompanying said coded information are detected to determine the orientation of said surface and determination o the scan results in electronic rotation of the television ~can to the extent necessary to achieve a more suitable angle for scanning the information.

Figure 1 show~ a schemati~ view of parcels bearing encoded labels in use with the television equipment;
Figure 2 shows a suggested label for use in aeeord with the invention;
Figures 3 and 4 show schematic views of the output signal of the television camera scan output during the deteetion of the presence of the label and the extraction of the information thereon;
Figure 5 shows the circuitry for deriving information from the television camera scan output information;
Figure 6 shows a television camera scanning raster;
Figure 6a shows a rotated raster;
Figure 7 shows a raster scanning method in aceord with the invention;
Figure B shows circuitry for rotating the raster;
Figure 9 (a) and 9 tb) show the horizontal and vertieal sean signals.
Although the invention eovers the extraetion of eoded information from the surfaee of an objeet moving relative to the extraetion means, the most eommon use of the invention is, at -this time, thought to be, the reading of labels, containing in- -formation such as destination and contents, in coded form on pareels. It will of course be realized that, as a result of the extraetion of sueh information, the pareels may be automatieally sorted and routed, and inventory and shipping reeords automatieally eompiled.
A label suitable for use with the preferred embodiment of the invention is ~hawn in Figure 2.
~he label as sh~wn provides information defining areas ~0 10 ~ordered on two opposite sides by thiek parallel orientation -- 2 ~

stripes 12, also known herein as location marks between which the information is arranged so that it may be scanned perpendi-cular to the parallel lines. In order that ordinary languaye text may appear on the surface (as shown) without causing confusion with the coded information, the two stripes 12 are preferably made a color other than black or dark blue (the preferred color for any plain language) and the stripes 12 of a selected lighter color (say red) will contrast with any plain language writing for the reader. Although provision is thus made for the writing of plain language, if desired, the reading of such pla n language forms no part of this invention. When the encoded information is to be scanned, the surface is illuminated with a color (here green or cyan) complementary to the bar coloring, so that the bars, as well as the encoded information, appear dark in contrast to the background (and hence render the plain language invisible to the TV camera). The method of decoding the information involves detecting the contrast between the coded information and the background. Since the scan will include not only the label but a portion of the surface on which the label is placed and a portion of the conveyor, these portions will preferably contrast with the marks.
However, the logic circuitry for detection of the information on the label will achieve such detection in almost all cases whether or not such surface and conveyor contrast with the marks.
If desired, for any reason, and noting the comments regarding the parcel and conveyor, it will be appreciated that the surface, coding and illumination could be selected, so that the back-ground ix dark and the encoded information light. The information, preferably in binary form, i~ conveyed by bars 10 present or not ?~ i~ a specific location, here in columns separated by the dimensions hl) ~
SC and r~ws by the dimensions SR. l~e red coloured bars may be replaced by black in applications where no plain language need appear. The terminology 'row' and 'column' is selected in relation to the scan of the image of the label in the television camera, which will take place (if the label is arranged within the required angular tolerance) with individual scan lines transverse to the location bars in Figure 2 with successive scan lines successively displaced from left to right or from right to left in the figure.
In the label shown, a binary code is shown, wherein rows of locations in pairs, disposed from one anothertransversely relative to the longitudinal extension direction of the bars, i.e. such as 10 and 14, either have an information bar in one location or an information bar in the other, except in the start locations lOS, where two bars appear. Thus a simple parity check is provided at all locations but the start position. If, in normal coding position, rows (extending vertically in Figure 2) having two marks (other than in the start position) or having no marks, then in accord with well known techniques an error in encoding may be detected~ Although only 14 coding position (plus the start positions) are sh~wn, this is for ease of illustration.
It will be obvious that any number of coding positions may be provided, limited only by the size of the label. Further, although only one data and one data parity column are shown, it will be obvious that as many data columns as desired may be used (preferably combined with a data parity line) limited only by the width of the label. The rectangular shape of the bars selected is not essential but is preferable in view of the rectilinear nature of the television scan detection means, and also demonstrates fO that the label information may be physically produced by a standard lO~h~J ~' bar printer, printiny the ~utput of a computer.
Figure 1 shows a conveyor 16 with a series of packages thereon, and it will be noted that these are arranged at random with regard to the orientation of the stripes 12 relative to the viewing of the camera 18 to be described here-after. (In certain instances, two camera will be used, focussed on the same or on adjacent areas of the conveyor path). While the patent application 206,177 filed August 2, 1974 dealt with reading only labels oriented within predetermined angular limits about the viewing axis, this application discloses means whereby labels oriented up to 360 about the viewing æ is may be read. Herein, as in the previous application, (limits de-signed for practical purposes of simplicity of logic design) are set on the angles of pitch and roll of the label (deviations of the label from a plane perpendicular to the viewing axis about axes respectively perpendicular and parallel to the travel direction of the conveyor). Suitable limits in this regard are +15 for pitch and +30 for roll.
A television camera 18 is arranged to have a viewing area on the conveyor indicated by the dotted area 20 and a viewing axis preferably perpendicular to the plane of the conveyor.
For simplicity the television camera 18 is shown as vertically disposed over the horizontal conveyor with its viewing axis disposed vertically theretowards. HoweverO it will in practice often be found more convenient to locate a 45 mirror over the conveyor to direct the vertical rays from the label and conveyor at a 90 angle to a horizontally disposed camera. In any event, the camera is disposed so that the direction of its scan lines may be measured relative to a datum which bears a predetermined ~0 relation~hip to the conveyor travel direction.

10~
The camera in accord with the invention will be designed to scan in the conventional raster pattern as indicated in Figure 6. Figure 6 is, as will be appreciated, simplified for illustration purposes as there might be something of the order of 262 lines in each field. (Typicalcameras will provide interlaced scanning with two fields comprising a complete frame).
In this invention however, the scanning does not provide the basis for a picture but the results of scanning are analyzed from the video output signal. Accordingly, if the camera used in the processes of the invention uses interlaced scanning, each field may be considered as a separate unit.
In discussing the orientation of the raster, its direction (indicated by the vector R in figure 6 and perpendicular rasters by the vectors Rl, R2 in Figure 7) will arbitrarily be assigned as the direction of the trace lines of the scan, i.e.
those which are sensed as distinct from the retrace lines which are blanked out in the scan output signal.
It is one of the principal features of the invention herein described, that the scanning raster of the television camera may be rotated to scan randomly oriented coded information at a consistent angle.
Although the means for detecting the random angle which the coded information assumes in the camera image will be des-cribed hereafter, the means and method for rotating the tele-vision scan will now be discussed.
The scan as shown in Figure 6 results as is well known - from conventional TV camera design from the combination of a saw tooth signal H for controlling (in conventional cameras) the horizontal deflection (~uch signal being commonly known as the horizontal sweep) of the scanning beam with a saw tooth vertical .. . .. .. .

lO~'~h~ ~
signal. The riyhtward rising portion of the horizontal signal H (Figure 9a) corresponds to the scanning trace when the camera image scanned thereby is reproduced in the video scan output signal.
The rightward, sharply falling portion of the saw tooth (Figure 9a) represents the retrace position (dotted in Figure 6) which is blacked out in the television scan output signal.
Although the vertical deflection signal V is also a saw tooth, it represents, during a single field, a signal, uniformly increasing with time and is so portrayed on Figure 9~b).
The deflection forces controlling the direction of the scan during the duration of a single scan line are therefore a horizontal vector H uniformly increasing with time and the vertical vector V uniformly increasing with time and producing the resultant vector R, which also represents the raster direction of Figure 6~
The signals represented by the vectors H and V are provided by the circuitry of the television camera referred to as Horizontal Sweep and Vertical Sweep signals respectively are conventially supplied to the Horizontal and Vertical, respectively, deflection circuits. These connections are altered at least part of the time, in accord with the invention.
Most elements and circuitry of the television camera are not disclosed or discussed herein as these are well known and conventional.
It may be shown that the rotation of the resultant R
or the ra~ter through an angle ~ may be achieved by applying in lieu of the horizontal and vertical sw~ep signals, the signals H' = H cos e + KlV sin e V' = V cos e + K2H sin e ~ Jl' where H is the horizontal sweep signal supplied by the conventional camera circuitry.
V is the vertical sweep signal supplied by the conventional camera circuitry.
H' and V' are the modified signals supplied for actuation of the Horizontal and Vertical deflection circuitry respectively.
e is the absolute value of the raster or resultant rotation angle.
The upper value for the sign of the second term, in each case represents counterclockwise rotation, while the lower value in each case, represents clockwise rotation. (It will be obvious that the conventions could be altered by having +e represent counterclockwise rotation and -e clockwise and using only the upper of the two signs in each case -- hawever the convention set out in the equations above, represents more closely the preferred circuitry which requires selectively applied inverters to represent the change of sign.
As stated, the method of detecting the angle of the information pattern to the scan will now be described.
In Figure 8, about to be discussed the horizontal and vertical deflection circuits may involve more cOmpGnents than those shown. Such components are well known (in each case usually include an amplifier) and are here represented in block form.
As shown in Figure 8 the Horizontal sweep signal, instead of being directly applied to the Horizontal deflection circuitry as in conventional circuits is applied to multiplier Ml and to Line Ll. The signal on line Ll, by means of a two position switch i~ alternatively connectible through an invertor 12 or directly to a mwltiplier M~. Multiplication at multiplier Ml is by cos e and M4 by sin e.
The vertical sweep signal is applied to the input of multiplier M3 and to line L2. The signal on line L2, by means of a two-position switch is alternatively connectible through an invertor 11 or directly to a multiplier M2. Multiplication at multiplier M3 is by cos ~ and at multiplier M2 by sin e.
The switches to determine each of the invertors -direct line choices are shown as ganged and for counterclockwise o e will be in the upper position.
Although these switches are shown schematically, the switches will preferably be of the electronic, solid state type in order to provide rapid switching action.
The output of multipliers Ml and M2 is added at adder Al and the summed output supplied to the horizontal deflection.
The output of multipliers M3 and M4 is added at adder A2 and the summed output supplied to the vertical deflection circuit.
The above described circuitry is effective to produce the desired scan rotation through an angle e if the wiring of the horizontal and vertical deflection means, and the horizontal and vertical sweep signals are such that (a) the horizontal sweep signal causes equal vertical deflection when applied either to the vertical or horizontal deflection circuits and (b) if the vertical sweep signal likewise has the same deflection effect whether applied to the vertical or the horizontal deflection circuit.
It will be obvious rom the circuit, that in this event, the output of the adder ~1 to the horizontal deflection circuit will be H cos e + v sin e and the output of the adder ~2 to the vertical deflection circuit will be V cos e + H sin e, _ 9 _ o ~
the upper and lower signs in each term representiny the upper and lower positions respectively of the ganged switches and counterclockwise and clockwise respectively.
It will be noted that most cameras are not equivalently designed in their horizontal and vertical deflection circuits, i.e. a signal having a given deflection effect when applied to the horizontal deflection circuit would have a different deflection effect when applied to the vertical deflection circuit.
Since the relationship between deflection and signal amplitude would be linear in each case the difference may be compensated for by increasing or decreasing the signal by a constant.
Reference is now made to the dotted boxes M5 and M6 in Figure 8.
These represent multipliers by Kl and K2 respectively. Thus K2 represents the constant by which the horizontal sweep signal H
must be multiplied to produce the equivalent vertical deflection to the horizontal deflection it conventionally would have caused, while Kl, conversely, represents the constant by which the vertical sweep signal V must be multiplied to produce the equivalent horizontal deflection to the vertical deflection it conventionally would have caused. The vertical arrow to each multiplier M2 and M6 represents the terminal at which the indicated multiplying factor is applied.
Thus with the multipliers M5, M6 in the circuit the equation becomes :
Signal to Horizontal Deflection Circuit H C08 e - Kl V sin e Signal to Vertical Deflection Circuit v co~ e + K2 H sin e The re~ult is rotation of the raster counterclockwise ~0 for the upper ~ign~ in the term~ and clockwise for the lower signs b()~;' through an anyle e.
This is the situation with the preferred form of camera (the vidicon) for use with the invention. However, it has been found convenient and is the preferred method to use a vidicon camera built to provide equal deflection effects in response to vertical or horizontal signals. In this event of course Kl and K2 become 1 and the multipliers M5 and M6 need not be used in the circuit. The preferred circuit therefore does not use M5 and M6.
In general any television camera may be used although the equal deflection vidicon is preferred. If intermittent illumination of the camera is used the camera must of course be of the type to retain the image from the time of illumination to the time of scanning.
In the operation of this part of the circuit therefore, labels randomly disposed are preferably initially scanned in the normal orientation, thus e is zero degrees and the factors applied to the multipliers are cos e = 1 and sin e = 0 and the Horizontal and Vertical sweep signals are H and V as if the novel circuitry were not included. When, as discussed hereinafter the orientation of the pattern is determined and hence the necessary rotation e of the raster in order to scan it the multipliers are then actuated to cause multiplication by the amounts cos e and sin e as indicated. The invertors are also switched to create the desired sign for rotation in the proper sense.
Although little has been said about the flyback or retrace o~ the horizontal and the vertical saw tooth scan, the actuation to cause rotation of the raster also causes rotation of horizontal and vertical retrace in the right direction and of the right aTnount.

~V'~h~ ~
Raster rotations of ~reater than ~0 caus~ complications in the logic required for switching and in fact logic and control requirements are simpler if raster rotations are maintained at less than 45. An information pattern is used so that the information direction is known, so that it may, in fact, be scanned in either direction. As will be appreciated, being able to scan from either direction reduces the maximum rotation e to not more than 90~. The maximum rotation e may be reduced to not more than 45 by initially scanning the label with two rasters at 90 to each other, as indicated in Figure 7. The raster may then be selected which is at less than 45 (or one of the rasters at 45 if the information scanning direction is located at exactly 45 to each raster) and rotated through the angle e with required sense to allow scanning of the information, again as hereinafter discussed.
The provision of two scans at 90 to each other, may be achieved either by providing two cameras each initially scanning at 90 to the other. The angle of each raster to the pattern is then detected, as hereinafter discussed, and the raster requiring the smaller amount of rotation is rotated to align the raster with the desired pattern scanning direction.
As an alternative to the provision of two cameras, a single camera may be used to scan alternately in rasters at 90 to each other using the circuitry of Figure 8. Thus on alternate scans e is made O whereby the signals ~ and V are applied to the horizontal and vertical deflection amplifiers respectively (cos e -sin e = o) as previously noted. On the other alternate scans e is made 90~ so that cos e = O sin e = 1 and the signal H is applied to the vertical deflection plates while V is applied to the hori-?~ zontal deflection plates This effects a rotation of the raster lO~h~l ,' through g0. It will be appreciated that control of the invertor may be used to determine the sense of the 90 anyle between the scans. If the labels may be oriented at any angle in a 360 range and read in either direction the sense of the 90 angle will not be of major importance. With the rasters scanning alternatelyO the orientation of the pattern to each raster is detected, as hereinafter described and a raster requiring 45 or less rotation is then rotated, in accord with the operation of the circuitry of Figure 8.
In preference to alternating rotation of the scan signals through alternation of the sine e and cose e multipliers, however, it is preferred to achieve the initial 90 rotations by leaving the value of ~ in the circuit of Figure 8 at O and alternately interchanging the signals applied to the horizontal and vertical sweep terminals with suitable alteration in saw tooth frequency and scale.
Although the circuitry of Figure 8 modifying the conventionally supplied horizontal and vertical sweep signals, is the preferred method of rotating the scan, it will be under-stood that the generation of the necessary signals for the rotatedscan may instead (and within the scope of the invention) be generated within the means for producing the horizontal and vertical sweep signals themselves, by techniques of signal pro-duction and shaping well kn~wn to those skilled in the art.
On the basis of the discussion it will be noted that following the directions of the preferred embodiment without further modification, not only will the scan of the type indicated in Figure 6 be rotated, but the rectangular raster shape will also be rotated. It may be desired to rotate the scan while leaving the #hape of the pattern unchanged, i.e. a rotation of 90 of the pattern of ~igure 6 might be desired, while leaviny the over-all raster rectanyle or 'envelope' oriented as before.
In this event it will be obvious that the trace and retrace lines must be shorter in travel but greater in number as illustrated in Figure 6a to produce the raster direction Rl with the same line density while the vertical signal will have to be increased in slope to produce the same line spacing. Modifications of the signal to produce rotations of the raster scan of less (or more) than 90 while leaving the envelope oriented as before are more complex but well within well known techniques of those skilled in the art. This is in addition to the pre-ferred scan rotation techniques shown and the alternative techniques discussed it will be understood that modification of the horizontal and vertical sweep signals either within the circuitry shown or without is within the scope of the invention.
In general the value H and V of the horizontal and vertical sweep signals may be altered between their values before and after scan rotation to produce such dimensional changes in raster dimensions and raster line density as are required.
Such changes will therefore take place at approximately the time of rotation of the scan. Thus H and V are not necessarily constant quantities where circuitry such as that of Figure 8 is used but may bear different values before and after rotation.
In accord with preferred embodiment of the invention, the viewing area of the camera or cameras 18 on the conveyor, is intermittently illuminated by a strobe light 26 (i.e. light which may be turned on for a short controlled period and then turned o). In order to allow the use of the red strip 12 as ~riting locations but to have the~e strips contra~t with the back-ground, the label i~ illuminated with green light so that the l~J~ J~jS
black marks lO and the red marks 12 both give su~icient contrast to the camera. It will be appreciated, for the purpose of decoding-the information, that although it i5 more convenient to have the information marks within the standard range of color of a bar printer, it is possible in general, for both the information and the location marks, to use any color, which in the illumination provided will contrast with the background of the label.
The television camera, as is well known, scans the image formed therein, to provide an electrical current output (known herein as a 'video scan output signal' or a 'scan output signal') wherein dark and light areas scanned in each line produce signals of high and low amplitude. (If desired, equally available within the known techniques in the art and equally useful within the scope of the invention, the video scan output may be provided, for processing by the invention herein des-cribed, in the form of a larger amplitude signal for the bright areas scanned and smaller for the dark). As is well known, the scanning progresses line by line down a field with the video scan portraying the scanned results of each trace line serially from the top to the bottom of the field with the scan signals for each line separated by the retrace which does not appear in the scan output and is comtemporaneous with the line synchroni-zation pulses, and so on from one field to the next, with the fields separated by synchronization pulses known as 'frame sync pulses'. As is well known, the television camera conventionally scans, in one field every second line of those required to completely scan the image, and then scans the omitted lines in the next field. However, for the purposes of the invention, each field may be considered as a complete scan of the image, separated by frame ~ynchron~zation pulses.

lO ~ 3~
The detection of information received through the line by line scan of a moving image or label places limitations on how close the information marks may be placed and/or how fast the label may travel, since the label may travel a material distance during the scanning of a single frame and will cause ; ambiguity in information marks too closely spaced, having regard to the speed of the conveyor. Therefore it is preferred to limit the illumination entering the camera to produce the image, to a short enough interval that the moving information marks cannot move sufficiently, or be sufficiently blurred, to be ambiguous. The most suitable timing for such illumination to occur, is during the frame sync pulse and the interval of said illumination is therefore made the approximate interval of such pulqe. It will be appreciated however, that the length and occurrence of the short-time illumination may be varied to suit specific situations and that, once the scan has located the location marks in the desired position for scanning the information, the short-time illumination (here sometimes referred to as 'strobing') takes place at a time relative to the frame scan, so that the information may be completely scanned between such strobing.
Thus although the invention applies to the use of a television camera with deflection and interpretation equipment as described, with continuous illumination during the location of the pattern and the reading of the information, it is highly preferable to use strobed illumination for the reading of the information and preferable in most applications to use strobed illumination at all times.
In the logic circuitry reference is made to A~D and OR gates~ It is assumed however, that for each of such logical elements, the counterpart inverse loyical element may be substituted with due attention to the sense of the input and output signals required for each stage. Thus where an AND
gate is referred to, the gate is of the type where enabling signals of the same sense are required at all inputs simultaneously to provide an output of predetermined sense, the outputs at all other times being of the other senses.
Further, where an OR gate is referred to, the gate is of the type where an enabling signal of predetermined sense is only required at at least one 2nput to provide an output of pre-determined sense, and provides the opposite sense only when no enabling signal occurs at any of its inputs. Thus by an AND gate, I include a NAND gate which may be considered a~ an AND gate with an inverted output, and by an OR gate, I include a NOR gate which may be considered as an OR gate with an inverted output. In general the application does not discuss the relationship between the sense of the output signals of one stage and the required input to the following stage, it being realized that it is elementary to those skilled in the art of logic circuitry that such senses are obviously known and controllable; and that where the sense at the output of one stage is the opposite from that required at the next stage, the necessary inversion may easily be accomplished between stages.
The video scan output signal of the television camera (shown in Figure 3 (b)) derived from 'scan A' of Figure 3(a) is provided to an analogue-to-digital convertor for the signal. The convertor is designed to discriminate bet~1een levels in the video scan output signal above and below a predetermined value. The predetermined value is selected 10~
to be between the level correspondiny to the scan output from scanning in the illumination provided, a location or information mark, on the one hand and the level corresponding to the scan output from scanning the background on the other hand. The discriminator is designed to provide an output which has one of two levels, as shown (Figure 3(c)) wherein the two' levels respectively correspond to video scan output signals above and below the predetermined level and the Figure 3(c) level is switched, depending on the crossings of its analogue input with the predetermined level. The output of the convertor 1 at gate "D" where the 'dark' or information signals are of high value and the low or background signals are of low value is applied as one of the inputs to AND gate 4. The convertor is so designed that a signal which is the inverse output to that of Figure 3(c) is developed at output 'I' of the convertor and applied to AND gates 2 and 3, along lines 42 and 44.
A Clock 46 is provided to achieve synchronism in the logic circuit. ~he clock 46 must pulse at a rate relative to the television scan rate, and to the dimensions of the in-formation and location bars so that by sampling the signal ofFigure 3(c) at the leading edge of each clock pulse meaningful results may be obtained evidencing the spatial relationship between the location bars and the background, and also between the information marks and the background. Since the scan rate is regular and punctuated by line and frame sync pulses, the number of clock pulses occurring between the start of a line or other position on the scan line or scan line output and a spaced location on the same scan line is a measure of distance along a scan line and a definite width (which it is convenient to reer to as a 'pulse width') defines the distance travelled ~(3~ 3~

by the scan during the period of the clock pulse, ~ere, as in the method described, the video scan output is sampled at the frequency of the clock pulse, it will be obvious that for the ac~urate extration of information, the length of a 'pulse-width' must be short relative to the dimension in the scanning direction of the smallest marks to be determined, namely the information marks.
In practice, the number of pulse-widths (and this is of course directly related to location and information mark dimensions in the label design) is preferably 12 for each location bar and 24 in between. However, for ease of illust-ration in the drawings, only half the pulse frequency is shown, i.e. 6 clock pulses during the scanning of each location bar and 12 between and the specific embodiment is therefore described using the 6 and 12 clock pulse measures. The location marks or bars printed by a computer bar printer will have widths of approximately six pulse widths and a spacing of four pulse widths in between (three and two respectively in the example).
The rising (here leading) edge of the clock pulse indicated by transverse lines on the time base (Figure 3 (c) is used to open gate 4 to sample the output of convertor 1. The results of such sampling are shown in Figure 3(d). Shown immediately below in Figure 3 (c) is pulse output fromgate 3 resulting from the inverted output from gate 1 convertor 1 gated at gate 3 by the output of clock 46.
Por convenience of illustration the finite width of the clock pulBe iB not shown in the drawings. The clock pulse lines shown in E'igure 3 therefore represent the leading edge of the pulse while the negative clock pulse lines of Figure 4a correspond to the ~railing edge of the clock pulse and in the l~J~O~' preferred embodiment trail the clock pul~e by slightly more than 1/2 the pulse period~ The state of shift register 5 reflects the state of the inverse signal at gate 2, at ~ampling times occurring at the frequency of pulses from clock 46 but out of step therewith as hereinafter described.
Figure 3(a) shows a portion of the image formed inside the television camera, and scan lines A, B and C following portions of Figures 3 and 4 are derived from scan line A in accord with the normal scan of the camera, extending thereacross.
Figure 3 (b) shows the video scan output signal resulting from scan line A, television camera being conventionally but not necessarily designed to provide a high amplitude output signal for dark areas and low amplitude for light areas. The scan output signal is supplied along the line 01 to the analogue to digital convertor 1. The convertor 1 is designed, as previously explained, to discriminate between outputs along line 01 above and below a predetermined level and to provide a signal of one level when the magnitude is above the predetermined level and of another level when the magnitude is below the predetermined level. The predetermined level PL (Figure 3(b) is selected approximately midway between the magnitude of signal resulting from the dark information of location marks and the magnitude of the signal resultin~ from the bright background.
The output of the convertor at terminal D is then shown in Figure 3(c) as 'digitized video' and is provided along line 40 to AND gate 4. The analogue to digital convertor is also designed to provide at gate 1 an output which is the inverse of that shown in Figure 3 to AND gates 2 and 3.

The description of the use of the analogue to digital 3~ convertor in the circuitry of Figure 5 and the illustration of lU~
Figure 3(b) discuss an analogue to digital convertor wherein the video scan output signal is compared with the signal level PL to derive the signal of Figure 3(c) and its inverse. In applicant's co-pending application serial number 205,673 filed July 25l74, there are described methods of deriving the signal of Figure 3(c) from the signal itself. The operation of the circuitry of Figure 5 modified to include means of de-riving the graph of Figure 3 (c) from the signal itself are considered within the scope of the invention.
Gate 3 and 4 also have inputs from clock output 46 and are designed to provide an output pulse created by the leading edge of the clock pulse.
The output of A~D gate 4 (Figure 3(d)) is fed to counter 7 where the pulse output is counted. The inverse pulse output of Gate 3 delayed by a convenient fraction of the clock pulse period to avoid ambiguity with incremented additions to counter 7 is used to reset counter 7. (Figure 3(e) shows the gate 3 output without delay). Thus the counter 7 is designed and connected to count the number of each series of pulses appearing at the output of gate 4 corresponding to the scanning of a dark area and to be reset by the first pulse of a series from gate 3 indicating the beginning of a bright area scanned.
The values in counter 7 are provided to decoder 8 and the decoder 8 is connected to provide decoded outputs when the pulse counts in counter 7 correspond to the range of widths of a location bar 12 and within the acceptable height range (which height determines the bar width in the image). Thus with an expected width of 6 pulses for a location bar the decoder will be designed to produce output~ at counts between 5 and 8 inclusiveO When the counter 7 stand~ at any of these values decoder 8 provides lO'~h(~ ~
an output on one of the four (i.e. '5', '6', '7', '8') lines to OR gate 9, produciny at its output an enabling signal to AND
gate 10.
AND gate 10 is also enabled by a pulse from gate 3 (signalling the end of a dark period) along line 46 and from OR gate 16 when the counter 14 stands at O or '17' - '24'.
Since ~unter 14, as hereinafter explained, is only enabled to count after a location bar has been scanned, counter 14 is at O at the beginning of a scan line. Thus starting with scan line A, as the scan moves from left to right across the frame, gate 10 provides an output to counter 11, the first time during the scan of line counter 7 stands at a count of 5-8 at the end of a dark area.
Thus, in response to the scan crossing location bar (within the orientation range) or dark area of corresponding width, counter 11 counts 1 and activates the '1' output of decoder 12. While the decoder 12 output is '1', AND gate 13, enabled thereby, provides pulses resulting from the leading edge clock pulses from clock 46 to counter 14 alo~g line 48 as long as counter 11 stands at '1'.
The decoder 15 connected to counter 14 provides three types of output. Firstly, outputs corresponding to counter values of O and '17' to '24' are connected to OR gate 16 to provide an enabling signal to gate 10. When counter 14 stands at these values. The scan length represented by the pulse counts between 17 and 24 represents the sum of the pulse width spacing between the location bars (12-16) and the width 5-8 of the second-scanned location bar, both within the acceptable range of orientation. Secondly, decoder 15 outputs corresponding to 1 ~o 16 are provided to gate 17 whose output, in combination with gate 18, is d~siyned to enable inverted clock pulses (from clock 46 and inverted by invertor 35) to pasg through gate 18 when the count on counter 14 is 1-16 inclusive and to inhibit the passage of such pulses at other times. The inverted clock pulses are the pulses from clock 46 inverted at invertor 35 but remaining in synchronism therewith. Thirdly, output from decoder 15 corresponding to a value of 25 in counter 14 is used to provide a reset signal to the reset terminal 14R
of counter 14 and counter 11.
In operation then with the circuit as described this far, no signals are provided to the counter 14 until a dark area (see scan line A) is scanned. If a dark area smaller than 5 pulse widths or larger than 8 pulse widths is scanned, this is counted on counter 7 but the counter is reset by the first pulse after the commencement of the pulse of gate 3 at the commencement of a bright interval and no resultant output occurs at gate 10 since the pulse at gate 3 did not occur when counter 7 stood at 5, 6, 7 or 8. Since there is no output on the decoder 12 '1' output, counter 14 remains at O and through decoder 15 and OR
gate 17 disables gate 18 so that nothing is shifted into shift register 15, counter 14 at O also provides one of the three necessary enabling signals for gate 10.
This state continues until counter 7 has 'counted' a dark area of between 5 and 9 pulse widths at the time the first pulse from gate 3 signals the passage by the scan from a dark to a light area. Then all three inputs to gate 10 are enabled.
The counter 11 then counts '1' indicating that a location bar (or dar area of similar width) has been scanned. The counter 7 is of course reset after such total count of a dark area by the dela~ed reset pulse from gate 3.

As soon as counter 11, as descri~ed abo~e, reaches the count '1'. the output of decoder 12 enables gate 13 and the resulting clock pulses to pass through gate 13 to counter 14 and are counted therein from '1' upward causing the output of decoder 15 for counts from '1' - '16' to disable gate 10 through gate 16 until at least 17 is reached in counter 14 and to enable gate 18 through gate 17 for counts from 1-16.
For counts on counter 14 from '1' - '16' the inverted clock pulse actuates the shift register 5 on the rising (trailing) side of the inverted pulse and clocks the input (Figure 4(a)) thereto from gate 2 at intervals trailing the regular pulse output by the pulse width or approximately 1/2 the clock period. The shift register has 16 positions corres-ponding to the 16 pulse positions fed thereto during a line scan. The pattern of pulses produced from the output of gate 2 in shift register is shown in Figure 4(b) where pulses occur in the areas between the bars, and no pulses occur during scanning the two information marks 10. Those pulses or their absence appear as binary signals (pulse or nor pulse) in successive stages of the shift register. In case it had been preferable, for the use of the computer, to provide a shift register 5 carrying record of the presence of pulses during in-formation marks and no pulses when there are no information marks, then gate 2 could have been fed from the gate D of the analogue to digital convertor 1 rather than from the inverse output, and the contents of the shift register would have~een as shown in Pigure 4 (c) indicating 2 information bars scanned (scan line A) between the location bars. In either event the shift register after clocking by the inverse clock pulses permitted through by gate 18 contains a ~erie~ of #tage~ contining ~ 'one' or 'zero' l()~'~h~ ~J
for each pulse position correspondiny to a dark area and a 'zero' or space for each pulse position corresponding to a bright area or vice versa, and in either event, the record of the scan in the shift register may easily be read by the computer. It will be noted that since 16 pulses are read into the shift register and the space between the bars may be 12-16, depending on the angle of skew, that the shift register, in addition to a binary record of the information may have 1-4 stages corresponding to a portion of the second location bar.
However, the location of the stages of the shift register, corresponding to the second location bar scanned makes the character of such stages easily detectable by the computer which will discriminate between an information bar and a location bar. Note also that the only information row, with two bars indicates the start of the information so that from the position of the start bars the computer may detect the correct order in which the information (which may be scanned in either orientation) is to be processed.
~s will be obvious, the aceeptable angle of skew and the consequent tolerance for variation in width of the bar width as scanned is variable to suit particular design require-ments and depends upon the accuracy of the scan rotation performed in accord with the teaching of this invention.
When counter 14 reaches the counts of 17 to 24 inclusive, the minimum to maximum pulse width of the expected space between the bars plus the pulse width of the second location bar, has been scanned. For counts from 17-24 in counter 14, respective outputs from decoder 15 through OR gate 16 supply an enable signal to gate 10 which i8 also enabled by the first pulse from gate 3 ~ignalling the transition from dark to light in the scan.

I f a second dark area of the width of a location bar of 5-~pulse widths (correct tolerance) is scanned over an interval ending in counts in counter 14 between 17-24 (correct location relative to first location bar) then gate lO enabled by simultaneous enabling outputs at gate 3, 9 and 16 and counter ll is shifted to the count of 2. The '2' output of decoder 12 is activated to provide one enabling signal to gate 26. Signals passing gate 26 as hereinafter explained, are counted by counter l9. Counter l9 is connected to be reset at the time of the frame sync pulse (i.e. reset between frames) and, when gate 26 is enabled, counts the number of lines, in a frame, w~erein the two correctly spaced location bars are detected.
As with the tolerance for the number of placed in shift register 5 it will be appreciated that the tolerances expressed above and at various locations in the application, dependent upon the angle of skew and hence on the tolerance for the angular rotation of the scan to read the label.
At the sa~e time, as counter 11 moves from 1 to 2, gate 13 formerly enabled by the 1 output of decoder 12, is disabled. Counter 14 will be reset at the end of each line, by a signal derived from the line sync pulse, if it has not reached 25, or each time it reaches 25, by the '25' output of its own decoder 15.
When the counter 11 reaches '2' the pattern of in-formation marks (or any other contrasting material) for the scan of a single line, will be recorded in shift register 5.
Such pattern will not, however, in the preferred embodiment of the invention be transferred to the computer until it has been determined that the whole information label is present in ~0 thefield of view of the television camera and until the direction 1O~
of the scanning raster is such that the info~mation represented by the information marks or bars scanned in the appropriate direction (within design limits of skew tolerance) to allo~ the information desired from the scan to be handled by the computer or other data treatment means. This is so that the computer will only receive the line by line information from the shift register when the position of the label and its orientation relative to the scan is such that the sequential scan records from shift register 5 will provide a record of the scan of a complete label. The determination of the presence of the label in t~ field of view is achieved by counting, per field, at counter 19, the number of lines per field in which two properly spaced location bars are detected. The location of the label at a desired position in the field of view is also determined by AND gate 26 provided between the '2' output of decoder 19 ~-and counter 19 to prevent the initiation of counting lines with two properly spaced location bars by counter 19 until a certain frame line has been reached. Thus a line counter 22 is arranged in any desired manner to count the lines of each field (such as (as shown) by counting line sync pulses and resetting on every frame sync pulse). A decoder 23 is arranged to provide ; an output corresponding to the desired upper line position occupied by the label at the time of the frame scan. For ; example, with 262 lines to a field, assuming that a properly oriented label will encompass 155-160 lines and it may be de-sirable to detect the label in the upper half of the field, say between the 40th and 200th lines. The decoder 23 will therefore, be arranged to provide an output at line counts 40 to 200 (incl.) to enable gate 26 during this interval to allow the counting of line~ with properly spaced location bars producing a '2' output from decoder 12. Counter 19 is connected to be reset by a signal originated by each frame sync pulse. ~etween such reset signals counter 19 counts the lines with correctly spaced double bars starting with line 40. Decoder 20 is designed to provide an output with the minimum number of good lines f~r the label being in the correct position has been detected, in this example 120 lines. The '120' output of decoder 20 is used to signal the computer, that the shift register 5 will contain information about a correctly positioned label in the scan lines of the next field. As separate indication to the computer will be provided to inform it that any necessary scan rotation has taken place. If the computer is so programmed, the computer will on notification of a correctly positioned label and of the completion of any scan rotation store and process the successive line recoxds in the shift register resulting from scanning between the location bars, on the next field. From the read-out of the shift register the computer may decode the encoded information.
The use of 120 lines to indicate the presence of a label whose bars encompass 160 lines is determined by the fact that it has been found that such determination will ensure that in substantially all cases the complete label will be in the next field scanned. Thus the '120' count between lines 40 and 200 may indicate that some lines have not been counted due to noise in the scan signal or that part of the label is above line 40 although within the field with 120 lines between lines 40 and 200. In either event the detection of 120 lines will indicate in a high enough percentage of cases for efficient operation, that the nèxt field may be used to extract the information. ~bviously the number 120 will vary with the h~
illumination, the camera and other parameters. Given the occurence of a '2' output (or other locations indentification signal) from decoder 12 or equivalent device, combined with an ability to count the number of scan lines down a field, there are many alternative counting or logical arrangements to deduce the correct positioning of the label. However, such alter-native arrangements will be dependent on ability to recognize that two location bars (or other arrangement of location bars) have been detected in a scan line.
The counters herein are reset as follows :
Counter 7 from delay 6 Counter 11 at each line sync pulse and each count of '25' from decoder 15 Counter 19 at each frame sync pulse Counter 14 at each line sync pulse at each count of '2' from decoder 12 at each count of '25' from decoder 15 Counter 22 at each frame sync pulse Counter 25 at each frame sync pulse The feeding of the information to the computer with a continuously repeating scan of a moving image places limitations on how close the information marks may be placed and/or how fast the label may travel, since the label may travel a material distance during the scanning.
The short interval illumination may be achieved in various ways. The regular green illumination provided here by the fluorescent lamps, may be continued while light admitted to the camera, may be restricted by a mechanical shutter or for speed, an electro-optical shutter. However, I prefer to provide a ~trobe light in addition to the fluorescent source, so that, l~J~h(J ,~
on detection of the label in its correct location, the fluorescent light may be switched off and the strobe light turned on and off during the frame sync interval. The strobe light may be any light source which may be switched on and off quickly enough to provide the interval within the desired tolerance and which will provide sufficient illumination to create a sufficiently bright image for scanning. If red or other non-black stripes are used it may be necessary to use a complementary color for the strobe usually by placing a colored filter in front of a conventional strobe.
The computer will be programmed to detect the output of decoder 20 and responsive thereto to cause a series of contents for the shift register to be fed in one of the pulse forms shown, to the computer. Thus the operation of the circuitry shown in Figure 5 is the same when the operation is performed by a continuous scan.
It will be appreciated that the speed and reaction time of the circuitry and computer software may be sufficiently fast that there will, in some design alternatives, be the chance that the same label, scanned to extract the information, be again detected in the correct location and the information again scanned. This may be avoided by sufficient spacing of the labels bearing parcels on the conveyor (which may be assisted by making the conveyor of the tray-type or of some other divided type with one label bearing parcel to be placed per division).
Without restriction of the parcel location the logic circuitry may be augmented to avoid scanning the same parcel, by requiring that there be detected the absence of the required number of double bar lines in the scanning range (here between frame line~ 100 and 160) between one acceptance of information by the computer and the next.

1{~h(~ i' l~here will now be described, the mechanism for detectiny skew or the deflection of the label about an axis parallel to the viewiny direction of the camera.
In accord with the invention described herein the skew measurement is used to determine the angle through which the raster scan must be rotated in order to provide a raster scan which is parallel (with acceptance tolerance) to the desired direction for scanning the information.
It will be obvious that the angle of skew may be determined by counting for two trace lines in a raster of known spacing the number of clock pulses that occur between a reference point and a location stripe and vice versa. The reference point is preferably the beginning or end of a scan line. The preferred method for determining skew therefore is (for two spaced scan lines) to count the number of clock pulses that occur in the time that the scan moves from the end of the location bar to the end of the scan line. The difference between the counts for two different lines is a measure of the 'skew' or the angle e between the scan lines and the desired direction for reading the information (here perpendicular to the location stripes).
Thus it will be obvious that Tan e = K.~ Y
~X
Where e is the angle of skew a Y is the number of lines between the two lines selected for measurement.
X is the difference in clock counts on the two lines K is a constant selected to compensate for any scale differences between X and Y.

~3~
The ~et~lod of the invention involve~ maintaining - the number of lines between the two lines selected for measurement, constant preferably by making the counts whose difference results in ~ X on the same lines each time.
Thus ~X is proportional to tan e and this value fed to the computer, programmed for this purpose will allow e to be determined, and the sign of ~ X will indicate the direction of the required angular rotation. As will be appreciated the computer may readily be programmed to provide from the sign and value of ~ X provided, the settings sin e and cos e for the multipliers and the setting of the ganged invertor switches to produce the desired camera rotation.
The preferred method of calculation of the skew of the label will now be described. The skew angle 5A is shown in Figure 3. The skew measurement involves the use of a line counter 22. The line counter is connected to count signals originating with the line sync pulse and is reset by a signal originating with the frame sync pulse. Thus, in any frame, the line counter 22 contains a count indicating the line being scanned. Two lines are selected sufficiently spaced that a good skew measurement may be obtained. These lines need not necessarily be within the information scanning area.
These lines are chosen in the position of the frame preceding that position where it is desired to scan the infor-mation for reading. Thus the lines selected might be 102 and 150.
The decoder 23 for line counter 22 is therefore provided with outputs which enable AND gates 21 and 24 respectively at line counts 102 and 150 respectively. Each gate 21 and 24 is also enabled by the '2' output of decoder 12 through gate 26 and by the clock pulse from clock 46. The output of gate 21 is connected o iJ
to the 'count-up' directional terminal of a ~i-directional counter 25. The output of gate 24 i8 connected to the count-down directional terminal in counter 25. The counter 24 is reset at the end of each frame. Thus, when the 102nd line is encountered, counter 21 is enabled after the output of decoder 12 reaches the '2' output, signalling the end of the second bar. The clock pulses passing gate 21 cause counter 25 to count up and supply at the end of the scan line a measure of the distance from the second location bar to the scan edge.
The clock pulses are stopped at the end of the 102nd scan line, by the disabling of the lead from decoder 23. When the count in counter 22 reaches 150 for the 150th scan line, gate 24 is enabled and on the enabling of '2' line from the decoder 12, the pulses are counted down by counter 25 to the end of the 150th line. The count remaining in the two way counter after the end of the 150th line is a measure of the slope or 'skew' of the label i.e. the angle between the then existent scanning direction 'R' of Figure 6 and the desired scanning direction; which, with the label shown is perpendicular to the location stripes. The sign of the count indicates the sense of the slope, i.e. a positive residual count indicates a slope as shown in Figure 3, while a negative count will indicate a slope in the opposite direction. The residual contents of - the two-way counter 25 after its 'count-up' and 'count-down' are therefore available for use by the computer, and may, if desired, be replaced by two separate counters, one forcounting line 102 from gate 21, the other for counting line 150 from gate 24. In ~uch alternative the information may be separately fed to the computer from the counter.
Although the embodiment described suggests the use ~ o~
of the same two raster Lines, each time, to measure sk~w, it will be noted that the procedure may be modified to provide that any two raster lines (spaced by a constant number of lines) may be used once the stripe pattern has been identified.
It will readily be appreciated that the technique discussed may be adapted to the use of overlation marks of a different for~ to the stripes shown and parallel or at another predetermined angle to the desired scanning direction for the information.
It will readily be appreciated that the methods and principles above discussed, for determining s~ews may be applied to each camera of a pair arranged to initially scan at right angles to each other. Moreover these methods may also be applied where a single camera only is used and is caused to scan initially with alternate fields at right angles to each other.
In the latter event the computer will be programmed to apply to the multipliers values of e = o and e = so for alternate fields. (The values of 0 and 90 may be replaced by other pairs of values for e differing by 90). (If the initial values of e, differing by 90, are not in directions which are an integral multiple of 90 it will be appreciated that, while well within the scope of the invention, the necessary programming will some-what more complicated and inversions will be required where a rotation of the scan is carried over a direction which is an integral multiple of 90).
It will be noted that the other limits or parcel orientations are required so that due to undue deviations from these orientations the information will not be ambiguous. Thus, pitch (rotation about an axis parallel to the conveyor but perpendicular to its motion direction) will tend in the camera U'i' image to shorten the in~ormation bars and the space b~tween them (increasing the apparent skew) while roll, orientation of the label about the travel direction axis, will tend to narrow the apparent transverse dimensions and to decrease the apparent skew. Thickness of the parcel or other article raising the level of the information surface relative to the conveyor increases the dimensions of the information bars and the location bars in the image. All of the suggested limit~
will be determined for the parameters including the mode of programming the computer, the vertical scan spacing of the image in the television camera (effectively setting the re-solution on the vertical dimension) and the clock pulse frequency, which effectively sets the resolution in the horizontal dimension.
The preferred embodiment refers to the provision of scanning with continuous lighting until a label is detected, ; correctly located, followed by the provision of a strobed or short period illuminated image for scanning the infor~ation.
It will be obvious that, if desired, short interval or strobed illumination maybe used for both location of the location bars as well as detection of the information.
Although location bars of specific width and spacing, and information bars of specific width and spacing are described in the specific embodiment, it will be obvious that other arrangements and dimensions of location bars may be used per-mitting the detection of the location and orientation of such location bars by suitably designed logic circuitry and that other shapes or dimensions of information marks may be used with obviou~ alteration of the logic circuitryO The information marks ~ill be for binary BystemB~ that iB, the information is ~ 7~
embodied in their presence or absence at specific locations.
The operation of the device in cpnnection with the scan rotation will n~w be described (it being appreciated that the means and method for detecting the label presence before rotation, and the means for reading the label information after rototion, has already been described).
With the conveyor moving parcels, two scans of the labels are provided, either under the action of two cameras scanning at right angles to each other or with a single camera alter-nately scanning in mutually perpendicular directions. For simplicity of operation the cameras will be arranged so that the scanning rasters in all cases will, relative to their deflection means be at an angle of 0, 90, 180 or 270.
The computer will be programmed to ensure that any information read from time to time into shift register 5 will not be read into the computer until after the scan has been rotated.
With the two scans at right angles to each other, either simultaneously or alternating, the results of the scan are handled by the logic circuit (two logic circuits will be used if there are two cameras) until, as previously described a label is located in the correct position in the scan image, as previously described.
With the location of the label in these camera (or mutually perpendicular scans in one camera) the skew measurements ~X from each camera or each mutually perpendicular scan is fed to the computer. rrhe computer is then able to determine which of the scans is at an angle of les~ than 45 to the desired scanning direction R, (if both scans are at exactly 45 to the desired ~canning direction the computer will be programmed to arbitrarily select one of the cameras).

L04~7 The computer will then be programmed to apply the correct values of sin e and cos e (derived from the skew measurement), and any necessary switches of the ganged invertor switch to rotate the scan of the camera whose raster was at an angle of less than 45 (or the selected camera) to an orientation substantially parallel with the desired scanning direction, (here perpendicular to the location stripes). It will depend on the accuracy with which this rotation can be performed, whether or not skew corrections will have to be made thereafter to the results received from shift register 5 after the raster has been rotated. However experience has shown that scan rotations may be achieved within ~ of the desired value and that with resultant skew angles of less than this amount the computer can read the information without the necessity of these skew corrections.
Although two mutually perpendicular scans are preferred, it will readily be appreciated that a single scan may be used, requiring resultant raster rotation of up to 90. Moreover scan rotations of greater than 90 may be provided with necessary inversion switching to provide the requisite sine or cosine sign changes.
When the scan has been rotated, as already described, the strobe is initiated if it has not been used during the location stages.
The computer conditioned by the scan rotation then reads the inforrnation then being stored in the shift register ~ a~ previously described. The logic circuitry inhibiting reading of the information in shift register 5 until the correct po~itioning of label i8 determined may not be needed after the rotation if 'chere i~ no concern about the label having left the correct area relative to the camera. If there is concern this logic circuitry may of course be used to disable -the reading of the shift register 5 until the correct positioning has been assured.
With the scan rotated and the label correctly positioned the results of scanning the information bars are sequentially supplied to the shift register 5 and sequentially read out by the computer, as previously discussedO A~ shown and discussed the label is coded here by two bars, to indicate the direction of the information.
Thus the information may be scanned in either direction and the correct sequence determined at the computer.
Obviously if more desirable in a particular application, the computer can be programmed to determine that the scan is from end to beginning relative to the information and scan in the opposite direction.

Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows :
1. In a method of extracting information encoded on a surface movable along a locus relative to a television camera, wherein location marks indicating orientation contrast with said background, providing a television camera constructed and de-signed to scan the image formed therein in a raster with a predetermined orientation, said television camera being designed to provide a video scan output signal and being designed to scan in accord with horizontal and vertical vertical deflection signals, moving said surface along a locus through the field of view of said camera, causing said camera to alternately scan in rasters whose orientations are more nearly perpendicular than parallel, analysing the video output signal resulting from said alternating rasters to obtain a measure of the angle of said location marks relative to each raster.
2. In a method of extracting information encoded on a surface, movable along a locus relative to a television camera, wherein location marks indicating orientation contrast with said background, providing a pair of television cameras each designed to scan the image formed therein in a raster with an orientation differing from the other by more than 45°, movable said surface along a locus through the field of view of said cameras, causing each said camera to scan the image formed therein, analyzing the video output signal resulting from each camera to obtain in each case a measure of the angle of said location marks relative to each raster.
CA302,160A 1973-08-31 1978-04-27 Label sensor Expired CA1044807A (en)

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US39355273 US3902047A (en) 1973-08-31 1973-08-31 Label reader with rotatable television scan
CA206,177A CA1041666A (en) 1973-08-31 1974-08-02 Label reader with rotatable television scan

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