US3783275A - Apparatus for the optical-electrical scanning of a drawing having a large number of points of different colors - Google Patents

Apparatus for the optical-electrical scanning of a drawing having a large number of points of different colors Download PDF

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US3783275A
US3783275A US00242071A US3783275DA US3783275A US 3783275 A US3783275 A US 3783275A US 00242071 A US00242071 A US 00242071A US 3783275D A US3783275D A US 3783275DA US 3783275 A US3783275 A US 3783275A
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signals
scanning
colour
color
points
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R Oelmayer
A Seelos
H Stock
W Reif
D Nagy
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Franz Morat GmbH
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Franz Morat GmbH
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/54—Conversion of colour picture signals to a plurality of signals some of which represent particular mixed colours, e.g. for textile printing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
    • G01J3/51—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors using colour filters

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  • ABSTRACT I Apparatus for scanning a drawing consisting of a large [Zl l Appl' 242071 number of points each of which is of a colour selected from a number of colours, and for converting the in- [30 ⁇ Foreign Application Priority Data formation obtained by scanning the points into colour Apr 17 I971 Germany P 21 18 7202 signals characteristic of the individual colours, comprising a scanning head movable relative to the draw- [52] Cl 250/226, 250/208, 307/235 ing having a number of optical electrical scanning ele- [51 1 Int. Cl.
  • the invention concerns apparatus for the opticalelectrical scanning of a drawing consisting of a large number of points each of which is of a colour selected from a number of colours, and for the conversion of the information obtained by scanning the points into electrical colour signals characteristic of the individual colours.
  • Apparatus of this kind is known for example from British Pat. specifications Nos. 1,170,947 and 1,190,600, and comprises a scanning head movable relative to the drawing and having a number of opticalelectrical scanning elements, each responsive to a definite spectral range, and which are followed by colour discriminators for the production ofa respective colour signal.
  • a serious disadvantage of such apparatus is that for producing the drawing only very definite colours may be used in order to permit clear and reproducible recognition of these colours. Also when the quality of the colour applied to the drawing paper fluctuates considerably or when, owing to poor covering power of the colour, the generally white colour of the drawing paper shows through with varying intensity the apparatus is.
  • the scanning head comprises for example three phototransistors, in front of each of which is placed a respective colour filter (for example blue, green and red) and each of which is followed by an amplifier.
  • a respective colour filter for example blue, green and red
  • an amplifier By adjusting the threshold value of these amplifiers, it is possible, if definite colours are used (for example blue, green and red), to ensure that in scanning these colours only one of the amplifiers delivers an output signal and thus produces a definite colour signal.
  • definite colours for example blue, green and red
  • difficulties occur because the reflection or transmission maxima of the two similar colours may overlap, depending on the for example, the colours blue, green, red, turquoise, vi-
  • apparatus for scanning a drawing consisting of a large number of points each of which is of a colour selected from a number of colours, and for converting the information obtained by scanning the points into colour signals characteristic of the individual colours, comprising a scanning head movable relative to the drawing having a number of optical-electrical scanning elements each responding to a definite spectral range and colour dis criminators connected to the scanning head for producing a respective colour signal only when the analogous output signals of all the scanning elements associated with it, or signals derived from the said output signals, lie within an upwardly and downwardly limited tolerance range.
  • the tolerance ranges are preferably upwardly and downwardly adjustable.
  • the invention provides the important advantage that any two colours can be differentiated from each other by means of a single scanning element if their tolerance ranges do not overlap. Forincreasing the accuracy, reproducibility and number of the colours used, however, for scanning each one colour there are used for example three scanning elements each having three associated tolerance ranges, so that each colour is recognised whenthe output signals of the three scanning elements lie in the three fixed tolerance ranges. It is sufficient, therefore, if the output signals of at least one scanning element are associated with different toler' ance ranges.
  • the scanning elements are followed by subtracting circuits for forming differential signals, the differential signals resulting from the subtraction of the analogous output signals of the scanning elements from a normalised white signal.
  • differential signals are considered expedient for the following considerations. It will be assumed that three scanning elements are provided by means of which the blue, green and red proportions of a colour drawn on a white background are measured, and that the scanning elements are followed by preamplifiers which in the scanning of the white background lead to normalised output signals of 1 volt. If with the three scanning elements a colour is scanned, which with full covering power, i.e., when the white backing does not show through, produces output signals of 0.2 volt for the blue portion, 0.6 volt for the green portion and 0.9 volt for the red portion, then in the case of half the covering power, i.e., when the white ground colour half shows through, these signals amount to about 0.6, 0.8 and 0.9 volt respectively.
  • the ratios of the differential signals therefore, remain practically constant, despite the different covering powers, so that different degrees of covering power have no substantial influence, whereas the ratios of the analogous output signals vary relatively considerably, so that the tolerance ranges would have to be made so wide that only a few colours could be used side by side.
  • the scanning elements are followed by dividing circuits for forming quotient signals, the quotient signals from the division of the analogous output signals of at least one scanning element being given by the sum of the analogous signals of the scanning elements.
  • This circuit offers the advantage that fixed factors, resulting for example from fluctuations of temperature, mains voltage, air humidity or for example by ageing, become negligibly small after division and cause only small errors.
  • the quotient method in addition, has the advantage that with the use of three scanning elements sensitive to blue, green and red, in general only the quotient signals of two scanning elements need be evaluated, because the sum of all three quotient signals is always unity.
  • dividing circuits being followed by further subtracting and dividing circuits for forming quotient signals, the quotient signals being proportional to the slope ofa line through two points in the colour triangle, and one of these points being fixed by the colour of the background and the other by the colour to be recognised.
  • This circuit has the advantage that relatively narrow tolerance ranges can be assigned to the slopes of the colours, which in the colour triangle are theoretically equal for all possible degrees of covering power, so that the number of usable colours is very large.
  • FIG. 1 shows apparatus embodying the invention for ensuring recognition of a number of colours
  • FIG. 2 shows diagrammatically the tolerance ranges of a number of colours scannable by means of three scanning elements
  • FIG. 3 shows part of an embodiment of the invention for the production of differential signals
  • FIG. 4 shows a circuitarrangement, modified in comparison with FIG. 1, for varying the tolerance ranges
  • FIGS. 5 and 6 show part of embodiments of the invention for the production of quotient signals
  • FIG. 7 shows diagrammatically the incorporation of all colours in a colour triangle.
  • scanning elements 31b blue channel
  • 31g green channel
  • 31r red channel
  • the drawing consists for example of white squared paper, the squares being filled in with different colours, so that a pattern of the type of a screen pattern is produced.
  • the drawing and the scanning elements 31 there are provided, also within the scanning head, colour filters or dichroic mirrors, so that there impinges on each scanning element only the light of a relatively narrow spectral range (for example, blue, green, and red).
  • FIG. 1 Connected to the outputs are the three inputs of a number of colour discriminators 411, 412 and 413 of which only the colour discriminator 411 is shown in detail in FIG. 1.
  • an operational amplifier 33 Connected to each input is an operational amplifier 33, connected as non-inverting preamplifier, to the negative input of which there is connected a voltage divider 35,37 having a fixed and an adjustable resistance, by means of which the amplification factor of the preamplifier 33 can be adjusted.
  • the outputs of the preamplifiers 33 can be connected by means of a push switch 38, individually or jointly, to voltmeters 39, it being assumed that the points B1 and B2, G1 and G2 and R1 and R2, respectively, are in each case connected together.
  • the suffixes b (blue), g (green) and r (red) will be omitted from reference numerals where the description applies to all three channels.
  • the colour discriminators comprise as essential parts three comparators 43b1, 43b2 and 43g1, 43g2 and 43r1, 43r2, respectively, and an AND element 451, whose six inputs are connected to the outputs of the six comparators 43.
  • the comparators consist of antiparallel-connected differential amplifiers having two inputs.
  • the output of the preamplifier 33b is connected to the inverting input of the comparator 43b] and to the noninverting input of the comparator 43b2, the output of the preamplifier 33g is connected to the inverting input of the comparator 43g1 and to the non-inverting input of the comparator 43g2, and finally the output of the preamplifier 33r is connected to the inverting input of the comparator 43rl and to the non-inverting input of the comparator 43r2.
  • each group of comparators 43b,g,r a respective voltage divider 47,48,49,50, each voltage divider having an adjustable resistance 49.
  • the positive ends of these voltage dividers are connected to the output of an operational amplifier 51, connected as non-inverting amplifier, while their negative ends are earthed.
  • the positive inputs of the comparators 43b1, 43g1 and 43r1 are in each case connected to the junction of the resistances 47 and 48, while the negative inputs of the comparators 43b2, 43g2 and 43r2 are connected in each case to the junction of the resistances 49 and 50.
  • the operational amplifier 51 is connectable by its non-inverting input, by way of the contact 4 of a switch 53 and two resistances 55 and 57, to the positive terminal of a battery.
  • the junction of the resistances 55 and 57 is earthed via a Zener diode 59, whose anode is connected by a resistance 61 also to the contact 4 of the switch 53.
  • the inverting input of the operational amplifier 51 is connected to the tap of a voltage divider 63,65, by means of which the operational amplifier 51 is adjusted to a fixed amplification factor of 2 for example.
  • the resistances 55,57 and 61 thus reduce the positive working voltage to a voltage, stabilised by the Zener diode, of for example 4 volts which, in the position of the switch 53 shown in FIG.
  • the non-inverting input of the operational amplifier 51 may, however, be connected by means of the switch 53 (positions 1, 2 or 3) also directly to an output of the preamplifiers 33.
  • the outputs of the comparators 43 are connected by suitable decoupling elements to the base of respective switching transistors 67, in whose collector-emitter circuits are connected respective lamps 69, indicated merely diagrammatically in FIG. 1.
  • the mode of operation of the arrangement described is as follows. First of all, a point of the drawing is brought below the scanning head such that it is fully covered by the three scanning elements 31. According to the colour of the point under the scanning head, there is obtained equal or different portions of the spectral ranges associated with the scanning elements 31, this being shown by the potentials of different magnitudes at the outputs of the preamplifiers 33.
  • the switch 53 is in position 4, so that a potential of 8 volts is applied to the positive ends of the voltage dividers 47 to 50.
  • the non-inverting inputs of comparators 43b1, 43g1 and 43:1, by adjustment of the resistances 49 can be connected to potentials of between about-4.16 and 5.40 volts, while the inverting inputs of the comparators 43b2, 43g2 and 43r2 are connected correspondingly to potentials of between about 3.84 and 2.60 volts.
  • the comparators 43b1, 43g1 and 43rl deliver output signals only when the output potentials of the preamplifiers 33 lie below a maximum potential of from 4.16 to 5.40 volts, while the comparators 43b2, 43g2 and 43r2 deliver output signals only when the output potentials of the preamplifiers 33 lie above a minimum potential of 3.84 to 2.60 volts.
  • the resistance 49b is first adjusted to zero value, so that the output potential of the amplifier 33b must lie between 3.84 and 4.16 volts if both lamps 69b are to light up. If the colour portion associated with the scanning element 31b is relatively small, the output potential of the preamplifier 33 is increased by means of the resistance 37b until it lies in the said tolerance range of 4 volts 1- 2 percent and the lamps 69b lightup. The same adjustment is then made with the preamplifiers 33g and 33r until finally the lamps 69g and 69r also light up. Lighting up of all the lamps means that there occurs at the output of the AND element 451 a colour signal which is characteristic of the colour under the scanning head.
  • the outputs of the scanning elements 31 may be connected to a number of colour discriminators 412, 413, etc., which are of the same construction as the colour discriminators 411.
  • These further colour discriminators in FIG. 1 are shown diagrammatically in block 71, which for example has seven outputs, which together with the output of the AND element 451 are connected to the eight inputs E1 to E8 of a logical circuit 73 in which a definite code signal can be formed for each colour.
  • the seven colour discriminators accommodated in block 71 as was described above with reference to the colour discriminator 411, are adjusted to points having other colours, whereby correspondingly other tolerance ranges are obtained.
  • a number of colour discriminators 411, 412, 413, etc. are used, it is sufficient if these differ from each other in at least one tolerance range.
  • the tolerance ranges may be of different sizes, especially also within the same colour discriminator, and for the weak colour portions may be larger than for the strong colour portions.
  • FIG. 2 indicates diagrammatically the possibilities for colour scanning presented by the use of the apparatus described with reference to FIG. 1.
  • the ranges I to IV combine with the ranges V to VIII to form a plurality of scannable colours, the lengths .A to M always indicating the tolerance ranges.
  • the ranges I and V be associated with the colour 1 and the range I and VII be associated with the colour 2.
  • the colour discriminators 411 and 412 associated with these colours have two common tolerance ranges, i.e., A and D, which however clearly differ from each other in the third tolerance range F or H.
  • colours which for example are composed from the ranges III, V; III, VII and IV, VIII can also be 'used very well side by side, since they differ relatively strongly from one another in at least one tolerance range.
  • the colours composed for example from the ranges I, VI or II, V or II, VII cannot be scanned so well side by side, although they also differ from one: another in at least one tolerance range. In the case of these colours, however, slight fluctuations in illumination or fluctuations in the scanning head/drawing distance or illumination lamp/drawing distance can lead to overlapping of the tolerance ranges and hence to errors.
  • switch 53 after calibration of the colour discriminator 411 can be switched to one of the contacts 1, 2 or 3, whereby instead of the stabilised potential of 4 volts, a potential is now applied to the positive ends of the resistances 47 which is dependenton the output potential of one of the preamplifiers 33.
  • By operating the push switch 38 it is possible to ascertain how the output potentials of the preamplifiers 33 behave in the said fluctuations.
  • switch 53 can be switched over to the output of the desired preamplifier 33, so that in the case of subsequent fluctuations during scanning, the tolerance ranges are also correspondingly shifted, and the output potentials at the preamplifiers 33 remain in the adjusted tolerance range despite possible considerable fluctuations. It will often be preferable to switch the switch 53 to the output of that preamplifier 33 which delivers the strongest output signal for the same adjustment of the resistances.
  • the effect of the adjustment is shown by line K2 in FIG. 2, which indicates the shift of the line Kl, drawn through the centres of the tolerances ranges C, E and H, when the amplification is increased.
  • FIG. 3 shows a device whereby it is not the analogous output signals delivered by the preamplifiers 33, but signals derived from the said output signals which are associated with the tolerance range described with reference to FIG. 1, the derived signals being defined as differential signals between normalised white signals and the output signals of the preamplifiers 33.
  • subtracting circuits 75 are provided as shown in FIG. 3, the points B3, G3 and R3 of the circuit of FIG. 3 being connected to the points Bl, GI and R1, and the points B4, G4 and R4 of the circuit of FIG. 3 being connected to the points B2, G2 and R2 of the circuit of FIG. 1.
  • the outputs of the preamplifiers 33 are in this way connected to inputs of a respective store unit 77, to whose other inputs timing signals are supplied by a lead 79.
  • the outputs of the store units 77 are connected to resistances 81, whose other ends are connected in common to the inverting input of an operational amplifier 83, and in addition are connected to the output of the latter by a resistance 85.
  • the non-inverting input of the operational amplifier 83 is earthed.
  • the junctions between the store units 77 and the resistances 81 are connected to the contacts 1 of three switches 87, which are switchable in common.
  • the movable contacts of these switches 87 are each connected to a respective voltmeter 89, the other sides of which voltmeters are earthed.
  • the output of the operational amplifier 83 is connected to a voltage divider of each of the subtracting circuits 75.
  • Each voltage divider comprises three series-connected resistances 91, 93 and 95, the resistances 95 being adjustable in common and being connected by their free ends to the outputs of respective amplifiers 97.
  • the outputs of the preamplifiers 33 and the junctions of the resistances 91 and 93 are connected to the inverting inputs of the operational amplifiers 97 by resistances 99b, 99gand 99r, while their non-inverting inputs are earthed.
  • the outputs of the operational amplifiers 97 lead on the one hand through the points B4,
  • G4 and R4 to the comparators 43 can be connected either to a further set of voltmeters or by matching circuits, not shown, to the contents 2 of the switches 87, so that the output signals of the operational amplifiers 97 can also be measured by means of the voltmeters 89.
  • the device described operates as follows. Before commencing automatic scanning of the drawing, the scanning elements 31 (FIG. 1) are adjusted to a white point of the drawing. This corresponds to a condition which always arises when a colour, for example blue,
  • the inputs of the store units 77 are thus supplied with analogue signals which in scanning, give a white point.
  • a key may be provided, on the operation of which, timing signals are supplied to the store units by the lead 79.
  • the output signals of the store units 77 are then increased or decreased by adjustment of the resistances 37 until all three voltmeters 89 give a full deflection or, if they are calibrated in percentages, stand at 100 percent. A voltage of exactly 1 volt may correspond for example to this value of 100 percent.
  • the potentials adjusted at the outputs of the three storage units 77 are averaged by means of the three resistances 81.
  • the averaged potential is inverted by the operational amplifier 83 so that a voltage of, for example, exactly 1 volt appears at its output if the ratio of the resistance 85 to the parallel circuit of the resistances 81 is equal to 1:1.
  • the second extreme condition is then adjusted by the scanning elements 31 being directed to one of the colour points having optimum covering power associated with the said colour discriminator, at which point, therefore, the white colour of the background shows through as little as possible.
  • the preamplfiers 33 analogue signals which, in the embodiment of FIG. 1, would lie within the tolerance ranges adjusted for the corresponding colour discriminator.
  • the formation of the differential signals is obtained by supplying to the inverting input of the operational amplifiers 97, on the one hand, directly those analogue signals corresponding to the colour portions of the colour just scanned, and on the other hand, by way of the resistances 91, the inverted white signals formed at the output of the operational amplifier 83, while at the same time the output signals of the operational amplifiers 97 are returned by way of the adjustable resistances and the resistances 93 also to the inverting inputs of the operational amplifiers 97.
  • the potentials appearing at the output of the three operational amplifiers 97 are measured and compared with one another by means of the voltmeters 89.
  • the maximum potential at the three amplifier outputs, by adjustment of the resistance -95, which fixes the amplification factor of the operational ampliifer 97, is brought to an arbitrarily normalised value of 100 percent,
  • the voltmeters 89 are calibrated in percentages, so that the value of 100 percent can be read off directly on the voltmeter 89b.
  • the outputs B4, G4 and R4 of the circuit of FIG. 3 are connected to the inputs of the comparators 43. In using the circuit of FIG. 3, therefore, a signal will always appear at the output of the AND element 451 when the conditions of the three differential signals are in a certain ratio to one another.
  • the points B4, G4 and R4 are not connected to the points B2, G2 and R2 of the circuit of FIG. 1, but to the points B5, G5 and R5 of the circuit of FIG. 4.
  • the point B5 is connected to the non-inverting input of an operational amplifier 101 and in addition by a resistance 103 to the inverting input of an operational amplifier 105, whose non-inverting input is earthed and whose output is connected to its inverting input by a resistance 106.
  • the inverting input of the operational amplifier 101 is earthed by a resistance 107 and is connected to its output by a resistance 109.
  • the outputs of both operational amplifiers 101 and 105 are connected together by two leads 111 and 113, which, as shown in FIG. 4, are connected together by four pairs of resistances 115,117; 119,121; 123,125; 127,129.
  • the resistances 117, 119, 125 and 127 have an adjustable tap.
  • the taps of resistances 117 and 125 are connected respectively to the non-inverting inputs of comparators 131 and 133 and the tappings of the resistances 119 and 127 are connected to the inverting inputs of comparators 135 and 137, respectively.
  • the inverting inputs of the comparators 131 and 133 and the noninverting inputs of the comparators 135 and 137 are connected to the points G5 and RS, respectively.
  • the outputs G6, G7, R6 and R7 of the comparators lead by means of suitable switching circuits to the AND element 451 (FIG. 1), which gives an output signal when the differential signal supplied to the inputs G5 and R5 lie within the tolerance ranges adjusted at the resistances 117, 119, 1 25 and 127.
  • the tolerance ranges can be adjusted independently of one another and independently of the centre of the tolerance ranges.
  • only two groups of comparators are provided, while the strongest output signal at the output of the amplifiers 97, in the example selected the output signal of the operational amplifier 97b, is supplied to the two amplifiers 101 and 105.
  • the end voltages of the tolerance ranges are fixed by the output signals of the two operational amplifiers 101 and 105, in a manner similar to that whereby this is achieved by the operational amplifier 51 in the circuit of FIG. 1.
  • the operational amplifiers 101 and 105 therefore, undertake regulation, i.e., for the case where the potential at the point B5 has not reached or has exceeded the normalised value of 100 percent, the end voltages of the tolerance ranges are varied accordingly. If, for example, in the case of illumination which is too weak, the differential signal at the point B5 is only 50 percent of the normalised value, the end potentials of the tolerance ranges will be correspondingly 50 percent lower.
  • the adjustable resistances 117, 119, and 127 are advantageously calibrated in percentages and have such values that the tolerance ranges of the two differential signals appearing at the inputs G5 and R5 can be adjusted relative to the strongest signal at the input B5 between about 0 and 150 percent at the resistances 117 and 125 or between about -50 and +100 percent at the resistances119 and 127.
  • three groups of comparators may likewise be provided.
  • the signal appearing at the point B5 would have to be regulated, by an additional regulating circuit, to a constant value of 100 percent, as is described for example in British Pat. specification No. 1,190,600.
  • suitable switches may be provided for always connecting to the point B5 the strongest output signal of the three operational amplifiers 97.
  • a further embodiment of the invention is obtained if the points B1, G1 and R1 are connected to the points B8, G8 and R8 of the circuit of FIG. 5, and its points B9 and G9 are connected to two of the three points G2, B2 or R2 of the circuit of FIG. 1.
  • the circuit of FIG. 5 has as essential components two dividing circuits 139 and 141, as well as an adding circuit 143.
  • the analogue signals delivered by the preamplifiers are added in the adding circuit 143, while the quotients of the signal delivered by a preamplifier and the sum of signals delivered by all three preamplifiers is formed in the dividing circuits 139, 141.
  • the quotient signals appearing at the points B9 and G9 are evaluated in FIG. 1 by groups, each consisting of two comparators with an adjustable tolerance range.
  • the quotient formation precludes for example errors which, due to external factors, such as temperature, il lumination or voltage fluctuations, are formed by variations in the absolute value of the signals delivered by the preamplifiers. If it is assumed, for example, that due to a variation in illumination, the output signals of the preamplifiers 33 instead of the values 8, G and R have the values kB, kG or I R, where k is any constant which acts on all three colour portions in substantially the same manner, then this constant k is eliminated in the formation of the quotients.
  • a further embodiment of the invention is obtained by connecting the points B1, G1 and R1 of the circuit of FIG. 1 to the points B8, G8 and R8 of the circuit of FIG. 5, and the points B9, G9 and I of the circuit of FIG. 5 to the points B10, G10 and I of the circuit of FIG. 6.
  • the point B10 is connected to a subtracting circuit and the point G10 to a subtracting circuit 147.
  • the output signals of the subtracting circuits :145 and 147 are supplied to a dividing circuit 149, in which the absolute value of the quotient (g al/(b 12 is formed.
  • the output signal of the dividing circuit 149 is evaluated by means of two comparators 151 and 153 as in the embodiments described so far, it being possible to fix at the point 155 the upper limit and at the point 157 the lower limit of a tolerance range.
  • signals thus arrive at one input of a further AND element 161 only when both comparators 151 and 153 deliver an output signal, i.e., when he output signal of the dividing circuit lies in the fixed tolerance range.
  • the mode of operation of the circuit described with reference to FIGS. 5 and 6 follows from FIG. 7, showing diagrammatically the usual colour triangle 173.
  • the values of r and g give the red or green portion of a colour point referred to the total intensity. Because b g r l, the blue component b R/(B G R) need not be considered separately.
  • the colour triangle 173 forms an area comprising all possible colours and colour combinations.
  • the colour triangle 173 in addition is enclosed by a line 175, along which the wavelength ofthe colours is plotted between 4,000 and 7,000 A.
  • the point denoted by 177 with the coordinates r 0.33 and g 0.33 (and correspondingly b 0.33) corresponds to the colour white, or, depending on the total intensity, different shades of grey up to the colour black; white, black and grey points, therefore, can be differentiated not by their position in the colour triangle, but only by their total intensity (output I in FIG. 5).
  • the point 177 is termed the base point.
  • a colour is recognised in FIGS. 5 and 6 when the straight line associated with it in the colour triangle 173 lies within a tolerance region 181.
  • the quadrant in which the straight line should lie is fixed by the coding unit 165, with reference to the base point 177, since for example in the first quadrant a yellow colour is obtained (tolerance range 181), in the third quadrant, on the contrary, for the same value of the output signal of the dividing circuit 149, a blue colour is obtained (tolerance range 183).
  • the form of the different amplifier stages orcomparators, of the switches and verification or check elements is in itself optional, provided only that, for the purpose of recognising a colour with certainty, at least one variable tolerance range can be adjusted.
  • the number of scanning elements selected for each colour discriminator or the number of colour discriminators themselves is freely selectable. In individual cases, a single scanning element per colour discriminator is in itself sufficient for distinguishing a number of colours with certainty.
  • FIG. 2 it is possible, for example, to connect to a scanning element sensitive to blue three colour discriminators with the tolerance ranges A, L and C. If tolerance ranges narrower than i 2 percent are desired, the resistances 48 may be omitted.
  • the lower tolerance limit can also be fixed at 0 volt by switches which bridge the resistances 50.
  • FIGS. 4 to 6 which of the two colour portions is used for evaluation is optional and in the individual case depends on which colour portions lead to strong, readily'evaluatable signals.
  • FIG. 4 it is indicated that only green and red colour portions are evaluated, whereas according to FIGS. 5 and 6 blue and green colour portions are evaluated.
  • FIG. 7 instead of using the values r and g, colour triangles are also obtained with the values r and b or g and b.
  • the manner in which the timing signals supplied over the lead 79 are produced depends on the device for scanning the drawing. If, for example, this is a device according to British Pat. specifications No.
  • the apparatus is also not limited to the colour of the background of the drawing.
  • a white, grey or black background is used. It is also possible to use a background with a light blue, red or green undertone.
  • the base point for example is shifted to the place marked 185 in FIG. 7, so that only the zero point of the coordinate system selected is altered, and the circuit of FIG. 6 has merely to be adjusted to a new base point (b g r
  • the subtracting circuits 145, 147 have suitable potentiometers. A correct adjustment always occurs when the output signals of the subtracting circuits 145, 147 disappear when the background is being scanned.
  • FIG. 7 the circuits of FIGS. 5 and 6
  • the colour of the background plays no part because it is the intensities of the individual colour portions, divided by the total intensity, which are evaluated.
  • the signals appearing at the output I there is finally the possibility of distinguishing colours which certainly lie on the same straight lines in the colour triangle according to FIG. 7, but are characterised by different degrees of covering power or different mixtures with white colour.
  • Apparatus for scanning a drawing consisting of a large number of points each of which is of a color se lected from a number of colors, and for converting the information obtained by scanning the points into color signals characteristic of the individual colors, comprising a scanning head movable relative to the drawing having a number of optical-electrical scanning elements each responding to a definite spectral range by producing analog output signals; at least one electrical circuit coupled to said scanning elements for producing derived signals by combining said output signals with other signals; at least one color discriminator connected to said electrical circuit, said discriminator pro ducing a respective color signal only when the derived signals of the electrical circuit associated with it lie within an upwardly and downwardly limited tolerance range; and means for upwardly and downwardly adjusting the tolerance range.
  • Apparatus according to claim 1 including means for forming a normalized white signal wherein the electrical circuits are subtracting circuits for forming differential signals, the differential signals being formed by subtraction of the analogous output signals of the scanning elements from the normalized white signal, and the derived signals being said differential signals.
  • Apparatus according to claim 2 wherein one derived signal is used for the dynamic regulation of the tolerance ranges of the other derived signals and wherein only the other derived signals are provided for forming the color signal.
  • the electrical circuits are first dividing circuits for forming first quotient signals, the first quotient signals being formed by division of the analogous output signals of at least one scanning element by the sum of the analogous output signals of all the scanning elements, and the derived signals being said first quotient signals.
  • the electrical circuits include first dividing circuits for forming first quotient signals, said first quotient signals being formed by division of the analogous output signals of at least two scanning elements by the sum of the analogous output signals of all the scanning elements, and further including subtracting circuits and second dividing circuits for producing second quotient signals, the second quotient signals being proportional to the slope of a line formed by two definite points in the color triangle, one of these points being fixed by the color of the background and the other point by the color to be recognized, and the derived signals being said second quotient signals.
  • Apparatus according to claim 5 wherein there is associated with the second dividing circuit a means for detecting selected output signals of the second dividing circuit.
  • the means for adjusting the tolerance ranges being voltage dividers.
  • Apparatus according to claim 8 including means for selectively applying a fixed stabilized voltage to at least one of all the voltage dividers.
  • Apparatus according to claim 9 including a switch by means of which to one end of all the voltage dividers of a color discriminator can be supplied a derived signal.
  • each derived signal being supplied to two connected inputs of a pair of comparators, to the other inputs of which are connected the taps of a voltage divider for upwardly and downwardly adjusting the tolerance range.
  • each comparator is followed by a verification element which indicates the presence or non-presence of an output signal at the comparator.
  • each color discriminator has an AND element coupled to said comparators for producing the color signal.
  • Apparatus according to claim 1, including means for measuring the analog output signals at the scanning elements.
  • Apparatus according to claim 1 including preamplifiers with variable amplification factors connected between each scanning element and the color discriminator.
  • Apparatus for scanning a drawing consisting of a large number of points each of which is of a color selected from a number of colors, and for converting the information obtained by scanning the points into color signals characteristic of the individual colors, comprising a scanning head movable relative to the drawing having a number of optical-electrical scanning elements each responding to a definite: spectral range; preamplifiers with variable amplification factors coupled to saidscannin'g elements; color discriminators conwardly adjusting the tolerance ranges; and wherein the outputs of said comparators are connected to the inputs of an AND gate which produces a color signal only when all comparators produce an output signal.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Textile Engineering (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Spectrometry And Color Measurement (AREA)
  • Facsimile Scanning Arrangements (AREA)
US00242071A 1971-04-17 1972-04-07 Apparatus for the optical-electrical scanning of a drawing having a large number of points of different colors Expired - Lifetime US3783275A (en)

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DE19712118720 DE2118720A1 (de) 1971-04-17 1971-04-17 Einrichtung zur optisch-elektrischen Abtastung einer farbigen Zeichnung

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US (1) US3783275A (de)
AT (1) AT322646B (de)
BE (1) BE782210A (de)
CH (1) CH553452A (de)
CS (1) CS161945B2 (de)
DD (1) DD99494A5 (de)
DE (1) DE2118720A1 (de)
ES (1) ES402698A1 (de)
FR (1) FR2136475A5 (de)
GB (1) GB1388026A (de)
IL (1) IL39140A (de)
IT (1) IT951426B (de)
NL (1) NL7204478A (de)
ZA (1) ZA722304B (de)

Cited By (3)

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US4110826A (en) * 1975-10-07 1978-08-29 Dr. -Ing. Rudolf Hell Gmbh. Apparatus and process for color-identification
US4414635A (en) * 1978-11-28 1983-11-08 Dr.-Ing. Rudolf Hell Gmbh Method and circuit for recognition of colors
US4953012A (en) * 1983-03-08 1990-08-28 Canon Kabushiki Kaisha Image processing system for combining a character image with an image including a gray level

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JPS52144459A (en) * 1976-05-28 1977-12-01 Silver Seiko Setting method of needle selection unit for knitting machine
JPS6052429B2 (ja) * 1979-02-28 1985-11-19 大日本スクリ−ン製造株式会社 色修正演算方法
JPS5660439A (en) * 1979-10-22 1981-05-25 Dainippon Screen Mfg Co Ltd Color separation method
ATE30638T1 (de) * 1983-12-14 1987-11-15 Hell Rudolf Dr Ing Gmbh Verfahren und einrichtung zur herstellung von farbauszuegen fuer den einzelfarbendruck.
DE3371693D1 (en) * 1983-12-14 1987-06-25 Hell Rudolf Dr Ing Gmbh Method of and circuit arrangement for the recognition of chrominances and colours
EP0144463B1 (de) * 1983-12-14 1987-06-16 DR.-ING. RUDOLF HELL GmbH Verfahren und Einrichtung zur Herstellung von Farbauszügen für den Einzelfarbendruck
DE3751050T2 (de) * 1986-11-14 1995-06-22 Canon Kk Farbbildverarbeitungsgerät.
US5140413A (en) * 1986-11-14 1992-08-18 Canon Kabushiki Kaisha Image processing apparatus including processing means for moving image and performing conversion
EP0741490B1 (de) * 1995-05-05 2000-11-15 Agfa-Gevaert N.V. Originalgetreues Farbwiedergabeverfahren zur Vermeidung von Moiré
ES2142438T3 (es) * 1995-10-13 2000-04-16 Schablonentechnik Kufstein Ag Procedimiento para confeccionar una plantilla, especialmene para imprimir sobre papel o tejidos.

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US3003388A (en) * 1958-05-09 1961-10-10 Hunter Associates Lab Inc Color difference measuring instrument
US3389265A (en) * 1965-05-03 1968-06-18 Du Pont Colorimeter for measuring the tristimulus coefficients of color in a laterally moving material
US3527540A (en) * 1967-05-08 1970-09-08 Itek Corp Color concentration discriminators
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US3389265A (en) * 1965-05-03 1968-06-18 Du Pont Colorimeter for measuring the tristimulus coefficients of color in a laterally moving material
US3578976A (en) * 1966-12-27 1971-05-18 Morat Gmbh Franz Optical scanning device
US3527540A (en) * 1967-05-08 1970-09-08 Itek Corp Color concentration discriminators

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4110826A (en) * 1975-10-07 1978-08-29 Dr. -Ing. Rudolf Hell Gmbh. Apparatus and process for color-identification
US4414635A (en) * 1978-11-28 1983-11-08 Dr.-Ing. Rudolf Hell Gmbh Method and circuit for recognition of colors
US4953012A (en) * 1983-03-08 1990-08-28 Canon Kabushiki Kaisha Image processing system for combining a character image with an image including a gray level
US6192146B1 (en) 1983-03-08 2001-02-20 Canon Kabushiki Kaisha Image processing system

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BE782210A (fr) 1972-10-17
IL39140A0 (en) 1972-06-28
ES402698A1 (es) 1975-10-01
DE2118720A1 (de) 1972-11-16
GB1388026A (en) 1975-03-19
AT322646B (de) 1975-05-26
NL7204478A (de) 1972-10-19
ZA722304B (en) 1973-06-27
CH553452A (de) 1974-08-30
IL39140A (en) 1975-11-25
IT951426B (it) 1973-06-30
FR2136475A5 (de) 1972-12-22
CS161945B2 (de) 1975-06-10
DD99494A5 (de) 1973-08-05

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