GB2158325A - A method and apparatus for facilitating alignment of images - Google Patents

Abstract

Register marks for aligning colour separation images mounted on a transparent substrate e.g. a layout sheet comprise complementary shapes viz. crosses A on yellow separation TA and crosses B on magenta separation TB. The marks A, are provided on non-image areas of the separations during the scanning of the original by utilising synchronising pulses to produce linear images parallel to the main- and sub-scanning axes. By inverting the signals, negative crosses B can be formed. <IMAGE>

Description

SPECIFICATION A method and apparatus for facilitating alignment of images THIS INVENTION relates to a method and apparatus for facilitating alignment of images, in particular a method and apparatus for providing register marks on colour separation images using a colour scanning apparatus for recording the full colour image.

It is known in the printing art that when colour images are to be printed, the full colour original is printed to produce yellow, magenta, cyan and black colour separation plates, which when printed in registration on the same paper in ink of respective colours, reproduce the original full-colour image.

In such cases, it is necessary to ensure exact registration between the colour separation plates, because if they are not exactly registered, non-alignment of colours in the reproduction image or print results in a poor quality print.

In order to secure a sharp and clear setting in the print without non-alignment of the colour separation images, the registering of colour separation image plates is very important. As shown in Fig. 15 of the accompanying drawings, the common practice is to prepare a transparent lay-out film 4 having a size corresponding to that of the plate to be processed, and to provide pins 5 in openings 6 whereby the film is fixed in position. Then a colour separation halftone positive 3 for the first colour plate (usually the magenta plate) is secured to the film 4 in accordance with the desired lay-out using adhesive tape. When all the halftone positives 3 are printed, the operation is finished for the first colour plate.

Then, a second transparent film 4 is firmly set by reference to the first colour plate (i.e.

the magenta plate), with the use of the pins 5, and a second colour separation halftone positive 3 is printed after it has been brought into registration with the magenta halftone positive, thereby finishing the second operation with respect to the second colour plate (e.g. the cyan plate). Likewise, the printing is carried out for the third colour (e.g. yellow) and the fourth colour (e.g. black). When the second to fourth colour images are registered with the first reference colour images, crossshaped register marks 2 can be used to secure the exact registering of the colour images.

The Applicants have previously proposed a method of recording register marks during scanning for securing arl exact registration of colour separation image, which method is disclosed in Japanese Patent Application Laid Open Publication No. 54-46602. As shown in Fig. 17 of the accompanying drawings, according to this method positive crossshaped register marks 24 are produced by cross directional lines 25 in parallel with the subsidiary scanning direction, and grain directional lines 26 parallel with the main scanning direction. In this way the register marks 24 are continuously and exactly recorded in a blank area T2 of the film, that is, in an area outside the colour separation image areas Yl, Ml, Cl and KI.

However, with this previous method of producing the register marks 24, slight increases or decreases in the line widths due to misalignments of the register marks are apt to be overlooked, and an allowance for registering below the actual line widths of the register marks is often permitted. As a result, the operators must continuously pay utmost attention to the registration process, which is a heavy burden for them, and leads to inefficiency.

It is an object of the present invention to overcome or at least mitigate the above mentioned disadvantages.

According to one aspect of the present invention, there is provided a method of facilitating alignment of a plurality of images, which method comprises providing register marks in an area of each image outside a desired image area thereof so that at least part of at least one register mark of one image is a negative of the other register marks.

The present invention also provides a method of recording register marks, which comprises: a first step of producing a first group of picture signals in a cross direction parallel to a subsidiary scanning direction, and a second group of picture signals in a grain direction parallel to a main scanning direction, with the use of timing pulses; a second step of producing positive linear picture signals by combining the first and second groups of signals; a third step of recording by exposure register marks in a blank area outside the reproduction image area of the respective colour separation image by using the positive linear picture signals as register mark signals; and a fourth step of reversing the positive linear picture signals to produce negative linear picture signals, and of outputting the positive and negative linear picture signals selectively so as to produce register mark recording signals, thereby ensuring that the register marks are produced from the positive and negative linear pictures.

According to another aspect of the present invention, there is provided a method of recording register marks, which comprises: a first step of producing a first group of picture signals in a cross direction parallel to a subsidiary scanning direction and a second group of picture signals in a grain direction parallel to a main scanning direction, with the use of timing pulses; a second step of producing positive linear picture signals by combining the first and second groups of signals; a third step of recording by exposure register marks in a blank area outside the reproduction image area of the respective colour separation image by using the positive linear picture signals as register mark signals; and a fourth step of producing the register mark recording signals by dividing the positive linear picture signals at a desired timing so as to produce omitted portions in a part or parts thereof.

In a further aspect, the present invention provides apparatus for facilitating alignment of a plurality of images, which apparatus comprises means for providing a method of facilitating alignment of a plurality of images, which method comprises providing register marks in an area of each image outside a desired image area thereof so that at least part of at least one register mark of one image is a negative of the other register marks.

For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a schematic view showing the register marks produced using a first embodiment, Example 1, of a method according to the present invention; Figure 2 is an enlarged view to illustrate how portions A and B of Fig. 1 can be registered with one another; Figure 3 is a circuit diagram showing apparatus for use in producing the register marks shown in Fig. 1; Figure 4 is a schematic view showing the register marks produced using a second example, Example 2, of a method embodying the present invention; Figure 5 is a circuit diagram showing apparatus for use in producing the register marks shown in Fig. 4;; Figure 6 is an enlarged view showing how the register marks produced using a third example, Example 3, of a method embodying the invention are registered with each other; Figure 7 is a schematic view showing the register marks produced using a further example, Example 4, of a method embodying the invention; Figure 8 is an enlarged view of a row of positive register marks shown in Fig. 7; Figure 9 is an enlarged view of a row of register marks having missing portions at desired positions shown in Fig. 7; Figure 10 is an enlarged view showing a state at which a portion A1 shown in Fig. 8 and a portion B1 shown in Fig. 9 are brought into registration with one another; Figure 11 is a circuit diagram showing a control system for use in producing the register marks shown in Fig. 7;; Figure 12 is a schematic view showing the register marks produced by a fifth example, Example 5, of a method embodying the invention; Figure 13 is a circuit diagram showing a control system for use in producing the register marks shown in Fig. 12; Figure 14 is a schematic view showing the register marks previously used for registering colour separation printing plates; Figure 15 is a plan view showing colour separation films placed on a transparent layout film using the previously proposed method; Figure 16 is a schematic view showing colour scanning apparatus for use in carrying out a method embodying the present invention; and Figure 1 7 is a plan view showing a film on which register marks have been recorded by exposure using the previously proposed method.

Referring now to the drawings, Fig. 16 shows a colour scanner for carrying out a method embodying the present invention.

As shown in Fig. 16, the colour scanner comprises an original image carrying drum or cylinder 12 around which is placed an original colour image 11 and a recording drum or cylinder 14 around which is placed a photosensitive substrate or recording film 13 on which a reproduction image is to be formed.

The two drums 12 and 14 are driven for rotation by means of a common shaft 15, which is itself driven by a motor 16. Reference numeral 17 designates a pick-up or scanning head for scanning the original image 11 to pick-up the image data or information in the image 11, while reference numeral 18 designates a recording head for scanning the drum 14 to record reproduction images on the film 13. The pick-up or scanning head 17 supplies red, green and blue (R, G and B) colour signals to a colour and tone correction circuit 20 which corrects the colour and tone of the R, G and B colour signals and supplies yellow, magenta, cyan and black colour image signals (Y, M, C and K colour image signals) to a memory 21.The Y, M, C and K colour image signals are supplied to control the recording head 18 via a drive circuit 22 under the control of a timing pulse generator which receives pulses Pr and Pc from rotary shaft encoders 23a and 23b.

Example 1 Referring now to Fig. 1, there is illustrated a first embodiment of a method in accordance with the invention for facilitating alignment of colour separation images. In the arrangement shown in Fig. 1, a series of four colour separation plate areas Ty, TM, Tc, and TK are provided on a photosensitive substrate, each plate area comprising a desired image area T and adjacent blank areas T2. As can be seen in Fig. 1, two types of different register marks are provided and are recorded as rows or areas of marks between the colour separation images Yl, Ml etc. Thus, in a first area A the register marks are positive, and in a second area B, the register marks are negative.The register marks in the area B have transparent lines, whereas those in the area A have opaque lines, and in the illustrated example the widths of the two lines are equal. As shown in Fig. 1, a blank area surrounding a magenta colour separation image Ml is formed with areas B of negative register marks while the blank areas surrounding the other colour separation images Yl, Cl and KI are formed with areas A of positive register marks. The negative and positive register marks are provided by respective negative and positive crosses formed by parallel lines 25 separated at a pitch t1 and parallel lines 26 separated by a pitch t2.

Fig. 2 shows the overlaying of the portions A and B in an attempt to register the same and thereby register, for example, the magenta Ml and yellow Yl colour separation images. As shown, the portions A and B are misaligned and therefore a gap 27 appears which would not be present if the portions A and B were correctly registered. It will be apparent from Fig. 2 that in order to secure an exact registration of register marks it is easier to use positive and negative register marks than positive ones alone.

Fig. 3 shows a circuit used for selecting the rows or portions of positive and negative register marks to be recorded for the respective colour separation images.

As shown in Fig. 3, a clock pulse Pc from the rotary encoder 23a is input to a terminal 31, and an image area scanning signal Ck of low level is input to a terminal 32 of the circuit while the recording head 18 (Fig. 16) is scanning an image recording area T,. The low level signal Ck is continuously output from the time the timing pulses are generated so as to read out colour separation signals Y, M. C. and K from a memory 21 (Fig. 16) up to the time another circuit (not shown) counts the number of timing pulses specified by the peripheral dimensions or borders of the image areas of the colour separation images.

The signals input to the terminals 31 and 32 are supplied to respective inputs of a NAND gate 33, from which a pulse H1 is output while the recording head 18 is scanning a blank area T2 adjacent an image area of a colour separation image. The pulse H1 is input to a counter 34.

The signal Ck is inverted by an inverter 35 which supplies a pulse Ck as a reset signal to the counter 34, thereby counting the input pulses H,. Each time a given number N, of pulses are input, the counter outputs a single pulse H,', which is input to a monostable multivibrator 36 where it is converted into a pulse signal H2 having an amplitude sufficient to be input to an OR circuit 43. This modified signal H2 is used for recording lines 25 in a subsidiary scanning direction F (Fig. 1).

A one revolution pulse Pr from the rotary encoder 23b is input to a terminal 37 of the circuit shown in Fig. 3 while a terminal 38 thereof receives a signal Dr which is generated while the recording head 18 is driven in the subsidiary scanning direction F. The signals Pr and Dr are input to respective inputs of an AND gate 39. The AND gate 39 generates a single pulse for each revolution of the recording drum 14 and supplies the same to a counter 40.

Position detecters, such as magnetic sensors, are located along the scanning path followed by the recording head 18. The position detectors output signals Ms which are input to a terminal 41 of the circuit of Fig. 3 as reset signals to enable the counter 40 to count the one-revolution signals Pr from the moment the recording head 18 passes a certain point during the scanning stroke, and to generate a single pulse signal V, each time a desired number N2 of the pulses Ms are counted. The pulse V, is input to a monostable multivibrator 42, and converted into a pulse signal V2 having a desired amplitude.

The pulse signal V2 is then input to an OR circuit 43. The signal V2 is used for recording lines 26 in the main scanning direction E.

As described above, the OR gate 43 generates a signal H2 + V2 (where "+" indicates the logical OR operation in Boolean Algebra).

This signal is obtained by converting the signals generated by the counter 34 or 40 into pulses having a desired amplitude each time they reach the desired number N, or N2.

A A terminal 72 receives a signal tM corresponding to a magenta image area TM (or a signal ty, or tK or tc corresponding to the image area of any other reference colour separation plate), which signal is input to one of the terminals of an exclusive-OR (EX-OR) gate 45. The output signal (H2 + V2) from the OR gate 43 is input to the other terminal of the EX-OR gate 45. When the signal tM is low, that is when a colour separation plate other than the magenta separation plate is being scanned, the output signal (H2 + V2) from the OR gate 43 is gated through the EX-OR gate 45 to be output thereby for recording positive register marks.However, when the signal tM is high, that is when the magenta separation plate is scanned, the output signal 102 from the EX-OR circuit comprises the inverse of the OR gate output signal, that is (H2 + V2) for recording negative register marks.

As mentioned above, the signal Ck is at a low level while the colour separation signals Y, M, C and K are read from memory. When the signal Ck is low, a switch 53 is closed and the colour separation signals Y, M, C, K are supplied in succession to the recording head via a terminal 52 to the output terminal 54 through the switch 53. When the signal Ck is high, a switch 51 is closed to allow the output signal from the EX-OR gate to be supplied to the recording head to enable register marks to be recorded in the blank areas of the colour separation images.

A switch 45 normally supplies the output of the EX-OR gate to an amplifier 47. However, the switch 45 may be operated to override the EX-OR gate 45 and to supply the output of the OR gate 43 to the amplifier 47 so that only positive register marks are formed. The signal Ck input to the terminal 32 controls the switch 51 via an amplifier 49. The signal Ck controls the switch 53 via an inverter 48 and an amplifier 50.

In this way colour separation images are recorded on the image recording area T1, and the register mark rows or portions shown in Fig. 1 are recorded on the blank area T2 of each colour separation plate in accordance with the signals from the EX-OR gate 45.

EXAMPLE 2 The negative register marks shown in Fig. 1 are formed by thin transparent lines drawn on a black background. Accordingly, when positive register marks are overlaid exactly on the negative register marks, the positions of the negative register marks cannot be discerned.

To avoid such an inconvenience, an alternative method of recording register marks as illustrated in Fig. 4 may be used.

As shown in Fig. 4, a series of register marks AY, AM, AC and AK (the AK is omitted), are produced as rows of register marks in the blank areas between the colour separation images Yl, Ml etc. As the rows of register marks show, the AY register lines are recorded in the blank areas before and after the yellow image Yl, and the AM lines are recorded in the blank areas before and after the magenta image Ml and this is repeated for the cyan and the black images Cl and KI. Each row of register marks has negative transparent crosses or register marks 30 which are arranged such that their position in the row of register marks is different for each colour.

The transparent lines making up the negative register marks and the lines making up the positive register marks are of the same width. When the separation images are to be aligned using these register marks, it is not necessary to specify a type of register mark (that is, a reference colour separation plate) for a reference register mark, unlike the arrangement described in Example 1, because each colour separation image has both positive and negative register marks associated therewith. Instead, it is possible to carry out an exact registration by using the alternating positive and negative register marks. The resulting registration will be equal to that shown in Fig. 2. Also, if four plates are simultaneously overlaid, it is easy to carry out registering, which is a great advantage.Particularly, the problem of not being able to make out the register marks which occurs with the arrangement of Fig. 1 is overcome. After register marks of a positive type have been used to secure an exact registration, it is possible then to use register marks of both positive and negative types so as to ensure a more precise registration.

Fig. 5 shows a circuit for use in recording the register mark rows shown in Fig. 4. It should, of course, be understood that like references numerals are used in Figs. 5 and 3 to designate like components and elements, and that the description of components common to Figs. 3 and 5 have, in the interests of simplicity, not been repeated.

As mentioned above, in the arrangement shown in Fig. 4, each row of register marks AY, AM, AC and AK has negative or transparent crosses or register marks 30, the positions of which are different for each colour separation image. Therefore the circuit shown in Fig.

5 includes a switching means for supplying a particular signal to one input of the EX-OR gate 45 in response to the state of the signals input to terminals 71, 72, 73 and 74, which signals indicate whether the yellow, magenta, cyan and black plate, respectively, is being scanned.

In the circuit shown in Fig. 5, the OR gate 43 outputs pulses (H2 + V2) having a pulse width determined by the monostable multivibrator 36 or 42 based on the respective signals supplied to each multivibrator when the predetermined number N1 or N2 of input signals are counted by the respective counter 34 or 40.

The output signals V1 from the counter 40 are also input to a counter 61 and a shift register 63 of the switching means 60. The start signal Ms input to a terminal 41 is input to the counters 40 and 61, and the shift register 63 to provide a reset signal.

The counter 61 outputs two kinds of signals, for example, signals V3 and V4 obtained by dividing the number of pulses V1 by two and four, respectively, and delaying them by a given number of pulses from the start signal Ms (which is produced at intervals corresponding to 1/2 the pitch t2 between the adjacent grain directional lines 26). The delayed signals V3 and V4 are input to respective inputs of an AND gate circuit 62.

The AND gate 62 outputs pulse signals Vy, which are input to the shift register 63 and also to one input of an AND gate 64.

The shift register 63 outputs in sequence signals VM, Vc, and VK which are delayed by a time corresponding to the t2 pitch wherein the signal VM is delayed relative to the input signal Vy the signal Vc is delayed relative to the signal VM, and the signal VK is delayed relative to the signal Vc.

A decoder can effectively be employed instead of the AND gate 62 and the shift register 63 to obtain the signals VM, Vc, VK. A signal ty indicating whether the yellow separation image area ty is being scanned is input via a terminal 71 of the switching means 60 to the other input of AND gate 64, which gate 64 supplies a signal ty.Vy, (where "." indicates the logical AND operation in Boolean Algebra) to one of the input terminals of a four-input OR gate 68.

A signal tM corresponding to the magenta plate separation image area TM is similarly input via a terminal 72 to one input of an AND gate 65, the signal VM being input to the other input of the gate 65 which supplies a signal tM.VM to another one of the input terminals of the OR gate 68.

A signal tc corresponding to the cyan separation image plate area Tc is input via a terminal 73 to one input of a AND gate 66, the other input of which receives the signal Vc, so that the AND gate supplies a signal tc.Vc to a further input of the OR gate 68.

A A signal tK corresponding to the block separation plate image area TK is input via a terminal 74 to one input of an AND gate 67.

The other input of the AND gate 67 receives the signal VK, and the gate therefore outputs a signal tKVk to the OR gate 68.

Thus, the OR gate 68 outputs a signal: tyVy + tM#VM + tc#Vc + tK#VK.

When the output signal from the OR gate 68 is low, the EX-OR gate 45 outputs the signal V2 + H2, whereas when the output of the OR gate 68 is high, the gate 45 outputs the inverse signal (V2 + H2). Accordingly, when the line indicated by the arrow 105 in Fig. 4 is scanned, the signal (V2 + H2) is initially output, then at the blank or empty areas of the yellow colour separation image, that is the free area bounding the yellow image on each side in the main scanning direction E, the inverted signal (V2 + H2) is output by the EX-OR gate 45 for producing negative register marks 30. Over blank or empty areas of the magenta and cyan colour separation image areas along the direction of the arrow 105, the signal V2 + H2 is again output in order to produce positive register marks.

When the line indicated by the arrow 106 is scanned, the signal V2 + H2 is output over the yellow, cyan and black blank areas, but at the magenta blank area the inverted signal (V2 + H2) is output so that negative register marks 30 are provided on the magenta blank areas in line with the arrow 106 as shown in Fig. 4.

The output signal of the EX-OR gate 45 is supplied to the recording signal output terminal 54 through the amplifier 47 when the switch 51 is closed. As described above, the colour separation signals Y, M, C and K are supplied via the terminal 52 to the output terminal 54 through the switch 53 when the switch 54 is closed, the switches 51 and 53 being controlled by the signal CK as described above with reference to Fig. 3.

In carrying out the method, the same procedure as for Example 1 is used. Thus, as shown in Fig. 4, the colour separation images are recorded in the respective image recording areas on the film, and the register marks corresponding to the colour separation plates are recorded in the respective blank areas before and after each colour separation image.

As will be appreciated from above, the position and order of the negative crosses 30 in Fig. 4 is selectively predetermined by the switching means 60 and the method used has the advantage that two or more colour separation plates can be easily brought into registration at the same time.

EXAMPLE 3 In Examples 1 and 2 described above, the widths of the lines forming the positive and negative register marks are equal. However, if the film is over-exposed, thereby causing an unwanted thickening in either or both of the negative and positive register marks, it is no longer possible to secure the exact registration with the use of known register pins. In contrast, in the Example 3 to be described below, the transparent lines making up the negative register marks are thicker than the opaque lines making up the positive register marks so that exact registration can be obtained even when the films are over-exposed because of the symmetrically thickened line width of the negative register marks in comparison with that of the positive register marks.Thus, the circuit shown in Fig. 3 can be modified to reduce the frequency dividing ratio of the counters 34 and 40 and advance the timing for triggering the monostable multivibrators 36 and 42 by a time corresponding to 1/2 of the pulse length so increasing the widths of the pulses output by the monostable multivibrators 36 and 42 by a time corresponding to the desired line width thickening. A gate circuit is used to reduce the number of pulses input to the counters 34 and 40 appropriately so as to be keep the pitch of the negative register marks to be recorded equal to those of the positive register marks. This modified circuit can be constituted using a counter, a shift register and a gate circuit.

In the illustrated arrangement, four colour separation images C, Y. M and K are registered around the registering drum, but it is possible to register them colour by colour in a single process.

In the Example 1 shown in Fig. 1 the register mark rows are made up of either positive or negative register marks but, as shown in Fig. 4, where necessary it is possible to use a mixture of negative and positive register marks.

EXAMPLE 4 Fig. 7 is a schematic view showing register mark rows produced in a further Example, Example 4, and Figs. 8 and 9 are enlarged views showing the register mark rows of Fig.

7. Fig. 8 shows the positive register marks and Fig. 9 the register mark row in which the register marks have missing portions 30a, 30b at desired positions.

As shown in Fig. 10 if, when the register marks of Figs. 8 and 9 are overlaid, two kinds of register marks are not exactly in registration with each other, a transparent or blank portion 27a is produced. It is merely necessary therefore to overlay the marks without causing such a blank portion 27a to occur to ensure registration of two images. When there are no missing portions 30a and 30b, and if the white blank portion is smaller in amount than the width of the thickening of the lines of the register marks. However, when the missing portions 30a and 30b are provided, it is easy to recognize misregistration even if the blank portion is small.

Referring now to Fig. 11 there is shown a circuit for controlling the recording head to produce the register marks shown in Fig. 7. It should, of course, be appreciated that like reference numerals in Figs. 3 and 11 designate like parts.

As shown in Fig. 11, the NAND gate 33 outputs a pulse signal H1 when the signal Ck is high, that is, when the recording head 18 scans a blank area. The signal Ht is input to the counter 34 and a shift register 69.

The signal Ck is inverted to provide an inverted signal Ck by the inverter 35, which inverted signal is input to the counter 34 and the shift register 69 as a reset signal.

When the signal Ck is high, the counter 34 counts the input pulses H1, and outputs a pulse Hia each time it receives a given number N1 of pulses H,. The pulses Hia are individually input to the monostable multivibrator 36, where their pulse widths are converted into pulse signals H2 having a desired pulse width at the falling edge of the pulses.

The pulse signals H2 are input to the OR gate 43 and the shift register 66. The pulse signals H2 are used to record the lines 25 in the subsidiary scanning direction F.

The AND gate 39 outputs one pulse Pr for each revolution of the recording drum while the recording head 18 (Fig. 16) is driven, and the pulses are input to the counter 40 and a shift register 70.

A terminal 41 receives output signals M5 from a position detector, such as a magnetic sensor, arranged along the moving path of the recording head 18. The signals M5 are input to the counter 40 and the shift register 70 as reset signals.

The counter 40 counts the pulses Pr immediately after the recording head has passed a certain point in its scanning operation, and outputs one pulse signal V1 each time it counts a given number N2 of pulses Pr. The pulse signal V1 is input to the monostable multivibrator 42, and its pulse width is converted into a pulse signal V2 having a desired width at the falling point of the signal V1. The signal V2 is input to the OR gate 43 and the shift register 70 and is used to record the lines 26 in the main scanning direction E.

The OR gate 43 outputs a signal H2 + V2 having a pulse width determined by the monostable multivibrator 36 or 42 each time the counter 34 or 40 counts the desired number N1 or N2 of pulses. The output signal H2 + V2 is used to cause a positive type of register mark to be recorded.

The shift register 69 outputs a signal H2a at a time corresponding to the distance L1 in Fig.

9 relative to the signal H2, the signal H2a being input to an OR gate 80.

Likewise, the shift register 70 outputs a signal V2a at a time corresponding to the distance L2 in Fig. 9 relative to the signal V2, the signal V2a also being input to the OR gate 80.

As a result, the OR gate 80 outputs a signal H2a + V2a at a time corresponding to the positions L1 and L2 in the main scanning direction and the subsidiary scanning direction, respectively, relative to the signal (H2 + V2) output from the OR gate 43. The signal H28 + V28 is input to one of the input terminals of a NAND gate 90. The values of the L1 and L2 may be either equal or different.

A terminal 72 receives a signal tM corresponding to the magenta colour separation image area TM, which signal is input to the other input terminal of the NAND gate 90.

The NAND gate 90 outputs an inverted signal tM.(H2a + V2a), which output signal is supplied to one of the input terminals of an AND gate 95. The other input of the AND gate 95 receives the output H2 + V2 of the OR gate 43.

In this way the AND gate 95 outputs the logical sum J of the signals (H2 + V2) and tM.(H2a + V2a). The signal J is supplied to the output terminal 54 via the amplifier 47 and the switch 51 when the switch 51 is closed in response to a high signal Ck. When this signal J is high, and the switch 51 is closed, the recording head 10 is controlled to record the positive register marks in their regular form, and when the signal J is low, the output signal via the closed switch 51 becomes low, switching off the register mark recording signal so that register marks having missing portions corresponding to the line width in Fig. 9 are recorded.

It is desirable to add a further monostable multivibrator to be used to convert or correct pulse widths, or to use a shift register having a plurality of output terminals and a gate circuit, so that the omitted line width of the register marks is larger than the actual line width to facilitate the registration process.

Colour separation plate image signals Y, M, C and K are supplied to the terminal 54 when the switch 53 is closed by a low clock signal Ck to enable the recording head 18 to record the colour separation images while, as mentioned above, when the signal Ck is high, the switch 51 is closed to supply the signals J to the terminal 54, to enable the recording head to record register marks in the blank areas adjacent the colour images.

As shown in Fig. 7, the colour separation images are selectively recorded for the image recording areas T, and, as shown in Figs. 8 and 9, the register mark rows selectively recorded for the blank areas T2. In Example 4 the register mark rows shown in Fig. 9 are recorded for'the magenta plate as a reference plate, and the register mark rows shown in Fig. 8 are recorded for the other colour plates.

EXAMPLE 5 Referring now to Fig. 12, reference numerals 30a and 30b designate missing portions of register marks, the missing portions being located at different positions in each register mark row for each different colour separation plate. When the registering is carried out with these register marks, it is not necessary to specify the reference colour separation plate, and it is possible to proceed with the registration by selecting one of the register marks with respect to the other as exactly as shown in Fig. 10. As compared with the Example 4 shown in Fig. 7, Example 5 provides the advantage that the different locations of the two missing portions 30a and 30b facilitate the registration work, particularly for a plurality of plates.

Referring to Fig. 13, there is shown a circuit for use in producing the register marks of Fig. 12. In Figs. 11 and 13 like reference numerals designate like elements and components and a description of these like elements and components will be omitted below in the interests of simplicity. As described above, control means are provided in Example 5 to record the missing portions 30a and 30b at different positions in each register mark row AT, AM, AC and AK, the position of the missing portions 30a and 30b being characteristic of each colour separation plate image.

As shown in Fig. 13, the OR gate 43 outputs the regular register mark signal (H2 + V2). The output signal H, from the NAND gate 33 is input to a counter 85 which divides the frequency of the pulses to a suitable sub-multiple (for example a divide-by-two counter) of the original frequency for use as clock pulses for the shift register 69. For the shift register 69 a multi-stage type having a plurality of output terminals is effectively employed. The signal H2 input to the register 69 is shifted under control of the clock pulses to produce respective signals H5, H6, H7 and H8 in succession at each of four output terminals of the shift register, the four signals H5 to H5 being delayed one after another by a time corresponding to the desired pitch.The four signals H6 to H8 are each input to one of the input terminals of a respective one of four OR gates 81, 82, 83 and 84. The output signals H8 to H8 from the shift register 69 determine the location of the missing portions 30b in the line 26 (Fig. 12) parallel to the main scanning direction E of each colour separation plate.

The output signal from the AND gate 39 is input to a counter 86 where it is divided to provide pulses of an appropriate frequency (for example a divide-by-two counter) for use as clock pulses for the shift register 70. A multistage type shift register 70 having a plurality of output terminals is employed. The input signal V2 to the shift register is shifted by the clock pulses input thereto to produce respective signals Vst V6, V7 and V8 in succession at each of four output terminals, the four signals V5 to V5 being delayed one after another by a time corresponding to the desired pitch in the subsidiary scanning direction. The four signals V8 to V8 are each input to the other input terminal of a respective one of the OR gates 81, 82, 83 and 84.The output signals V8 to V6 from the shift register 70 determine the location of the missing portions 30a in the line 25 (Fig. 12) parallel to the subsidiary scanning direction of each colour separation plate.

Each OR gate 81, 82, 83 and 84 outputs a signal (H8 + V5), (H5 + V6), (H7 + V7) and (H8 + V8), respectively, against the regular register mark signal (H2 + V2) in the main scanning direction and the subsidiary direction, wherein the output signals (H8 + V5) to (H5 + V8) being delayed one after another by a time corresponding to the desired pitch, thereby enabling the signals to correspond to the respective colour separation plates. These signals are each input to one of the input terminals of a respective NAND gate 91, 92, 93 and 94.

The terminal 71 receives a signal ty for the yellow area Ty (Fig. 12), which signal is input to one of the inputs of the NAND gate 91, the other input thereof receiving the signal (H5 + V8) so that an output signal ty.(H5 + V8) is generated by the NAND gate 91 to control the recording of register marks for the yellow plate.

Likewise, the NAND circuit 92 outputs a signal tM.(H8 + V6), the NAND circuit 93 outputs a signal tC.(H7 + V7)and the NAND gate 94 outputs a signal tK.(H8 + V8) respectively, to control recording of register marks for the magenta, cyan and black plates.

As mentioned above each of the OR gates output a respective signal (H8 + V5) to (H8 + V8) which together with the output signal (H2 + V2) from the OR gate 43 control the positions at which missing portions are provided in the register marks for each colour image. Thus, when the signal H2 + V2 is high to indicate the recording head is in a position where register marks are to be recorded, that is adjacent a blank area of a colour separation image area, and the signal ty, tm, tc or tk is high indicating the Y, M, C or K colour image, then when the corresponding signal H8 + Vst H8 + V6, H7 + V7 or H8 + V8, respectively, is high, a low output will be supplied by the respective NAND gate 91, 92, 93 or 94.

The recording control signals and the regular register mark signals are combined by an AND gate 96 to produce a signal J,. When the signals ty.(H8 + V5) to tK.(H8 + V5) are all high, positive register marks are recorded, but when any of the four signals is low, the output signal J, becomes low so that the recording of register marks is stopped. As a result the register marks having missing portions differently located in accordance with the colour separation plate are recorded. The signal J, is supplied to the output terminals 54 through the amplifier 47 and the closed switch 51.Thereafter, the same procedure as that in the Example 4 is used: that is the colour separation images are recorded for the image recording areas T2, and the register mark rows (Fig. 12) corresponding to the colour separation plates are recorded for the blank areas T,.

The missing portions 30a, 30b (Figs. 7 and 12) in the register mark rows are provided at different positions, in different orders and to different lengths, the positions, orders and lengths being determined by means of the counters 85 and 86, the shift registers 69 and 70, and by differently constructing the OR gates 81 to 84, and the NAND gates 91 to 94, or by arranging other circuits containing one of the above-mentioned elements.

In the arrangements described above, the four colour separation images Yl, Ml, Cl and Kl are arranged at four places around the peripheral surface of the drum, to enable the simultaneous recording of the four pictures colour separation image to be effected However, the present invention is not limited to such an arrangement and it is possible to record one kind or two kinds of colour separation images in one process.

Also the shapes of the register marks can be variously selected to be other than the cross-shaped marks so far mentioned. For example, the register marks can be: L-shaped, 1-shaped, -shaped,#l -shaped or inversions thereof.

Thus, a method and apparatus embodying the invention enables the provision of register marks which ensure that a non-alignment of the register marks can readily be checked regardless of the fact that an apparent thickening or thinning of the line width may occur due to an inappropriate registering, thereby securing the efficient and exact registering of the register marks and also the colour separation images.

Claims (44)

1. A method of facilitating alignment of a plurality of images, which method comprises providing register marks in an area of each image outside a desired image area thereof so that at least part of at least one register mark of one image is a negative of the other register marks.

2. A method according to claim 1, wherein each register mark is provided by controlling a recording head of apparatus for recording the image.

3. A method according to claim 1 or 2, wherein the images are colour separation images to be aligned to produce a full colour image.

4. A method according to claim 1, 2 or 3, wherein each register mark is made up of rectilinear elements.

5. A method of providing register marks on a colour image separation using colour image scanning apparatus, the method comprising: producing first image signals parallel to the subsidiary direction of the colour scanning apparatus and second image signals parallel to the main scanning direction, with the use of timing pulses; producing positive linear image signals by combining the first and second image signals; recording by exposure register marks outside a desired colour image area for the respective colour separation image, by using the positive linear image signals as register mark signals; and inverting the positive linear image signals to produce negative linear image signals so as to produce register mark recording signals, thereby ensuring that the register marks are produced from the positive and negative linear images.

6. A method according to any preceding claim, wherein, for at least one image of the plurality of images, at least some of the register marks are negative images of the other register marks.

7. A method according to any preceding claim, wherein the negative register marks or negative parts of register marks are provided at selected different positions for each image of the plurality of images.

8. A method according to any preceding claim, wherein the negative register marks or negative parts of register marks are of substantially the same width as the positive register marks.

9. A method according to any one of claims 1 to 7, wherein the negative register marks or negative parts of register marks are thicker than the positive register marks.

10. A method according to claim 9, wherein the negative register marks or negative parts of register marks are symmetrically thicker than the positive register marks.

11. A method according to any preceding claim, wherein each negative register mark or negative part of a register mark is bounded by positive image lines.

1 2. A method according to claim 1, 2, 3 or 4, wherein each negative part of a register mark comprises a missing or negative portion or portions of a positive register mark.

13. A method of providing register marks on a colour image separation transparency using colour scanning apparatus, the method comprising: producing first image signals parallel to a subsidiary scanning direction of the colour scanning apparatus and second image signals parallel to a main scanning direction thereof, with the use of timing pulses; producing positive linear image signals by combining the first and second signals; recording by exposure register marks outside the image area for the respective colour separation image, by using the positive linear image signals as register mark signals; and producing the register mark recording signals by dividing the positive linear picture signals at a desired timing so as to produce a missing or negative portion or portions therein.

14. A method according to Claim 12 or 13, wherein, for at least one of the images, at least some of the positive image register marks have a missing or negative portion or portions.

15. A method according to Claims 12, 13 and 14, wherein the position of the missing or negative portion or portions is dependent on the particular image associated therewith.

16. A method of providing register marks on a transparency carrying a colour separation image substantially as hereinbefore described with reference to Figs. 1 to 3, Figs. 4 to 5, Fig. 6, Figs. 7 to 11 or Figs. 12 and 13 of the accompanying drawings.

17. Apparatus for facilitating alignment of a plurality of images, which apparatus comprises means for providing register marks in an area of each image outside a desired image area thereof so that at least part of at least one register mark of one image is a negative of the other register marks.

18. Apparatus according to Claim 17, wherein the register mark providing means comprises means for controlling a recording head of recording equipment to record register marks on the images.

19. Apparatus according to Claim 17 or 18, wherein the register mark providing means is arranged to provide at least some negative register marks for at least one image.

20. Apparatus according to Claim 19, wherein the register mark providing means is arranged to provide all negative register marks for one image.

21. Apparatus according to Claim 17, 18 or 19, wherein the register mark providing means is arranged to provide negative register marks at predetermined positions for each image.

22. Apparatus according to Claim 17 or 18, wherein the register mark providing means is arranged to provide positive register marks one or more of which have a negative part or parts formed by a missing or negative portion or portions of the positive register mark.

23. Apparatus according to Claim 22, wherein the register mark providing means is arranged to provide a negative missing portion or portions in at least some of the positive register marks of at least one of the images.

24. Apparatus according to Claim 22, wherein the register mark providing means is arranged to provide a missing or negative portion or portions in register marks for each image, the missing or negative portion or portions being at predetermined different positions for each image.

25. Apparatus according to any one of Claims 17 to 24, wherein the register mark providing means comprises logic circuitry for providing register marks in response to signals indicating a particular image.

26. Apparatus according to Claim 17, wherein the register mark providing means comprises a recording head movable in a first scanning direction along a drum which is rotatable in a second scanning direction to record register marks on a substrate carried by the drum and control means for controlling the recording head.

27. Apparatus according to Claim 26, wherein the control means comprises means for providing a first signal when a blank area adjacent an image area is being scanned by the recording head, means for detecting the position of the recording head relative to the substrate, means for producing a second signal at selected relative positions of the recording head and the substrate, means for producing a third signal when the recording head is scanning a selected image, and means for receiving the first, second and third signals to control the recording head to produce a positive register mark when the first and third signals are received and to produce a negative or part-negative register mark when the first and second signals are received.

28. Apparatus according to Claim 27, further comprising switching means for receiving the output of the receiving means and for supplying either image signals to the recording head or signals for a register mark, the switching means being operable to supply the register mark signals to the recording head in response to the first signal.

29. Apparatus according to Claim 27 or 28, wherein the first signal providing means comprises first counting means for counting clock pulses when the recording head is scanning a blank area and for providing the first signal when a predetermined count is reached.

30. Apparatus according to Claim 27, 28 or 29, wherein the second signal providing means comprises second counting means for counting clock pulses when the recording head is scanning a blank area and for providing the second signal when a predetermined count is reached.

31. Apparatus according to Claim 29 or 30, wherein each counting means comprises a counter and a monostable circuit for modifying the output of the counter.

32. Apparatus according to any one of Claims 27 to 31, wherein the receiving means comprises an OR gate having respective inputs for receiving the first and second signals and an exclusivc OR gate for receiving the output of the OR gate and the third signal.

33 Apparatus according to any one of Claims 27 to 32, wherein the third signal is provided by means for detecting when a selected image is scanned.

34. Apparatus according to any one of Claims 27 to 32, wherein the third signal providing means comprises means for detecting when each image is scanned and for supplying a respective signal to each of a plurality of AND gates, decoding means for deriving a series of control signals delayed relative to one another from the second signal and for supplying each control signal to the other input of a respective one of the AND gates, the output of each AND gate being supplied to an OR gate for supplying the third signal to the receiving means.

35. Apparatus according to any one of Claims 27 to 31, wherein the receiving means comprises a decoding means for receiving the first and second signals to produce modified first and second signals, a first OR gate for receiving the first and second signals and a second OR gate for receiving the modified first and second signals, the output of the first OR gate being supplied to an AND gate and the output of the second OR gate to a NAND gate which also receives the third signal, the output of the NAND gate being input to the AND gate to control the recording head.

36. Apparatus according to any one of Claims 27 to 31, wherein the receiving means comprises a decoding means for receiving the first and second signals to produce a respective series of modified first and second signals, the signals of each series delayed relative to one another, a first OR gate for receiving the first and second signals and a plurality of second OR gates for each receiving a respective modified first signal and a respective modified second signal, the output of each second OR gate being supplied to one input of a respective NAND gate, and wherein the third signal providing means comprises a plurality of detecting means for each detecting when a respective image is being scanned by the recording head, the output of each detecting means providing the other input of a respective one of the NAND gates and the outputs of the NAND gates being supplied together with the output of the first OR gate to an AND gate the output of which is arranged to control the production of register marks by the recording head.

37. Apparatus for facilitating alignment of colour separation images in accordance with any one of Claims 17 to 36.

38. Apparatus for facilitating alignment of colour separation images, substantially as hereinbefore described with reference to, and as illustrated in, Figs. 1 to 3, Figs. 4 to 5, Figs. 4 to 5 as modified by Fig. 6, Figs. 7 to 11 or Figs. 12 and 13 of the accompanying drawings.

39. A method of producing a composite image whenever using a method in accordance with any one of Claims 1 to 16 and/or apparatus in accordance with any one of Claims 17 to 38.

40. Apparatus for producing a composite image whenever using a method in accordance with any one of Claims 1 to 16 and/or apparatus in accordance with any one of Claims 17 to 38.

41. Colour image reproducing apparatus for reproducing a composite image whenever using a method in accordance with any one of Claims 1 to 16 and/or apparatus in accordance with any one of Claims 17 to 38.

42. Colour image reproducing apparatus substantially as hereinbefore described with reference to, and as illustrated in, Fig. 16 in combination with Figs. 1 to 3, Figs. 4 to 5, Figs. 4 to 5 as modified by Fig. 6, Figs. 7 to 11 or Figs. 12 and 13 of the accompanying drawings.

43. A method of reproducing a colour image substantially as hereinbefore described with reference to Fig. 16 in combination with Figs. 1 to 3, Figs. 4 to 5, Figs. 4 to 5 as modified by Fig. 6, Figs. 7 to 11 or Figs. 12 and 13 of the accompanying drawings.

44. Any novel feature or combination of features described herein.