GB2104340A - Color scanner system for making color separations - Google Patents

Abstract

The system described which may be used to make color separations without need of highly skilled operators comprises first scanner means (12, 14, 18, 24, 32) for roughly scanning an original (10) with a white light beam (26) to produce a first electrical signal representative of optical densities of separated colors; second scanner means (12, 14, 20, 24, 32) for finely scanning the original document (10) to produce a second electrical signal representative of densities, encoders (48, 50) for producing a third electrical signal representing a scanning position of the first and second scanners, a processor (38) for processing the electrical signals to form image signals, and a recording unit (102, 104, 108, 112, 116, 118, 122, 1 24, 1 26, 128) for recording an image on a photosensitive material (100) in response to the image signals. The processor obtains values concerning the densities and colors of a selected area of the original image from the first electrical signal associated therewith, and compares them with reference values to produce corrections of tones and colors, which are in turn stored in a memory (40). The processor modifies the second electrical signals in accordance with the corrections to provide the recording unit with the modified signals as the image signals. <IMAGE>

Description

SPECIFICATION Color scanner system for making color separations The present invention relates to a color scanner system for making color separations, in particular to a system comprising scanning means for scanning an original image or document with a white light beam to produce electrical signals representative of optical densities, processor means for processing the electrical signals to form image signals for recording, and recording means operative in response to the image signals for generating and modulating an optical beam with the image signals to form an image on a photosensitive material.

Conventionally, scanning conditions are set into a color scanner by manually operating the keys and switches of the console thereof in accordance with the natures and characteristics of the original document or image (hereinafter referred to as an "original"). In some cases, the features of an original are determined by visual inspection, in which case differences in operator experience may cause variations in color separations, and hence in the recorded image produced. Therefore, an original document classification system has been developed by the use of which data relating to the natures and characteristics of an original may be determined and the scanning conditions which are to be set in a color scanner calculated.

Such an original document classification.

system was, however, independent of the color scanner system, and the data produced from the classifying system were not in the form which may directly bs received by a color scanner for setting the scanning conditions.

For example, a prior art document classification system had a monitoring display and an operating console with keys and switches similar to those of the color scanner. In operation, the operator observed an original visualized on a monitor display, adjusted the keys and switches on the console to obtain desired tones and colors on the display, memorized the values indicated by the keys and switches, and in turn set those values into the color scanner to be utilized to produce a color separation having an image formed thereon of substantially the same tones and colors as displayed on the monitor. With such prior art apparatus, variations in tone and color due to difference in experience of operators may be introduced since manual operations intervene between the displayed picture and the keyboard. Memorizing setting values of the keys and switches by the operator is troublesome.

The document classification apparatus has therefore difficulties in providing appropriate reproducibility of original images.

There are many kinds of color scanners which are different in arrangement and operability of keyboards. For example, relationships between coior-separated optical densities obtained from an original document scanned and output characteristics of exposing a photosensitive recording material for color separations are different system by system. Therefore, one kind of classification apparatus may not commonly be applicable to all color scanners.

Another kind of apparatus for measuring features of an original image is adapted to roughly scan an original image to get optical densities for the respective separated colors, for instance, red (R), green (G) and blue (B), together with intensity (V), which are accumulated for each separated color to calculate the distributions thereof so as to be compared with reference values to produce scanning conditions for setting a color scanner. Such a kind of apparatus determines scanning conditions by sensing not colors but only tones of an original image. This fails to correct or modify minute color differences. Additionally, the apparatus is not adapted to provide resultant data in the form appropriate for the direct entry to a scanner system.

Accordingly, there is a need for a color scanner system for making a color separation by simplified operations without setting sophisticated scanning conditions on tones and colors, and hence without document classifying apparatus and highly trained operators.

According to the present invention there is provided a color scanner system for producing color separations comprising: first scanner means for roughly scanning an original with a white light beam to produce a first electrical signal representative of optical densities of separated colors; second scanner means for finely scanning the original with a white light beam to produce a second electrical signal representative of optical densities of the separated colors; means operative in response to said first and second scanner means for producing a third electrical signal representative of a scanning position of said white light beam; processor means for processing the electrical signals to form image signals for recording; recording means operative in response to the image signals for generating and modulating an optical beam with the image signals to form an image on a photosensitive material; input means for receiving signals representing scanning conditions and a magnification by which an image comprised in the original is to be recorded on the photosensitive material, said scanning conditions including a position of an area selected from areas into which the image comprised in the original is divided, parameters relating to optical densities and colors in the selected area, and reference values of optical densities and colors which are appropriate for a printed image reproduced from the original; and sto rage means for storing the first and second electrical signals in association with the third electrical signal, as well as the signals representing the scanning conditions and the mag nification, said processor means obtaining values concerning the optical densities and colors of the selected area from the first electrical signal associated with the area, and comparing the obtained values with the reference values to produce correction values of tones and colors to be stored in said storage means, and said processor means modifying the second electrical signals in accordance with the correction values to provide said recording means with the modified signals as the image signals associated with the magnification received by the input means.

In a preferred aspect of the invention, said first and second scanner means comprise a common rotary drum for carrying thereon the original to be scanned with a white light beam, said first scanner means including a first scanning head for roughly scanning the original with a scanning spot of a first size, said second scanner means including a second scanning head for finely scanning the original with a scanning spot of a second size, which is smaller than the first size, said first and second scanner means comprising common driving means for transferring said first and second scanning heads along the cylindrical surface of the drum in a longitudinal direction thereof.

In another preferred aspect of the invention, said first and second scanner means comprise a common rotary drum for carrying thereon the original to be scanned with a white light beam, and a single scanning head capable of moving along the cylindrical surface of the drum in the longitudinal directons thereof, said scanning head being adapted to roughly scan the original with a scanning spot of a first size while moving in one longitudinal direction, and to finely scan the original with a scanning spot of a second size which is smaller than the first size while moving in the other longitudinal direction.

Preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic block diagram showing a preferred embodiment of a color scanning system for making color separations in accordance with the present invention; Figure 2 is a flow chart schematically illustrating the operations of the system shown in Fig. 1; and Figure 3 is a schematic block diagram illustrating a portion of another embodiment of a color scanning system in accordance with the invention.

With reference to Fig. 1, a color scanning system in accordance with the present inven tion includes a rotary drum 12, which has a cylindrical surface 11 on which one or more original documents or copies, such as a nega tive or positive film or paper, may be sup ported. Drum 12 is supported by a central shaft 1 6 that is rotatable by means of a motor 14. Closely to cylindrical surface 11 of drum 12, two scanner heads 1 8 and 20 are thread edly carried by a threaded, rotary shaft 22, which is linked to driving means, such as a motor 24, so that scanner heads 18 and 20 may, in a normal operation, move in the direction of an arrow A shown in Fig. 1.

In the illustrative embodiment, a light source (not shown), which generates a beam 26 of white light, for example, is mounted within rotary drum 1 2 so as to move in the longitudinal direction of drum 1 2 in synchron ism with the movements of head 1 8 or 20.

One head 1 8 has an optical aperture (not shown) of a relatively longer diameter, such as one millimeter, as well as an optical system (not shown) for receiving a light beam 26, which is emitted from the light source to pass through a part of an original 10 mounted on peripheral surface 1 of drum 12, while the other head 20 has also an optical aperture (not shown), which is however smaller in diameter (e.g., 50,us) than that of head 18, and forms a part of an optical system for receiving a light beam 26 transmitted through original 10 from the optical source. It may thus be seen that head 1 8 receives optical beam 26 passing through a larger portion of the original 10 than does head 20.In other words, original 10 is scanned with a scanning spot of a larger size by rough scan head 18, and with a scanning spot of a smaller size by fine scan head 20. In the above discussion, original 10 is a transparent type, through which light beam 26 transmitted enters the apertures of heads 1 8 and 20, but the other type of original 10, a reflective type, is of course applicable to a different embodiment of the invention, in which an optical source may be provided outside the rotary drum to generate optical beams of different diameters, which beams are directed to the reflective original on the cylindrical surface of the drum and reflected thereon to be received by the optical systems of heads 1 8 and 20.

The optical systems of hads 1 8 and 20 are optically coupled to a color separating optical system and photoelectric conversion circuitry 32, as depicted schematically in Fig. 1 by arrows 28 and 30. Circuitry 32 separates the light received by heads 1 8 and 20 into three colors, red (R), green (G) and blue (B), for example, to form electrical signals representa tive of the respective intensities of the color separated light.

Conversion circuitry 32 has outputs 33R and 33F interconnected respectively through logarithmic amplifiers 34R and 34F, and an alog-to-digital (A/D) converters 36R and 36F to a processor 38. Processor 38 may be, for example, a microprocessor commercially available, and is connected to a memory 40 in which control sequences and data may be stored. Processor 38 may be provided with an input device 42, from which scanning conditions, discussed later, are manually entered into the system, as well as an output device 44, such as a CRT display unit or a printer.

Motors 14 and 24 for driving rotary drum 1 2 and heads 1 8 and 20 are connected by way of a driver 46 to processor 38. To motors 14 and 24, coupled mechanically are encoders 48 and 50, which are electrically interconnected via a multiplier 52 to processor 38.

Driver circuit 46 is responsive to commands supplied from processor 38 to drive motors 14 and 24 so as to perform scanning lines of original 10 in the direction parallel to the revolutionary direction of drum 12, namely, primary or horizontal scanning, and gradually shifting the primary scanning in the direction parallel to the longitudinal driving shaft 16, that is, secondary or vertical scanning. During the primary and secondary scannings, encoders 48 and 50 produce signals representing an angular position of rotary drive shafts 1 6 and 22, respectively. The signals are sent to multiplier 52. Processor 38 thus identifies the position of a scanning point or pixel on original 10.

The color scanner system illustrated in Fig.

1 includes a recording drum 102, that has a cylindrical surface 111 on which a sheet of photosensitive material 100 may be mounted.

Drum 102 is supported by a rotary shaft.

driven by a motor 1 04. In the vicinity of cylindrical surface 101, a head 108 for scanning the surface is movably carried by a threaded, drive shaft 110. Drive shaft 110, which is rotatable, is coupled to a motor 11 2 so as to, when driven by motor 112, revolve to move head 108 in the direction of arrow B in Fig. 1 in the normal operation.

Recordng head 108 includes a laser (not shown) generating a laser beam 114 impinging upon photosensitive sheet 100. Laser 108 is fed with an output from a light source control 11 6 to modulate laser beam 114.

Light source control 11 6 has an input 11 7 connected via a dot image forming circuit 11 8 and a digital-to-analog (D/A) converter 120 to an output 121 from processor 38. Dot image forming circuit 11 8 also has an input 11 9 connected via dot generator 1 22 to an output 1 23 from processor 38.

Motors 104 and 11 2 for driving recording drum 102 and recording head 108, respectively, are connected through a driver circuit 1 24 to an output 1 25 from processor 38.

Two encoders 1 26 and 1 28 are mechanically coupled to drive shafts 106 and 110, respectively, and electrically connected to a muliplier 130, which has an output 131 connected to processor 38.

Driver 1 24 is responsive to commands sent from processor 38 to drive motors 104 and 11 2 so as to effect secondary and primary scanning with laser beam 114 on photosensitive sheet 100. Both encoders 126 and 128 produce signals representative of respective angular positions of the rotation of drive shafts 106 and 110 to feed muliplier 1 30 therewith so that processor 38 identifies the position of a scanning point of recording head 108, or pixel, on photosensitive sheet 100.

It is to be noted that Fig 1 shows only for simplicity a set of logarithmic amplifiers 34R and 34F, A/D converters 36R and 36F, and the circuitry associated therewith, but in practice a set of those components are provided for each color, R, G and B, separated by color separating system 32.

Memory 40 stores scanning conditions entered from input machine 42, such as a keyboard. The scanning conditions include the conditions under which original image 10 is to be roughly scanned by rough scan head 1 8 to accomplish so-called "rough scan". Specifically, those conditions include the following:: (1) Aperture size, representative of a diameter of the aperture for receiving light of rough scan head 18; (2) Sampling pitch, representing an interval between adjacent two scanning lines in the direction of secondary scanning for rough scan head 1 8 to sample optical densities of separated colors, i.e. a time interval at which processor 38 fetches densities sensed by rough scan head 1 8 by way of A/D converter 36R; (3) Position of a highlight point, which is the position of a point which should be formed on a color-separation as the brightest point in original 10;; (4) Density range, designating the relationship between respective optical densities for separated colors measured on original 10, and tones that are to be reproduced on a color separation, namely, by which characteristics are selected for correcting tones and colors appropriately for the kinds and features of original 10; (5) Reference values, representative of standard optical densities and colors for resultant printed materials; (6) Area, which may be selected from small areas or sections into which the whole area of original 10 is subdivided; and (7) Features, specified on optical densities and colors involved in the area selected as in above paragraph (6).

Additionally, the scanning conditions also include those under which original 10 is to be scanned with a relatively smaller beam spot by fine scanning head 20 to perform so-called "fine scan", as listed below: (8) Aperture size of fine scan, representing a diameter of the light receiving aperture of fine scanning head 20; and (9) Magnification, by which the image on original 10 should be recorded to photosensitive sheet 100.

Now, the operations of the color scanner system shown in Fig. 1 will be discussed with reference to the flow chart of Fig. 2. Basically, the operations include two main procedures; one is a rough scanning sequence shown in the left flow of Fig. 2, and the other fine scanning and recording sequences in the right flow thereof.

In the rough scanning operation, in response to the operative command supplied from processor 38, rough scan head 1 8 runs along drum surface 11 in the direction parallel to the longitudinal axis of drum 1 2 to effect the secondary scanning of original 10, with drum 1 2 revolving by motor 14 to achieve the primary scanning of original 1 0. Thus, original 10 is roughly scanned by head 1 8 having the larger aperture for receiving light beam 26 transmitted from original 10. Color separating system and photoelectric conversion circuitry 32 produces the electrical signals which are representative of color-separated components, R, G and B, in dependence upon the transmissivity or reflectivity of a portion of original 10 scanned with beam 26.

The signals are amplified in a logarithmic fashion by logarithmic amplifier 34R, and in turn converted into corresponding digital signals through A/D converter 36R. Processor 38 receives the digital signals to obtain therefrom signals representative of intensity, V, of the scanned pixel, and then stores both signals into memory 40.

Processor 38 also receives positional signals which come through multiplier 52 from encoders 48 and 50 for drum 1 2 and head 18, respectively. The positional signals, representing the position of the scanning beam spot on original 10, are used in processor 38 to address a location of memory 40 in which the optical density signals are to be stored. Upon completion of scanning the entire image of original 10, the densities of all the pixels or scanning points on original 10 will be stored for the respective, separated colors in memory 40 (box 200, Fig. 2).

Processor 38 reads out the density values stored from memory 40 to execute the necessary operations. With respect to an area selected by the keyboard of input equipment 42, as discussed in above item (6), values associated with the densities and colors are evaluated from the stored density values associated with that area (box 202). The values thus evaluated are then compared with the reference values discussed in above item (5) to obtain correction values for tones and colors as suitable scanning conditions (box 204). The tone and color correction values may be modified in accordance with a highlight point and/or a density range, if specified, as listed in items (3) and (4). The tone and color corrections thus calcurated will be stored in memory 40 in association with the areas involved in original 1 0.

The operations are transferred via the letter B, Fig. 2, from the left flow to the right flow to execute the fine scanning and recording operation sequences.

Processor 38 causes fine scan head 20 to scan original 10 finely with a light receiving aperture selected as discussed in above iten (8). Head 20 responds to the command pro vided from processor 38 to move along cylin drical surface 11 of rotary drum 1 2 in the direction of arrow A to effect the secondary I scanning while rotary drum 1 2 revolves in response to the command to cause the pri mary scanning of original 1 0. Original 10 will therefore be scanned with the light receptacle aperture of head 20 which is smaller in dia meter than that of rough scan head 1 8. The R, G and B component signals are obtained from the optical beam passing through or reflected from original 10 by color separating system and photoelectric conversion circuitry 32 to be amplified in a logarithmic fashion by logarithmic amplifier 34F. The amplified sig nals are in turn converted by A/D converter 36F into corresponding digital signals, which are then received by processor 38 to be stored in memory 40.

Similarly to the rough scanning discussed earlier, processor 38 also receives the posi tional signals which represent the position of a scanned pixel on original 10 from encoders 48 and 50. The signals are also used in processor 38 to address a storage location of memory 40 in which a digital value is to be stored which is representative of an optical density under the fine scan.

For example, assuming that original 10 is composed of a positive of 4 X 5 inches (100 X 1 25 millimeters), which is roughly scanned with a light receiving aperture of one millimeter in diameter of head 18, then mem ory 40 is required to have storage locations of approximately 1 3K bytes for storing therein data representing densities of the respective three separated colors in 256 levels, which require eight bits. When the same document 10 is finely scanned with the aperture of about 50 pm in diameter of fine scan head 20, for example, the same 13K-byte storage area is capable of storing therein density data associated with four to six lines of the fine scanning because one horizontal scanning line includes approximately 600 pixels. Box 206, Fig. 2, is directed to the fine scanning opera tion.

The density values thus obtained and stored in memory 40 are then modified in tone, color and sharpness in accordance with the tone and color correction values calcurated and stored in memory 40 with respect to the corresponding areas involved in original 10 during the rough scan performed (box 208).

Processor 38 then instructs driver 1 24 to drive motors 104 and 112 to perform scanning of recording head 108 over photosensitive sheet 100 for recording. The angular or revolutionary position of recording drum 102 during the primary scanning is entered by encoder 1 26 via multiplier 1 30 into processor 38, while the longitudinal position of head 108 along cylindrical surface 101 is also received from encoder 1 28 through multiplier 1 30 by processor 38.

Processor 38 forwards the recording signals which have been modified in tone, color and sharpness in process 208, Fig. 2, to dot image forming circuit 118 through D/A converter 1 20. Dot image forming circuit 11 8 modulates in turn the dot pattern signals generated and supplied from dot generator 1 22 with the recording signals supplied from processor 38. The modulated signals will then be fed to light source control 116. Light source control 11 6 controls the laser of recordng head 108 in response to the modulated dot image signals to modulate the laser beam 114 therewith. This results in recording several horizontal lines, or a part of the original image on photosensitive material 100.

If a specific magnification is entered by the keyboard as described in above item (9), processor 38 causes driver 1 24 to drive recording head 108 and drum 102 at a scanning rate associated with the specified mangification. In other words, recording head 108 runs at a rate into which the moving rate of fine scanning head 20 is multiplied by the entered magnification, while recording drum 102 revolves at a rate into which the revolving speed of rotary drum 1 2 is multiplied by the magnification. The number of scanning lines per unit length in the secondary scanning direction and the number of pixels per unit length of a scanning line are therefore magnified by the designated magnification.

An enlarged or reduced image will be reproduced on photosensitive sheet 100 (box 210).

In such a manner, the fine scanning and recording operations are continued until the entire image on original 10 has been scanned by fine scan head 20, and reproduced on photosensitive material 100 (box 212). The photosensitive sheet 100 on which the original image has been reproduced may be used through appropriate and necessary processes for producing a printing plate.

The color scanner system in accordance with the present invention has been described with reference to the preferred illustrative embodiment. It will be appreciated that the invention is not specifically restricted thereto, and those skilled in the art may change or modify it without departing from the scope of the invention. For example, Fig. 3 shows a part of another embodiment of the invention, and in the figure, like components are designated by the same reference numerals. In the scanner system shown in Fig. 3, a single scanner head 1 8A is provided on the threaded drive shaft 22 instead of rough and fine scan heads 1 8 and 20 of color scanner system illustrated in Fig. 1.Accordingly, for the single head 18A, a single set of color separating system and photoelectric conversion circuitry 32, logarithmic amplifier 34, and A/D converter 36 are provided with respect to the three separated colors, R, G and B. Processor 38 has an output 302 connected to head control 300, that has an output 304 connected to the sole scanner head 18A. Head control 300 is responsive to the operational commands to control head 1 8A to select an appropriate size of light receiving aperture of head 18A.

In the scanner system depicted in Fig. 3, head 1 8A runs under the control of processor 38 in the direction of arrow Al to perform the rough scanning of original document 10. In the rough scanning mode, processor 38 selects a larger diameter, for example, one millimeter, of the aperture size of head 1 8A through head control 300, and selects a longer interval for sampling original image 10 under scanning. In the fine scanning mode, processor 38 controls head 1 8A via driver 46 so as to move it in the direction of arrow A2 and via head control 300 so as to select a smaller diameter, for example, 50,us, of the aperture size for receiving optical beam 26.

Processor 38 selects a shorter sampling interval to scan original image 10 at a higher pixel density. It is to be noted that the remaining portions of the system shown in Fig. 3 are the same as the corresponding portions of the embodiment of Fig. 1, and will therefore be neither described nor illustrated repeatedly in detail for simplicity.

While the embodiments are described with reference to dot patterns generated by the circuits 11 8 and 122, Fig. 1, the invention, however, is not necessarily restricted thereto, but is applicable also for example to a color scanner system in which image signals of a continuous tone are produced rather than such dot signals.

Claims (4)

1. A color scanner system for producing color separations, comprising: first scanner means for roughly scanning an original with a white light beam to produce a first electrical signal representative of optical densities of separated colors; second scanner means for finely scanning the original with a white light beam to produce a second electrical signal representative of optical densities of the separated colors; means operative in response to said first and second scanner means for producing a third electrical signal representative of a scanning position of said white light beam; processor means for processing the electri cal signals to form image signals for recording; recording means operative in response to the image signals for generating and modulating an optical beam with the image signals to form an image on a photosensitive material;; input means for receiving signals representing scanning conditions and a magnification by which an image comprised in the original is to be recorded on the photosensitive material, said scanning conditions including a position of an area selected from areas into which the image comprised in the original is divided, parameters relating to optical densities and colors in the selected area, and reference values of optical densities and colors which are appropriate for a printed image reproduced from the original; and storage means for storing the first and second electrical signals in association with the third electrical signal, as well as the signals representing the scanning and the magnification, said processor means obtaining values concerning the optical densities and colors of the selected area from the first electrical signal associated with the area, and comparing the obtained values with the reference values to produce correction values of tones and colors to be stored in said storage means, and said processor means modifying the second electrical signals in accordance with the correction values to provide said recording means with the modified signals as the image signals associated with the magnification received by the input means.

2. A system as claimed in claim 1, wherein said first and second scanner means comprise a common rotary drum for carrying thereon the original to be scanned with a white light beam, said first scanner means including a first scanning head for roughly scanning the original with a scanning spot of a first size, said second scanner means including a second scanning head for finely scanning the original with a scanning spot of a second size, which is smaller than the first size, said first and second scanner means comprising common driving means for transferring said first and second scanning heads along the cylindrical surface of the drum in a longitudinal direction thereof.

3. A system as claimed in claim 1, wherein said first and second scanner means comprise a common rotary drum for carrying thereon the original to be scanned with a white light beam and a single scanning head capable of moving along the cylindrical surface of the drum in the longitudinal direction thereof, said scanning head being adapted to roughly scan the original with a scanning spot of a first size while moving in one longitudinal direction, and to finely scan the original with a scanning spot of a second size which is smaller than the first size while moving in the other longitudinal direction.

4. A system substantially as herein described with reference to the accompanying drawings.