GB2155274A

GB2155274A - A method of and apparatus for recording an image

Info

Publication number: GB2155274A
Application number: GB08504874A
Authority: GB
Inventors: Takashi Sakamoto
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1984-03-03
Filing date: 1985-02-26
Publication date: 1985-09-18
Also published as: GB8504874D0; GB2155274B; JPS60185469A; DE3507351A1

Abstract

A single light beam scans unit reading regions of an original image, each covering a predetermined number (e.g. 2) of picture elements and each occupying a plurality (e.g. 2) of scanning lines, the single light beam being arranged to cover the said plurality of scanning lines. A pick-up lens (2) and a beam splitter (3) divide light from the original image into three light paths. Light on one path (111) passes via a lens (41) to a series of dichroic mirrors (5,6,7); reflected light passing via respective colour filters (18R,G,B) to photoelectric converter (8, 91,10) produces three colour signals (RO, GO, BO) from which four colour separation signals are derived for a representative picture element in a region of picture elements. Light on a second path (112) reflected from a dichroic mirror 62 is passed via a filter 18G to a photoelectric converter (92) to enable signals representing green brightness of each of the other picture elements of the region to be derived. Light on a third path, not shown, may fall on a photo-electric converter to provide an unsharp signal, used in detail enhancement. <IMAGE>

Description

SPECIFICATION A method of and apparatus for recording an image This invention relates to a method of and apparatus for recording an image. In particular, this invention relates to a method of and apparatus for use in an apparatus such as a colour scanner.

In an image processing apparatus, such as a layout scanner system in which image data received by an input unit of the scanner and corresponding to a plurality of tone-corrected original images are stored on a memory medium such as a magnetic disk and then an editing process is carried out subject to a layout designated by a central processing unit (CPU) so that a reproduction image may be recorded on a film or the like by an output unit of the scanner based on the processed image data, it is known that the time taken by the editing process can be shortened by adopting a technique of condensing the image signals so as to reduce the amount of memory occupied thereby before reproducing the colour image having variable denisty.

Thus, the data processing is speeded up by decreasing the amount of digital image data which has to be processed, by the adoption of hardware in the editing process and by the speeding up of the hardware itself.

Several proposals for methods of condensing and reproducing colour images having variable density have been made, and the Applicants have proposed a method of condensing and reproducing image signals which takes advantage of the correlation between the characteristics of human eyesight and the image signal and is disclosed in Japanese laid open Publication (unexamined) No.

55-22708. According to the Applicant's proposal, taking advantage of the characteristics of the human eye, which is very sensitive variations of brightness in minute regions but not so sensitive to variations in colour, a unit condensing region comprising a plurality of picture elements adjacent one another is established, and the signals representing brightness are retained for all the picture elements while the signals representing colour are omitted for all except a representative picture element of the unit region so that the number of bits required to store the data is decreased.

In the above proposed method, the memory capacity required to store the data is greatly reduced, and, at the same time, editing can be speeded-up in inverse proportion to the degree to which the data is condensed because the arrangement of the image to be reproduced can be easily carried out using the unit region as a reference unit in the editing process. Furthermore, even in the case of a complicated reproduction image composed of many original images, the recording of the reproduction image does not take so long because the necessary operations merely comprise the step of reading the edited image signals from the memory in sequential order and recording the reproduced image in accordance with the image signals.

However, if the image signals for every picture element are picked up by the input unit of the colour scanner and the condensing step is carried out afterwards in the input unit, the capacity of the memory in which the original image signals are initially stored must be considerable.

Accordingly it may be an idea to condense the image signals in real time while scanning the original image using a conventional rotatable cylinder type of scanner input unit. For that purpose, however, if, for example, a 2 x 2 matrix of picture elements is established as the unit condensing region, it is necessary to provide a buffer memory for at least one scanning line x 4 colours for the condensing process before the condensed data can be stored in the memory of the input unit of the scanner, and moreover, another problem arises in that the input speed is not increased since the condensed image signal is transferred to memory only every two rotations of the cylinder on which the original image is mounted.

Accordingly, if the foregoing method of condensing and reproducing of colour original image having variable density is adopted, although the editing time is greatly shortened, it is impossible to increase the speed at which the original image is scanned and finally speeding up of the whole processing is not achieved. As a result, the speeding up of the scanning operation is an important problem at present.

In an attempt to solve this problem, the Applicants have already proposed a method of scanning image signals corresponding to a plurality of scanning lines in one revolution of the cylinder carrying the original image as is disclosed in Japanese laid open Publications (unexamined) No.58-i 23540 and 58-137361, and it may be an idea to use this method. The adoption of this method, however, is not so easy because there is normally a change in magnification between the original image and the reproduction image and it is therefore necessary to consider the adjustment of the subsidiary scanning line pitch.

According to one aspect of the present invention, there is provided a method of recording an image, comprising: scanning an original image having a predetermined number of picture elements each occupying a plurality of scanning lines with a scanning beam covering the said plurality of scanning lines; splitting light from the original image into at least two light paths; deriving colour separation signals for a representative picture element of a group of picture elements from the first light path; and deriving signals representing a specific characteristic of each of the other picture elements of the group from light on the second light path.

In a second aspect, the present invention provides a method of reading an image, wherein an image of each picture element corresponding to a plurality of scanning lines adjacent one another in a subsidiary scanning direction of a colour original image is scanned by using a single scanning light beam covering at least the said plurality of scanning lines, and a picture element scanned by the scanning light beam is photoelectrically projected onto a photoelectric element through a colour separating optical system having a single pick-up lens and a beam splitter so as to obtain simultaneously a specified image signal corresponding to the said plurality of scanning lines, in which method a unit condensing region composed of a plurality of picture elements adjacent one another on the said plurality of scanning lines is established, and signals other than the colour separation signals for a representative picture element of a group of picture elements are not retained but only data representing a specified characteristic of the other picture elements.

In a third aspect, the present invention provides apparatus for recording an image, comprising: scanning means having a single light beam for scanning an original image having a predetermined number of picture elements each occupying a plurality of scanning lines, the single light beam being arranged to cover the said plurality of scanning lines; means for splitting light from the original image into at least two paths; means for deriving colour separation signals for a representative picture element of a region of picture elements from the first light path; and means for deriving signals representing a specific characteristic of each of the other picture elements of the region from light on the second light path.

The present invention also provides a method of recording an image, which method comprises: establishing an unit region comprising a plurality of picture elements, for example 2 x 2 picture elements, adjacent one another in a colour original image; scanning the colour original image using a single scanning light beam covering a plurality of scanning lines, for example two scanning lines, adjacent one another in a subsidiary scanning direction of the region; projecting the scanning light beam onto each of a plurality of photoelectric transfer means through a single pick-up lens and a colour separation optical system equipped with such means as beam splitter so that colour separation image signals may be simultaneously obtained for the said plurality of scanning lines; converting the colour separation image signals into digital signals; omitting the digital image signals other than at least one signal, for example the signal representing the brightness of each digital image signal in the unit region; and obtaining image data for which the number of bits is decreased for every unit region.

In a preferred arrangement, the method further comprises a step of rapidly changing the pitch at which the colour original image is scanned in the subsidiary scanning direction when changing the reproduction magnification.

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 diagrammatic plan view of apparatus for use in a method in accordance with the invention; Figure 2 is a side view of part of the apparatus of Figure 1; Figure 3 is a block diagram showing one example of an image signal processing device for use in a method in accordance with the invention; Figure 4 illustrates a method of producing a condensed image signal for use with a method in accordance with the invention; and Figure 5 illustrates a data format of a signal output from a format converting circuit of the device of Figure 3.

Figures 1 and 2 illustrate apparatus for carrying out one example of a method in accordance with the invention. A colour original image is mounted on a cylinder 1, and the image is scanned by a scanning light beam in minute picture elements which correspond to a plurality of scanning lines, two in this embodiment. Light reflected from or transmitted through the original image is supplied via a pick-up lens 2 to a beam splitter 3. The beam splitter 3 comprises a combination of a mirror 14 having an oval or ladder-like (rectangular) aperture 13 with an angled or roof-shaped mirror 15. Light passing through the aperture 13 is incident on the angled mirror 15 and is split thereby into scanning light beams 111 and 112, representing the picture elements being scanned on respective scanning lines.The scanning light beam 111 is incident, via a converging lens 4, on a series of dichroic mirrors 5, 6 and 7 each of which reflects a different band of wavelengths of light. Light reflected from each of the dichroic mirrors 5, 6 and 7 is supplied via a respective filter 18R, 18G and 18, to a respective photoelectric converter 8, 9 and 10. The filters 18R, 18G and 18, being red, green and blue filters respectively and the photoconverters 8, 9 and 10 producing signals Ro, Go and B,, respectively, representing the red, green and blue components of the light reflected from or transmitted through a picture element of the original image.The scanning light beam 112 is converged by a converging lens 42 and is incident on a dichoic mirror 62 which reflects, for example, only green light. Light reflected from the dichroic mirror 62 passes through a green colour separation filter 18G to a photoelectric converter 92 to provide a colour separation signal G1.

As is shown in Figure 2, light reflected from the mirror 14 of the beam splitter 3 is supplied via a converging lens 43 and a filter 18a to a photoelectric converter 12 to produce an unsharp signal U.

Thus, by scanning the colour original image, three types of signals are simultaneously obtained, that is, the image signals Ra, G,, Ba, the image G1 corresponding to the two scanning lines adjacent each other in the subsidiary scanning, and the unsharp signal U. The photoelectric converters 7, 8, 9, 10, 92 and 12 for producing the signals Ro, G,, Ba, G1 and U are adjusted so as to have the same photoelectric transfer characteristic in relation to an absolute quantity of light, even though the filters to be used are different.

Referring now to Figure 3, there is shown a block diagram of a processing circuit which outputs a colour image signal having variable density and to which a two dimensional condensing procedure has been applied. The circuit comprises a colour operation circuit 20 by which such processing as tone correction is carried out, differential amplifiers 21, to 27, analogue to digital (A/D) converters 28 to 32 and a format converting circuit 33.The image signals R,, G,, Ba supplied by the arrangement shown in Figure 1 are subjected to the necessary processing in the colour separation circuit 20 which outputs plate signals corresponding to the quantity of four colours, cyan (C), magenta (M), yellow (Y) and black (B) in the respective picture element of the original image.Details emphasizing signals A0 and Al are prepared by deriving the difference between the unsharp signal U and the image signals Go and G,, respectively. The detail containing signal A0 is supplied to the differential amplifiers 23 to 26 with the respective colour signal C, M, Y, K to produce detail emphasized signals. C0, M,, YO, K0 while the detail emphasizing signal Al is supplied to the differential amplifier 27 with the magenta signal M to produce a detail emphasized signal M1.

The colour plate signal corresponding to the image signal G1 should be output from the colour operation circuit 20 with respect to the picture element on the scanning line from which the image signal G1 is derived and which is adjacent the picture elements on the scanning line from which the image signals R,, G,, Bo are derived. However, in the case of such a small distance as one picture element, the variation in each colour plate signal C, M, Y and K is quite small in view of the correlation between these kinds of image signals and the human eye cannot identify such a small variation in such a minute portion.Accordingly, the colour plate signal corresponding to the image signal G can be substituted for a colour plate signal corresponding to the image signal Go without any problems, and thus the colour plate signal M1 in which detail is emphasized is prepared by adding the detail emphasizing signal Al of the picture element from which the image signal G1 is derived to the colour plate signal M.

In order to sample the analogue signals at the pitch of picture elements for the magnification of the image to be output, that is the image to be reproduced, a basic clock signal generated by an encoder (not illustrated) mounted on the same axis as the cylinder 1 of Figure 1 is used to control the A/D converters 28 to 32, the timing of the clock signal being adjusted by a known timing pulse generator. Thus, the signals C,, M,, Y,, K0 and M, are converted by the A/D converters 28 to 33 to form, for example, 8-bit digital signals at the pitch of picture elements corresponding to the reproduction magnification required. The digital signals are input to a format converting circuit 33.The format converting circuit 33 is a kind of data selection circuit, and outputs colour plate signals C,, Y0 and K0 in sequential order every time the format converting circuit receives two clock signals corresponding to the pitch required for the picture elements in the reproduction image. Colourplate signals Mo and M are output from the format converting circuit 3 when each clock signal is received.Thus, in the present embodiment, as shown in Figure 4, there is established a unit region 2 x 2 in the form of a matrix of picture elements for which only the colour plate signal M representing the brightness of a picture element is supplied by the circuit 33 for every picture element in the unit region, the colour plate signals C, Y, K only being output for a single representative picture element (or elements) in the unit region. In this connection, the subscripts 00, 01, 10 and 11 in Figure 4 show the relationships positional between the representative picture element (00) and the other picture elements (01, 10, 11) of a unit region. The condensed signals are transferred sequentially to an image processing device.

In order to carry out such editing operations as determining the layout in the reproduction image to be produced using the condensed image signals, it is preferred that the density of picture elements of the image signal is adapted to or corresponds to the pitch of picture elements required in the reproduction image.

The size of the picture elements of the reproduction image is usually constant and, therefore, in order to change the magnification of the reproduction image, without overlapping the image signals representing the same picture element or spreading out the image signal for every specified picture element as disclosed in Japanese laid open Publications (unexamined) Nos. 54-35613 and 54-65601, it is necessary to set up an appropriate sampling pitch and to determine a unit region to be actually read as one picture element (hereinafter called a "unit reading region") corresponding to the reproduction magnification required when inputting the image signal. In the previous colour scanner, such a unit reading region is set up by apropriately selecting the diameter of aperture in the input unit of the colour scanner.In other words, in the existing colour scanner, the region for setting up the magnification is divided into several small parts and an aperture of suitable diamater is selected to be used by each part, and in the case of a colour scanner in which the image signal is read by scanning sequentially the picture elements on one scanning line, not only the sampling pitch in the main scanning direction and the subsidiary scanning direction but also the unit reading region is adjustable to enable the consecutive variation-of the reproduction magnification by using a zoom lens as a pick-up lens.

However, where image signals are read by using simultaneously image signals from two adjacent scanning lines, although it is possible to adjust each unit reading region to allow for variation of magnification by the selection of the diameter of the aperture, it is difficult to adjust the pitch interval, that is the distance between the picture elements to be read, in each unit reading region.

However, as it is possible to adjust simultaneously each unit reading region and the distance between the picture elements to be read by using the zoom lens as a pick-up lens, it is not necessary to change the diameter of the aperture and it is possible to meet satisfactorily the required variation of the reproduction magnification.When the above-described arrangement is used, it is not necessary to make any adjustment to the optical system following the beam splitter 3 but, according to the change in the magnification provided by the zoom lens, such processes as adjustment of the gain of each amplifier of the photoelectric converters 81, 91 101, 92 or the adjustment of the quantity of light becomes rather complicated, and therefore a zoom lens having an automatic diaphragm mechanism is used so as to synchronize with the variation of the magnification.

The adjustment of the corresponding distance on the original image, that is, the adjustment of the distance between the picture elements to be read, need not necessarily be performed in particularly strict relation to the selected magnification, particularly in the case of a step-wise variation, and therefore it is sufficient to provide a plurality of lenses of different magnifying powers arranged at positions from which the distance to the original image and light beam splitter is constant so that the lens most closely approximating the desired magnification can be used.

Although the optical system disclosed in Japanese laid open Publication No. 58-123540 is used to read the image in the foregoing embodiment, it is also possible to use the optical system disclosed in Japanese laid open Publication No. 58-137361.

Thus, the present invention enables the provision of a method of recording an image for which the scanning efficiency is high without the scanning process picking up unnecessary image signals from the original image, which is smoothly adaptable to changes of magnification and in which the necessary image signal is picked up from the original image making use of the method disclosed in Japanese laid open Publication Nos. 58-123540 and 58-137361, and at the same time the image signals are condensed using a method as disclosed in Japanese laid open Publication 55-22708.

Thus, using a method embodying the invention, unnecessary signals are not read from the outset and it is possible to obtain an image signal to which a two-dimensional condensing process is applied in real time during the period of one revolution of the cylinder carrying the original image thereon, resulting in a simple construction for the input unit of scanning apparatus. Furthermore, even when it is necessary to store the obtained image signal once in memory, the storage capacity of the memory need not be so large, and editing processes can be carried out for every unit region so that the editing speed can be increased in inverse proportion to the degree to which the data is condensed, resulting in a speeding-up of the image data processing as a whole.

Further, when the magnification for the reproduction image is to be changed, it is easy to change the reading pitch in the subsidary scanning direction to the specified magnification value to be established without causing a problem because of the difference in the magnification between the original image and the output or reproduction image.

Claims

1. A method of recording an image, comprising: scanning an original image having a predetermined number of picture elements each occupying a plurality of scanning lines with a scanning beam covering the said plurality of scanning lines, split ting light from the original image into at least two light paths; deriving colour separation signals for a representative picture element of a region of picture elements from the first light path; and deriving signals representing a specific characteristic of each of the other picture elements of the region from light on the second light.

2. A method according to claim 1, wherein light from the original image is picked up by a single lens and is split into at least two light paths by a beam splitter.

3. A method of reading an image, wherein an image of each picture element corresponding to a plurality of scanning lines adjacent one another in a subsidiary scanning direction of a colour original image is scanned by using a single scanning light beam covering at least the said plurality of scanning lines, and a picture element scanned by the scanning light beam is photoelectrically projected onto a photoelectric element through a colour separating optical system having a single pick-up lens and a beam splitter so as to obtain simultaneously a specified image signal corresponding to the said plurality of scanning lines, in which method a unit condensing region composed of a plurality of picture elements adjacent one another on the said plurality of scanning lines is established, and signals other than the colour separation signals for a representative picture element of a group of picture elements are not retained but only data representing a specified characteristic of the other picture elements.

4. A method according to claims 2 or 3, wherein the single pick-up lens is a zoom lens.

5. A method according to claims 2 or 3, wherein the single pick-up lens is selected from a plurality of pre-arranged lenses, each lens having a different magnifying power.

6. A method according to any preceding claim, wherein the specific characteristic is the brightness of the picture elements.

7. A method according to any preceding claim, wherein the colour separation signals for the representative picture element of a region and the signals representing the specific characteristic of each of the other picture elements of the region are processed to provide a digital signal representing the region of picture elements.

8. A method according to any preceding claim, wherein one of the colour separation signals of the representative picture element of a region of picture elements is taken to represent the specific characteristic of the representative picture element.

9. A method according to claim 8, when dependent on claim 7, wherein the signals representing the specific characteristic of each picture element are sampled at a rate n times greater than the rate at which the colour separation signals of the representative picture element are sampled, where n is related to the number of picture elements in the region so that a digital signal repre senting the colour separation signals for the representative picture element and the specific characteristics of the picture element is produced in real time.

10. A method according to claim 9, wherein each region of picture elements comprises four picture elements and the signals representing the specific characteristic are sampled at a rate four times that of the colour separation signals.

11. A method according to any preceding claim, wherein the colour separation signals for the representative picture element of a region are derived by using a colour filter arrangement to produce three first colour signals and then processing the three first colour signals to produce four colour separation signals.

12. A method according to claim 11, wherein the three first colour signals are red, green and blue and the four colour separation signals are cyan, magenta, yellow and black.

13. A method according to claim 12, wherein the magenta colour separation signal of each of the picture elements is used to represent the specific characteristic thereof.

14. A method according to claim 11, 12 or 13, wherein light from the original image is split into three light paths, light on the third path being used to derive unsharp signals.

15. A method according to claim 14, wherein the unsharp signals are compared with one of the three first colour signals to produce a detail emphasizing signal which is then used to modify the four colour separation signals.

16. A method of recording an image substantially as hereinbefore described with reference to the accompanying drawings.

17. Apparatus for recording an image, comprising scanning means having a single light beam for scanning an original image having a predetermined number of picture elements each occupying a plurality of scanning lines, the single light beam being arranged to cover the said plurality of scanning lines; means for splitting light from the original image into at least two paths; means for deriving colour separation signals for a representative picture element of a region of picture elements from the first light path; and means for deriving signals representing a specific characteristic of each of the other picture elements of the region from light on the second light path.

18. Apparatus according to claim 17, wherein means are provided for processing the colour separation signals for the representative picture element of a region and the signals representing the specific characteristic of each of the other picture elements of the region to provide a digital signal representing the region of picture elements.

19. Apparatus according to claim 18, wherein the processing means is arranged to sample the signals representing the brightness of each picture element at a rate n times greater than the rate at which the colour separation signals of the representative picture element are sampled, where n is related to the number of picture elements in the region so that a digital signal representing the colour separation signals for the representative picture element and the specific characteristics of the picture elements of a region is produced in real time.

20. Apparatus according to claim 19, wherein the processing means is arranged to sample the signals representing the specific characteristic at a rate four times that at which the colour separation signals are sampled when each region of a picture elements comprises four picture elements.

21. Apparatus according to any one of claims 17 to 20, wherein the means for deriving the colour separation signals comprises a colour filter arrangement for producing three first colour signals and means for processing the first colour signals to produce four colour separation signals.

22. Apparatus according to claim 21, wherein the three first colours are red, green and blue and the four colour separation signals are cyan, magenta, yellow and black colour separation signals.

23. Apparatus according to claim 21, wherein the magenta colour separation signals for each of the picture elements are used to represent the specific characteristic.

24. Apparatus according to any one of claims 17 to 23, wherein the splitting means comprises a single pick-up lens.

25. Apparatus according to claim 24, wherein the single pick-up lens is a zoom lens.

26. Apparatus according to claim 24, wherein the single pick-up lens is selected from a plurality of lens each lens having a different magnifying power.

27. Apparatus according to any one of claims 17 to 26, wherein the splitting means comprises a beam splitter for splitting light into the first and second light paths and a third light path.

28. Apparatus according to claim 27, wherein the beam splitter comprises a first and second light reflecting means arranged at an angle to each other for directing light incident thereon along the first and second path, respectively, and a third light reflecting surface for reflecting light onto the third light path, the third light reflecting surface having an aperture for allowing light to pass to the first and second light reflecting surfaces.

29. Apparatus according to claim 27 or 28, wherein means are provided for deriving an unsharp signal from light on the third path.

30. Apparatus according to claim 31, wherein means are provided for using the unsharp signals to produce detail emphasising signals to modify the colour separation signals.

31. A method of reproducing an image, which method comprises: establishing an unit region comprising a plurality of picture elements, for example 2 x 2 picture elements, adjacent one another in a colour original image; scanning the colour original image using.a single scanning light beam covering a plurality of scanning lines, for example two scanning lines, adjacent one another in a subsidiary scanning direction of the region; projecting the scanning light beam onto each of a plurality of photoelectric transfer means through a single pick-up lens and a colour separation optical system equipped with such means as beam splitter so that colour separation image signals may be simultaneously obtained for the said plurality of scanning lines; converting the colour separation image signals into digital signals; omitting the digital image signals other than at least one signal, for example the signal representing the brightness of each digital image signal in the unit region; and obtaining image data for which the number of bits is decreased for every unit region.

32. Apparatus for recording an image substan tially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

33. Any novel feature or combination of fea tures described herein.