GB2145896A - Controlling memory of separate-type scanner system - Google Patents

Abstract

In reproducing images using a separate type scanner in which the input scanning drum 1, and the recording drum 2 are revolved separately, image line data are written successively into at least three line memories 20 and read out from one thereof which is not simultaneously being written into, thereby preventing the appearance of "confused recording" from taking place on a reproduction image. <IMAGE>

Description

SPECIFICATION A method and apparatus for controlling a memory of a separate type scanner apparatus Background of the Invention This invention relates to a method and apparatus for controlling a memory of an image reproducing system such as a colour scanner.

In particular the invention relates to such a method and apparatus for a separate type scanner apparatus in which an input scanning drum and a recording drum are individually rotatable.

Field of the Invention When reproducing an image using an image reproducing apparatus, such as a colour scanner in a photomechanical process, a reproduction image must be recorded in a desired position on a photosensitive film. Image data obtained by scanning an original picture is stored into a memory and then read to a recording head. In this case, the magnification ratio of the main scanning direction factor depends on the frequency ratio between a writing pulse for writing the image data into the memory and a reading pulse for reading the image data from the memory, whereas the recording position depends on the start timing of reading the image data from the memory.

The input scanning and recording drums are of a conventional scanner coaxially connected and mounted for rotation together, ordinarily employ line memories, each of which can store image data of one scanning line. Such conventional scanners are frequently called a "coaxial type scanner" and will be so referred hereafter. However, a "coaxial type scanner" apparatus has a drawback of "confused recording". By "confused recording" is meant that one recording line is recorded by the image data of more than two scanning lines. Essentially, when image data is written into or read from a memory, the reading process must be carried out after the writing process is finished. Further, when an input scanning position (angular position) and a recording position (angular position) are in a specific relation or in a specific magnification ratio, the reading process is carried out while the writing process is unfinished on the image data of the same scanning line. Thus, the image data of the previous scanning line is read instead of that of the present scanning line, which results in the said "confused recording".

Conventionally in an attempt to resolve the above drawback, the recording position (angular position) is rendered not to overlap with the input scanning position (angular position).

For example, when one reproduction image is to be recorded, an original picture A is placed on the position of angle 0" to 1 80' of an original picture drum 1, and a photosensitive film B is placed on the position of angle 180" to 360" of a recording drum (2) as shown in Fig. 1(a). When four colour separation images are to be recorded, an original picture A' is placed on the position of angle 0" to 72 of the original picture drum (1), and four colour separation films Y (Yellow), M (Magenta), C (Cyan) and K (Black) are placed in order at angles of 72" to 360" around the circumference of the recording drum (2) as shown in Fig. 1(b). However, this method has a problem in that the usable areas of both drums are limited as being obvious from the above two examples.

The above problem may be resolved by using two line memories as shown in Fig.

2(a)(b), each of which can store image data of one scanning line. In Fig. 2(a)(b), each pulse P1 P2 P3,... is a one revolution pulse which is output from a rotary encorder being revolved in connection with an input scanning drum every one revolution of the input scanning drum. In the interval between the pulse P and the pulse P2, image data A2 of a certain scanning line are input to a line memory M1, while image data A1 of the previous scanning line which is already stored in a line memory M2 and are read from the line memory M2 as recording image data B1 which underwent magnification conversion and timing-adjustment. In the next interval between the pulse P2 and the pulse P3, image data A3 of the next scanning line is input to the line memory M2, while the image data A2 is read from the line memory MX as recording image data B2 which underwent aforesaid processes. This routine is repeated for the subsequent scanning lines.

Recently it has become desirable that some reproduction images should be made to be larger size than previously. In order to satisfy the desire for larger reproduction images, larger input scanning and recording drums are necessary. In practice, it is not only difficult to coaxially mount such large drums but such an image reproducing system is not easily handled or transported. Moreover, a large installation space is needed for such a large system.

This problem can be resolved by assembling the input and output components separately (a scanner system constructed like this is called a "separate type scanner" hereinafter). In such a separate type scanner, although as a matter of course both drums are rotated individually, when two line memories are used, the aforesaid "confused recording" can occur.

In the 'separate type scanner", the input scanning drum and the recording drum are rotated synchronously and, sometimes the drums are rotated with a certain phase difference. Further, it is assumed that the phase difference T between both drums is "'= a as shown in Figs. 2(a) and 2(b'). Until the single revolution pulse P1 is output, recording image data B'o corresponding to the input scanning image data Ao (not shown in Drawings) are output from the line memory M1. In the interval from the output of the pulse P1 to that of the one revolution pulse P'1, the input scanning image data A2 begin to be written into the line memory M1 while the recording image data B'o are stillbeing read from the line memory M1. Therefore, as seen in the case that one line memory is used in a coaxial type scanner, the above condition too causes the "confused recording". The same phenomenon occurred when the phase difference between both drums is X = ss as shown in Figs. 2(a) and (b").

To eliminate this phase difference, motors for revolving both drums must be driven synchronously and in same phase which requires a complicated and expensive motor driving circuit.

Summary of the Invention The method of this invention is proposed to resolve the above mentioned conventional problem. A prime object of this invention is to provide a method for controlling line memories of a separate type scanner and rendering the scanner capable of eliminating or at least substantially reducing the possibility of the reading process taking place concurrently with the writing process and based upon image data held on an identical line memory, even when both the input scanning and the recording drums of the system are rotated synchronously with a certain phase difference. Preferably, the system of this invention includes at least three line memories, whereupon, the writing and the reading processes are carried out on different line memories.

Thus, according to the present invention, there is provided a method for controlling the memory of a "separate type scanner" as herein defined in which image data obtained by scanning an original picture placed on an input scanning drum which is rotatable independently of a recording drum, is stored in a memory and an output is used for recording a reproduction image, the method comprising the steps of: (a) successively writing image data contained in at least three scanning lines into corresponding lines of a line memory having the same number of lines on the scanning lines, and, (b) reading the image data from one memory line which is not undergoing a writing process under step a.

The invention also includes apparatus for controlling a memory of a separate type scanner in which image data obtained by scanning an original picture placed on an input scanning drum which is rotatable independently of a recording drum is stored in a memory and output from the memory is used for recording a reproduction image, the apparatus compris ing: (a) at least three memory lines; (b) writing means for performing a writing process on any designated one of the said at least three memory lines; and (c) reading means for performing a reading process of data on one memory line which is not undergoing the writing process.

The invention will now be described by way of example with references to the accompany ing drawings.

Brief Description of the Drawings Figure 1 shows arrangement examples of original pictures and photosensitive films in a conventional scanner apparatus; Figure 2 shows a timing chart of a writing pulse and a reading pulse when two line memories are used; Figure 3 shows a scanner system embody ing the method of this invention; Figure 4 shows the phase difference of 180" between a writing pulse and a reading pulse; Figure 5 shows a timing chart of a writing pulse and a reading pulse when three line memories are used; Figure 6 shows a timing chart of a writing pulse and a reading pulse when four line memories are used; Figure 7 shows a memory system of this invention; Figure 8 shows a memory unit of the memory apparatus shown in Fig. 7; Figure 9 shows another memory apparatus of this invention, and, Figure 10 shows a use example of a RAM.

Preferred Embodiment of the Invention Fig. 3 shows a separate type scanner to which the method of this invention is applied.

An input rotatable scanning drum 1 is driven by a motor 9 via a pulley 3, a belt 7 and a pulley 4, whereas a rotatable recording drum 2 is driven by a motor 10 via a pulley 5, a belt 8 and a pulley 6 as shown in Fig. 3.

Image data obtained by scanning an original picture A with an input scanning head 1 3 is transmitted as an input to a computer module 1 9 to undergo colour and gradation correction prior to forming an input to a memory system 20. One pulse per revolution Pjn and an N'h time pulse Nin from a rotary encoder 11 mounted coaxially with the input scanning drum 1 forms inputs to a memory system 20.

In addition, one pulse Pout per revolution and an N'h time pulse N001 form inputs from a rotary encoder 1 2 mounted coaxially with the recording drum 2. The once per revolution pulses Pin and Pout and the N'h time pulses Ni, and N001 are used for controlling the line memories (mentioned later) of the memory system 20 when the image data is written into and read from the line memories. The image data read from the memory system 20 are inputs to a recording head 14 to be used for recording a reproduction image B.

In this system, timing belts (for example tooth belts) are used as the belts 7 and 8 instead of plane belts, which may slip, in order to keep synchronization between the motor 9 and the input scanning drum 1, and between the motorl0 and the recording drum 2. The gear ratio between the pullies 3 and 4 are made to match with that between the pullies 5 and 6 in order that the drums 1 and 2 rotate at the same angular velocity.

In this embodiment of the invention, the phase difference 7 shown in Fig. 2 takes place as mentioned below. Electric power is supplied to the motors 9 and 10 simultaneously from a power source 18 when a switch 1 7 is turned on, and the motors 9 and 10 begin to be rotated synchronously. At this stage, even if the revolutions of both motors 9 and 10 synchronize at the same time,.the drums 1 and 2 are not always in phase because the gear ratio between the pullies 3 and 4 is not 1:1.

The phase difference 7 is also affected by different loads applied to the motors 9 and 10 may be loaded with different loads, and by the start-up characteristics of both motors which may also differ.

It will be understood from the relationship between Fig. 2(a) and Fig. 2(b"), thatthe rotary encoders 11 and 1 2 output the one revolution per pulse Pin and Pout respectively produces a phase difference 7 (- 180" < r < + 180") there between as shown in Fig. 4.

When a memory system 20 is provided with three line memories Mt, M2 and M3, each of which can store image data of one scanning line, image data is written into the line memories according to the single revolution pulse Pin and read according to the single revolution pulse Pout as shown in Fig. 5. Fig. 5 shows several cases of the reading timings, determined by the output of the single revolution pulse Pout (Poutl to Poutg) with respect to that of the one revolution pulse P,.

In this condition, image data of each scanning line is written into the three line memories M1, M2 and M5 successively according to the single revolution pulse P,,. When the writing process begins on a line memory (i.e., on command of the one revolution pulse Pin as shown as a broken line in Fig. 5), the reading process is carried out on the line memory which is holding the image data of the second previous scanning line. That is, for example, when the writing process is carried out on the line memory M1, the reading process is carried out on the line memory M2. When the line memories MX, M2 and M3 are controlled in the above-mentioned manner, the writing and the reading processes are not carried out on the same line memory simultaneously except for the following case.

When the phase of the single revolution pulse P001 slightly delays as against that of the single revolution pulse P10 as shown as PoUt5 in Fig. 5, the writing and the reading processes accidentally fail on the same line memory.

However, from a practical point of view the overlap is within 0.75". In other words, it is within 3.75mm when the circumferenceof the recording drum is 1800mm, and since this rate is insigificant it can be ignored.

Fig. 6 showsa timing chart of the method of this invention, in which four line memories are used to avoid the above-mentioned problem.

In this condition, image data of each scanning line is written into four line memories M1, M2, M3 and M4 successively according to the single revolution pulse P,,. When the writing process is carried out on a half (180" in angle) line memory,the reading process is carried out on the line memory which holds the image data of the second previous scanning line. That is, for example, when the writing process is carried out half (1 80" in angle) (as shown as a broken line in Fig. 6) on the line memory M1, the reading process is carried out on the line memory M3. When the writing process is carried out on less than half (in between 0" and 180" in angle) (as shown as a chain line in Fig. 6) the line memory M1, the threading process is carried out on the line memory M3 or M2. In this case, the writing and the reading processes never fall on the same line memory.

Fig. 7 shows a block chart of a memory system for embodying the method of this invention.

In Fig. 7, a counter 22 and an AND-gate 24 compose a trinary counter for the input side. That is, when the count number of the counter 22 becomes "3", the AND-gate 24 outputs the "H" (high level) signal to the clear terminal, which signal clears the count number of the counter 22, whereas a counter 23 and an AND-gate 25 form another trinary counter for the output side which has the same function as the above.

A flip-flop circuit 44 consisting of NANDgates 42 and 43 is set by a start pulse Sp which is an input thereto when the motors 9 and 10 begin to be rotated synchronously.

The output signal of the flip-flop circuit 44 and the one per revolution pulse Pjn render a NAND-gate 41 output to form a load signal to the load terminals of the counters 22 and 23.

At the same time the load signal forms an input to the NAND-gate 43 to reset the flipflop circuit 44.

When the initial state of the count number of the counter 22 is "0" and that of the counter 23 is "1", both the counters begin to operate from the given numbers "0" and "1" respectively on command of the load signal.

The counter 22 outputs a signal corresponding to the count number thereof and this changes in order of O > 1~2 1212 to a decoder 26, at the same time the counter 23 outputs a signal corresponding to the count number thereof which changes in order of 1o2 0 1 2 0 to a decoder 27. By decoding the signals, the decoder 26 produces an output writing enabling signal WE, and the decoder 27 produces an output reading enabling signal U to the line memories M1, M2 and M of respective memory units 34, 35 and 36.

On theother hand, the said N'h time pulse Nin output from the rotary encoder 11 of the input side is an input to a synthesizer 28. The synthesizer 28 multiples the frequency of the Nth time pulse N10 by a magnification ratio MD and outputs the product as a timing pulse fw to an A/D converter 21. Analog image data output from the said computer module 1 9 is converted into the corresponding digital image data synchronizing with the timing pulse fw and then input to the line memories M1, M2 and M3.

The timing pulse fw is also an input to acounter 29, the output signal of which, namely the count number, forms an input via RAM 31 (mentioned later) to the line memories M1, M2 and M3 as a writing address signal WRADD.

The said Nm time pulse N001 output from the rotary encoder 1 2 of the output side is input to a PLL circuit 33 and undergoes a frequency multiplication and forms as input to a counter 30 as a timing pulse fR. The output signal (count number) of the counter 30 is input via a RAM 32 (mentioned later) to the line memories M1, M2 and M3 as a reading address signal READD.

The reading and the writing processes are carried out on the line memories M1, M2 and M3 according to the obtained writing enabling signal WE, the reading enabling signal RE, writing address signal WRADD and reading address signal READD. When, for example, the writing process is carried out on the line memory M1, the reading process is carried out on the line memory M2 as mentioned before.

The magnification ratio MD can be expressedas fw/fr (few: the frequency of the writing pulse; fr: the frequency of the reading pulse).

The counters 29 and 30 are cleared by the one revolution pulses Pjn and Pout respectively.

The RAM 31 is used for processing image data of plural original pictures As and Ab arranged as shown in Fig. 10 on the input scanning drum 1 (shown as a development chart). That is, when the magnification ratio MD is high enough, sometimes image data volume of one scanning line exceeds the capacity of one line memory M1 (M2, M3). In such a case, the RAM 31 secures the locations AD5 and ADb in the line memory for the image data of the original pictues A. and Ab as shown in Fig. 10.

A RAM 32 is used for outputting image data of one original picture a quired number of times (independently of the magnification ratio) in the main scanning direction.

By using preset counters such as the counters 29 and 30, and by varying the initial count numbers of the preset counters, the RAMs 29 and 30 can be eliminated.

Fig. 8 shows a block chart of each of the memory unit 34, 35 and 36 which comprise the line memories M1, M2 and M3 respectively.

When the decoder 26 outputs a writing enabling signal WE of "L" to one memory unit 34 (35, 36), image data are input via a buffer 51 to the input/output terminal l/O of the memory (iine memory) 58. Since the output of a NOT-gate 53 becomes "H", the writing address signal WRADD is input via an AND-gate 55 and an OR-gate 57 to the line memory 58. Consequently, the image data is written into the line memory 58 according to the writing address signal WRADD.

When the decoder 27 outputs a reading enabling signal RE of "L" to one memory unit 34 (35, 36), the output of a NOT-gate 54 becomes "H" to input the reading address signal READD via an AND-gate 56 to the line memory 58. According to the reading address signal READD, the image data being stored in the line memory 58 is output from the l/O terminal of the line memory 58 via a buffer 52. The writing enabling the signal WE and the reading enabling signal Rye never becomes "L" at the same time. When both the signals are "H" at the same time, the line memory 58 is cut off.

Fig. 9 shows a block chart of an apparatus for carrying out the method of this invention and the following explanation is based on that part of the apparatus shown in Fig. 9 which is different from the system of Fig. 6. A reset signal for a flip-flop circuit 44 is generated as follows. The N'h time pulse N, output from the rotary encoder 11 is an input to a counter 61.

When the count number of the counter 61 becomes more than half of the frequency of the N'h time pulse N,, the reset signal is an output from a coincidence circuit 62. When the reset signal is input to a NAND-gate 41, the NAND-gate 41 outputs a load signal to the counter 22 and 23 as well as to the NAND-gate 43 to reset the flip-flop circuit 44.

Consequently, the line memory which is to be used is determined at the time the revolution of the input scanning drum proceeds to the point of an angle of 1 80" after which the single revolution pulse N10 is output (Time T in Fig. 6). Thecounters 22 and 23 are sexadecimal counters. Therefore, each of the lowest two bits of the count number becomes the same value every four counts. So, when the initial count numbers of the counters 22 and 23 are "0" and "2" respectively, the counters 22 and 23 begin to count the single revolution pulses P10 and Pout respectively ac cording to the said load signal. The count number of the counter 22 changes in order of 0- > 1- > 2- > 3- > 0- > 1- > 2- > 3 ..., while that of the counter 23 changes in order of 2-3-0-,1 - > 2- > 3- > 0- > 1. . . . . . According to the outputs of the counters 22 and 23, the decoder 26 outputs the writing enabling the signal WE, and the decoder 27 outputs the reading enabling the signal flE In this system, as in the system of Fig. 6, when for example the writing process is carried out on the line memory M1, the reading process is carried out on the line memory M2.

As mentioned above, the method of this invention overcomes the conventional problem of "confused recording" from taking place.

This is achieved by using three line memories instead of a complicated synchronous motor driving circuit when the input scanning and the recording drums are revolved individually keeping a synchronous relation.

Therefore, by using the method and apparatus according to this invention, an economical separate type scanner can be obtained.

Claims (11)

1. A method for controlling the memory of a "separate type scanner" as hereindefined in which image data obtained by scanning an original picture placed on an input scanning drum which is rotatable independently of a recording drum, is stored in a memory and an output is used for recording a reproduction image, the method comprising the steps of: a. successively writing image data contained in at least three scanning lines into corresponding lines of a line memory having the same number of lines as the scanning lines, and b. reading the image data from one memory line which is not undergoing a writing process under step a.

2. A method according to Claim 1 including three memory lines.

3. A method according to Claim 1 or Claim 2 in which where the writing process begins on one memory line, the reading process carried out on that memory line which is holding image data of the second previous scanning line.

4. A method according to Claim 1 including four memory lines.

5. A method according to any preceding claim wherein the writing process is carried out on one half of a memory line,and corresponds to the angle of revolution of 1 80" of the input scanning drum, and wherein the reading process is carried out on that memory line which is holding the second previous scanning line.

6. Apparatus for controlling a memory of a separate type scanner in which image data obtained by scanning an original picture placed on an input scanning drum which is rotatable independently of a recording drum is stored in a memory and output from the memory is used for recording a reproduction image this apparatus comprising: a. at least three memory lines; b. writing means for performing a writing process on any designated one of the said at least three memory lines, and c. reading means for performing a reading process of data on one memory line which is not undergoing the writing process.

7. Apparatus according to Claim 6 including: a. at least three line memories; b. the writing means comprises (i) a writing enabling signal generator for outputting a writing enabling signal to the said at least three memory lines successively each revolution of the input scanning drum and (ii) an address signal generator for outputting a common writing address signal to each memory line, and c. the reading means comprises (i) a reading enabling signal generator for outputting a reading enabling signal to the said at least three memory lines successively each revolution of the recording drum and (ii) an address signal generator for outputting a common reading address signal to each line memory.

8. Apparatus according to Claim 7 includ-- ing: a. three memory lines; b. the writing enabling signal generating means comprises (i) a trinary counter for counting pulses generated each revolution of the input scanning drum and (ii) a decoder for decoding the count number of the counter to output a writing enabling signal; and c. the reading enabling signal generating means comrises (i) a trinary counter for counting pulses generated each revolution of the recording drum and (ii) a decoder for decoding the count number of the counter to output a reading enabling signal.

9. Apparatus according to Claim 7 including: a. four memory lines; b. the writing enabling signal generating means comprises (i) a sexadecimal counter for counting pulses generated each revolution of the input scanning drum and (ii) a decoder for decoding two lowest bits of the count number of the counter to output a writing enabling signal; and c. the reading enabling signal generating means comprises (i) a sexadecimal counter for counting pulses generated each revolution of the recording drum and (ii) a decoder for decoding two lowest bits of the count number of the counter to output a reading enabling signal.

10. Apparatus according to Claim 8 including a flip-flop circuit set by a start pulse formed when the revolution of the input scanning drum synchronizes with that of the recording drum and is reset by a subsequent pulse generated each revolution of the inputscanning drum, whereby, when reset, the flipflop circuit renders the said two counters to commence counting from respective pre-set numbers corresponding to the memories to be driven.

11. Apparatus according to Claim 9 including a fiip-flop circuit set by a start pulse formed when the revolution of the input scanning drums synchronizes with that of the recording drum and is reset by a subsequent pulse generated every one-half revolution of the input scanning drum, whereby, when reset, the flip-flop circuit renders said two counters to commence counting from respective pre-set numbers corresponding to the memories to be driven.