JPH01213616A - Image recorder provided with output line buffer - Google Patents

Abstract

PURPOSE:To attain the speed-up of recording a duplicate image at low cost by providing a memory for storing optically modulated control data, performing reading from the memory synchronously with a 2nd clock having a frequency in proportion to the speed of a beam and performing writing by using a 1st clock. CONSTITUTION:The line memory 9 for storing the optically modulated control data is newly provided in the pre-stage of an optical modulator 4 and the reading of the optically modulated control data from the memory 9 is performed based on the 2nd clock (b) having the frequency related to the scanning speed of the light beam, while the writing of the optically modulated control data in the memory 9 is performed based on the 1st clock (f) whose frequency is different from that of the 2nd clock (b). Generally, the scanning efficiency of the light beam is smaller than '1' in a linear scanning deflecting unit, so that the speed of writing in the memory 9 can be made lower to be equal to the product of the speed of reading from the memory 9 with the scanning efficiency. Thus, an inexpensive screen pattern memory 3 whose action speed is low can be used and the speed of the recording the duplicate image can be raised by making the scanning speed of the deflecting unit higher.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an image recording device used in the output section of an image scanning recording device such as a so-called flat scanner, and in particular to an image recording device that uses a light beam modulated based on an image signal. , galvanometer mirror
The present invention relates to an image recording apparatus that records a predetermined image by scanning and exposing a flat photosensitive material using a linear scanning deflector such as a mirror or a polygon mirror.

(Prior Art) FIG. 4 shows a schematic configuration diagram of an image recording device used in the output section of a conventional flat scanner. As shown in the figure, the image signal a, which has been subjected to necessary signal processing such as sharpness emphasis, one color correction, and one gradation change, is a digital image with multi-till (for example, 25611i11) expressive ability associated with the original image density. It is applied as a signal to one input terminal of comparator 1. - On the other hand, in synchronization with the clock b (details of which will be described later) output from the PLL circuit 2, a digital screen pattern having a multi-gradation expressive ability associated with the contact screen density distribution is generated from the screen pattern memory 3. Signal C is applied to the other input terminal of comparator 1. The comparator 1 compares the image signal a and the screen pattern signal C in synchronization with the clock b, and specifically performs 2Ii1 processing on the screen pattern signal C using the image signal a as a threshold signal. Thus, a luminous intensity mti11@signal d is created. This light modulation control signal dG,tA is given to a light modulator 4 such as an acousto-optic modulator (OM), and the light modulator 4 exposes a light beam 5 such as a laser beam based on the light modulation control signal d. Switching is performed in dot units. The light beam 5 switched in units of exposure dots is scanned onto a flat photosensitive material 7 such as an unexposed film through a linear scanning deflector 6 such as a galvano mirror or a polygon mirror, and a desired halftone dot image is created. recorded.

Incidentally, in an image recording apparatus having such a linear scanning deflector 6, in order to improve the recording accuracy of a duplicate image, the timing of switching the light beam by the optical modulator 4 is adjusted to match the light beam on the photosensitive material 7. Need to synchronize speed. In particular, a galvano mirror is used as the deflector 6.
When using a galvanometer mirror, the beam movement speed on the photosensitive material 7 changes faster at the center and slower at the periphery due to the swinging operation of the galvano mirror. It is extremely important to synchronize the Therefore, in the conventional image recording apparatus, as shown in FIG. 4, a grating sensor 8 generates a pulse signal e having a frequency proportional to the beam speed, and a PLL circuit 2 raises this pulse signal e to a required frequency rate. The above-mentioned clock b is created. As described above, by controlling the operation timing of the screen pattern memory 3 and the comparator 1 based on this clock b, the optical modulation control signal d is created at a timing synchronized with the beam speed, and the optical modulator 4 I'm trying to get it to work.

(Problem to be Solved by the Invention) However, in the conventional image recording device, when a polygon mirror is used as the deflector 6, it is necessary to increase the rotation speed of the polygon mirror in order to prevent the axis from being captured. When a galvano mirror is used as the deflector 6, only the outward or return side of its reciprocating motion is used for image recording. It is necessary to swing - at a relatively high speed. From this point of view, if the rotational speed of the polygon mirror or the swinging speed of the galvanometer mirror, in other words the scanning speed of the deflector 6, is set,
Along with this, the beam speed has also increased and the frequency of clock b has also increased, so the readout speed of the screen pattern memory 3 has also increased, making it necessary to prepare a large-capacity screen pattern memory 3 that can withstand high-speed operation, which reduces costs. The problem was that it was expensive. In addition, the deflector 6
Even if an attempt is made to increase the recording speed of a duplicate image by increasing the scanning speed of the screen pattern memory 3, there is a limit to the reading speed of the screen pattern memory 3, so there is a problem in that the recording speed cannot be increased any further.

The present invention was made in order to solve the above-mentioned conventional problems, and an object of the present invention is to provide an image recording apparatus that can increase the recording speed of duplicate images at low cost.

(Means for Solving Problem M) This invention is based on light modulation control data obtained from an image signal, and a light beam is switched in units of exposure dots by a light modulator, while a light beam is switched through a deflector for linear scanning. An image recording device that records a predetermined image by scanning on a flat photosensitive material, and in order to achieve the above object, it includes a memory for storing the light modulation control data and a light modulation control obtained by an image signal. means for inputting data into the memory in synchronization with a first clock; and control of the light modulation from the memory to the light modulator in synchronization with a second clock having a frequency related to the scanning speed of the light beam on the photosensitive material. and means for reading data.

In this case, it is preferable that the frequency of the second clock is set higher than the frequency of the first clock.

(Function) According to the image recording device of the present invention, a memory for storing light modulation control data is newly provided before the light modulator, and reading of the light modulation control data from the memory is controlled at the light beam scanning speed. The writing of the luminous intensity 11i control data to the memory is performed based on a first clock having a different frequency than the second clock, while writing the luminous intensity 11i control data into the memory. In general, in linear scanning deflectors such as galvanometer mirrors and polygon mirrors, the scanning efficiency η, which represents the ratio of the effective scanning area (the scanning area where image recording is performed) to the actual scanning area of the light beam, is approximately 0 for polygon mirrors. .8, about 0.3 to 0.4 and 1 with galvanometer mirror
Because it is smaller, it is possible to slow down the speed to the memory (1) to η (2), which is the product of the read speed (2) from the memory and the scanning rate η, resulting in a lower cost It becomes possible to use screen pattern memory. Furthermore, when the operating speed of the screen pattern memory is set to be the same as the conventional one, the scanning speed of the deflector can be increased to increase the recording speed of the duplicate image.

(Embodiment) FIG. 1 shows a circuit block diagram of an image recording apparatus which is an embodiment of the present invention. As shown in the figure, a memory 9 consisting of a set of 1-bit line memories 9a and 9b is connected between the comparator 1 and the optical modulator 4, and a A line memory control circuit 10 is provided to control write and read operations. Each of the 1-bit line memories 9a and 9b has a capacity capable of storing light modulation control data corresponding to one scanning line of the light beam on the photosensitive material. While controlling the optical modulation control data to be written into the 1-bit line memories 9a and 9b alternately for each scanning line, in parallel with this write operation, the data is written from the 1-bit line memory on the opposite side. Control is performed so that optical modulation control data is read. Further, a clock generation circuit 11 is provided which generates a first clock f which is also used as an internal clock of the scanner. The frequency of the first clock f is set lower than the frequency of the second clock b, which has a frequency related to the beam speed output from the PL circuit 2. Then, in synchronization with the first clock f generated by the clock generation circuit 11, the operation timings of the screen pattern memory 3 and the comparator 1 are controlled, and the write operation of the memory 9 is controlled via the line memory control circuit 10. 111111
On the other hand, in synchronization with the second clock b generated by the PLL circuit 2, the memory 9
The read operation is 1III! It is configured so that it can be used. The other circuit configuration is the same as the conventional circuit configuration shown in FIG.

FIG. 2 shows a mechanical diagram of an image recording device constituting the output section of a flat scanner. In this embodiment, a galvanometer mirror is used as a deflector 6 for linear scanning. The structure and operation of this mechanism section are as follows. That is, as shown in FIG. 2, the laser beam emitted from the laser device 12 is divided into two parts by the half mirror 13, one part is sent to the optical modulator 4, and the other part is taken out as the grating laser beam 14. The optical modulator 4 is connected to the memory 9
Luminous intensity XI IIJ l signal q given from (Fig. 1)
Based on this, the laser beam is switched in units of exposure dots and outputted as a recording laser beam 15. This recording laser beam 15 is reflected by a galvanometer mirror (deflector) 6 that is driven back and forth with a sine function, scanned left and right, and focused onto a flat photosensitive material 7 such as an unexposed film via an F-theta lens 16. be done. The photosensitive material 7 is sent out at a constant speed in a direction Y perpendicular to the scanning direction X of the recording laser beam 7, so that a desired halftone dot image is two-dimensionally recorded on the photosensitive material 7. On the other hand, half mirror 1
The grating laser beam 14 separated by 3 is
It is guided to a galvanometer mirror (deflector) 6 via a mirror system 17 so as to be parallel to the recording laser beam 15.

The grating laser beam 14 guided by the galvano mirror (deflector) 6 is scanned in the left and right direction by the galvano mirror (deflector) 6 at the same speed as the recording laser beam 15, passes through the F-theta lens 16, and passes through the mirror. The light is reflected by the grating sensor 8 and focused on the light receiving surface of the grating sensor 8 .

The grating sensor 8 is made by attaching a glass with a thin black and white bar pattern on top of the 7-otodiode array, and when the grating laser beam 14 runs on the bar pattern, it emits a frequency proportional to the beam speed. A pulse signal e having the following values is output. This pulse signal e
is raised to the required frequency rate by the previously described PLL circuit 2 (FIG. 1), thus creating a second clock b having a frequency proportional to the beam speed.

FIG. 3 shows a time chart for explaining the operation of this device. In the same figure, (a) represents a galvanomirror drive signal, and when it is at "H" level, the forward side operation is performed.
11 level, commands the drive system of the galvanomirror to operate on the return path. (b) and (c) show read/write signals given from the line memory control circuit 10 to the 1-bit line memories 9a and 9b, respectively;
When it is at level, it commands a read operation, and when it is at "L" level, it commands a self-loading operation. (d) and (0) represent read data and write data from the memory 9, respectively. To explain the operation of this device, in FIG. 1, an image signal a that has been subjected to various signal processing such as sharpness enhancement, 9 color corrections, 0 gradation changes, etc. is applied to one input terminal of a comparator 1, while a clock generation circuit The screen pattern signal C is read out from the screen pattern memory 3 in synchronization with the first clock f generated by the comparator 11 and is applied to the other input terminal of the comparator 1. Similarly, in comparator 1, the first clock f
In synchronization with , the image signal a and the screen pattern signal C are compared to create a light modulation control signal d. The optical modulation control signal d created in this way is sequentially written as optical modulation control data into one 1-bit line memory 9a, for example, based on commands from the line memory control circuit 10, also in synchronization with the first clock f. In this case, the write operation is executed over almost the entire period of one cycle of the galvanometer mirror 6 as shown in FIGS. will be written into the 1-bit line memory 9a. In parallel with the writing operation, the optical modulation control data that is one scanning line before the optical modulation control data for which the writing operation is being performed is transmitted from the other 1-bit line memory 9b to the PLL circuit 2. In synchronization with a second clock b having a frequency proportional to the output beam speed, the signals are sequentially read out to the optical modulator 4 based on commands from the line memory control circuit 10. In this case, the read operation
As shown in Figures (a) and (d), this readout operation is carried out only in the effective scanning area excluding both ends of the light beam actual scanning area within the outgoing operation section of the galvanometer mirror 6, and this readout operation covers one scanning line. The optical modulation control data is given to the optical modulator 4 as an optical modulation control signal q.

In the reciprocating section of the next cycle of the galvanometer mirror 6, 1
Writing and reading of the bit line memories 9a and 9b are switched by a command from the line memory control circuit 10, that is, the light modulation control data for one scanning line written in the one bit line memory 9a in the previous cycle is switched. is read out to the optical modulator 4 in synchronization with the second clock b, while the optical modulation control data for one new scan output from the comparator 1 is read out on one bit line in synchronization with the first clock a. The data is written to memory 9b. In this way, writing and reading to and from the 1-bit line memories 9a and 9b are repeated alternately for each scanning line, and the optical modulation control signal 9 corresponding to each scanning line is continuously created, and this optical modulation control signal 9, a predetermined halftone image is recorded on the photosensitive material 7 in the same manner as in the prior art.

According to this image recording device, a memory 9 for storing light modulation control data is provided, and reading is performed in synchronization with the second clock b having a frequency proportional to the beam speed, and writing is performed using the second clock b. Since the first clock f having a lower frequency than b is used, it is possible to use an inexpensive screen pattern memory 3 that operates at a slower speed than conventional ones. Further, various signal processing performed at the previous stage before the image signal a is input to the comparator 1 can also be performed at low speed using the first clock f having a low frequency. Further, when the reading speed of the screen pattern memory 3 is set to be the same as the conventional one, the swinging speed of the galvanometer mirror 6 can be increased to increase the recording speed of the duplicate image.

In the above embodiment, a galvano mirror with a scanning efficiency η of about 0.3 to 0.4 was used as the deflector 6, but a polygon mirror with a scanning efficiency of about 0.8 was used. The same effect as above can be obtained.

Further, in the above embodiment, a case where a duplicate image is recorded using a single light beam has been described, but the present invention also applies when a duplicate image is recorded using a plurality of so-called multi-beams. Applicable. In this case, screen pattern memory 3. Comparator 1. A number of memories 9 and optical modulators 4 corresponding to the number of light beams are prepared, each having a circuit configuration as shown in FIG. 1, and these are connected to a common clock generation circuit 11. Line memory control circuit 10. They may be operated simultaneously in parallel using a PLL circuit 2 or the like.

(Effects of the Invention) As described above, according to the image recording device of the present invention, a memory for storing light modulation control data is provided, and the readout is synchronized with the second clock having a frequency proportional to the beam speed. In addition, since writing is performed using the first clock having a frequency different from that of the second clock, it is possible to obtain the effect that the recording speed of the duplicated image can be increased at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of an image recording apparatus which is an embodiment of the present invention, and FIG. 2 is a mechanical diagram of the image recording apparatus.
FIG. 3 is a time chart for explaining the operation of the image recording apparatus, and FIG. 4 is a schematic configuration diagram of the conventional image recording apparatus. 1... Comparator, 2... PLL circuit,
3... Screen pattern memory, 4... Light modulator, 5... Light beam, 6
...deflector, 7.photosensitive material, 8.
...Grating sensor, 9...Memory, 10...
・Line memory control circuit, 11... Clock generation circuit

Claims (2)

[Claims] (1) Based on light modulation control data obtained from an image signal, a light beam is scanned onto a flat photosensitive material via a linear scanning deflector while being switched in units of exposure dots by a light modulator to create a predetermined image. An image recording apparatus for recording, comprising: a memory for storing the light modulation control data; a means for writing the light modulation control data obtained from the image signal into the memory at a first clock cycle; and light on the photosensitive material. and means for reading out the light modulation control data from the memory to the light modulator in synchronization with a second clock having a frequency related to a beam scanning speed. . (2) An image recording apparatus having an output line buffer according to claim 1, wherein the frequency of the second clock is set higher than the frequency of the first clock.