JP2003287900A - Image exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image exposure device for recording a desired image on a recording medium by scanning and exposing the recording medium wound round the outer peripheral surface of a drum rotating at constant speed with an exposing beam, and capable of detecting the float of the recording medium in the midst of exposure recording with simple and inexpensive device constitution. <P>SOLUTION: The image exposure device 10 is provided with the drum 12 equipped with the outer peripheral surface round which the recording medium is wound, a light source part 14 generating the exposing beam, an optical system 16 focusing the exposing beam radiated from the light source part 14, a position measuring part 18 measuring the position of the recording surface of the recording medium, a medium float discrimination part 20 for discriminating whether or not the-recording medium floats from the outer peripheral surface of the drum 12 by using a measurement signal from the measuring part 18, and an autofocus controlled variable adjusting part 22 for performing the positional adjustment of the optical system 16 by using the measurement signal from the measuring part 18 so that the focused position of the exposing beam by the optical system 16 may come onto the recording surface of the recording medium. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image exposure for recording an image by guiding an exposure beam by an optical system to a desired position on the surface of a recording medium wound around an outer peripheral surface of a drum and scanning and exposing the recording medium. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, at a desired position on the surface of a recording medium wound around the outer peripheral surface of a drum rotating at a constant speed,
There is an outer-drum type exposure beam scanning device that guides an exposure beam such as a laser beam by an optical system to scan and expose a recording medium to record an image. This outer drum type exposure beam scanning device focuses the exposure beam on the surface position of the recording medium and scans it in the main scanning direction.
The exposure beam is moved in the rotation axis direction (sub-scanning direction) of the drum to perform two-dimensional scanning recording. An example of such an outer type exposure beam scanning device is a CT in the printing field.
An image exposure apparatus including a scanning type exposure recording head in a P (Computer To Plate) or the like can be used.

In this image exposure apparatus, for example, 0.2 m
A PS plate (Presensitized plate) coated with a photosensitive material on an aluminum plate with a thickness of about m is wrapped around the outer peripheral surface of the drum, and the exposure beam focused on the recording surface of the PS plate is used to achieve high resolution in a short time. The image can be exposed and recorded. For example, the drum wound with the PS plate is 1000 rp
Rotate at m for exposure recording. In this case, the PS plate is fixed and held by a chuck provided on the outer peripheral surface of the drum so that the exposure position of the exposure beam does not shift and the spot light of the exposure beam on the recording surface does not blur. Therefore, the PS plate may float from the outer peripheral surface of the drum, so-called plate floating may occur. In particular, when the drum is rotated at a high speed in order to expose and record an image in a short time, the PS plate is likely to float.

On the other hand, in order to detect such plate floating of the PS plate during exposure recording, a plate floating sensor for detecting plate floating is provided, and safety measures for plate flying are taken. As a result, when the plate floating occurs during the exposure recording, the exposure recording can be stopped or the operator can be notified of the plate floating. It is also possible to avoid the worst case in which the PS plate comes off the chuck during exposure recording.

[0005]

However, providing such a plate floating sensor separately from the image exposure apparatus main body is
There is a problem in that the configuration of the entire apparatus is unnecessarily complicated, and a plate floating sensor, a mounting member, a processing circuit for processing signals of the plate floating sensor, and the like are required, resulting in an increase in cost.

In order to solve the above-mentioned problems of the prior art, the present invention provides an image exposure apparatus capable of detecting plate floating of a recording medium during exposure recording with a simple structure and without cost. The purpose is to provide.

[0007]

In order to achieve the above object, the present invention records a desired image by scanning and exposing a recording medium wound around an outer peripheral surface of a drum rotating at a constant speed with an exposure beam. An image exposure apparatus for recording on a medium,
A drum having an outer peripheral surface around which the recording medium is wound, a light source section for generating an exposure beam, an optical system for converging the exposure beam emitted from the light source section, and a perpendicular to the recording surface of the recording medium rotating with the drum. A position measuring unit that measures the position of the recording surface that fluctuates in a direction; a determining unit that determines whether or not the recording medium floats from the outer peripheral surface of the drum using a measurement signal from the position measuring unit; and the optical system. And an auto-focus adjustment unit that adjusts the position of the optical system by using the measurement signal of the position measurement unit so that the focus position of the exposure beam is on the recording surface of the recording medium. An image exposure apparatus is provided.

Here, it is preferable that the discriminating section discriminates the presence or absence of floating of the recording medium on the basis of a variation amount of the position measurement data of the recording surface obtained from the measurement signal from a predetermined reference data. For example, the exposure recording on a recording medium is exposure recording performed by moving in the rotation axis direction of the drum while performing scanning recording by rotation of the drum,
The position measurement data is data for each rotation of the drum on the scanning line of the recording medium by the scan recording, and the determination unit determines whether the recording medium is floating based on the position measurement data for each rotation. In this determination, the position measurement data for one rotation before one scanning line or more, which has already been used for determining the floating of the recording medium, is used as the reference data. Alternatively, the drum is provided with a fixing member for fixing the recording medium by winding the recording medium around the outer peripheral surface, and the discriminating unit is provided on a portion of the recording medium immediately after the fixing member passes by the rotation of the drum. The value of the corresponding position measurement data is used as the reference data. Alternatively,
The discrimination unit uses the drum surface position measurement data obtained by measuring the position of the outer peripheral surface of the drum using the position detection unit as the reference data. Alternatively, the exposure recording on the recording medium is exposure recording performed by moving in the rotation axis direction of the drum while performing scanning recording by the rotation of the drum, and the position measurement data is for each rotation of the drum. The data is the recording medium wound around a portion of the outer peripheral surface of the drum, and the portion of the position measurement data for each one rotation corresponding to the remaining portion of the outer peripheral surface of the drum which is not wound around the recording medium is exposed. , Used as the reference data.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An image exposure apparatus of the present invention will be described below in detail based on the preferred embodiments shown in the accompanying drawings. FIG. 1 is a schematic configuration diagram showing a schematic configuration of an image exposure apparatus 10, which is an example of the image exposure apparatus of the present invention.

The image exposure apparatus 10 is a cylindrical outer surface scanning type (outer drum type) optical scanning apparatus, and focuses an exposure beam such as a laser beam used for exposing a recording medium wound around the outer peripheral surface of a rotating drum. Exposure recording is performed with an exposure beam while performing autofocus adjustment so that the position is always on the recording surface of the recording medium.

The image exposure apparatus 10 includes a drum 12, a light source unit 14, an optical system 16, a recording surface position measuring unit 18, a position calculating unit 19, a plate floating discriminating unit 20, and an autofocus control amount adjusting unit. 22 and VCM (voice coil motor)
The driver 24, the VCM 26, and the optical system position measuring unit 28
And an alarm device 30 are mainly included. Position calculator 19,
The plate floating determination unit 20 and the autofocus control amount adjustment unit 22 are configured by a digital signal processing device (DSP) 23. In addition, the light source unit 14, the recording surface position measuring unit 18,
The VCM 26 and the optical system position measuring unit 28 are fixedly provided in the housing 31. Here, the autofocus control amount adjustment unit 22, the VCM driver 24, and the VCM 26 are
The autofocus adjusting unit in the present invention, the plate floating discriminating unit 20 in the discriminating unit in the present invention, the recording surface position measuring unit 1
Reference numerals 8 correspond to the position measuring unit in the present invention.

The drum 12 is a drum having an outer peripheral surface around which a recording medium P, for example, a PS plate is wound, and chucks 32 and 34 for fixing and holding the recording medium P are provided on the outer peripheral surface. The rotation of the drum 12 around the drum rotation shaft 36 is controlled by a drive motor (not shown), and the position of the outer peripheral surface of the drum is known.
A rotary encoder (not shown) is provided so that the arrangement position of the recording medium and the arrangement positions of the chucks 32 and 34 can be known, and a drum rotation position signal from the rotary encoder is supplied to the DSP 23.

The light source unit 14 is, for example, a light source for emitting a laser beam. The optical system 16 is composed of a combined lens that focuses the parallel laser light on the recording surface of the recording medium P. The recording surface position measuring unit 18 is a portion that measures the position of the recording surface that fluctuates in the direction perpendicular to the recording surface of the recording medium P that rotates with the drum 12, and outputs two types of digital signals.

FIG. 2 is a configuration diagram showing the configuration of the recording surface position measuring unit 18. The recording surface position measuring unit 18 uses an LED element 18a that emits a measurement light beam and a photodiode P that receives the reflected light from the recording surface of the recording medium P.
SD (Position Sensitive Detector) 18b and PS
An amplifier circuit 18c ₁ that amplifies the received light signal output from one terminal of D18b, a filter circuit 18d ₁ that removes a noise component of the amplified signal, and a filter circuit 18d
An analog / digital conversion circuit (hereinafter referred to as an AD conversion circuit) that uses the signal filtered in ₁ as a digital signal 1
Digital and 8e _1, an amplifier circuit 18c ₂ a light-receiving signal outputted from the other terminal of PSD18b, a filter circuit 18 d ₂ to remove noise components of the amplified signal, the filtered signal by the filter circuit 18 d ₂ and a AD converter circuit 18e ₂ to signal, digital signal D _1, D ₂ is supplied to the DSP23 as a measurement signal. Also,
The AD conversion circuits 18e ₁ and 18e ₂ perform sampling according to different sampling timing signals supplied from the DSP 23.

The recording surface position measuring unit 18 is
Two systems of circuits corresponding to the terminals from both D18b are configured, the sampling timings of the AD conversion circuits 18e ₁ and 18e ₂ are adjusted separately, and the value of the digital signal corresponding to the light reception signal at the same time is calculated by the DSP 23. Therefore, the DSP 23 described later can accurately calculate the position variation of the recording surface of the recording medium P. The recording surface position measuring unit 18 measures a change in the position of the recording surface one line ahead or several lines ahead of the main scanning line for starting the exposure recording. It should be noted that it is also possible to measure the variation of the position of the recording surface on the main scanning line from which exposure recording is started from now.

The position calculating section 19 of the DSP 23 is a section for calculating the distance x according to the following equation (1) using the digital signals D ₁ and D ₂ supplied from the recording surface position measuring section 18. _{x / L = (D 2 /} D 1) / (1+ (D 2 / D 1)) (1) where, L is the length of the light receiving portion of PSD18b, x
Is the distance from the end of the light receiving portion (see FIG. 2). Thus, the light receiving position of the reflected light on the recording surface of the recording medium P is set to the distance x
It can be specified by
Then, the position of the recording surface of the recording medium P can be obtained from the positional relationship between the light receiving portion of the PSD 18b and the LED 18a. When the recording surface of the recording medium P changes from the solid line to the broken line as shown in FIG. 2, the light receiving position in the PSD 18b also changes, and the calculated distance x also changes to the distance x ′.
Therefore, the changed position of the recording surface of the recording medium P can be obtained from the distance x ′.

In this way, the position calculation section 19 is arranged so that the recording medium P
The position measurement data representing the position change of the recording surface due to one rotation of the drum 12 can be calculated according to the drum rotation position signal supplied from the rotary encoder (not shown). At that time, the position measurement data includes data of the portions of the chucks 32 and 34 and the portion where the recording medium P is not wound and the outer peripheral surface of the drum 12 is exposed. Chucks 32, 34
The area corresponding to the chuck 32 is an area having abruptly changing parts on both sides obtained by obtaining the differential value of the position measurement data.
Since it corresponds to the portion corresponding to 34, the value of the position measurement data in the above area may be replaced with the value of the dummy signal separately supplied to the DSP 23. Such position measurement data is supplied to the plate floating determination unit 20.

The plate floating discriminating unit 20 compares the position measurement data supplied from the position calculating unit 19 for one rotation of the drum 12 with the recorded reference data, and the plate floating occurs according to the comparison result. It is a part for determining whether or not it is present. The exposure recording on the recording medium P is performed by exposing and recording in the main scanning direction by one rotation (one revolution) of the drum 12, and at the same time, moving in the rotation axis direction of the drum 12 and exposing and recording in the sub scanning direction. For example, as shown in FIG. 3A, the position measurement data on the main scanning line one cycle before used for discriminating the plate floating is stored and used as reference data. If there is a portion where the amount of change from the above exceeds a predetermined amount, it is determined that the plate floating has occurred.
Instead of the position measurement data on the main scanning line one cycle before,
It is also possible to use position measurement data on the main scanning line several revolutions ago or averaged position measurement data on the main scanning line for several revolutions.

Further, the following reference data may be used. For example, as shown in FIG. 3B, the reference data is set to a preset constant value, and if there is a portion that exceeds this constant value, it is determined that the plate floating has occurred. If the eccentricity of the drum 12 is small and the roundness is accurate, the position measurement data can be compared with a constant value. Alternatively, the recording medium P
Of the chucks 32 and 34 for fixing and supporting the recording medium P
Position measurement data corresponding to the portion of the recording medium P immediately after passing through the chuck 32 that fixes at the tip in the rotational direction, FIG.
The position measurement data at the position Q at is used as reference data, and when there is a portion where the amount of change from this reference data exceeds a predetermined amount, it is determined that plate floating has occurred. Chuck 32
This is because the plate floating does not occur in the portion of the recording medium P immediately after the passage. In addition, as shown in FIG.
The average value of the portion R of the position measurement data corresponding to the outer peripheral surface of the drum may be used as the reference data. Also in this case, if there is a portion where the amount of change in the position measurement data with respect to the reference data exceeds a predetermined amount, it is determined that plate floating has occurred.

Alternatively, the drum surface position measurement data obtained by previously measuring the position of the outer peripheral surface of the drum 12 using the recording surface position immediate bottom portion 18 along the rotation axis direction may be used as the reference data. In this case, the corrected data obtained by subtracting the reference data corresponding to the same position on the outer peripheral surface of the drum 12 from the position measurement data obtained by measuring the change in the position of the recording surface of the recording medium P has a predetermined amount. It is determined by whether or not there is a portion that exceeds.

When it is determined by the plate floating determination unit 20 that the plate floating has occurred, an alarm signal is generated to activate the alarm device 30 and is supplied to the alarm device 30. The alarm device 30 is, for example, a buzzer that notifies the occurrence of plate floating, or a monitor of a computer (not shown) that controls each component of the image exposure apparatus 10. That is, the buzzer or monitor notifies the operator of the alarm. Also, the rotation of the drive motor that drives the drum 12 is forcibly stopped,
The exposure recording may be stopped by forcibly stopping the irradiation of the laser light from the light source unit 14.

When it is determined that the plate floating does not occur as a result of the determination by the plate floating determination unit 20, the position calculation unit 19
The position measurement data created in step S4 and supplied to the plate floating determination unit 20 is supplied to the autofocus control amount adjustment unit 22.

Since the supplied position measurement data is the position measurement data at the main scanning line preceding the main scanning line at which the exposure recording is currently started, the autofocus control amount adjusting unit 22 temporarily stores it in its own memory. In addition to storing and holding, position measurement data representing the fluctuation of the position of the recording surface corresponding to the main scanning line for starting the current exposure is called, and the position adjustment amount of the optical system 16 to be moved is calculated using this position measurement data. It is a part to do. Specifically, the position measurement data representing the variation in the position of the recording surface corresponding to the main scanning line for starting the exposure is converted into the position representing the variation in the position of the optical system 16 supplied from the optical system position measuring unit 28 described later. Feedback control is performed while measuring the position of the optical system 16 so that the focus position is located on the recording surface of the recording medium P using the measurement data. Furthermore, since the autofocus control amount adjustment unit 22 previously obtains position measurement data representing the variation in the position of the recording surface of the main scanning line for starting exposure recording, feedforward control is performed using this position measurement data. You can go. The position adjustment amount of the optical system 16 to be moved is supplied to the VCM driver 24.

The VCM driver 24 is a portion that generates a drive signal to be supplied to the VCM 26 based on the position adjustment amount of the optical system 16 and supplies the drive signal to the VCM 26. VCM26
Is a known drive mechanism that utilizes the force generated in a coil by passing an electric current through the coil placed in a magnetic field. VC
A support member 38 that supports the optical system 16 is provided on the M26, and the support member 38 can be swung in a direction in which the support member 38 moves toward and away from the drum 12 by driving the VCM 26. Therefore, the optical system 16 moves as the support member 38 moves.
Moves toward and away from the drum 12. Thereby, the exposure beam B can be focused on the recording surface of the recording medium P.

Like the recording surface position measuring unit 18, the optical system position measuring unit 28 has a PSD element having two output terminals, and includes an amplifier circuit, a filter circuit, and an AD conversion circuit as a P element.
Two systems are provided corresponding to the output terminals of the SD element, and the optical system 16
Is a part that outputs a measurement signal for measuring the position of. The output measurement signal is supplied to the autofocus control amount adjustment unit 22.
At, the position of the optical system 16 is calculated from the measurement signal. Specifically, the member 40 fixed to the optical system 16 is emitted toward the measurement light beam, and the reflected light is received by the light receiving portion of the PSD element to output the measurement signal of the optical system 16. This measurement signal is supplied to the autofocus control amount adjustment unit 22 described above, and is used to calculate the position of the optical system 16 and the position adjustment amount to be moved.

As described above, the measurement signal obtained by the recording surface position measuring unit 18 is used for the autofocus adjustment of the exposure beam B and also for determining whether or not the printing medium P has a plate floating. Therefore, as compared with the case where the presence or absence of the plate floating is determined using the conventional plate floating sensor, the presence or absence of the plate floating can be checked by using the measurement signal of the recording surface used for the autofocus adjustment of the exposure beam. The device configuration can be simple and inexpensive.

In the image exposure apparatus 10 having such a configuration, the change in the position of the recording surface on the main scanning line is caused by the recording surface position measuring unit 18.
Position measurement unit 1 outputs two measurement signals.
9 is supplied. The position calculation unit 19 uses the two measurement signals to calculate the distance x by the above equation (1), and
The position of the recording surface of the recording medium P is obtained from a predetermined position, and a drum rotation position signal supplied from a rotary encoder (not shown) attached to the drum 12 is used to determine a position as shown in FIG. Measurement data is obtained. The position measurement data is supplied to the plate floating determination unit 20.

In the plate floating determination unit 20, the position measurement data is compared with the reference data, and if there is a portion where the amount of change in the position measurement data from the reference data exceeds a predetermined amount, it is determined that the plate floating has occurred. , An alarm signal is generated and supplied to the alarm device 30 to notify the operator. Alternatively, the exposure recording may be forcibly stopped. When the amount of change in the position measurement data from the reference data is less than or equal to a predetermined amount, the plate floating determination unit 20 determines that the plate floating has not occurred, and the position measurement data is determined by the autofocus control amount adjustment unit 2.
2 is supplied.

In the autofocus control amount adjusting section 22,
Since the position measurement data supplied from the plate floating determination unit 20 is position measurement data that represents a change in the position of the recording surface of the main scanning line that precedes the main scanning line for starting exposure recording by one to several lines. The supplied position measurement data is temporarily stored and held. Further, the position measurement data corresponding to the main scanning line for starting the exposure recording is called and used together with the position measurement data of the optical system obtained from the measurement signal of the optical system 16 supplied from the optical position measuring unit 28, Set the focus position of the exposure beam B on the recording surface,
A position adjustment amount to be moved with respect to the current position of the optical system 16 is obtained. The calculated position adjustment amount is supplied to the VCM driver 24.

The VCM driver 24 generates a drive signal based on this position adjustment amount and supplies it to the VCM 26. The VCM 26 moves in a direction in which the optical system 16 moves toward and away from the drum 12 via the support member 38 based on the drive signal. At that time, the optical system position measuring unit 28 keeps the optical system 1
The position of 6 is measured, and the autofocus control amount adjustment unit 22
Feedback control is performed. Further, since the position measurement data indicating the variation of the position of the recording surface of the main scanning line to be exposed and recorded is previously obtained, the feedforward control may be performed using this position measurement data. In this way, autofocus adjustment is performed so that the focus position of the exposure beam B is always on the recording surface of the recording medium P.

As described above, since the measurement signal obtained by the recording surface position measuring unit 18 is used for the autofocus adjustment and for determining the plate floating, the plate floating sensor is used for the autofocus adjustment as in the conventional case. Since it is not necessary to provide the image exposure apparatus as a separate body, it is possible to realize an image exposure apparatus with a simple structure and at low cost.

The image exposure apparatus of the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

[0033]

As described above in detail, according to the present invention, a position measuring unit for measuring the position of the recording surface of the recording medium for autofocus adjustment of the optical system for focusing the exposure beam is provided. Although provided, the measurement signal from this position measuring unit is also used to determine whether or not the recording medium floats from the outer peripheral surface of the drum. Since it is not necessary to provide the image exposure apparatus as a separate body, it is possible to provide an image exposure apparatus having a simple structure and no cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a schematic configuration of an embodiment of an image exposure apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a schematic configuration of a recording surface position measuring unit of the image exposure apparatus shown in FIG.

3A and 3B are diagrams showing an example of position measurement data obtained by the image exposure apparatus shown in FIG.

[Explanation of symbols]

10 Image exposure device 12 drums 14 Light source 16 Optical system 18 Recording surface position measurement unit 19 Position calculator 20 Plate floating discrimination section 22 Autofocus control amount adjustment unit 24 VCM driver 26 VCM 28 Optical system position measurement unit 30 alarm device 31 housing 32,34 chuck 36 drum rotating shaft 38 Support member

Claims (5)

[Claims] 1. An image exposure apparatus for scanning and exposing a recording medium wound around an outer peripheral surface of a drum rotating at a constant speed with an exposure beam to record a desired image on the recording medium, the outer periphery around which the recording medium is wound. A drum having a surface, a light source section for generating an exposure beam, an optical system for converging the exposure beam emitted from the light source section, and a recording that changes in a direction perpendicular to a recording surface of a recording medium rotating together with the drum. A position measurement unit that measures the position of the surface, a determination unit that determines whether or not the recording medium floats from the outer peripheral surface of the drum using the measurement signal from the position measurement unit, and the focusing of the exposure beam by the optical system. And an autofocus adjustment unit that adjusts the position of the optical system by using the measurement signal of the position measurement unit so that the position is on the recording surface of the recording medium. Image exposure apparatus. 2. The discriminating unit discriminates the presence or absence of floating of the recording medium on the basis of a variation amount of position measurement data of a recording surface obtained from the measurement signal from a predetermined reference data. Image exposure device. 3. The exposure recording on a recording medium is exposure recording performed by moving in the rotation axis direction of the drum while performing scanning recording by rotation of the drum, and the position measurement data is obtained by the scanning recording. It is data for each rotation of the drum on the scanning line of the recording medium, and the determination unit determines whether or not the recording medium is floating based on the position measurement data for each rotation. The image exposure apparatus according to claim 2, wherein the position measurement data of one rotation before one scanning line or more, which has already been used to determine the floating of the medium, is used as the reference data. 4. A fixing member for winding and fixing the recording medium on the outer peripheral surface is provided on the outer peripheral surface of the drum, and the discriminating section is provided immediately after the fixing member has passed by the rotation of the drum. The image exposure apparatus according to claim 2, wherein the value of the position measurement data corresponding to the portion is used as the reference data. 5. The image exposure according to claim 2, wherein the discriminating section uses, as the reference data, drum surface position measurement data obtained by measuring the position of the outer peripheral surface of the drum using the position detecting section. apparatus.