JPS5834424A - Control of light beam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method that can be employed to achieve great accuracy in writing text and images on photosensitive surfaces with a light beam. In this method, a special scale or grating with slits or lines is used to measure the position of the light beam. Through this measurement, the position 1a of the light beam during writing is accurately known, and thereby the actual scratching operation can be accurately guided to the desired position on the image plane. Position measurement in one direction on the image plane uses a clever technique that uses a slit placed on the opposite side of the image plane, and the position of the light beam is recorded at the edge of the slit.
The light beam is deflected based on this.

Since the movement of the light beam can be performed repeatedly and with good reproducibility, this allows the -C ratio to be adjusted in this direction everywhere on the image plane.
It is possible to know the tit coordinate of the beam.

ilZ I'li on the image plane in the direction perpendicular to this direction
Coordinates are measured using another scale with multiple slits or lines. The writing beam or a reference beam taken out from the writing beam is dropped onto the scale ``-'' and a signal indicating the position 1i'f of the beam or beam σ) of the scale 1- is provided as writing progresses in that direction.

The light beam can be used for phototypesetting, printing plate production, digital computer output, facsimile transmission, and text and/or +I! printing on two-dimensional surfaces. It is used in the task of recording the image. In such cases, if the output is required to be reliable, a laser beam is used.

When using a laser beam, a very bright small spot can be obtained. In this respect, a method of deflecting and modulating a laser beam to suppress the laser beam is already known. In these techniques, the position of the laser beam is controlled based on GJ positive J@ mechanical motion and, in some cases, t, c, ip< signals given as the beam travels on the scale. However, in this method, the required 46 (tli I', F, is so Iyil
You can't get it from IJi.

In contrast, the invention described in the claims of the present specification provides accurate information about the instantaneous position 1a of the light beam at the image plane by a scale provided outside the image plane,
This information is used to control the (II loading process i1+1).

The invention will be explained in detail with reference to the drawings.

An example of non-inventive method 7) is shown in Fig. 1V at a time
:The image plane is exposed for each strip of 1 h. When the light spot moves horizontally from left to right, it is simultaneously rapidly deflected a distance G in the vertical direction. If the light beam is time-varying, it will cover all the areas of the area.
The text of ( and the image of 111j are written in. If the adjacent strips are exposed a sufficient number of times one by one, the entire page will be filled in. At this time, the important thing is that each strip stops (i). (The next step is to press the adjacent A, Article 111, exactly on It.The measurement and control of the position required for this is done as shown in +゛t +:. Calibration is performed by deflecting the light beam in the vertical direction and dropping it on the upper left corner of the strip. Hit the slit in the lower left corner (Syu and 82 in Figure 1).

Record the driving voltage of the deflection device rt when the light beam crosses the upper edge of the slit S2 and the upper edge of the slit S2, or the time value or similar information. The light beam is then deflected to the right edge of the image ``n'' and the corresponding values for the slit in the corner and the lower right corner (84 in FIG. 1) are recorded. This resulted in very accurate measurement of the position of the strip.

Since this measurement is made with the same beam used for writing, any errors due to misalignment and inaccuracies in mechanical components and mechanical interlocks are automatically corrected. Similarly, even if the electronic device a that performs vertical deflection has a vertical deflection or drift, this will not cause an error during writing.

After the calibration and the correct calculation of the error associated with the calibration are completed in this way, the preparation of the strip (b in FIG. 1) is started. The strip is written by sweeping the light beam a height h from one end of the strip to the other. Thus, for example, to write the width of a newspaper/page, such a sweep is performed approximately 11,000 times. Then, for each sweep, the voltage value period 4iti for the point B) in FIG. Similarly, the position tti of the lower boundary point of the strip is also calculated. Accordingly, J, Article 111, 1% '2' and 1 each
1. The ^L of the III element is known. Based on this information, the modulation of the light beam can be synchronized with the vertical 1fj-deflection of the light beam, and each pixel can be injected into the correct position 1a to the positive I'β m. Particular attention should be paid to the border of the strip (point B relative to strip A in the figure).
2iI! The measurement is performed using the same slits used when determining I, that is, the slits (S□ and S3) located at the left and right ends of the image plane and at the same height as the boundary. This means that the trivial problem of correctly attaching the following details can be solved with high reliability.

In some cases, due to lens distortion, even if the deflection pressure (m) is constant, the height (h) of the single line becomes larger toward both ends of the image plane than at the center. This and other 4'4
Another calibration procedure can be added to correct for the 11 distortions. For this reason, the image appears above or below the image plane:
Linear horizontal slits (L and L2 in Figure 1) and edge slits corresponding to these slits (S in Figure 1)
a, Sb, so.

Sd) and use these slits to radically calibrate the device, e.g. 7 times a day. First, apply the light beam to the height of the slit 5 as described above.
Measure a-8d. After that, the light beam is deflected to straddle the strip between L and L2 in the same way as when writing the strip. Then, during each vertical sweep or a suitably selected few sweeps, the voltage or time values are recorded when the light beam crosses the slit L2 and when it crosses the slit L2. This performs fundamental calibration, and then fills in the image plane, resulting in If'-7 linear upper boundary and lower boundary that are positive 1iIIIi with respect to the strip G on the image plane. can be given.

To measure the position in other dimensions, i.e. horizontally, use a scale with a suitable vertical slit or line in the horizontal direction.
Measure by taking a loaf. One method is then to run the reference beam along a scale Ia outside the image area. Such a scale is schematically illustrated at the top of FIG. Associating such a scale G with a photodetector,
The horizontal X coordinate will be known from the signal that will be output from now on. The first method is to use the return beam itself. An example of this is shown in Figure 2. Here, the photosensitive image surface is moved so that the desired strip or one line of the one-in-one beam is formed. Then, if you place the required strips in the correct position, this 14
Slit corresponding to Article 11 (Slit 5a-8 in Figure 2)
d) Perform vertical position measurements using Q&, 1:,. In addition, in writing for the main examination, the horizontal slit (L and L21 in Figure 2) is used to accurately control the page deflection for each vertical sweep. In Figure 2, such a horizontal scale is made of a short diagonal slit on the lower side of L□.

During each vertical sweep, the writing beano travels over a scale consisting of these diagonal slits. A photodetector detects at what precise location the light beam crosses the horizontal scale, and this signal gives the X coordinate of the vertical sweep. This method has the advantage that only one beam is required, namely the writing beam. This eliminates errors due to differences between the pointing of the imprint beam and the pointing of the reference beam.

At the laboratory, the method of the present invention was studied using the apparatus shown in FIG. It comprises a laser/ from which a light beam is emitted towards the modulator. It is also equipped with an acousto-optical deflection device (3) for vertical deflection (11). Additionally, a galvanometer mirror p'tv was placed along the light beam path to effect a horizontal deflection across the image area. In the latter stage, the light beam passes through a converging lens and a beam splitter that reflects only a portion of the light beam. A beam splitter t splits the light beam into a writing beam and a reference beam. The reference beam falls onto a scale 7 cut through two horizontal slits. If such a scale 7 is used, the vertical position and vertical deflection speed of the light beam can be accurately determined during each sweep. In FIG. 3, a dotted line is used to indicate the second reference beam. This second reference beam is unmodulated and falls on the horizontal scale r and the photodetector 9 behind it. The X coordinate is constantly determined from the output signal G of this photodetector.

An important feature of a device M of the type shown in FIG. 3 is the use of an acousto-optical deflection device, so that the vertical deflection can be effected electronically without moving any mechanical parts.

The control device a for positioning the light beam can also be purely electronic. Mechanical deflection using a galvanometer mirror allows the constant periodic drive a to run freely once a month. The vertical deflection is synchronized with this free running deflection so that the vertical deflection starts when the beam measured on the scale reaches the correct X coordinate value. The electronic control then provides the correct X coordinate value for each sweep. Similarly, in the y direction, by measuring the y coordinate (+m) of the light beam and synchronizing the modulation of this light beam, the pixels are correctly positioned 1a, and each pixel is written when the light beam reaches the correct 7 position 1a. This position control in the y direction is also performed electronically and does not adversely affect the manufacturing tolerance or accuracy of mechanical parts.It should be noted that this position control can be easily manufactured with high precision. , based on a geometric scale whose accuracy is guaranteed to be maintained.

The proposed position rt measuring device can be of the type not shown in FIG. The transition from one of the seven strips to the next strip takes place with a second galvanometer mirror /≦ placed after the IIM bundle lens /j. This results in an essentially randomly accessible device in the vertical direction. The rotation time of the galvanometer is on the order of /θ milliseconds,
It is independent of the degree of rotation angle. None of the conventional devices provide such random access operation. This is because the indicating accuracy of the galvanometer mirror is insufficient to reach the required writing accuracy. However, the control device f proposed in the invention in particular uses a writing beam to
? Since it measures L and operates electronically, it is extremely fast and accurate in H2 and can be accessed randomly using a galvanometer. Randomly accessible device? This is useful, for example, in phototypesetting. In this case, the 4j text and the image can be written separately when they are different, and there is no need to write the entire page in a fixed order, for example from the upper left corner to the right F corner. This provides much easier computer control when photosetting entire pages containing various types of graphic elements.

81￥1 In the device shown in the figure, the image plane /g of the lens is cylindrical. The axis of this cylinder is the same as the axis of the galvanometer/B.

However, in some cases it is important that the image plane is flat. This is accomplished by guiding the light beam as shown in FIG. A set of plane mirrors 1 are arranged along a paraboloid after the second galvanometer 26.

At this time, by selecting the dimensions appropriately, the following conditions can be achieved. Direct the light beam to any one plane mirror 1
When guided toward the center of the image plane I, the light beam is focused on a flat image plane I. Also, since the horizontal deflection galvanometer 2'l and the acousto-optical vertical deflection device are clearly located in front of the converging lens, in the case of a flat field converging lens, the light beam is at the I of the deflection device.
J: 6 The image continues to be focused on a flat image plane regardless of the direction angle. Thus, a device of the type shown in Figure S does not physically move the image plane, and thus can write on large flat surfaces while retaining the random access capability.

The device assembled in the laboratory works as a laser with a wavelength of 11,! I
An argon-ion laser that emits light at I nm is used. The light beam emerging from this was modulated using an acousto-optical modulator with a bandwidth r MHz. Short vertical deflections are acoustic −
Obtained using a light deflection device. The maximum value of deflection on the image plane is l
f nm, and the vertical deflection time required for one sweep was between Sθμsec and 2 m5ec, although it differed from experiment to experiment. The deflection angle of the horizontal deflection galvanometer was up to 3θ0, the random access time was about lo m5ec, and the horizontal deflection was 220 to 130 degrees depending on the converging lens. The height of the stripes was 3.2 mm, and the height of the entire image area was 300-20 mm.

Scales were placed on the left and right boundaries of this image area, and the stiffness was used to measure the y-coordinate. These scales #l-J
J, 5θ/1mIIv at 2 myn 1llI intervals
It contained 11 slits. The distance between the slits was set to Ht±2°371 m. An X-coordinate measurement scale was provided outside the image area, but the kneading consisted of identical transparent vertical lines and opaque vertical lines of each Bpm width. The tolerance for these lines was ±2°S μm.

The light transmitted through the vertical scale was guided to a semiconductor detector using a light-transmitting optical fiber. The light transmitted through the horizontal scale was detected by a long line photodetector. In addition, apparatus a was equipped with a slit line scale of the type shown in FIG. 3, and the light behind it was observed using a light m-tube detection gain. The control circuit was digital. This device also has 3
A clock of 2 Mn2 was provided. The maximum vertical deflection speed of the light beam is 2oo prn /μS80, and the time interval between two clock pulses is 6.2! Compatible with rpm.

The vertical distance is within IE (7) from when the light beam crosses one slit to when it crosses the other slit.
Measured by counting the number of clock pulses. Also the distance is known. Just measure the number of clock pulses between the two slits! 1i direct deflection coverage can be accurately measured. The correction calculations for s:ln were performed using digital technology. After that, when the light beam changes during each vertical deflection sweep, 9.1 calculates the start time for each pixel, and when the clock indicates that the start time has arrived, by outputting the star 1- (g and 1
I recited it. 1I711υ1 in the X direction is the horizontal scale'' - every time the boundary between a transparent line and an opaque line is crossed, ie! Starting signals for vertical deflection were generated at intervals of 311 m (obtained from this).The accuracy of position measurement and control of the device r't over the entire image area was 2 Kpm with a resolution of 2 Kpm. .

Depending on the application, the proposed method may be more or less complicated. For example, the horizontal deflection galvanometer should be of sufficiently high quality and the required degree is performed only on the scale at the left edge of the image plane before the write operation,
The operating speed of device n is multiplied by 116.

Whether horizontal lines L and L2 are required also depends on the required accuracy. When the application is difficult, in addition to vertical TFT measurement, attach a long narrow straight line 4 (mi straight line) to the image plane, and measure +lff1 at the moment when the seeding beam crosses this line.
By recording I-E values or time values, the horizontal position of the image plane must be determined more accurately. A highly accurate measurement of the X coordinate, as explained in connection with FIG.
This can be obtained by combining it with an Ft measuring device.

An embodiment of the present invention is obtained when the height of the strip is 7 pixels (1), in which case only one horizontal slit or line with a length or image area greater than 41j straight position 1a measurement can be performed using the 41j straight position 1a measurement.

The preferred t,C embodiment splits the reference beam from the writing beam and drops this reference beam onto a scale consisting of a long horizontal slit or line. Light passing through the slit li
The amount of light reflected by t or a line depends on the relative position li\ between the image of the slit or line and the light beam. A deflection device i'#, for example an acousto-optical detection device P't.

A piezoelectric mirror, a galvanometer, or a similar device is used to change the direction of the light beam, and a scale is used to compensate for the 1g4 difference to obtain an accurate vertical position when writing.

In this case, the horizontal position can be determined using the same reference beam or another reference beam. In the former case -n
? It must have a structure with some additions to the scale consisting of water\IL slits or lines for iM position measurement. This number depends on the 101X coordinate and is used for X position measurement. An example of this is Ronchi, which consists of a long horizontal line superimposed on a short vertical line.
-It is a scale. When separate reference beams are used for horizontal and vertical measurements, each of the two scales required is simpler in construction than a combined scale.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a specific example of the method of the present invention.
Figure 2 is an explanatory diagram of an example of a horizontal school, Figure 3 is an explanatory diagram of apparatus a used in laboratory research, and Figure 2 is an explanatory diagram of an example when the image plane is cylindrical. FIG. 5 is an explanatory diagram of an example in which the image plane is set to the iF plane. a, b... Thread, S work ~ S4... Thread for thinning, h... Thread height, Sa ~ SdI Ll'
L2...Fundamental adjustment slit or line, /...
Laser, 2... Modulator, 3... Acoustic-optical deflection device +R
s'l... galvanometer mirror! ...Convergence 1/ns, Otsu...
・Beam splitter, 7...scale, g...horizontal scale, w...photodetector. Patent applicant Eero Bickling

Claims (1)

[Claims] 1. A method for controlling a light beam when writing on an image plane using a light beam, the method comprising: deflecting the light beam on the image plane using at least seven deflectors; In the ft7IJ control method of the light beam, which measures the position 1d of the light beam using a scale with a line, e.g. a slit, located in the vicinity of the area to be written on the image plane, A method for controlling a light beam, characterized in that the position is determined by deflecting the light beam along the scale during the last writing by at least &1- minutes and obtaining a signal depending on the position of the line. 2. The deflection of the light beam is controlled by the 7L signal, and the relationship between the electron fm and the position is determined by moving the light beam along at least one scale line prior to writing. Did you get it? II child signal and place 1
? 2. The method of controlling a light beam according to claim 1, wherein the calibration is performed by determining the position of the light beam during writing using the relationship J. 3. Deflecting the light beam at a substantially constant speed, and determining the instantaneous position of the light beam based on how much time has passed since the instant the light beam crossed a scale line of at least 1. A method for controlling a light beam according to claim 1. 4. Divining on the image plane one strip at a time,
Such stripes are written adjacent to each other with a sufficient Wl to fill the entire image plane, and each strip is written by deflecting the light beam so as to sweep the strip, so that the length of the sweep is is approximately the same as 1llllA of the strip, and at the same time move the light beam in the longitudinal direction of the strip more slowly than this,
1a Deflect the light beam 9 degrees horizontally across the scale line to ensure that the strips to be F& are connected accurately and to control the position on the strip area, depending on the position of the line ( g, and use this signal to modulate the light beam during sweeping! 1. The method of controlling the light beam described in Section 1 of the O. 5. When writing, move the optical element and the image plane in the same direction, By deflecting the light beam across the 11141 force between the optical element (J) and the scale attached to the screen, we find the relationship between these two coordinate systems moving to JJ, , This information is used to control the penetrating beam that falls on the image plane ]2, so that writing is performed at the position fl:,.
The method for controlling a light beam according to item 1, Wd range. 6. Trigger the sweep across the strip in a t-force fashion, measure the magnitude of the deflection of the written pixel along the length of the strip, and measure the magnitude of the deflection of this slow As soon as the deflection in the direction has traveled the required distance, H(
a light beam according to claim 4, characterized in that the light beam is controlled by triggering the deflection of the opposite side, the light beam being modulated to generate pixels as it sweeps across the strip; and the pixel position 1a is J>t of the deflection of the light beam.
and the calculated value, and the write time interval of each 1llII search is obtained from the calculation]. Claim 4 FIL! The light beam of the shrimp
t method. a At each sweep, the optical vino has at least 7 scales.
Using the information obtained from this about the position of the light beam at the time of the sweep, the position 1i'j !
fi is controlled, and the modulation of the light beam is controlled by ilj to obtain 1lIl.
5. A method of controlling a light beam according to claim 4, wherein the i-element falls at exactly the right position. 9. Claim 1, characterized in that seven or more reference beams are separated from the writing beam, and these non-quasi beams are added to the writing beam to perform measurements on a scale of 1M. A method of controlling a light beam as described. 10. A method of controlling a light beam according to claim 4, wherein the light beam is deflected across the strip by using an acousto-optic deflector. IL Directing a light beam towards each strip is carried out by reflecting the light beam off a mirror that is rotated so that it falls onto the desired strip, and the position of the light beam is measured. 5. The method of controlling a light beam according to claim 4, which is carried out using the light beam reflected from the rotating mirror. 1z In order to write on a plane, a mirror consisting of m plane mirrors is installed after the rotating mirror used to select the stripes, and one point is set on each element mirror of this mirror, and the light beam is If it hits this point, the light beam will form a flat image 1rli
12. The method of controlling a light beam according to claim 11, wherein the light beam is focused on the light beam.