JPH0254937B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention is applicable to, for example, PWB (printed wiring board)
A device that performs main and sub-scanning while controlling the exposure beam on and off according to the given dot pattern data, such as raster plotters used to draw wiring patterns and precision exposure machines for plate making. The present invention relates to a method of controlling an exposure beam when performing exposure recording for printing a desired pattern onto a photosensitive material.

(Prior art and its problems) For example, when printing the PWB wiring pattern shown in Fig. 12 on a photosensitive material, the so-called vector drawing method using an automatic drawing machine exposes the pattern according to the pattern of land → wiring part → land. While moving the head in the X and Y directions, the land pattern is flash-exposed through a slit of a predetermined shape, and the wiring pattern is continuously exposed through a slit of a predetermined shape, or only the land pattern is completely exposed through a slit of a predetermined shape in advance. A desired pattern was formed by performing flash exposure and then continuously exposing the wiring pattern between each land through a slit of a predetermined shape. Note that the differences in how these patterns are formed are due to differences in the data input to the automatic drafting machine. According to this method, the pattern can be printed smoothly without unevenness at the boundary portion, but it takes a very long time to print the pattern.

Therefore, for example, a plane scanning or cylindrical scanning method called the so-called raster scan method using a raster plotter has been developed, but while this method is capable of high-speed processing, the pattern boundary lines that intersect with the main scanning direction are smooth. The disadvantage is that it cannot be printed on. In general, a light source for scanning exposure such as a raster plotter uses a point reduction control method for minute spots with a light intensity distribution close to a Gaussian distribution, which makes it possible to draw pattern boundaries in the main scanning direction without any unevenness. However, on the other hand, the border line of the pattern that intersects with the main scanning direction is the first one because the printing spot by the exposure beam is a minute circle.
As shown in FIG. 3, a large number of depressions with a diameter slightly smaller than the printing spot radius are generated at each line pitch of the exposure beam. If the focus of the exposure beam is sharp and the γ (gamma) characteristic of the photosensitive material is high contrast, exposure will be performed approximately as shown in FIG. (8th
The same applies to FIGS. 10, 10, and 11. ) Patterns for PWB require accuracy and smoothness of line width, especially for vertical lines and horizontal lines, so the 13th
Irregularities in the boundary line portion as shown in the figure are unacceptable.

(Object of the Invention) Therefore, an object of the present invention is to provide an exposure beam control method that can smoothly print pattern boundaries intersecting the main scanning direction in raster scan exposure recording. .

(Means for Achieving the Object) In order to achieve the above object, in the exposure beam control method according to the present invention, the inclination angle of the pattern boundary line intersecting the main scanning direction is detected, and according to the detected inclination angle, at least the boundary line is The diameter of the printing spot by the exposure beam is increased in some areas.

(Example) The following explanation will be made regarding the case of printing a PWB pattern, but of course the present invention can also be applied to a precision exposure machine for plate making by using an image signal as an input signal.

In this invention, as shown in FIG. 11a, the diameter of the printing spot by the exposure beam is increased at the pattern boundary portion intersecting the main scanning direction, thereby obtaining a relatively smooth boundary line. At this time, in order to ensure the smoothness of the border line of the pattern that intersects with the main scanning direction and at the same time to print thin patterns with high density, preferably, as shown in FIG. The spot diameter is controlled only for the burned spots. The spots other than the left and right ends in FIGS. 11a and 11b have their spot diameters increased at the upper and lower ends, but the spot diameters may or may not be increased in the middle.

FIG. 1 is a block diagram showing the circuit configuration of a cylindrical raster plotter to which an embodiment of the exposure beam control method according to the present invention is applied. In a magnetic storage device (not shown) connected to the computer 1, there is data (a plurality of vector data) indicating, for example, which coordinates in FIG. 12 should be connected by what route.
is stored, and the computer 1 imports this data and uses a known method to determine which timing of the raster data (nth raster (scanning line) is ON).
OFF data) and outputs this in scanning order.

The line memory 2 has a capacity for 4 lines (scanning lines), and the raster data output from the calculator 1 is sequentially transferred line by line to the line memories M1 to _M1 under the control of the memory address control unit 3. It is written in circulation to _M4 .

1 and 2 from a rotary encoder 4 attached to a rotating drum of a cylindrical raster plotter (not shown), for example.
Start pulse (1 pulse/rotation) and encoder clock 2 are received, and based on this, 3 to 6
Continuation/write control signal (high to instruct write, low to instruct to read) and the seventh
The memory address control signal shown in FIG. 8 is created and applied to each line memory _M1 to _M4 . Figure 3 shows 2-4
An example of a circuit configuration for creating the read/write control signal R/W using a decoder is shown.

As is clear from the timings in Figure 2 3 to 6, while any one of the line memories M ₁ to _{M 4} is writing data for one line, the other three line memories are in the read state. Become. Data reading and writing are performed in synchronization with the encoder clock signal of FIG.

The shift register 5 includes four serial registers, and each serial register is connected to a line memory M ₁ to
It is connected one-to-one with _M4 , and sequentially temporarily stores data for three pixels read from the corresponding line memory. In this way, shift register 5
, data of a 3×3 pixel area is temporarily stored in order.

The pattern determination circuit 6 determines whether the exposure pattern boundary line intersecting the main scanning direction has a specific inclination angle, based on the data in the 3×3 pixel area. There are 10 types of tilt angles that can be determined in a 3x3 pixel area as shown in Figure 4, but if you want to detect even more angles, increase the number of pixels to be determined and select an arbitrary mxn (m, n >3)
It is necessary to expand into other areas. however,
For example, there are several types of inclination angles of the boundaries of PWB patterns, and there is no need to detect that many angles. Furthermore, the number of pixels for determination may be increased or decreased depending on the tilt angle to be detected.

In Figure 4, the 3x3 central pixel indicated by the bold line is the pixel that is about to be output, and when outputting this pixel, the diameter of the printing spot by the exposure beam is determined according to the detected tilt angle. and controls its output timing. usually
The ON pattern indicates that exposure is in progress and is normally
The OFF pattern indicates non-exposure. Furthermore, an ON pattern other than normal indicates detection of a position at which exposure should start, and an OFF pattern other than normal indicates detection of a position at which exposure should end.

Figures 5A and 5B are 45°ON as an example.
A circuit diagram is shown in which a pattern discrimination circuit and a normal ON/OFF pattern discrimination circuit are constructed using gates, and pattern discrimination circuits other than these are constructed in the same manner. 45°ON in Figure 5A
In the pattern discrimination circuit, AND gates 51 to
54 is for detecting the 45°ON pattern in the upper right corner,
AND gates 55 to 58 are for detecting a 45° ON pattern downward to the right. For example, in the case of detecting an upward-rightward 45° ON pattern, one of the AND gates 51 to 54 goes high in response to a high memory read/write control signal, and the three shift registers connected to that AND gate (SR1
When the 3x3 pixel data from ~3 of SR4 matches the 45° ON pattern in the upper right corner,
A 45°ON pattern detection signal c is output from the AND gate. In the normal ON/OFF pattern discrimination circuit shown in Figure 5B, the non-normal pattern discrimination outputs a to h
In order to give priority to the pattern discrimination outputs a to h, the AND gate group 59 is set low to prevent the normal ON/OFF pattern detection signals I and j from being output.

The beam control signal generation unit 7 controls the printing spot diameter control signal P and the beam ON/OFF according to the pattern discrimination signals a to j from the pattern discrimination circuit 6.
Create control signal Q. Then, depending on the contents of these control signals P and Q, the AOM
(Acousto-optic modulator) control section 8 and
By driving the AOM 10 via the AOM driver 9, the diameter of the printing spot by the exposure beam and the exposure timing are controlled in accordance with the angle of the detected pattern boundary line.

6A and 6B are circuit diagrams showing in detail an example of the configuration of the beam control signal generating section 7, and FIG. 7 is a timing chart showing its operation. The decoder 601 receives the pattern discrimination signal a
Preset values to be given to counters 611-614 are determined according to j. This preset value is for correcting the exposure timing.
Therefore, it differs depending on each pattern in FIG.
For example, as shown in Figure 8A a, parallel ON,
Let us consider the case where the diameter of the burned spot at the boundary portion of the OFF pattern is doubled. In this case, as shown in FIG. 8A b, the exposure beam with a double printing spot diameter of 81 needs to be irradiated with timing corrected by ±T/2 compared to the exposure beam with a normal printing spot diameter of 82. be. Here, T is one pixel clock time, and the required timing correction time changes depending on the ratio of the printing spot diameters 81 and 82. Also, each of 45°, 26°, 33°
Explanatory diagrams similar to the above-mentioned FIG. 8A for ON and OFF patterns are shown in FIGS. 8B to 8D, respectively. From these drawings, 45°ON,
The required timing correction time for the OFF pattern is ±√2/2・T, and the required timing correction time for the 26°ON, OFF pattern is ±(√5−
2)/4・T, and the required timing correction time for the 63° ON/OFF pattern is ±√5/
It turns out that it is 2.T.

Considering the possibility of negative timing correction, for example, 2T is selected as the basic preset value (preset value when no timing correction is required). The input/output relationship of the decoder 601 in this case is as follows.

Input (pattern discrimination signal) output (preset value) a (parallel ON) 2T+1/2・T b (parallel OFF) 2T−1/2・T c (45°ON) 2T+√2/2・T d (45° OFF) 2T−√2/2・T e(26°ON) 2T+(√5−2)/4・T f(26°OFF) 2T+(√5−2)/4・T g(63°ON) 2T + √6/2・T h (63° OFF) 2T−√6/2・T i (normally ON) 2T j (normally OFF) No output The frequency division counter 602 is the encoder from the rotary encoder 4 in Fig. 1. The clock 2 is frequency-divided to output four-phase clocks 11 to 14 whose phases are shifted by one pixel clock. Counter 611-61
4 receives the four-phase clocks 11 to 14 as load signals, respectively, and loads the preset value outputted from the decoder 601 at that time.
The PLL circuit 603 outputs a clock 7 that multiplies the encoder clock 2,
synchronizes with this multiplication clock and counts down the preset value.

Now, the contents of the data 9 of the target pixel (the pixel that is about to be output, the center pixel of the 3×3 pixel area) read out according to the address signal in FIG. 7 and 8 are as shown in 10, for example. to T ₀ ~
It is ON (i.e. burn-in) during the T ₂ period and the T ₅ - T ₇ period, and the burn-in part of the T ₀ - _{T 2} period starts with a 45° ON pattern and ends with a 63° OFF pattern, and T ₅ - _{T 7} Assume that the baking portion of the period begins with a 26° ON pattern and ends with a 45° OFF pattern.
At this time, 2T+√2/2·T is loaded into the counter 611 by the first four-phase clock 11 in the _T0 period, and the c signal (45° ON pattern detection signal) is latched into the flip-flop 621, and the AND gate 631 and 651 become high. Then, when 2T+√2/2・T has passed,
A borrow pulse 15 is output from the counter 611, and this borrow pulse sets the flip-flop 641 through the AND gate 631, so that the output signal 16 of the flip-flop 641 goes high. After that, the point at which 3 pixel clocks have passed (T ₃
When the four-phase clock 14 is output at the beginning of the period), the four-phase clock 14 is output from the flip-flop 6.
21 and AND gate 651.
reset the flip-flop 641 via
Therefore, at this point, AND gates 631, 6
51 becomes low and flip-flop 6
The output signal 16 of 41 goes low.

Furthermore, at the time of the first four-phase clock 12 in the _T1 period and the first four-phase clock 13 in the _T2 period,
Since normal ON patterns are detected in both cases, each counter 61 is activated by these four-phase clocks.
By the same operation as described above, the output signal 18 of the flip-flop 642 goes high during the T ₃ period, and the output signal 20 of the flip-flop 643 goes high during the T ₄ period.

Next, the first four-phase clock 14 of the _T3 period loads the 2T-√6/2·T counter 614, and the h signal (63° OFF pattern detection signal) is latched into the flip-flop 664.
This latch output causes flip-flop 644
is immediately set and its output signal 22 goes high, and AND gate 674 goes high.
Then, when 2T−√6/2·T has elapsed, the counter 614 outputs a borrow pulse 21,
This borrow pulse resets flip-flop 644 through AND gate 674, and the output signal 22 of flip-flop 644 goes low.
Thereafter, when three pixel clocks have elapsed (at the beginning of the _T6 period), the flip-flop 664 is reset by the four-phase clock 13, and the AND gate 664 is reset.
74 becomes low.

When a normal OFF pattern is detected, such as during the T ₃ to T ₄ period of data 10, the pattern detection signal j is applied to the data input terminals D of flip-flops 661 to 664 that act on the OFF pattern detection signal. Therefore, flip-flops 641-644 are not set at this time and their output signals remain low.

Hereinafter, by the same operation as described above, data 10
Corresponding to the ON period from _T5 to _T7 , the output signal 18 of the flip-flop 642 goes high during a part of the _T7 period, the output signal 20 of the flip-flop 643 goes high during the T8 period, and the output signal of the flip-flop 644 goes high during the _T8 period. 22 is high during period _T9 , and the output signal 16 of flip-flop 641 is high during period _T8 and part of period _T9 . Output signals 16, 18, 2 of flip-flops 641 to 644 obtained in this way
By ORing 0 and 22, a beam ON/OFF control signal Q shown in 23 can be obtained.

FIG. 6B shows a configuration for obtaining the spot diameter control signal P, in which the flip-flop 621'
The configuration is similar to that of FIG. 6A, except that the normal ON pattern detection signal i is not input to the data input terminal D of ~624'. Therefore, the output signals from flip-flops 641' to 644' are
Among the high output signals of flip-flops 641 to 644, those corresponding to the normal ON pattern detection signal i ( _T3 period of output signal 18, T4 period of output signal ₂₀ )
period, T of output signal 20 ₈ period, of output signal 22
_T9 period). Therefore, the spot diameter control signal P for data 10 is 24
The signal will be as shown in .

FIG. 9 is a circuit diagram showing the AOM control section 8 in detail. The selector 91 receives the spot diameter control signal P and the beam ON/OFF control signal Q.
Based on the table below, switch SW1~
Select SW3.

P Q SW selection High High SW1−ON Low High SW2−ON Low Low SW3−ON High Low SW3−ON When SW1 is ON, a voltage V _L higher than the normal (standard) voltage is applied to the AOM driver 9 through the amplifier 92. , the power of the beam controlled by the AOM 10 increases, and the diameter of the printing spot due to exposure increases. When SW2 is ON, amplifier 9
3, a regular (standard) voltage V _S is applied to the AOM driver 9, the beam power becomes the regular state, and the printing spot diameter becomes the regular size. When SW3 is ON, the voltage is O and the beam is OFF. Therefore, in the case of 10 data, the input signal of the AOM driver 9 becomes as shown in 26, and 25 beam trajectories are finally drawn.

Furthermore, when the inclination of the pattern to be formed is large with respect to the sub-scanning direction as shown in FIGS. 8B and 8D, even if the pattern is formed using the above method, there may still be unevenness on a part of the boundary line. Since this may occur, we will explain how to print the pattern smoothly.

FIG. 10A relates to an improvement of FIG. 8B, and when forming a pattern, the lines other than the second line (scanning line) from the left end are exposed as described above. For the second line from the left end, use the exposure beam described above.
The timing to turn on is T/ from the timing mentioned above.
At the same time, the frequency of the signal applied to the AOM is changed and the deflection angle is controlled only by T/2 hours so that the center of the exposure beam is located between the left end and the second line from the left end. After exposure is performed so that the locus is as shown by the dotted line, subsequent exposure is performed as described above to further reduce the unevenness.

Similarly, FIG. 10B relates to an improvement on FIG. 8D, and when forming a pattern, the lines other than the second line from the left end are exposed as described above. 2 from the left
For the main line, use the exposure beam described above.
In addition to setting the timing to turn on T hours earlier than the above-mentioned timing, the frequency of the signal applied to the AOM is changed so that the center of the exposure beam is located between the left end and the second line from the left end, and the deflection angle is changed only by T time. After controlling and exposing so that the locus of the exposure beam becomes as shown by the dotted line, the following exposure is performed as described above to further reduce the unevenness.

The above is an example of applying it to the ON side of pattern formation, but such means can also be applied to the ON side of pattern formation.
It can also be applied to the OFF side.

Note that it is also possible to perform pattern discrimination, control of the printing spot diameter, and exposure timing control in the above explanation using software using a computer, and changes in the printing spot diameter can be made without changing the beam power. It is also possible to perform this optically using a zoom lens or the like.

Further, although the above description has been made regarding printing using a single beam, when the present invention is applied to printing using multiple beams, a control circuit as described above may be provided for each channel.

(Effects of the Invention) As explained above, according to the present invention, the inclination angle of the pattern boundary line intersecting the main scanning direction is detected and the printing spot diameter is increased in accordance with the detected angle. When performing exposure recording using the raster scan method, pattern boundaries that intersect with the main scanning direction can be printed smoothly, which is particularly effective for printing PWB patterns, and improves the dimensional accuracy of printed PWB patterns. can be achieved. Furthermore, the quality and dimensional accuracy of edges such as characters and images can be improved in precision exposure machines for plate making and the like.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the exposure beam control method according to the present invention, FIG. 2 is a timing chart showing the operation of FIG. 1, and FIG.
A circuit diagram showing an example of a write control signal generation circuit,
FIG. 4 is an explanatory diagram showing a discrimination pattern, FIGS. 5A and 5B are circuit diagrams showing an example of a pattern discrimination circuit using gates, and FIGS. 6A and 6B are an example of the configuration of a beam control signal generation section. 7 is a timing chart showing the operation of FIGS. 6A and 6B, FIGS. 8A, 8B, 8C and 8D are explanatory diagrams of exposure timing correction, and FIG. 9 is a timing chart showing the operation of FIGS. 6A and 6B. The detailed circuit diagrams of the AOM control section, Figures 10A and 10B, are the same as Figures 8B and 8D, respectively. In order to print even more smoothly, in addition to correcting the exposure timing, the position of the exposure beam is moved by the desired amount of time. Explanatory diagram, 1st
Fig. 1 is an explanatory diagram of the control of the burning spot diameter according to the present invention, Fig. 12 is an explanatory diagram of the PWB wiring pattern,
FIG. 13 is an explanatory diagram of printing using the conventional raster scan method. DESCRIPTION OF SYMBOLS 1... Computer, 2... Line memory, 3... Memory address control section, 4... Rotary encoder, 5... Shift register, 6... Pattern discrimination circuit, 7... Beam control signal generation section, 8...
AOM control section, 9...AOM driver,
10...AOM.

Claims (1)

[Claims] 1. In exposure recording using a raster scan method in which a desired pattern is printed on a photosensitive material by performing main and sub-scanning while controlling ON/OFF of an exposure beam according to given dot pattern data. , the inclination angle of the pattern boundary line intersecting the main scanning direction is detected, and control is performed to increase the diameter of the printing spot by the exposure beam in at least the boundary portion in accordance with the detected inclination angle. , an exposure beam control method. 2. The exposure beam control method according to claim 1, wherein the exposure timing is controlled at the same time as the printing spot diameter is controlled. 3. The exposure beam control method according to claim 1, wherein the diameter of the printing spots other than the left and right ends of the pattern boundary line in the main scanning direction is controlled. 4. The exposure beam control method according to any one of claims 1 to 3, wherein the printing spot diameters of a plurality of desired exposure beams are controlled simultaneously and exposure is performed using multiple beams. 5. The exposure beam control method according to claim 1, wherein the position of the exposure beam is moved with respect to a printing spot on a pattern boundary line intersecting the main scanning direction. 6. The exposure beam control method according to any one of claims 1 to 5, wherein the printing spot diameter is controlled by changing the beam intensity.