Patent Grant
7957043
1. Field of the Invention
The present invention relates to an image recording apparatus and an image recording method for recording an image on a recording medium by using a plurality of light modulator elements.
2. Description of the Background Art
Developed has been a diffraction grating type light modulator element which is capable of changing the depth of grating by alternately forming fixed ribbons and moving ribbons on a substrate with a semiconductor device manufacturing technique and sagging the moving ribbons relatively to the fixed ribbons. It is proposed that such a diffraction grating is used for an image recording apparatus in techniques such as CTP (Computer to Plate) as a switching element of light, since the intensities of normally reflected light and diffracted light are changed by changing the depth of grooves on the diffraction grating as above.
For example, a plurality of diffraction grating type light modulator elements provided in the image recording apparatus are irradiated with light, and then reflected light (zeroth order light) from light modulator elements in a state where the fixed ribbons and the moving ribbons are positioned at the same height from a base surface is guided to the recording medium and non-zeroth order light (mainly first order light) from light modulator elements in a state where the moving ribbons are sagged is blocked, to achieve an image recording on the recording medium.
Japanese Patent Application Laid Open Gazette No. 2004-4525 (Document 1) discloses a technique correcting the timing of transition between ON and OFF states of a light modulator element in such an image recording apparatus to correct asymmetry between transition from the OFF state to the ON state and transition from the ON state to the OFF state, difference in characteristics of each photosensitive material, and positional shifts of writing regions caused by difference in length or position in a scan direction of irradiation regions of light modulator elements.
Japanese Patent Application Laid Open Gazette No. 2001-150730 (Document 2) discloses a technique for forcedly interrupting light from liquid crystal shutters during a transient response period with a mechanical shutter to remove effects of unevenness in exposure by the liquid crystal shutters and difference in transient responses of the liquid crystal shutters in an image forming apparatus.
In the diffraction grating type light modulator elements, amounts of light derived from light modulator elements slightly vary even if all light modulator elements are made the ON state, because there are nonuniformity of light from a light source and differences of characteristics among the light modulator elements. Since such a variation causes striped moire in writing an image of a fine pattern, it is important that a light amount from each light modulator element is corrected to be uniform by controlling the height of the moving ribbons in the ON state.
However, in a case where the heights of the moving ribbons in the ON state are different in light modulator elements, since the amounts of movement of the moving ribbons between the ON and OFF states are not uniform, a time from when a signal instructing ON is inputted to a driving element of the light modulator element to when the light modulator element is actually brought into the ON state (hereinafter, referred to as “rise time”) and a time from when a signal instructing OFF is inputted to the driving element of the light modulator element to when the light modulator element is actually brought into the OFF state (hereinafter, referred to as “fall time”) are different from those in another light modulator element.
In Document 1, the unevenness of the rise times and the fall times, that is, temporal unevenness in movement of the light modulator elements with respect to the signal instructing driving is not taken into consideration. Consequently, when a line with a constant width extending in a sub scan direction is written, the line width slightly changes. Though Document 2 discloses a technique for removing effects of unevenness in the transient response at the rise in liquid crystal shutters by using the mechanical shutter, since light is blocked mechanically, the mechanism of the apparatus becomes complicated and speed-up of writing is prevented. Further Document 2 also discloses a technique of controlling timing at the fall to make the exposure amount uniform, however, unevenness in the transient response at the fall is not considered.
The present invention is intended for an image recording apparatus for recording an image on a recording medium by irradiation with light and when writing for a predetermined period of time is instructed to light modulator elements, it is an object of the present invention to perform writing by a constant distance in a scan direction, that is, to write lines with a constant width in a direction perpendicular to the scan direction. Further, even if a photosensitive level of a recording medium is unknown, when writing for a predetermined period of time is instructed to each light modulator element, it is an object to write by a constant distance in the scan direction.
The image recording apparatus in accordance with the present invention comprises a spatial light modulator having a plurality of light modulator elements which are arranged in a predetermined direction; a holding part for holding a recording medium on which an image is recorded with signal lights from the plurality of light modulator elements; a moving mechanism for moving the holding part relatively to the spatial light modulator at a constant speed in a main scan direction crossing an arrangement direction of positions irradiated with light from the plurality of light modulator elements and moving the holding part relatively to the spatial light modulator in a sub scan direction crossing the main scan direction; a control part controlling the spatial light modulator and the moving mechanism, to perform image recording on a recording medium; a photodetector for detecting light from each element of the plurality of light modulator elements; and a shift-time determining part for determining a shift time of a switching timing of each element after input of an output start signal instructing start of output of signal light or an output stop signal instructing stop of output of signal light to a driving element connected to each element, on the basis of output of the photodetector after input of an output start signal or an output stop signal and in the apparatus, the driving element comprises a shift section for shifting a switching timing of each element at the time when an output start signal or an output stop signal is inputted to the driving element in image recording, in accordance with the shift time, and when writing for a predetermined period of time is instructed, a distance in the main scan direction of writing actually performed on a recording medium by the plurality of light modulator elements is made constant by shift of a switching timing of each element by the shift section.
By providing the shift section, when writing for a predetermine period of time is instructed, it is possible to made a distance in the main scan direction of writing actually performed on a recording medium by the plurality of light modulator elements constant and achieve appropriate image recording, without complicating the apparatus.
According to a preferred embodiment of the present invention, the shift-time determining part comprises a circuit generating a reference voltage; a comparator for comparing output from the photodetector with the reference voltage; a clock generating circuit for generating sampling clocks; and a counter for counting the sampling clocks, to acquire a rise time from when an output start signal is inputted to the driving element connected to each element to when the comparator detects that output from the photodetector is above the reference voltage and a fall time from when an output stop signal is inputted to the driving element to when the comparator detects that output from the photodetector is below the reference voltage, and the shift time of each element is determined on the basis of the rise time and the fall time.
In a case where a photosensitive level of a photosensitive material is known, the rise time is equal to a time from when an output start signal is inputted to the driving element connected to each element to when photosensing of a recording medium is started, and the fall time is equal to a time from when an output stop signal is inputted to the driving element to when photosensing of the recording medium is stopped. The shift time of each element is determined as a time for compensating a difference between a predetermined value and a difference between the rise time and the fall time in the shift-time determining part. This makes it possible to determine the shift time easily.
In a case where a photosensitive level of a photosensitive material is unknown, the shift-time determining part obtains a plurality of provisional shift times for compensating a difference between a predetermined value and a difference between the rise time and the fall time of each element at a plurality of correction ratios, and lines extending in the sub scan direction are written onto the recording medium by the control part and the shift section while the plurality of provisional shift times are sequentially applied to each element. By specifying a preferable line out of a plurality of lines, a correction ratio corresponding to the preferable line out of the plurality of correction ratios can be selected and inputted to the shift-time determining part and the shift time of each element is determined on the basis of the correction ratio. This makes it possible to determine the shift time relatively easily.
It is preferable that the present invention is applied to an image recording apparatus comprising a spatial light modulator with elements in each of which the rise time and the fall time change when intensity of signal light is changed and as such an element, can be used a light modulator element of diffraction grating type in which strip-like fixed reflection surfaces and strip-like moving reflection surfaces are alternately arranged.
The present invention is also intended for an image recording method for recording an image on a recording medium by irradiation with light.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The holding drum 70 rotates about a central axis of its cylindrical surface by a motor 81 and the optical head 10 thereby travels relatively to the recording medium 9 at a constant speed in a main scan direction (in a direction perpendicular to an arrangement direction of positions irradiated with light from a plurality of light modulator elements later discussed). The optical head 10 can be moved by a motor 82 and a ball screw 83 in parallel to a rotation axis of the holding drum 70 in a sub scan direction (orthogonal to the main scan direction). The position of the optical head 10 is detected by an encoder 84. In other words, a moving mechanism including the motors 81 and 82 and the ball screw 83 moves the outer surface of the holding drum 70 and the recording medium 9 relatively to the optical head 10 having a spatial light modulator at a constant speed in the main scan direction and moves those relatively to the optical head 10 also in the sub scan direction crossing the main scan direction. The motors 81 and 82 and the encoder 84 are connected to a general control part 21, and the general control part 21 controls the motors 81 and 82 and emission of signal light from a spatial light modulator in the optical head 10, to record an image on the recording medium 9 on the holding drum 70 by light.
Data of the image to be recorded on the recording medium 9 is prepared in a signal generation part 23 in advance, and a signal processing part 22 receives an image signal in synchronization with the signal generation part 23 on the basis of a control signal from the general control part 21. The signal processing part 22 converts the received image signal into a signal for the optical head 10 and then transmits the signal.
At the side of the holding drum 70, a detection part 71 for detecting light from each light modulator element of the spatial light modulator in the optical head 10 is provided, and the optical head 10 can be transferred by the motor 82 and the ball screw 83 up to the position to which the optical head 10 passes the detection part 71. An output from the detection part 71 is inputted to a calculation part 24. The calculation part 24 performs computation with circuits such as a CPU, which generates data for controlling the optical head 10 by computation of the output from the detection part 71. The calculation part 24 has a memory 243 for storing information from the detection part 71 and the CPU, the memory and the like implement functions shown as a corrected light amount determining part 241 and a shift-time determining part 242 which are later discussed. An input part 25 receiving an input from a user is connected to the calculation part 24.
Each light modulator element in the spatial light modulator 12 is individually controlled on the basis of a signal from a device driving circuit 120 and each light modulator element can be changed between a state of emitting a zeroth order light beam (normally reflected light beam) and a state of emitting non-zeroth order diffracted light beams (mainly first order diffracted light beams ((+1)st order diffracted light beam and (−1)st order diffracted light beam)). The zeroth order light beam emitted from the light modulator element is returned to the prism 132 and the first order diffracted light beams are guided to directions different from that of the prism 132. The first order diffracted light beams are blocked by a not-shown light blocking part so as not to be stray light.
The zeroth order light beam from each light modulator element is reflected by the prism 132 and guided to the recording medium 9 outside the optical head 10 through a zoom lens 133 and a plurality of spot images of the light modulator elements are so formed on the recording medium 9 as to be arranged in the sub scan direction. In other words, in the light modulator elements 121, the state of emitting the zeroth order light beam is an ON state and the state of emitting the first order diffracted light beams is an OFF state. The magnification of the zoom lens 133 can be changed by a zoom lens driving motor 134 and the resolution of the image to be recorded is thereby changed.
The clock selection data 303 which is temporarily stored in the register 441a is inputted to the clock selection part 442a in response to the reference control clock 304a (which is inputted antecedently) and one of the group of control clocks 304 is thereby selected. The selected control clock is outputted to the D/A converter 442b as an update clock 302.
The driving voltage data 301 is inputted to the D/A converter 442b from the register 441a and when the update clock 302 is inputted thereto, an analog signal of the driving voltage data 301 is outputted. The driving voltage data 301 for each update clock 302 corresponds to a target driving voltage for one operation of driving the light modulator element 121 and an output from the D/A converter 442b is inputted to a current source 32 and further converted into a current therein. One end of the current source 32 is connected to a side of high potential Vcc through a resistance 33 and the other end is grounded.
Both ends of the current source 32 are also connected to the moving ribbons 121a of the light modulator element 121 and the base surface 121c, respectively, through connecting pads 34. Therefore, when the driving voltage data 301 is converted into the current through the D/A converter 442b and the current source 32, it is further converted to an actual driving voltage between both connecting pads 34 by a voltage drop with the resistance 33. Thus, the driving element 120a can control (shift) a switching timing of the light modulator element 121 on the basis of the clock selection data 303.
For example, when eight control clocks (referred to as “clock 0”, “clock 1”, . . . “clock 7” from the earliest control clock) are inputted to the clock selection part 442a as shown in
Here, since the reference control clock 304a is generated as a clock used as a reference for switching the light modulator element 121, an operation of inputting the reference control clock 304a to the driving element 120a in a state where the driving voltage data 301 instructing the ON state is inputted to the register 441a corresponds to an operation of inputting an output start signal instructing a light modulator element 121 to start output of signal light into the driving element 120a connected to the light modulator element 121, and an operation of inputting the reference control clock 304a to the driving element 120a in a state where the driving voltage data 301 instructing the OFF state is inputted to the register 441a corresponds to an operation of inputting an output stop signal instructing the light modulator element 121 to stop output of signal light into the driving element 120a. Then, the clock selection part 442a selects one control clock in accordance with a shift time which is obtained in advance and a switching timing of the light modulator element 121 at the time when an output start signal or an output stop signal is inputted to the driving element 120a in image recording is shifted. In short, the clock selection part 442a is a shift section for substantially shifting a switching timing of the light modulator element 121.
In the above operation, actually, the delay process is appropriately performed for selection of the control clock, however, explanation is simplified for easy understanding. Since there is stray capacitance between the connecting pads 34, the actual driving voltage between the connecting pads 34 changes with the time constant defined between the connecting pads 34 and moves toward the target driving voltage gradually.
The device driving circuit 120 has a driving-voltage/control-clock shift register 441 which sequentially stores data outputted from the signal processing part 22 and a driving unit 442. The driving-voltage/control-clock shift register 441 is an array of registers 441a shown in
An image signal 511 representing an image is sequentially inputted from the signal generation part 23 (see
The driving voltage data 301 and the clock selection data 303 are sequentially stored into the driving-voltage/control-clock shift register 441 in synchronization with a predetermined clock signal. The operation up to this point is a serial process, but when the driving voltage data 301 and the clock selection data 303 as many as the light modulator elements 121 are stored into the driving-voltage/control-clock shift register 441, these data are transmitted to the driving unit 442 in response to the reference control clock 304a, as discussed with reference to
With this operation, the rise timing (the timing of switching from the OFF state to the ON state) of the light modulator element 121 is shifted by the shift time for rising related to the above light modulator element 121 from the original switching timing (the timing of the clock 4 above discussed) and the fall timing (the timing of switching from the ON state to the OFF state) is also shifted by the shift time for falling. In cases where the light modulator element 121 changes from the ON state to the ON state and changes from the OFF state to the OFF state (i.e., switching is not performed at switching timing), since the operation is not affected by any selected control clock, distinction between rising and falling of the light modulator element 121 is not detected in the signal processing part 22. Therefore, when the image signal 511 indicates the ON state, the shift time is simply selected from the rise shift-time table 222 and when the image signal 511 indicates the OFF state, the shift time is simply selected from the fall shift-time table 223.
In a case where confirmation of modification of the correction data is unnecessary, the correction data is read out from the memory 243 of
Specifically, the recording medium 9 moves relatively to the plurality of light modulator elements 121 at a constant speed in a direction perpendicular to an arrangement direction of positions irradiated with light from the light modulator elements 121 by rotating the holding drum 70, while outputting signal lights from the plurality of light modulator elements 121, and correction of light amounts and shifts of switching timing are performed in parallel with irradiation. Then, in synchronization with rotation of the holding drum 70, the optical head 10 moves in the sub scan direction, to record an image on the whole recording medium 9. The moving direction (main scan direction) of the outer surface of the holding drum 70, that is, the moving direction of the recording medium 9, is not limited to be perpendicular to the arrangement direction of positions irradiated with light but may be a direction crossing the arrangement direction.
In other words, it is also possible that a direction crossing the arrangement direction of the irradiation positions at an angle other than 90 degrees is defined as the main scan direction and a direction perpendicular to the main scan direction is defined as the sub scan direction. In this case, the image signal 511 applied to each light modulator element 121 is controlled to delay appropriately so as to compensate variation in positions with respect to the main scan direction of each light modulator element 121, to perform the same image recording as a case where the arrangement direction of the irradiation positions is parallel to the sub scan direction. With respect to this control method, known are techniques disclosed in Japanese Patent Application Laid Open Gazette No. 6-91928 or Japanese Patent Application Laid Open Gazette No. 6-316106, or the like, and the disclosures of which are herein incorporated by reference. As disclosed in these documents, the main scan direction may be largely tilted with respect to a direction perpendicular to arrangement direction of irradiation positions, and the main scan direction and the direction perpendicular to the arrangement direction of irradiation positions have only to be different directions.
When recording of the next image is performed after recording of an image on the recording medium 9 is complete, the recording medium 9 on the holding drum 70 is exchanged for a new one, and the operation goes back to Step S11 (Step S15).
In a case where a photosensitive material on the recording medium 9 has not been used in the past and the correction data for the photosensitive material is not stored in the memory 243 in recording of an image, first, the optical head 10 moves up to a position opposed to the detection part 71 as indicated by double-dashed lines in
On the other hand, in another case where the correction data for the photosensitive material is stored in the memory 243 and it is determined in Step S12 that confirmation of modification of the correction data is necessary, measurement of light amounts is performed like in Step S16 (Step S17), and it is checked if the light amount from each light modulator element 121 falls within tolerance (Step S18). When the light amounts fall within tolerance, the process goes to reading out the correction data in Step S13 and when those do not fall within tolerance, the above-discussed correction of light amounts and determination of shift times are performed (Steps S19, S2) and then recording of image is performed (Step S14).
In the light amount measuring circuit 731 of
In Step S19 after measurement of light amounts in
Through the above correction of light amounts, for example, as shown in
As shown in
As a result, when a signal which changes between the ON state and the OFF state in each reference control clock 304a is simultaneously inputted to each light modulator element and lines extending in the sub scan direction (hereinafter, referred to as “image of horizontal 1-dot-on and 1-dot-off lines”) are written, the width of each line is not constant as shown in
Next discussion will be made on determining shift times of switching timings of each light modulator element 121 (Step S2).
When the photosensitive level of the photosensitive material is known, the reference voltage generated in the reference voltage generating circuit 723 shown in
In writing, the light amount from the light modulator element 121 increases according to input of the reference control clock 304a and photosensing of the photosensitive material is started at a time when the light amount is above the photosensitive level. Start of actual photosensing depends on not only type of photosensitive material but also scan speed of the recording medium 9 and spot diameter of light from the light modulator element 121, and also depends on width of line and density of line which is to be written. The reference voltage is set on the basis of the known photosensitive level so as to become a voltage of sensor output which is obtained assuming that light from the light modulator element 121 at starting of the photosensing is inputted to the photosensor 711. Also, the reference voltage is a voltage which is obtained assuming that light from the light modulator element 121 is inputted to the photosensor 711 at a time when the light amount is below the photosensitive level. Therefore, in
After setting the reference voltage, next, measured are a rise time in changing the light modulator element 121 from the OFF state to the ON state and a fall time in changing the light modulator element 121 from the ON state to the OFF state (hereinafter, “rise time” and “fall time” are collectively referred to as “response times”) (Step S212). In
Since the moving ribbons 121a of the light modulator element 121 oscillate, when the state of the light modulator element 121 changes (especially, changes from the OFF state to the ON state), the output from the photosensor 711 oscillates as shown in
In the actual measurement of response times, the optical head 10 moves in the sub scan direction while all light modulator elements 121 are simultaneously changed between the ON state and the OFF state in accordance with the reference control clock 304a, whereby response times of all light modulator elements 121 are sequentially measured.
The right part of
After the response times of each light modulator element 121 are obtained, the rise time and the fall time of each light modulator element 121, with which an image of horizontal 1-dot-on and 1-dot-off lines with a constant width can be written at equal pitches, are set as a target rise time and a target fall time (hereinafter, collectively referred to as “target response times”) by the shift-time determining part 242 of the calculation part 24 in
In a case where the photosensitive level of the photosensitive material is known, since output from the comparator 724 behaves in the same way as photosensing of the photosensitive material, the rise time is equal to a time from when an output start signal is inputted to the driving element 120a to when photosensing of the recording medium 9 is started, and the fall time is equal to a time from when an output stop signal is inputted to the driving element 120a to when photosensing of the recording medium 9 is stopped. As a result, the response times can be appropriately corrected only by determining a time for compensating a difference between the rise time before correction and the target rise time and a time for compensating a difference between the fall time before correction and the target fall time as a shift time at the rise and a shift time at the fall.
Through the above operation, it is possible to easily determine the shift times when the photosensitive level of the photosensitive material is known. For example, even if the rise time and the fall time acquired in Step S 212 vary between channels as shown by reference signs U1 and D1 in
Naturally,
In redetermination of the shift times, new shift times which further compensate differences between the present rise times and fall times and the target rise time and target fall time are determined (Step S214) and response times after correction are measured again (Step S215). Steps S214 and S215 are repeated as necessary and when unevenness of the response times falls within tolerance, the step for determining the shift times is complete. Thereafter, the operation goes back to Step S14 in
Next, discussion will be made on an operation of the image recording apparatus 1 in a case where the photosensitive level of the photosensitive material is unknown in the process of determining the shift time.
When the photosensitive level of the photosensitive material is unknown, since the reference voltage corresponding to the light amount for photosensing the photosensitive material can not be set, a predetermined provisional reference voltage is set in the reference voltage generating circuit 723 (Step S221). Subsequently, the response times of each light modulator element 121, that is, the rise time and the fall time are measured (Step S222).
In
However, when the actual photosensitive level of the photosensitive material is a reference voltage indicated by a reference sign 752 (hereinafter, the reference voltage is referred to as “ideal reference voltage”), if the response time is corrected by the shift times dT11 and dT12, a photosensing range on the photosensitive material in writing after correction (hereinafter, referred to as “excessively corrected output”) is indicated by a reference sign 757, and switching timings of the light modulator element 121 are excessively corrected. In other words, sensor output at the time when the ideal output 756 is obtained on the basis of an ideal reference voltage 752 forms waveform indicated by a reference sign 773 and it is needed that the shift time at the rise is made dT21 shorter than dT11 and the shift time at the fall is made dT22 shorter than dT12 for acquisition of the ideal output in this case.
Since the photosensitive level of the photosensitive material and the ideal reference voltage are unknown, the shift times dT21 and dT22 can not be obtained by theoretical calculation. Therefore, in the image recording apparatus 1, after the response times are measured on the basis of the provisional reference voltage 751 in Step S222 of
After all correction ratios are obtained, one correction ratio is selected (Step S33) and new provisional shift times at the rise and fall are determined by multiplying the maximum provisional shift times dT11 and dT12, which are derived from the target response times obtained in Step S223 of
As discussed above, in the calculation part 24, a plurality of provisional shift times for compensating a difference between the rise time and the target rise time of each light modulator element 121 and a difference of the fall time and the target fall time at a plurality of correction ratios are obtained, and lines extending in the sub scan direction on the recording medium 9 are written onto the recording medium 9 while the plurality of provisional shift times are sequentially applied to each light modulator element 121. With this operation, a plurality of lines extending in the sub scan direction corresponding to the plurality of provisional shift times are arranged in the main scan direction.
For example, when the number of times of experimental writings is 4 (actually, the number of more times of writings is set), 0%, 33%, 67% and 100% are obtained as the correction ratios in Step S32. The correction ratio of 0% is selected in Step S33 and the shift times at the rise and fall are set as 0 in Step S34 and switching timings are controlled at the rise time and the fall time indicated by the reference signs U10 and D10.
Next, the correction ratio of 33% is selected in Step S33 and the shift times at the rise are 33% of differences between the rise times U10 before correction and the provisional target rise time U20 (i.e., the differences are the maximum provisional shift times) and rise timings are shifted to become those indicated by a reference sign U11 in writing. Also, the shift times at the fall are 33% of differences between the fall times D10 before correction and the provisional target fall time D20 and fall timings are shifted to become those indicated by a reference sign D11.
Similarly, when the correction ratio of 67% is selected in the next Step S33, writing is performed after the rise times are made those indicated by a reference sign U12 and the fall times are made those indicated by a reference sign D12. Finally, when the correction ratio of 100% is selected, the rise times are made those indicated by the reference sign U20 and the fall times are made those indicated by the reference sign D20, and writing is performed.
Through the above operation, images of horizontal 1-dot-on and 1-dot-off lines in the cases of respective correction ratios are written on the recording medium 9. Subsequently, the operation goes back to Step S225 in
The correction ratio may be changed in a limited range (for example, from 10% to 90%). In this case, for example, in Step S31, information such as the correction ratio at the start of experimental writing, amount of change of the correction ratio from the previous writing at the next writing, and the number of times of experimental writings are inputted to the calculation part 24.
After a user confirms a writing result by visual check and select a correction ratio of a region where the most appropriate writing is performed, the correction ratio or a number of the selected region is inputted to the shift-time determining part 242 through the input part 25 (
As discussed above, in the image recording apparatus 1, when the photosensitive level of the photosensitive material on the recording medium 9 is unknown, since the plurality of provisional shift times are obtained on the basis of the provisional reference voltage 751 and the final shift times are determined after experimental writings, it is possible to determine the shift times relatively easily and record an image appropriately, even if the photosensitive level is unknown. Normally, if it is tried to obtain the ideal reference voltage, it is necessary to check writing results by writing many times while changing the reference voltage or the shift times by trial and error, however, in the above experimental writing, since the ideal shift times are obtained through one writing without changing the provisional reference voltage 751, it is possible to perform appropriate writing efficiently. It can be also said that to change the correction ratios is equivalent to assume a plurality of ideal reference voltages 752 in
In the above method of changing the correction ratios, when the ideal reference voltage 752 is lower than the provisional reference voltage 751, as shown in
Since an approximate photosensitive level can be known in advance, the provisional reference voltage 751 is set to satisfy the above conditions in the image recording apparatus 1. When it is found in experimental writing that the provisional reference voltage 751 does not satisfy the above conditions, the provisional reference voltage 751 is reset to satisfy the above conditions.
The shift times are set only to the rise times and the fall times are not changed, and writing of image of horizontal 1-dot-on and 1-dot-off lines with a constant width may be achieved. Specifically, by shifting only switching timing of each light modulator element after one of the output start signal and the output stop signal is inputted to the driving element 120a connected to each light modulator element 121, it is possible to correct switching timing more easily. In other words, if the shift time is obtained as a time for compensating a difference between a predetermined value (constant value) and a difference between the rise time and the fall time, the target rise time and the target fall time may not be set.
The method of correcting only one of the rise time and the fall time, that is, the method of shifting only switching timing after only one of the output start signal and the output stop signal is inputted to the driving element 120a connected to each light modulator element 121, may be used in experimental writing. In this case, the maximum provisional shift times, which make differences between the rise times and the fall times a predetermined value, are obtained only for one of the rise times and the fall times, and the plurality of provisional shift times are obtained by multiplying the maximum provisional shift times by the plurality of correction ratios, respectively. In other words, if the provisional shift time is obtained as a time for compensating a difference between a predetermined value (constant value) and a difference between the rise time and the fall time at the plurality of correction ratios, the target rise time and the target fall time may not be set.
The image recording apparatus 1a is an apparatus for recording an image of a pattern of mask, wire or the like on a glass substrate 9a (i.e., writing by exposure) for manufacturing a glass mask, a TFT (Thin Film Transistor) liquid crystal panel or the like, and in the image recording apparatus 1a, in the broad sense, the glass substrate 9a coated with a photosensitive material is a recording medium which is a physical material where information of image is recorded. The image recording apparatus 1a comprises a table 72 for holding the glass substrate 9a on its surface on the (+Z) side and on the other side of the table 72, a table moving mechanism 85 for moving the table 72 in the Y direction (main scan direction) is fixed on a base part 74. A position detecting module 85a for detecting position of the table 72 is provided on the base part 74. An optical head 10a for emitting light toward the glass substrate 9a is located above the table 72 and the optical head 10a is supported by a head moving mechanism 86, being movable in the X direction which is the sub scan direction. In other words, the main scan direction and the sub scan direction are parallel to the table 72, and the table moving mechanism 85 and the head moving mechanism 86 function as a mechanism for moving the table 72 relatively to the optical head 10a including the spatial light modulator 12 (see
As shown in
As shown in
An operation for recording an image onto the photosensitive material on the glass substrate 9a in the image recording apparatus 1a is the same as in
When the correction data corresponding to the photosensitive material of the glass substrate 9a which is to be exposed is not stored (Step S11), measurement of light amounts (Step S16) is performed and the operation goes to correction of light amounts (Step S19). When checking modification is necessary though the correction data is stored (Step S12), measurement of light amounts (Step S17) is performed and if it is confirmed that correction is not needed, writing (Steps S18, S13, S14) is performed and if correction is necessary, the operation goes to correction of light amounts (Step S19).
In measurement of light amounts (Steps S16, S17), the optical head 10a moves up to a position opposed to the detection part 71a by driving the table moving mechanism 85 and the head moving mechanism 86, and a light amount emitted from each light modulator element 121 is sequentially measured through the slit 712 like the first preferred embodiment while the optical head 10a is moved in the sub scan direction at a low speed by the head moving mechanism 86. In other words, the head moving mechanism 86 functions as a slit moving mechanism for moving the slit 712 relatively to the light modulator elements 121.
Following correction of light amounts (Step S19) after measurement of light amounts, determination of shift times (Step S2) is performed and the operation goes to writing (Step S14). Operations of correction of light amounts and determination of shift times are the same as those in the first preferred embodiment.
In writing on the glass substrate 9a (recording by exposure) (Step S14), first, the table 72 is moved relatively to the optical head 10a including the spatial light modulator 12 in the (−Y) direction by the table moving mechanism 85 and irradiation positions of light from the optical head 10a on the glass substrate 9a are thereby continuously moved relatively to the glass substrate 9a in the (+Y) direction (i.e., main scanning is performed). In parallel with movement of the table 72, writing is performed in synchronization with a signal outputted from the position detecting module 85a and in this time, the general control part 21 and the signal processing part 22 perform correction of light amounts according to the driving voltage table 221 (see
When the irradiation positions reach an end of the glass substrate 9a on the (+Y) side, the optical head 10a moves in the sub scan direction (X direction) by a distance corresponding to width of the strip-like region in the X direction and the moving direction of the table 72 is reversed. Writing in a backward path of the table 72 is performed on a new strip-like region in contact with the side of the strip-like region written in a forward path. Then, in the image recording apparatus 1a, the optical head 10a intermittently moves in the X direction while the table 72 reciprocally moves in the Y direction, to record an image on the whole of the plane glass substrate 9a.
As discussed above, in the image recording apparatus 1a, when light is applied to the glass substrate 9a for manufacturing a glass mask, a TFT liquid crystal panel or the like, since light amounts from respective light modulator elements 121 are made uniform and the rise times and the fall times are made uniform, it is possible to increase quality of a recorded image.
Though the preferred embodiments of the present invention have been discussed above, the present invention is not limited to the above-discussed preferred embodiments, but allows various variations.
The recording medium 9 and the glass substrate 9a may be traveled by other methods only if they can move relatively to the optical heads 10 and 10a. The recording medium carrying image information may be other material coated with photosensitive material such as a printed circuit board, a semiconductor substrate or the like, or may be other material with photosensitivity.
Though the zeroth order light beam is used as the signal light for writing in the above preferred embodiments, the first order diffracted light beams may be used as the signal light. Unlike the relative positional relation between the moving ribbons 121a which are not sagged and the fixed ribbons 121b in the above preferred embodiments, the light modulator element 121 which emits the zeroth order light beam in the state where the moving ribbons 121a sag may be used. In these cases, appropriate image recording can be achieved by shifting a switching timing of the light modulator element 121.
If the moving ribbons 121a and the fixed ribbons 121b can be regarded as strip-like reflection surfaces, these surfaces do not have to be in a ribbon shape in a strict meaning. For example, upper surfaces of block shapes may serve as the reflection surfaces of fixed ribbons.
The light modulator element 121 is not limited to the diffraction grating type one, but may be a liquid crystal shutter or the like only if it is a multichannel type. Further, the light modulator elements 121 are not limited to those that reflect light, but a laser array, for example, may perform the function as the light modulator element 121. Also in these cases, unevenness of the rise times and the fall times by irradiation with light from elements is corrected by shift of switching timings, thereby achieving appropriate image recording. The above correction of switching timings is especially suitable for a light modulator element where the rise time and the fall time change in correction of light amount, that is, when intensity of signal light is changed.
A two-dimensional spatial light modulator may be used and in this case, correction for the plurality of light modulator elements 121 in the above preferred embodiments is applied to each one-dimensional array of the light modulator element 121.
The structure of functions of the calculation part 24 may be partially or completely constructed as a dedicated electric circuits.
Though the shift times of each light modulator element 121 is obtained on the basis of the rise time and the fall time before correction in the above preferred embodiments, the shift times may be obtained on the basis of a state of output from the photosensor 711 at the rise and fall (for example, ratio of change in output to time). Generally discussing, the shift time of switching timing of a light modulator element 121 after input of the output start signal instructing start of output of signal light or the output stop signal instructing stop of output of signal light to the driving element 120a connected to the light modulator element 121 is obtained on the basis of output of the photosensor 711 which is a photodetector after input of the output start signal or the output stop signal, and it is thereby possible to achieve appropriate writing by correcting the switching timing with respect to the signal controlling output.
The light amount from each light modulator element 121 and the rise time and the fall time are measured by moving the slit 712 in the sub scan direction in the above preferred embodiments, but may be measured by a mechanism other than the slit, for example, a CCD having a plurality of light receiving elements which are long in the sub scan direction or a CCD having a two-dimensional array of light receiving elements.
Though the shift times are obtained after measurement of the response times of all light modulator elements 121 in Steps S212 to S214 of
While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.
This application claims priority benefit under 35 U.S.C. Section 119 of Japanese Patent Application No. 2005-283340 filed in the Japan Patent Office on Sep. 29, 2005 and Japanese Patent Application No. 2006-121708 filed in the Japan Patent Office on Apr. 26, 2006, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2005-283340 | Sep 2005 | JP | national |
| P2006-121708 | Apr 2006 | JP | national |
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| 20070070361 A1 | Mar 2007 | US |
