Apparatus for forming pattern

1. An apparatus for forming a pattern comprising:

a light source that emits a beam;

a scanning unit that scans the beam on a photosensitive material;

a time-interval detector that successively detects a time-interval that is a pass-time of the beam in each section of a series of fine sections, said series of fine sections being defined by dividing a scanning-line at constant-intervals larger than a dot-pitch;

a memory that is capable of storing a series of sets of pulse data that have a different data-array in accordance with the time-interval;

a pulse data selector that selects a set of pulse data, corresponding to the detected time-interval, from the series of sets of pulse data;

a control pulse signal generator that successively generates a sequence of control pulse signals in accordance with the selected set of pulse data;

a writing pulse signal generator that successively generates a sequence of writing pulse signals in accordance with the sequence of control pulse signals, the sequence of control pulse signals controlling the output-timing of the sequence of writing pulse signals; and

an optical modulator that modulates the beam in accordance with the sequence of writing pulse signals.

2. The apparatus of claim 1 , wherein said time-interval detector detects the time-interval by using a sequence of standard clock pulse signals with a given frequency that is higher than a frequency necessary for counting a time-interval corresponding to the dot-pitch.

3. The apparatus of claim 1 , wherein the series of sets of pulse data comprises a standard set of pulse data that corresponds to a standard time-interval detected by using a predetermined scanning-speed, and a plurality of corrected pulse data that respectively correspond to a plurality of correcting time-intervals that vary continuously and that deviate from the standard time-interval.

4. The apparatus of claim 1 , wherein said time-interval detector comprises a standard scale that has a plurality of slits, the slits being regularly formed at a constant-interval, the length of a fine section being defined in accordance with a slit-pitch;

wherein said scanning unit comprises a beam splitter that splits the beam from said light source into a scanning-beam for scanning and a monitor-beam for detecting a position of the scanning-beam, said scanning unit scanning the monitor beam on said standard scale, said time-interval detector detecting the time-interval on the basis of a sequence of scale signals obtained from passing-light that passes the slits periodically.

5. The apparatus of claim 1 , wherein said optical modulator comprises an AOM (Acousto-Optical Modulator).

6. The apparatus of claim 1 , wherein said scanning unit comprises a polygon mirror and an f-θ lens.

7. An apparatus for generating a sequence of control pulse signals comprising:

a time-interval detector that successively detects a time-interval that is a pass-time of the beam in each section of a series of fine sections, said series of fine sections being defined by dividing a scanning-line at constant-intervals larger than a dot-pitch;

a memory that is capable of storing a series of sets of pulse data that have a different data-array in accordance with the time-interval;

a pulse data selector that selects a set of pulse data, corresponding to the detected time-interval, from the series of sets of pulse data; and

a control pulse signal generator that successively generates a sequence of control pulse signals in accordance with the selected set of pulse data, the sequence of control pulse signals controlling the output-timing of a sequence of writing pulse signals for controlling an optical modulator.

8. A method for generating a sequence of control pulse signals comprising:

detecting successively a time-interval that is a pass-time of a beam in each section of a series of fine sections, said series of fine sections being defined by dividing a scanning-line at constant-intervals larger than a dot-pitch;

selecting a set of pulse data, corresponding to the detected time-interval, from a series of sets of pulse data, the series of sets of pulse data having a different data-array in accordance with the time-interval; and

successively generating a sequence of control pulse signals in accordance with the selected set of pulse data, the sequence of control pulse signals controlling the output-timing of a sequence of writing pulse signals for controlling an optical modulator.