Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-05-21
2001-04-03
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S235000
Reexamination Certificate
active
06211899
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image exposure apparatus in which an image is exposed onto a photosensitive material based on image data in such a manner that main scan and sub-scan are effected for the photosensitive material by a light source unit.
2. Description of the Related Art
Currently, a number of image exposure apparatuses each having a digital exposure system mounted thereon have been developed. Generally, in the digital exposure system, an image is recorded on a recording medium in such a manner that a light beam outputted from a semiconductor laser is modulated with image data and deflected by the high-speed rotation of a polygon mirror (main scan), and the light beam reflected by the polygon mirror is further subjected to sub-scanning by a galvano mirror or the like, or the above main scan is effected repeatedly while the recording medium is moved (or the recording medium is moved stepwise). Here, as the recording medium, a photosensitive drum electrified by corona discharge, or a photosensitive material may be used. Further, in place of the semiconductor laser, another light emitter such as a light emitting diode (LED) may be used as a light source.
In the above-described image exposure apparatus, it is necessary that the starting point of each main scanning line is aligned in the sub-scanning direction. For this reason, a sensor (which will be generally referred to as an SOS sensor) is provided within a widthwise range of main scan and at a position other than an image recording region, and at a predetermined time after light at the time of main scan is detected by the SOS sensor, an image data signal is outputted. As a result, the time when output of an image signal starts at each main scan becomes constant and distortion of an image, and the like can be prevented accordingly.
However, when the SOS sensor is used for the synchronization as described above, the time of detection by the sensor may not become constant. Namely, a detection surface of the sensor has a certain region, and the signal is not reversed unless a predetermined amount of light is detected in the certain region. For this reason, the time of the image signal outputted may change due to inconsistency of the reverse timing.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, it is an object of the present invention to provide an image exposure apparatus which can solve inconsistency of a main scan start time caused by variation of time of detection by a sensor for controlling a scan start timing.
In accordance with a first aspect of the present invention, there is provided an image exposure apparatus which controls emission of a light beam from a light source based on an image data signal to record an image on a photosensitive material by scanning the light beam, comprising: main scan means which moves the light source with respect to the photosensitive material in a predetermined main scanning direction; sub-scan means which moves relatively the light source and the photosensitive material in a direction perpendicular to the main scanning direction for each main scan effected by the main scan means; a detecting sensor which detects a start position of the main scan means; moving amount detecting means which detects an amount by which the light source is moved in the main scanning direction; and main scan exposure control means which controls an exposure start timing of a light beam in each of the second and subsequent main scan operations until the first main scan operation for scan recording starts, with reference to a detected value of an amount of movement detected by the moving amount detecting means when the start position of the main scan means is detected by the detecting sensor.
A second aspect of the present invention is characterized by that, in the first aspect, the detecting sensor is a start-position detecting sensor which detects a light beam from the light source at a predetermined position.
A third aspect of the present invention is characterized by that, in the first aspect, the detecting sensor is a main scan means-initial position detecting sensor which detects the main scan means at a predetermined position.
In accordance with the first aspect of the present invention, only in the first main scan, the detecting sensor is used to start the main scan. In subsequent operations, the main scan is controlled based on the moving amount detection value which is detected by the moving amount detecting means, with the time detected by the detection sensor as a reference. For this reason, high-accurate image exposure processing can be effected without depending on variation in time for detection by the detecting sensor itself.
Further, detection of light is effected by the start-position detecting sensor only in the first main scan, and therefore, exposure for producing a high image quality can be achieved, for example, not only in one-way scan, but also in reciprocating scan. Usually, although the reciprocating scan allows high-speed processing unlike the one-way scan, the image quality may deteriorate due to misregistration of dot positions caused by reciprocation. However, with the control of the amount of movement according to the present invention, the deterioration of the image quality does not arise.
According to the second aspect of the present invention, the start-position detecting sensor is disposed, as the detecting sensor, on the locus of an optical path of light beam so as to directly detect the light beam, and the position of the light beam can thereby be detected with high accuracy.
Further, according to the third aspect of the present invention, the main scan means-initial position detecting sensor which detects the main scan means at a predetermined position may be used as the detecting sensor.
The main scan means-initial position detecting sensor has the same function as the start-position detecting sensor according to the second aspect and also has the same effects as those of the start-position detecting sensor.
However, the start-position detecting sensor according to the second aspect is used to detect light and the kind of the sensor is limited. However, at the predetermined position on the locus of a mechanical movement of the main scan means for allowing main scan of the light beam, there may be applicable various kinds of sensors, for example, not only a mechanical switch such as a limit switch, but also a photoelectric sensor having a light emitting portion and a light receiving portion, a sensor using a Hall element which outputs different signals due to variation in magnetic flux density, and the like.
Further, the degree of freedom of the position where the main scan means-initial position detecting sensor is mounted increases and this detecting sensor can be provided at an appropriate location taking account of assembling efficiency thereof.
A fourth aspect of the present invention is characterized by that, in the first aspect, the main scan driving is effected by a stepping motor and a driving pulse for the stepping motor or a pulse prior to dividing, which is inputted to a stepping motor driving pulse generator, is used to detect the amount of movement of the light source.
According to the fourth aspect of the present invention, by using, as the moving amount detection value, the driving pulse of the stepping motor or the pulse prior to dividing which is inputted to the stepping motor-driving pulse generator, the amount of movement can be detected with high accuracy. Further, a driving system (i.e., a stepping motor) which actually effects main scan is used commonly so as to reduce detection errors.
A fifth aspect of the present invention is characterized by that, in the fourth aspect of the present invention, an exposure start timing for one dot of an image is synchronized with a driving pulse for the stepping motor or n times or 1
(n is an integer) the pulse prior to dividing.
According to the fifth aspect of the present invention, the detection errors can be reduced an
Fuji Photo Film Co. , Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tran Huan
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