Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-12-22
2001-03-27
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S235000, C347S236000, C347S246000
Reexamination Certificate
active
06208370
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an apparatus, which uses a scanning light beam, such as a laser light beam, for writing onto a media.
BACKGROUND OF THE INVENTION
In devices for writing onto media using a scanning light beam it is important to know when to turn on and start writing with the scanning light beam. In a typical prior art scanning writing apparatus, a laser light beam or other illuminated light, is directed to a rotating polygon having a plurality of mirror facets which direct the light beam onto a media. Each facet is used to write a successive line of data. These type of systems have the disadvantage of relying on ill-defined specifications for rotating stability of the polygon. Additionally, accumulative error in timing from the first facet to the last facet may occur. Thus, there is a need to provide appropriate timing for line start for each successive facet.
It is also important to maintain a predetermined intensity level of the writing beam. As is typical with writing beams, such as laser beams, over time the intensity can vary, which can affect the overall quality of the writing apparatus. Most systems monitor light beams in the static mode, that is, before scanning. Monitoring may be done right at the output of the laser, or after the acoustic optical modulator (AOM) or attenuator. A hand-held light meter can periodically be inserted into the beam for measuring of the intensity. The problem is that measuring the intensity at these positions does not actually reflect the amount of light that will be hitting the media plane, which may result in erroneous measurements. The intensity of the beam should be measured as close to the writing plane as possible in order to account for all possible attenuation. Another prior art method used to monitor the intensity is to scan and print an image onto a photosensitive material media, for example, photographic paper, then develop the paper and then measure the results of the developed paper with a densitometer. This is a tedious and time-consuming process.
The present invention provides a method for accurately determining a line start for each facet and also provides a method of measuring the light beam amplitude automatically and as close to the focal plane of the media as possible.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized according to one aspect of the present invention, there is provided a method of determining a line start writing position of a scanning light beam in a scanning light beam writing system, the writing system having a scanning light beam which projects along a scan path on a writing plane from a start position to an end position, a first detector and a second detector positioned in the scan path for detection of the scanning light beam as it is scanned along the scan path for detection of the light beam, the second detector being spaced a predetermined distance from the first detector at a point after the scanning light beam passes the first detector, the method comprising the steps of:
moving the scanning light beam at a known velocity along the scan path from the start position to the end position;
monitoring a first output parameter of the first detector produced by the scanning light beam passing over the first detector;
monitoring a second output parameter of the second detector produced by scanning light beam passing over the second detector;
noting a reference point when the parameter measured by the first and second detectors reach a predetermined relationship; and
determining the line start position on the scan path for start of writing by the scanning light beam based on the reference point.
In accordance with another aspect of the present invention there is provided an apparatus for writing onto a media using a scanning light beam, comprising:
a scanning light beam for projecting a scanning path on a writing plane for receiving a photosensitive media for writing thereon, the scanning path having a start position and an end position;
a first detector positioned in the scan path after the start position for detection of the scanning light beam;
a second detector positioned in the scan path at a point after the first detector for detection of the light beam, the second detector being spaced a predetermined distance from the first detector, the first and second detectors producing an output signal in response to the scanning light beam passing over the first and second detectors;
means for noting a reference point when a particular relationship occurs between the value of the output signals produced by the first and second detectors; and
means for generating a line start signal in response to the reference point and for commencing writing with the scanning light beam based on the photosensitive media.
In accordance with yet another aspect of the present invention there is provided a method of monitoring and/or calibrating a writing system, the writing system having a scanning light beam which projects along a scan path having a start position and an end position on a writing plane, a first detector positioned in the scan path for detecting the scanning light beam and a second detector positioned after the first detector in the scanning path for detection of the light beam, the second detector being spaced a predetermined distance from the first detector, the method comprising the steps of:
turning on a scanning light beam and moving the scanning light beam at a known velocity along the scanning path at a first power level;
monitoring a first output signal measured by the first detector in response to the scanning light beam passing over the first detector;
noting a reference position when the first output signal reaches a predetermined value and generating a pulse signal based on the reference position;
changing the power level of the scanning beam to a predetermined second level in response to the reference position;
measuring a second output signal measured by the second detector in response to the light beam passing over the second detector; and comparing the second output signal of the scanning light beam with respect to a predetermined reference value and making an adjustment to the power level of the scanning light beam in accordance with the predetermined value.
In still another aspect of the present invention there is provided a scanning light beam writing apparatus, comprising:
a scanning light beam which projects along a scan path having a start position and an end position on a writing plane;
a first detector positioned in the scan path producing a first output signal in response to the scanning light beam passing over the first detector;
a second detector positioned after the first detector in the scanning path for producing a second output signal in response to the scanning light beam passing over the second detector, the second detector being spaced a predetermined fixed distance from the first detector;
means for monitoring the first output signal produced by the first detector as the scanning light beam passes over the first detector;
means for noting a reference position when the first output signal reaches a predetermined value and generating a pulse signal based on the reference position;
means for changing the power level of the scanning beam to a predetermined second level in response to the reference position;
means for measuring the second output signal produced by the second detector when the scanning light beam passes over the second detector;
means for comparing the value of the second signal of the second detector with respect to a predetermined reference value; and
means for adjusting the power level of the scanning light beam in accordance with the predetermined value.
The above, and other objects, advantages and novel features of the present invention will become more apparent from the accompanying detailed description thereof when considered in conjunction with the following drawings.
REFERENCES:
patent: 4306807 (1981-12-01), Sakane et al.
p
Eastman Kodak Company
Le N.
Pham Hai C.
Pincelli Frank
LandOfFree
Method and apparatus for determining the starting position... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for determining the starting position..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for determining the starting position... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2463243