Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1999-04-20
2001-02-27
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S238000, C347S247000, C347S248000
Reexamination Certificate
active
06195114
ABSTRACT:
This application is based on application No. H10-110803 filed in Japan, the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of driving optical output media in an optical writing apparatus, said apparatus being used for digital printers and the like.
2. Description of the Prior Art
As a solid-state scanning optical writing apparatus, an array type using optical output media such as LEDs, PLZT, fluorescers and liquid crystal, etc. aligned in one direction has conventionally been known.
For example, an optical shutter using PLZT as an example of the optical output medium is provided as a ceramic wafer comprising lead, lanthanum, zircon and titanium that are sintered, and is cut out or arranged so as to have a pixel pitch for the necessary printing density and resolution. The PLZT optical shutter transmits or does not transmit light according to the polarization direction of the light between when a voltage is applied and when no voltage is applied. Therefore, the PLZT optical shutter transmits or intercepts light from a light source according to whether a voltage is applied or not, and outputs the transmitted light. For this reason, no special light source is necessary. In addition, the PLZT optical shutter has a responsiveness of as high as in nanoseconds, and easily handles an increase in writing speed.
The inventor has developed a solid-state scanning optical writing apparatus using PLZT optical shutters as optical output media, that is, an A3-ready sliver halide printer employing a print head. In such a printer, in addition to the formation of A3-size images, the formation of images of a small size such as the L size in photography is naturally performed.
When a large-size image is printed after a small-size image is printed on photographic paper, there are occasions when there is a difference in output density on the same photographic paper between the part of the large-size image coinciding with the small-size image printed therebefore and the part of the large-size image not coinciding with the small-size image.
As a result of various experiments and examinations conducted by the inventor, it was found that the output density difference is caused due to an electro-optic effect, that is, an optical hysteresis and an electric field hysteresis of the PLZT optical shutter.
FIG. 17
shows results of a measurement of the difference in quantity of the transmitted light with respect to the drive voltage between before and after the hysteresis due to the electric field.
FIG. 18
shows results of a measurement of the difference in quantity of the transmitted light with respect to the drive voltage between before and after the hysteresis due to light. In either case, it is apparent that the drive voltage is changed by the hysteresis.
FIG. 19
shows that the drive voltage varies with time due to the electric field hysteresis.
Thus, in the PLZT, when the hysteresis is caused, a value called a halfwave voltage where the quantity of the transmitted light is largest is varied, and this results in image writing non-uniformness and image output density non-uniformness. When the applied voltage is high or when an electric field is steadily applied like in a DC state, as shown in
FIG. 19
, the hysteresis quickly progresses.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a driving method in which writing non-uniformness is prevented even when a difference in optical hysteresis or electric field hysteresis is caused in the optical output media in a solid-state scanning optical writing apparatus.
To achieve the above-mentioned object, in a method, according to one aspect of the present invention, of driving a plurality of optical output media aligned in one direction in an optical writing apparatus that drives activation and deactivation of the optical output media based on image data to thereby perform optical writing onto an object onto which writing is to be performed, it is determined whether the number of optical output media that are writing-driven based on the image data in order to perform optical writing onto the object is smaller than the total number of optical output media, and when the number of writing-driven optical output media is smaller than the total number of optical output media, non-writing driving of optical output media other than the writing-driven optical output media is performed. The non-writing driving is a driving in which optical writing is not performed onto the object.
In a method, according to another aspect of the present invention, of driving a plurality of optical output media aligned in one direction in an optical writing apparatus that drives activation and deactivation of the optical output media based on image data to thereby perform optical writing onto an object onto which writing is to be performed, when writing driving of optical output media is performed based on the image data in order to perform optical writing onto the object, a total drive time of each of the writing-driven optical output media is computed, the computed total drive time is stored, and when the number of writing-driven optical output media is smaller than the total number of optical output media, non-writing driving of the writing-driven optical output media and optical output media other than the writing-driven optical output media is performed based on the total drive time of each optical output medium stored before so that the total drive times of all the optical output media are the same. The non-writing driving is a driving in which optical writing is not performed onto the object.
In a method, according to still another aspect of the present invention, of driving a plurality of optical output media aligned in one direction in an optical writing apparatus that drives activation and deactivation of the optical output media based on image data to thereby perform optical writing onto an object onto which writing is to be performed, when writing driving of optical output media is performed based on the image data in order to perform optical writing onto the object, an average total drive time of the writing-driven optical output media is computed, the computed average total drive time is stored, and when the number of writing-driven optical output media is smaller than the total number of optical output media, non-writing driving of optical output media other than the writing-driven optical output media is performed for a time equal to the average total drive time stored before. The non-writing driving is a driving in which optical writing is not performed onto the object.
In a method, according to a further aspect of the present invention, of driving a plurality of optical output media aligned in one direction in an optical writing apparatus that drives activation and deactivation of the optical output media based on image data to thereby perform optical writing onto an object onto which writing is to be performed, a preliminary driving of all the optical output media is performed before optical writing is performed onto the object based on the image data, wherein in said preliminary driving, non-writing driving of all the optical output media is performed at a predetermined voltage for a predetermined time, and after the preliminary driving, writing-driving of the optical output media is performed based on the image data in order to perform optical writing onto the object. The non-writing driving is a driving in which optical writing is not performed onto the object.
In a method, according to a further aspect of the present invention, of driving a plurality of optical output media aligned in one direction in an optical writing apparatus that drives activation and deactivation of the optical output media based on image data to thereby perform optical writing onto an object onto which writing is to be performed, when writing driving of optical output media is performed based on the image data in order to perform optical writing onto the obje
Le N.
McDermott & Will & Emery
Minolta Co. , Ltd.
Pham Hai C.
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