Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2000-02-07
2002-04-16
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S251000
Reexamination Certificate
active
06373514
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of testing a light emission condition of an exposing head. The invention relates, more particularly, to a method for use with a type of exposing head which includes a plurality of luminous elements disposed along a main scanning direction for forming dots in the form of a dot-line on a print paper and which is movable in a sub scanning direction relative to the print paper, the method including the step of comparing light emission amounts of the luminous elements to each other based on the densities of the respective dots obtained by exposure of the print paper.
2. Description of the Related Art
As an example of the method described above, the following method is known. In this known method, by driving the luminous elements of the exposing head under a predetermined load condition over a print paper, there is formed, on the print paper, a testing dot pattern in the form of a dot-line, more particularly, as shown in
FIG. 14
a,
a dot pattern Dp
1
including a plurality of dots adjacently aligned along the main scanning direction of the exposing head. Then, by applying a scanner along this linear dot pattern thus formed on the print paper (actually, the developed image of the dot-line which is obtained by first forming the latent image of the dot pattern Dp
1
on the print paper and then developing the image thereon), the densities of the respective dots are obtained, and the obtained density values, or any irregularities among them, are outputted as the testing result of the light emission condition of the exposing head
However, if the above test is conducted under such load condition as allowing the luminous elements to provide their full light emission performance, there occurs the tendency that in the dots formed on the print paper by the respective elements, one dot tends to extend into the adjacent area of another dot adjacent thereto. As a result, as shown in
FIG. 14
b
which shows the principal portion of
FIG. 14-
a
in an enlarged scale, there occurs overlapping between adjacent dots at their outermost portions. For this reason, in the step of determining the density of each individual dot by means of the scanner, the light emission condition of each luminous element cannot always be grasped with accuracy as each dot being influenced by its adjacent dot.
Then, as an improved method of testing a light emission condition of an exposing head devised to overcome the above problem, there is also known a method disclosed in the European patent published gazette EPO 925 941 (corresponding to the U.S. patent application Ser. No. 09/217,179) in the name of the same applicant as the present application. For overcoming the above problem, in this modified method, as shown in
FIG. 15
a
and also in
FIG. 15
b
which is an enlarged view, the method includes a first step of exposing and forming a plurality of arrays of dots (i.e. a plurality of “dot-lines”) on the print paper, each array including a plurality of dots equidistantly spaced from each other in the main scanning direction and also the dot arrays are spaced from each other in the sub scanning direction which is perpendicular to the main scanning direction and a second step of determining the densities of the respective dots of the resultant dot pattern Dp
2
one array after another by means of a scanner.
According to the above method, the dots within each array are spaced from each other in the main scanning direction. Hence, there occurs no overlap between the dots, so that the density of each dot may be determined without influence from the adjacent dot. Further, as the dot arrays are also spaced from each other in the sub scanning direction, the scanning operation by the line scanner may be effected in a plurality of steps separately for the respective arrays. And, with these plurality of scanning operations combined, the densities of all dots may be obtained. Consequently, the intended object of accurate grasping of the light emission condition of the individual luminous element may be achieved with ease. Further, if the exposing head consists of blocks provided separately for the respective color components of R (red), G (green) and B (blue), by effecting the above-described process for each of these blocks, the light emission conditions of all of the elements used in the exposing head may be tested.
With the above method proposed by the co-pending patent applications identified above, the print page remains completely ‘blank’, after its exposure, at those inter-dot areas thereof between each pair of dots spaced apart from each other. Therefore, in the second step, namely, the step of determining the densities of the respective dots of each array by using a scanner, such blank areas will affect the measurement values, thus hindering accurate testing (more particularly, this seems to be attributable to a phenomenon that a portion of the irradiating beam emitted from the optical reflection type scanner employed in the second step is reflected by the blank area to be ‘flared’ into the area of the dot which is the target dot of measurement, thus leading to inadvertent reduction in the measured density value.).
SUMMARY OF THE INVENTION
In view of the above-described drawbacks of the prior art described at the onset as well as the modified method of the invention described in the preceding patent applications, a primary object of the present invention is to provide a method of testing a light emission condition of an exposing head, which method is capable of overcoming such drawbacks of the prior art and achieving the original purpose of accurate grasping of the light emission condition of each luminous element of the exposing head.
For fulfiling the above-noted object, according to one aspect of the present invention, there is proposed a method of testing a light emission condition of an exposing head, which comprises the following:
(1) a first step of forming latent images of testing target dots on a print paper by driving luminous elements selected as target elements which are not adjacent each other in the main scanning direction;
(2) a second step of forming latent images of background dots in the peripheries of the latent images of the target dots so that the peripheries are completely filled with the latent images of the background dots with a density above a predetermined value;
(3) a third step of developing the latent images of the target dots and the background dots formed on the print paper and subsequently determining the densities of the respective developed images of the target dots by using a scanner; and
(4) a fourth step of outputting the density of each one of the target dots obtained by the third step as a light emission amount of each corresponding luminous element selected as one of the target elements.
According to the invention's method of testing a light emission condition of an exposing head having the above construction, in the first step, there are obtained latent images of target dots which are not adjacent each other in the main scanning direction; and in the third step there are determined the densities of the developed images of these target dots without mutual overlaps therebetween. Hence, the density of the individual dot may be determined with accuracy, without influence from the adjacent dots. Moreover, in the density determination of the third step, this determination is made with the periphery of each target dot being filled with the images of the background dots without leaving any blanks therein. Therefore, this method is free from the disturbance due to the ‘flaring’ of the irradiating beam emitted from the optical reflecting scanner. Consequently, the light emission condition of each luminous element may be readily grasped with accuracy.
Preferably, the first step includes following sub steps:
(1-1) a first sub step of forming a latent image of a first dot array by driving at one time those luminous elements of the exposing head assigned for odd-numbered pixels; and
(1-2) a secon
Fulbright & Jaworksi LLP
Noritsu Koki Co., Ltd.
Pham Hai
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