Printing press equipped with color chart measuring apparatus
View Patent ↗A reading time setting section ( 44 ) determines a read area for an imaging section ( 25 ) on the basis of color chart positional data (id). The imaging section ( 25 ) reads an image on printing paper during the reading time and readout image data (rd) is stored in an image data storage section ( 45 ). A reference mark detecting section ( 46 ) detects the positions of reference marks from the readout image data (rd). A color chart actual position calculation section ( 47 ) corrects a tilt of a color chart determined from the positions of the reference marks and calculates an actual position of each of color chart fields (cr). An image data readout section ( 48 ) reads out image data on a color chart field corresponding to the calculated actual position. At the same time, image data on a white color field immediately above the color chart field is also read out. A white color correction section ( 49 ) produces a white reference on the basis of the image data on the white color field and corrects the image data on the color chart field. A color chart information determination section ( 50 ) measures color chart information, such as a color density and a dot percentage, about each of the color chart fields. This printing press determines a reading time on the basis of the position of the color chart at the time of printing plate recording and thereby allows imaging of an area including the color chart on the printing paper being transported.
1. A color chart provided along a width of printing paper for checking at least an ink density in a printing press,
said color chart including:
at least two reference marks provided at a predetermined distance from each other in a direction of a print span; and
a plurality of kinds of color chart fields arranged in line between said reference marks,
wherein said reference marks each have a pattern to indicate positions of said color chart fields with respect to a print direction.
2. The color chart according to claim 1 , wherein
an unprinted area is formed adjacent to said color chart fields on said printing paper, and
said reference marks each further has a pattern to indicate a range of said unprinted area.
3. The color chart according to claim 1 , wherein
of said at least two reference marks, two reference marks are provided at about both ends of said printing paper across the width of said printing paper.
4. The color chart according to claim 1 , wherein
some of said plurality of kinds of color chart fields are arranged on both sides of any one of said at least two reference marks in symmetry with respect to a point about said any one reference mark.
5. The color chart according to claim 1 , wherein
said color chart fields are of multiple colors (YMCK), and
said reference marks are of a single black (K) color.
6. A color chart measuring method for measuring the color chart of claim 1 , comprising the steps of:
obtaining image data by imaging an area including said color chart on said printing paper;
computing positions of said reference marks from said image data;
computing a position of each of said color chart fields on the basis of said positions of said reference marks; and
measuring each of said color chart fields on the basis of said position of each of said color chart fields,
wherein a tilt of said image data obtained by reading said color chart is corrected on the basis of said positions of said at least two reference marks.
7. The color chart measuring method according to claim 6 , wherein
imaging of said printing paper being transported is carried out by means of at least one line sensor located along a width of said printing paper.
8. The color chart measuring method according to claim 7 , wherein
when said color chart includes three or more reference marks, imaging is carried out by using a different line sensor for every two adjacent reference marks out of said three or more reference marks.