JPS61164835A - Detector for printing paper with defective density register - Google Patents

Abstract

PURPOSE:To accurately detect the chrominance of a register mark color, making the replacement of color filters unnecessitated, by a method wherein, a register mark is color-separated into three primary colors i.e. red, blue and green, and their density are judged while being added with a signal from a margin blank. CONSTITUTION:A light source lamp 8 illuminates a yellow, a red, and a blue register marks 5, 6, and 7, the components in the infrared region are removed by a heat-ray absorption filter 9, and subsequently, the color-separation is performed by red, blue reflection dichromic mirrors 10, 11. The red, blue and green colors issued from red, blue and green transmissive filters 12, 13, 14 are received by photoelectric conversion elements 15b, 15c, and 15d while the light reflected from a margin black 3 of printing paper is received by a photoelectric conversion element 15a, then the signal therefrom is inverted-amplified by an inverting amplifier circuit 17. By adding the values thus obtained by an adding circuit 18, the generated output becomes chrominance value of the three primary colors. The chrominance value and the output of a threshold value generating variable resistance 19 are compared with each other resulting in judging signal. Thereby, the method mentioned herein ensures correct detection with regard to a density chrominance degree, and even if a printed color varies, the replacement of filters is unnecessitated.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a sheet-fed offset printing machine, a sheet-fed gravure printing machine, or a sheet-fed printed matter inspection machine, in which register marks printed in the margins of printed matter are checked. The present invention relates to an apparatus for inspecting printed matter with poor register density, which optically scans and inspects printed matter with poor registered density.

<Prior art> Conventionally, as this type of technology, for example,
523, a device that prepares a filter corresponding to each printing color, receives the reflected light for each registration mark with a photoelectric conversion element, and determines the presence or absence of the registration mark based on the density output value. was there.

Problems that need to be solved> However, with conventional inspection equipment for printed matter with poor registration density, it is necessary to prepare a filter corresponding to each printed color, so each time a different printed matter is produced, the filter must be replaced with a filter corresponding to that printed color. There is a problem that there is a need to
In addition, there are fluctuations in the output level due to temperature changes and changes over time in the photoelectric conversion element, as well as changes in the illuminance of the light source, so in order to accurately obtain the density of the registration mark, automatic gain is required to automatically correct the output level. There was a problem in that an adjustment circuit had to be prepared.

The present invention is intended to solve the above-mentioned problems, and it is possible to accurately detect the density change of each register mark, eliminate the need to replace the filter even if the printed color changes, and eliminate the need for changing the temperature of the charging conversion element. An object of the present invention is to provide an inspection device for printed matter with poor register density, which makes it unnecessary to adjust the offset voltage due to changes over time.

Solution to the above problems> The configuration of the inspection device for printed matter with poor register density according to the present invention, which solves the above problems, is to mark the register marks corresponding to each printing color serially printed in the conveyance direction of the printed matter in red. , a means for optically scanning the three primary colors of blue and green, a means for optically scanning the margin area other than the registration mark, and a means for optically scanning the margin area signal obtained by this means and color separation into the three primary colors. and a means for determining the target density based on whether or not this added signal exceeds a threshold value of a certain value or more.

<Example> Next, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing an embodiment of an inspection apparatus for printed matter with poor register density according to the present invention.

Register marks 5, 6.7 are printed in series in the transport direction A, corresponding to the printing colors, in the margin area 3 other than the pattern printing area 2 of the printed matter l, which is the object to be inspected. In addition, in this example,
Printed material l is printed in three colors, and register mark 5
is yellow, register mark 6 is red, and register mark 7 is blue.

Reference numeral 8 denotes a light source lamp. Each register mark 5, 6, 7 is irradiated by this light source lamp 8, and an infrared region component of the reflected light is removed by a heat ray absorption filter 9.

10 is a red reflective dichroic mirror, 11 is a blue reflective dichroic mirror, 12 is a red transmitting filter, L3 is a blue transmitting filter, 14 is a green transmitting filter, and the reflected light from the printed matter 1 is separated into three primary colors. Ru. The red light from the red transmission filter 2 is received by the photoelectric conversion element 15b, and the blue light from the blue transmission filter 15c is received by the photoelectric conversion element 15.
The green light from the green transmission filter [4 is received by the photoelectric conversion element 15d.

15a is a photoelectric conversion element that receives reflected light from the margin 3 of the printed matter 10 and outputs a margin signal. This margin signal is inverted and amplified by an inverting amplifier circuit 17.

L6b, 16c, and 16d are amplifier circuits that amplify the red signal, blue signal, and green signal, respectively. 1
8 is an addition circuit which adds the inverted signal of the margin signal, the red signal, the blue signal, and the green signal. As a result, the output of the adder circuit 18 is a change in the three primary colors. 19 is a threshold value generating variable resistor. 20 is a comparison circuit, and addition circuit 18
The signal change output from the threshold value generation variable resistor 19 is compared with the output of the threshold value generating variable resistor 19 to output a register mark determination signal.

<Effects of the Invention> As explained above, according to the inspection device for printed matter with poor registration density according to the present invention, each registration mark is separated into three colors and further subtracted from the total white area output, thereby detecting each registration mark. It is not a foolproof method for accurately detecting density changes, there is no need to replace filters even if the printed color changes, and there is also no need to adjust the offset voltage due to temperature changes or changes over time in the photoelectric conversion element. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an inspection apparatus for printed matter with poor register density according to the present invention. l...Printed material to be inspected 2...Pattern printed area 3...Margin area 5...Register mark (yellow) 6...Register mark (red) 7...Register mark (blue) 8 ...Light source lamp 9...Heat ray absorption filter 1
0...Red reflective dichroic mirror 11...Blue reflective dichroic mirror 12...Red transmission filter [3...Blue transmission filter L4...Green transmission filter

Claims (1)

[Claims] A means for optically scanning the register marks corresponding to each printing color printed serially in the conveyance direction of the printed matter into three primary colors of red, blue and green; means for scanning, means for adding the margin signal obtained by this means and the signal obtained by color separation into the three primary colors, and determining whether or not the added signal exceeds a threshold value of a certain value or more. What is claimed is: 1. An inspection device for inspecting printed matter with poor register density, comprising means for determining register density.