JPH04305128A - Printed matter inspector - Google Patents

Abstract

PURPOSE:To achieve a higher capacity of detecting defects of a printed matter by a method wherein scanning is performed separately using two filters and two systems of line sensors corresponding thereto and outputs thereof are added being weighted to make sensitivities of color inks equal with relative ease. CONSTITUTION:Multi-color printed matter running is lighted and the resulting reflected light is received and converted into an electrical signal with a line sensor. An inspection of the printed matter is performed based on the electrical signal. Line sensors 1a and 1b employ adhesion line sensors using a crystal semiconductor. A white light source uses a 3-wavelength type fluorescent lamp to perform a high frequency lighting. Adhesion line sensor filters 2a and 2b use interference film filters; the filter 2b is a blue color filter and the filter 2a a red color filter. Output signals of the line sensors 1a and 1b are added up with an inversion addition circuit. The weight of the two outputs varies depending on a ratio of a resistance R1 to that R2 and thus, sensitivity ratios of inks are kept almost constant by adjusting the resistance thereby enabling judgment of defects.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the condition of multicolor printed matter.

0002

[Prior Art] In recent years, in-line inspection of printed matter has been
This demand is becoming stronger as printing presses become faster and more precise. In particular, many printed materials are multicolored, and there is a need for inspection equipment that can inspect multicolored printed materials. Conventionally, a system has been proposed for inspecting printed matter using a line sensor. In particular, for multi-color printed matter, the methods for inspecting after printing in four colors (yellow, red, indigo, and black) are as follows: ■ Separate the colors into three colors using an RGB filter, and input these to three CCD cameras ■ RGB filter rotate and time-divide one C
Input to CD camera■ How to turn on the RGB light source alternately■ CCD
The transmittance of light between 400 and 500 nm is 50
A method of arranging a filter having a transmittance greater than 0 to 700 nm has been proposed (Japanese Patent Laid-Open No. 60-64851).

0003

[Problem to be Solved by the Invention] Method (2) described above requires an optical system to separate the colors into the three colors of RGB and a circuit to process data of the three colors separately, which leads to an increase in the size of the device. result. In addition, ■■ cannot keep up with the increasing printing speed due to time-sharing processing. Although the method (2) cannot separate defects of specific colors, it is superior in terms of making the device more compact and inexpensive. However, when designing a filter, it is necessary to
It is necessary to design a filter that attenuates light in the 700 nm band at a certain rate. Typical filters include: 1) a filter in which a coloring agent is added to glass or plastic; 2) a filter in which multiple thin films are deposited on the glass surface to enable selective light transmission through interference. Due to the characteristics of the colorant in the filter 1), it is difficult to design a filter that transmits light in the 400-500 nm band and absorbs most of the light in the 500-600 nm band. Although the filter 2) can achieve very sharp characteristics, it is difficult to change the ratio depending on the wavelength band, and the sensitivity is not the same depending on the color of the ink.

0004

[Means for Solving the Problems] In view of the above-mentioned problems, the present invention uses two lines of line sensors in which separate filters are arranged between objects, and weights and adds the outputs of the line sensors. The present invention proposes a print inspection device that has the same sensitivity for all ink colors by processing the ink colors separately or by processing the ink colors separately.

[0005] That is, by illuminating a traveling multicolored printed matter,
A line sensor receives the reflected light from the multicolored printed matter, converts it into an electrical signal, and in a device that inspects the printed material based on the electrical signal from the line sensor, it emits light of 400 to 700 nm to illuminate the target. Light from a white light source or mixed light from a blue light source that emits more light in the 400-500 nm band than other wavelength bands and a red light source that emits more light in the 600-700 nm band than other wavelength bands is projected onto the object. The first row of line sensors is equipped with an optical filter that transmits a large amount of light in the 400-500 nm band and an optical filter that transmits a large amount of light in the 600-700 nm band. A second row of line sensors arranged between objects captures images of the same position at the same time or at regular time intervals, and weights and adds the electrical signals output from the two line sensors. A print inspection device featuring:

[0006]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows the configuration of a sensor head according to the present invention. Examples of the white light source 5 include a daylight type or three-wavelength type fluorescent lamp with a continuous spectrum, a rod-shaped halogen lamp, a glow discharge lamp, etc. that achieve high color rendering properties. The object of the present invention can also be achieved by mixing a blue light source and a red light source, such as a method of arranging blue and red color fluorescent lamps in parallel.

Lenses 3a and 3b include gradient index lenses, roof mirror lenses, and the like. Also filter 2
As a and 2b, a color conversion filter made by adding a coloring agent to glass, a sharp cut filter, and an interference film filter can be used.

The line sensors 1a and 1b are realized by a contact line sensor using a crystalline semiconductor, a contact line sensor using a film semiconductor such as α-Si, or the like. In this embodiment, a three-wavelength type fluorescent lamp is used as the white light source and is lit at high frequency. Further, as the lens, a distributed refractive index lens is used, and as the line sensor, interference film filters are used as the α-Si contact line sensor filters 2a and 2b. However, here, the filter 2b uses a blue additive filter, and the filter 2a uses a red additive filter. Figure 3
The spectral distribution of the fluorescent lamp used in this example is also shown in Figure 5.
shows the spectral sensitivity characteristics of the line sensor, and Fig. 6 shows the filter 2.
The spectral transmission characteristics of a and 2b are shown. Further, FIG. 4 shows the reflection spectra of each color ink. The output ratio for each ink obtained by the line sensor without using a filter is yellow:
Magenta: cyan = 1.0: 1.8: 2.1.

[0010] With this method, there are many variations in sensitivity, and cyan defects can be detected, but yellow defects cannot be detected. Therefore, if we configure the configuration as shown in Figure 1, the sensitivity ratio of each ink at line sensor 1a is yellow: magenta: cyan = 1.0: 0.90: 0.34 The sensitivity ratio of each ink at line sensor 1b is yellow : Magenta: Cyan = 1.0: 1.2: 7.5. Here, the output signals are added to the line sensor 1a and the line sensor 1b using an inverting and adding circuit as shown in FIG. Here, the weights of the two outputs change depending on the ratio of R1 and R2. Further, R3 is a resistor that adjusts the output gain. Although not shown, the output of the line sensor includes a circuit for impedance matching and level conversion.

If R1=2R2, the output of the line sensor 1a will be added with twice the weight as compared to the output of the line sensor 1b. At this time, the sensitivity ratio of each ink in the output of the adding circuit is yellow: magenta: cyan = 1.0: 1.05:
0.95, and the sensitivity ratio is almost constant. This output is sent to a printing defect detection circuit, where it is digitized, and defects are determined.

In this embodiment, the outputs of the two line sensors are added together, but there is also a method in which the outputs of the two line sensors are processed separately in parallel, and the line sensor 1a performs defect detection processing for yellow and magenta, and the line sensor 1b performs defect detection processing for cyan. be. Further, in this embodiment, a method of simultaneously scanning the same position is used, but it is also possible to scan different positions and store the data in memory, thereby making correspondence between the two series of output data. Further, although two filters are used here, it is also possible to color-separate the reflected light using a dichroic prism.

[0013]

According to the present invention, the sensitivity of each color ink can be adjusted relatively easily by scanning separately using two filters and two lines of line sensors corresponding to each, and adding the outputs with weights. It is possible to improve the ability to detect defects in printed matter.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of FIG. 1;

FIG. 3 is a spectrum distribution diagram of a light source.

FIG. 4: Light reflection spectrum of printed ink.

[Figure 5] Spectral sensitivity characteristics of the sensor.

FIG. 6: Spectral transmittance characteristics of the filter.

[Explanation of symbols]

1a, 1b Line sensor 2a, 2b filter 3a, 3b Lens 4 Reflector 5 White fluorescent light 6 Printed matter

Claims (2)

[Claims] Claim 1: An apparatus for illuminating a traveling multicolored printed material, receiving reflected light from the multicolored printed material with a line sensor and converting it into an electrical signal, and inspecting the printed material based on the electrical signal from the line sensor. , 40 as illumination of the object
Light from a white light source that emits light in the range of 0 to 700 nm, or
A mixed light of a blue light source that emits more light in the 400 to 500 nm band than other wavelength bands and a red light source that emits more light in the 600 to 700 nm band than other wavelength bands is irradiated onto the object, and the light is reflected. An optical filter that transmits a lot of light in the 400-500 nm band is placed between the first line sensor and the object, and an optical filter that transmits a lot of light in the 600-700 nm band is placed between the object. Printed matter inspection characterized by taking images of the same position simultaneously or at regular time intervals using a second row of line sensors, and weighting and adding the electric signals output from the two line sensors. Device. 2. An apparatus for illuminating a traveling multicolored printed matter, receiving reflected light from the multicolored printed matter with a line sensor and converting it into an electrical signal, and inspecting the printed material based on the electrical signal from the line sensor. For illumination of an object, a white light source that emits light in the 400 to 700 nm band, or a blue light source that emits light in the 400 to 500 nm band with a large amount of light in other wavelength bands, and a blue light source that emits light in the 600 to 700 nm band as another wavelength band. The first row of line sensors and 600-nm line sensors are equipped with an optical filter that irradiates a target object with mixed light from a red light source that emits more light than normal light, and that transmits much of the reflected light in the 400-500 nm band between the objects. A second row of line sensors in which an optical filter that transmits a large amount of light in the ~700 nm band is placed between the objects, images the same position at the same time or at regular time intervals, and The output from the line sensor and the output from the second row of line sensors are processed in parallel, printing defects related to yellow and magenta are detected using the output from the first row of line sensors, and the output from the second row of line sensors is processed. A printed matter inspection device characterized in that it is configured to detect printing defects related to cyan.