JP2950172B2 - Mark detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mark printed for preventing color misregistration and cutting position control of a web to be multicolored, or a part of a printed pattern for the purpose of controlling these marks. The present invention relates to a mark detection device for detecting.

[0002]

2. Description of the Related Art In the case of performing overprinting on a web such as paper or film using a plurality of plate cylinders, a color shift occurs unless each color is printed in a predetermined position. Since this color misregistration is caused by rotation misregistration of the plate cylinder, web elongation, and the like, each plate cylinder is caused to print a pattern in each color and a register mark is printed at a predetermined position, and the register mark is detected. , Register control for preventing color misregistration is performed. A web on which a pattern or the like is printed on the plate cylinder is cut by a cutting machine for each pattern or the like having the plate cylinder circumference as one unit. In this case, a mark printed using a register mark or for cutting is used. Or a part of the printed picture is used to determine the cutting position and prevent the cutting position from shifting.

As an example of register mark detection, an example of printing on paper by a gravure rotary printing press shown in FIG. 11 will be described. The order of colors to be printed by the plate cylinder is arbitrary. For example, the printing order is such that the first color is yellow, the second color is red, the third color is blue, and the fourth color is black. The web 10 to be printed is unwound from the unwinding reel 1, pressed against the plate cylinder 2 by the impression cylinder 3, and printed by the plate cylinder 2. As many combinations of the plate cylinder 2 and the impression cylinder 3 as the number of colors to be printed on the web 10 are provided.
The compensator roll 5 moves in the direction of the arrow to prevent color misregistration. The guide roll 4 guides the web 10 to the compensator roll 5. The encoder unit 6 rotates in response to the rotation of the plate cylinder 2, and the speed of the web 10 and the rotation of the plate cylinder 2
Is detected and transmitted to the control unit 9. Each plate cylinder 2
Since a, 2b, 2c, and 2d are configured to rotate mechanically synchronously, the encoder unit 6 is installed on one plate cylinder 2b. Since the encoder unit 6 obtains a signal of the traveling amount of the web 10, it may be provided in a feed roll driving mechanism or the like. The register mark detector 7 is provided on the exit side of the second and subsequent plate cylinders 2, detects register marks, and transmits the register marks to the control unit 9. The correction unit 8 moves the compensator roll 5 in the direction indicated by the arrow in accordance with an instruction from the control unit 9 to prevent the register mark from shifting. The control unit 9 outputs control data to the correction unit 8 based on data from the encoder unit 6 and the register mark detector 7.

FIG. 12 shows a register mark printed by each plate cylinder 2 in a blank portion without a picture at the end of the web 10.
The register marks are printed at equal intervals, for example, at 20 mm intervals. The register mark detector 7a controls yellow and red register marks, the register mark detector 7b controls red and blue, and the register mark detector 7c controls blue and black. The register marks are each controlled. Each detector 7a, 7b, 7
c has a main and a sub light receiving element, and each light receiving element controls a predetermined register mark. For example, in the detector 7a, the main light receiving element detects a yellow register mark and the secondary light receiving element detects a red register mark.

[0005] Such a register mark detector includes a light source section for irradiating a detection target such as a register mark or a picture with light, and a light receiving section for receiving reflected light from the target. An incandescent bulb, a halogen lamp, or the like is used as a light source, and a light receiving element such as a silicon photodiode is used for a light receiving unit.

[0006]

Conventionally, incandescent bulbs and halogen lamps have been used as illumination light sources. The background of the web is usually white, and a transparent material such as a film has a reflection plate placed on the back side of the film. Register marks of such colors as black, red, blue, etc. on such a white background,
Although easy to detect, yellow is close to white and difficult to detect. FIG. 13 shows the emission spectrum of an incandescent sphere. The horizontal axis indicates the wavelength, and the vertical axis indicates the voltage value for detecting the luminance. The luminance decreases as the wavelength approaches blue, which is shorter than the wavelength red. In other words, blue light is decreasing. FIG. 14 shows light receiving sensitivity characteristics of a silicon photodiode (SPD) as a light receiving element. The horizontal axis indicates the wavelength, and the vertical axis indicates the voltage obtained by converting the detected current. As in the case of the incandescent light source of FIG. FIG. 15 shows the light receiving characteristics of a detector using the incandescent light source of FIG. 13 and the silicon photodiode of FIG. The horizontal axis indicates the wavelength, and the vertical axis indicates the voltage obtained by converting the detected current. In the following description, the output of the light receiving element is represented as a voltage. As described above, the amount of blue light emitted from the light source is small, and the detecting ability of the light receiving element for detecting the blue light is also small. The reflected light for the yellow printed matter is characterized in that the blue reflected light is smaller than the white background, and the sensitivity of the light receiving element to the blue irradiation light and blue is low, so that it was difficult to detect yellow. For this reason, conventionally, a blue filter or the like that allows blue light to pass through other colors well is provided on the light source side or the light receiving side to improve the yellow-based detection ability. Further, the incandescent bulb and the halogen lamp have a problem that their life is short. Further, in the case of a silicon photodiode or the like, there is another problem that the blue light receiving sensitivity is lower than the red light receiving sensitivity. There is also a drawback that using a blue filter makes it difficult to detect light blue.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to increase the yellow-based detection ability without using a blue filter or the like and to prolong the life of a light source. It is another object of the present invention to separate the reflected light into blue light and red light and adjust the respective detection sensitivities.

[0008]

According to a first aspect of the present invention, there is provided a mark detecting apparatus for detecting a mark or a picture printed on a web, comprising: a first light source having a blue light emitting diode as a light source; A second light source using a red light emitting diode as a light source, mixing means for mixing the blue light source of the first light source and the red light of the second light source and irradiating the object with light, and receiving reflected light from the object. It is provided with a light receiving means for converting the electric signal and an output means for amplifying and outputting the electric signal.

According to a second aspect of the present invention, in the mark detection device for detecting a mark or a picture printed on a web, a first light source using a blue light emitting diode as a light source and a second light source using a red light emitting diode as a light source. Mixing means for mixing the blue light source of the first light source and the red light of the second light source and irradiating the object with light; a separator for separating reflected light from the object into blue light and red light; Blue light receiving means for receiving the blue light from the separator and converting it to a blue electric signal, red light receiving means for receiving the red light from the separator and converting it to a red electric signal, the blue electric signal and the red electric signal Output means for amplifying the respective signals to adjust the light receiving sensitivity characteristics with respect to blue light and red light, and adding and outputting both signals.

According to a third aspect of the present invention, in the mark detection device for detecting a mark or a pattern printed on a web, a first light source using a blue light emitting diode as a light source and a second light source using a red light emitting diode as a light source. Mixing means for mixing the blue light source of the first light source and the red light of the second light source and irradiating the object with light; a separator for separating reflected light from the object into blue light and red light; Blue light receiving means for receiving the blue light from the separator and converting it to a blue electric signal, red light receiving means for receiving the red light from the separator and converting it to a red electric signal, the blue electric signal and the red electric signal And output means for outputting an electrical signal that better represents the characteristic of the register mark or the color of the pattern to be detected.

Further, in the invention according to claim 4, the output means amplifies the blue electric signal and the red electric signal, respectively, adjusts the light receiving sensitivity characteristics for blue light and red light, and then detects the register mark or picture. An electrical signal that better represents the color characteristics of the color is output.

According to the fifth aspect of the invention, the first light source comprises an optical fiber having one end connected to a blue light emitting diode and a lens, and the second light source comprises an optical fiber having one end connected to a red light emitting diode and a lens. It is to become.

Further, in the invention according to claim 6, the first light source comprises a blue light emitting diode arranged in a line.
The light source comprises red light-emitting diodes arranged in a line, and the light receiving means comprises a line sensor.

Further, in the invention according to claim 7, the first light source comprises a blue light emitting diode arranged in a line, the second light source comprises a red light emitting diode arranged in a line,
The blue light receiving means and the red light receiving means are both constituted by line sensors.

In the invention according to claim 8, the separator is a dichroic mirror.

[0016]

The invention of claim 1 will be described with reference to FIG.
The color is recognized as a result of combining monochromatic light or light in a certain wavelength range with various distributions. The relationship between the three primary colors and their complementary colors is schematically shown for explanation. FIG. 7 schematically shows a case where a white background and a yellow register mark are illuminated by a conventional light source, and FIG. 7B is a case where the register mark is illuminated by blue light and red light. Irradiation by a conventional incandescent bulb or halogen lamp corresponds to (A), and irradiation by a blue light emitting diode and a red light emitting diode corresponds to (B). In the case of (A), the irradiation light composed of red and green, which is weaker than that shown in (a), is reflected by the white background shown in (b).
(C) shows the reflected light from the yellow register mark, where blue is absorbed and green and red are reflected. In the case of (B), (a)
In response to the irradiation light of magenta light consisting of red and blue shown in
The white reflection of the ground shown in (b) is red and blue. (C) shows the reflected light from the yellow register mark, where blue is absorbed and red is reflected.

FIG. 8 shows the output of the light receiving means. The horizontal axis of each coordinate is the moving time T of the web, that is, the register mark, and the vertical axis is the voltage V corresponding to the amount of reflected light. FIG. 7A shows an output in the case of substantially white light shown in FIG. 7A, and shows that when a yellow register mark is detected, the output is reduced by the amount h of absorbed blue from the level of the ground (white). FIG. 7B shows the case of magenta light irradiation of FIG. 7B, which shows that the level is reduced by the amount of absorbed blue H from the level of the background (white) when the yellow register mark is detected.
The reason why h in (A) is smaller than H in (B) is that the irradiation light has a small blue component as shown in FIG. 7 (A). This is because there is little change. When the yellow printed matter is irradiated with magenta light consisting of blue and red, the detection sensitivity is improved. Further, the blue and red light emitting diodes serving as light sources have a much longer life than incandescent bulbs and halogen lamps. An incandescent bulb or a halogen lamp generates a large amount of heat, whereas a diode generates a small amount of heat, so that the temperature rise is small. Further, the efficiency of the luminous intensity with respect to the used power is high.

According to the second aspect of the present invention, the reflected light is separated into blue light and red light by the separator so that the light receiving sensitivity characteristic of the light receiving element shown in FIG. Fix it. In the case of the light receiving sensitivity characteristic of FIG. 14, since the sensitivity to blue is low, the detection value of the light receiving element for blue reflected light is amplified and adjusted with the detection value of the light receiving element for red reflected light. After such adjustment, by adding the two detection values, a detection value in which the sensitivity characteristic of the light receiving element is corrected flat with respect to the wavelength can be obtained.

According to the third aspect of the present invention, the reflected light is separated into blue light and red light by a separator, and the values obtained by converting each of the reflected light into a detection value by another light receiving element are examined. The detected value is output. For example, when detecting a yellow register mark, blue reflected light is absorbed, so that a yellow register mark can be detected by detecting a change in the output of the blue light receiving element.

In the invention of claim 4, in the invention of claim 3,
After adjusting the detection value of each light receiving element with an amplifier and adjusting the light receiving sensitivity characteristic of the light receiving element to be almost flat with respect to the wavelength, output the detection value of the one representing the characteristic of the color of the register mark or the picture. I have to. Thus, for example, in the case of detecting a yellow register mark, a change in the detection value from the blue light receiving element becomes large, and the detection accuracy is improved.

According to the fifth aspect of the present invention, the light emitting diode and the condenser lens are provided at one end of the optical fiber, and the light of each diode is condensed, put into the optical fiber and projected. This makes it possible to dispose the light emitting diode away from the position of the register mark on the web. For example, when the installation space is narrow, or when the web is in a dangerous atmosphere, it can be installed at an appropriate position away from the web.

According to a sixth aspect of the present invention, the light emitting diodes of the first light source and the second light source are arranged in an example to form a linear light source, and the reflected light is received by the line sensor. A wide area register mark or picture can be detected.

According to a seventh aspect of the present invention, in each of the second to fourth aspects, the first light source and the light emitting diode of the second light source are arranged in a line to form a linear light source, and the reflected light is used as a line sensor. By receiving light with the blue light receiving unit and the red light receiving unit, a register mark, a picture, or the like having a large area can be detected.

According to the eighth aspect of the present invention, a dichroic mirror is used as the separator of the second to fifth and seventh aspects, and blue light and red light are separated by reflecting one and transmitting the other.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an optical system according to an embodiment of the present invention. Reference numeral 10 denotes a web to be detected, on which a register mark 23, a cutting mark, and a picture are printed. In the case of the transparent web 10, a reflection plate 24 is provided below, and the reflection of the web 10 and the reflection from the reflection plate 24 are combined to form an object. Reference numeral 12 denotes a blue light-emitting diode, and 13 denotes a red light-emitting diode. Each of the light-emitting diodes has a condensing lens 14 disposed in front of the light-emitting diode. The optical axis of the second light source including the lens 14 is orthogonal to the optical axis. A first half mirror 15 inclined at 45 ° with respect to the optical axis from each light source is disposed at the orthogonal intersection, and the blue light of the blue light emitting diode 12 and the red light of the red light emitting diode 13 are mixed to form a magenta light. And irradiate the web 10. A second half mirror 16 inclined at 45 ° is disposed in the irradiation optical path 11 to transmit the irradiation light and reflect the regular reflection light from the web 10. When a film such as a film or aluminum is used as the web 10, specular reflection occurs. In the case of a transparent film, a reflection plate 24 is provided on the lower surface. The specularly reflected light is separated into a blue component and a red component by a dichroic mirror 17, and the blue light receiving element 18 and the red light receiving element 19 are respectively provided.
Incident on. Blue light receiving element 18, red light receiving element 19
Is a silicon photodiode having the same characteristics and has the light receiving sensitivity characteristics shown in FIG.

The dichroic mirror 17 reflects light in a specific wavelength range by a dielectric multilayer film having a different refractive index.
The blue reflection mirror reflects blue and transmits red and green, and the red reflection mirror reflects red and transmits blue and green. In this embodiment, since there is no green color, blue and red can be separated.

The dichroic mirror 17 is integrally formed with the blue light receiving element 18 and the red light receiving element 19, and rotates around a rotation center 20 to a position shown by a broken line. When the web 10 is paper, the irradiating light becomes weaker in the specular reflection light and becomes stronger in the diffuse reflection light. Separate into components. Note that the regular reflection light and the diffuse reflection light path 22
A slit 21 is provided to pass only the upper diffused reflected light and block the other.

FIG. 2 is a block diagram for electrically processing signals received by the blue light receiving element 18 and the red light receiving element 19. The reflected light is converted into a current by each of the light receiving elements 18 and 19, and is converted into a voltage by the current / voltage converters 25a and 25b. Each of the filters 26a and 26b is composed of a capacitor, and extracts a signal change. That is, a change signal when the register mark 23 changes from white on the background of the web 10 to each register mark 23 is extracted. The amplifiers 27a and 27b amplify this change signal. When a light receiving element having light receiving sensitivity characteristics as shown in FIG. 14 is used, the amplification of the output of the blue light receiving element 18 is increased, and the light receiving sensitivity characteristics are increased. Try to be close to flat. The selection of the amplification degree is selected in advance according to the light receiving sensitivity characteristics of the light receiving element to be used. The arithmetic processing unit 28 recognizes the register mark 23 from the value obtained by adding the outputs of the amplifiers 27a and 27b. When any of the outputs of the amplifiers 27a and 27b indicates the characteristic of the register mark 23 of a certain color, the register mark 23 is recognized. The register mark 23 recognized in this manner is sent to the control unit 9 described with reference to FIG. 11 and becomes register control data of each plate cylinder. Alternatively, the data is sent to the cutter and becomes data for determining the cutting position.

FIG. 3A shows the emission spectrum of the light source light of the present embodiment, in which the horizontal axis represents the wavelength and the vertical axis represents the voltage value at which the luminance was measured. 2B shows the waveform of the reflected light of the ground (white) with respect to the light source light shown in FIG. 2A by the arithmetic processing unit in FIG. 2, and is added after being detected and amplified by the blue light receiving element 18 and the red light receiving element 19. FIG. The dashed line S in (B) indicates the light receiving sensitivity characteristics of the silicon photodiode shown in FIG. 14. When the amplifiers 27a and 27b operate at the same amplification factor, the detected value of the waveform shown by the solid line is output as an added value. Is done. The broken line indicates a waveform obtained by increasing the amplification factor of the amplifier 27a for amplifying the blue light side compared to the amplifier 27b for amplifying the red light side and correcting the level of the light source light shown in FIG.

FIG. 4 shows the waveform of the reflected light from the black, red and blue register marks 23. The values obtained by amplifying and adding the outputs of the blue light receiving element 18 and the red light receiving element 19 correspond to these waveforms. (A) is a waveform of the reflected light of the black register mark 23. In the case of black, there should be no reflection and all light should be absorbed. However, since a dark current flows through the light receiving element as a detection current, it is assumed that such a waveform has such a waveform corresponding to the dark current. (B) is the case of the red register mark 23, (C)
Represents the waveform of the reflected wave in the case of the blue register mark 23. In the case of (C), the waveform has a waveform corresponding to the detection value obtained by correcting the light receiving sensitivity characteristic of the light receiving element by the amplifier 27a.

FIG. 5 shows the waveform of the reflected light from the yellow register mark 23. 3A shows the reflected light of the yellow register mark 23, which has a waveform in which blue light is absorbed from the light source light shown in FIG. (B) shows a waveform received by the red light receiving element 19 with respect to the reflected light of the yellow register mark 23, which is almost the same as (A). (C) is a waveform received by the blue light receiving element 18 and almost corresponds to a dark current as a waveform. In the case of the yellow register mark 23, if the detection value of the blue light receiving element 18 is examined, the detection value becomes almost 0, so that the difference from the ground (white) detection value becomes large, and the detection value of the red light receiving element 19 becomes large. Sometimes it is better not to add

FIG. 6 shows the output values of the outputs of the blue light receiving element 18 and the red light receiving element 19 after voltage conversion by the circuit shown in FIG. 2 and correction of the light receiving sensitivity characteristics of the light receiving element by the amplifier circuit. Is shown. The vertical axis indicates voltage, and the horizontal axis indicates position.
Since the difference between black and white on the ground is the largest, the detected value is also large.
Blue has almost the same sensitivity as red because the light sensitivity characteristic has been modified, and yellow has a detection value that is slightly smaller than red and blue but at substantially the same level. Although the gain of each amplifier is adjusted by using the two light receiving elements 18 and 19 in the above-described embodiment, a certain effect can be obtained by using the blue and red light emitting diodes and one light receiving element. In addition, a half mirror may be used instead of the dichroic mirror to separate the reflected light to the two light receiving elements.

In FIG. 1, after the light of the blue and red light emitting diodes is condensed by the condensing lens, the light is directly transferred to the register mark 23.
However, the optical path can be freely changed by using an optical fiber. FIG. 9 shows a case where separate optical fibers are used for light projection and light reception in the optical path of FIG. The light projecting optical fiber 30 and the light receiving optical fiber 31 are each composed of a single thick optical fiber or a bundle of a plurality of thin optical fibers. The light receiving optical fiber 31 shown by the solid line shows the case of regular reflection, and the broken line shows the case of diffuse reflection. FIG. 10 shows a case where the light emitting and receiving optical fibers shown in FIG. 9 are combined into one bundle. The light emitting / receiving optical fiber 32 is separate for the light emitting part 32a and the light receiving part 32b, but the main body 32c is a single bundle.
(B) is an XX cross section of (A). As shown in (B), the main body 32c has a configuration in which a light receiving optical fiber indicated by oblique lines is arranged at the center, and a light projecting optical fiber is arranged around the light receiving optical fiber. The solid line indicates the case of regular reflection, and the broken line indicates the case of diffuse reflection. The handling and arrangement are facilitated by forming the light emitting and receiving lights into one bundle. When an optical fiber is used as shown in FIGS. 9 and 10, light can be emitted and received even in a small installation space, and the mark of the web 10 in a dangerous atmosphere such as gas or steam is installed in a non-hazardous area. It can be detected by a light receiver.

Also, by using blue and red light emitting diodes arranged in a line to form a linear light source and using a line sensor as the light receiving element, a register mark, a picture or the like having a large area can be detected. A one-dimensional CCD image sensor or the like is used as the line sensor. Although the gravure rotary printing press has been described in the above embodiment, the present invention can be similarly applied to an offset rotary printing press. Instead of the silicon diode light receiving element used in the above embodiment, a light receiving element such as a photoelectric tube may be used.

[0035]

As is apparent from the above description, the present invention irradiates magenta light from a blue light emitting diode and a red light emitting diode onto an object to thereby register a register mark such as yellow without using a filter. It can be detected with high accuracy. Further, by dividing the reflected light into blue and red components and electrically calculating the respective signals, the light receiving sensitivity characteristics of the light receiving element can be corrected, and yellow and pale blue can be stably detected. In addition, using a light emitting diode as a light source has a much longer life than an incandescent bulb or a halogen lamp.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an optical system according to an embodiment.

FIG. 2 is a block diagram for electrically processing a signal received by a light receiving element.

FIG. 3A shows an emission spectrum of the light source of the present embodiment, and FIG. 3B shows a detection value of reflected light on a white background by the light source.

4A and 4B show waveforms of reflected light of the present embodiment, wherein FIG. 4A shows a waveform of reflected light of a black register mark, FIG. 4B shows a waveform of reflected light of a register mark of red, and FIG.

5A and 5B show a waveform of reflected light of a yellow register mark of the present embodiment, and FIG. 5A shows a waveform of reflected light of a yellow register mark;
(B) is a waveform of the reflected light received by the red light receiving element, and (C) is a waveform of the reflected light received by the blue light receiving element.

FIG. 6 shows black, blue, red,
It is a figure showing a detection value of a yellow register mark.

7A shows a case where a white background and a yellow register mark are irradiated by an incandescent bulb as a conventional light source, and FIG. 7B shows a case where the register mark is irradiated by a blue light emitting diode and a red light emitting diode.

8A and 8B show the output of the reflected light of the irradiation light shown in FIG. 7 received by the light receiving means, wherein FIG. 8A shows the case of the conventional light source, and FIG. 8B shows the case of the blue and red light emitting diodes.

FIG. 9 is a diagram illustrating a case where an optical fiber is used for the optical path in FIG. 1;

FIG. 10 is a diagram illustrating an optical fiber in which light projecting and light receiving are combined into one bundle.

FIG. 11 is a diagram illustrating register control by register marks of a rotary printing press.

FIG. 12 is a diagram illustrating a print example of a register mark.

FIG. 13 is a diagram showing an emission spectrum of an incandescent sphere.

FIG. 14 is a diagram showing light receiving sensitivity characteristics of a silicon photodiode.

FIG. 15 is a diagram showing optical characteristics of a detector using an incandescent light source and a silicon photodiode.

[Explanation of symbols]

 REFERENCE SIGNS LIST 9 control unit 10 web 11 irradiation light path 12 blue light emitting diode 13 red light emitting diode 14 condensing lens 15 first half mirror 16 second half mirror 17 dichroic mirror 18 light receiving element for blue light 19 light receiving element for red light 20 rotation center 21 slit 23 register Mark 24 reflector 25 current / voltage converter 26 filter 27 amplifier 28 arithmetic processing unit 30 light emitting optical fiber 31 light receiving optical fiber 32 light emitting / receiving optical fiber

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/89 B41F 33/14

Claims (8)

(57) [Claims] 1. A mark detecting device for detecting a mark or a pattern printed on a web, comprising: a first light source having a blue light emitting diode as a light source; a second light source having a red light emitting diode as a light source; Mixing means for mixing the blue light source and the red light of the second light source and irradiating the object with light; light receiving means for receiving reflected light from the object and converting the light into an electric signal; amplifying and outputting the electric signal A mark detection device comprising output means. 2. A mark detecting device for detecting a mark or a pattern printed on a web, wherein a first light source using a blue light emitting diode as a light source, a second light source using a red light emitting diode as a light source, and Mixing means for mixing the blue light source and the red light of the second light source and irradiating the object with light, a separator for separating reflected light from the object into blue light and red light, and a blue light from the separator Blue light receiving means for receiving light and converting it to a blue electric signal, red light receiving means for receiving red light from the separator and converting it to a red electric signal, and amplifying the blue electric signal and the red electric signal, respectively, for blue light And an output means for adjusting the light receiving sensitivity characteristic with respect to red light, and adding and outputting both signals. 3. A mark detecting device for detecting a mark or a picture printed on a web, wherein a first light source using a blue light emitting diode as a light source, a second light source using a red light emitting diode as a light source, and the first light source. Mixing means for mixing the blue light source and the red light of the second light source and irradiating the object with light, a separator for separating reflected light from the object into blue light and red light, and a blue light from the separator Blue light receiving means for receiving and converting to a blue electric signal, red light receiving means for receiving red light from the separator and converting it to a red electric signal, and a register mark for detecting among the blue electric signal and the red electric signal or An output means for outputting an electrical signal that better represents the feature of the color of the picture. 4. The output means amplifies the blue electric signal and the red electric signal, respectively, adjusts the light receiving sensitivity characteristics with respect to blue light and red light, and then well represents the color characteristics of the register mark or picture to be detected. 4. The mark detecting device according to claim 3, wherein the electric signal is outputted. 5. The light source according to claim 1, wherein the first light source comprises an optical fiber having a blue light emitting diode and a lens connected to one end, and the second light source comprises an optical fiber having a red light emitting diode and a lens connected to one end. Item 5. The mark detection device according to any one of Items 1 to 4. 6. The light source according to claim 1, wherein the first light source comprises a blue light emitting diode arranged in a line, the second light source comprises a red light emitting diode arranged in a line, and the light receiving means comprises a line sensor. 2. The mark detection device according to 1. 7. The first light source comprises blue light emitting diodes arranged in a line, the second light source comprises red light emitting diodes arranged in a line, and both the blue light receiving means and the red light receiving means comprise a line sensor. 5. The mark detection device according to claim 2, wherein: 8. The mark detection device according to claim 2, wherein the separator is a dichroic mirror.