JP2014172359A - Light detection element, mark sensor, and method for determining mark by light detection element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light detection element that enables output signals of respective lights easily to make an intensity difference when receiving the lights different in wavelength intensity distribution, and a mark sensor.SOLUTION: A light detection element includes: a light receiving element 31 that has a plurality of photoelectric conversion areas 32a-32c different in spectral sensitivity characteristics; an external terminal 39 that outputs a signal from each of the plurality of photoelectric conversion areas 32a-32c to the outside; and a plurality of switches SW1-SW3 that are provided in paths 41a-41c for connecting the plurality of photoelectric conversion areas 32a-32c and the external terminal 39 together, respectively.

Description

  The present invention relates to a light detection element that converts received light into an electrical signal, a mark sensor using the light detection element, and a mark determination method using the light detection element.

  When multicolor printing is performed by a multicolor printing system, a predetermined mark is printed on a web such as paper or film, the mark is detected by a mark sensor, and a printing position deviation between the plate cylinders is controlled based on the detection result. To do.

  The mark sensor generally includes a light source that irradiates light to the web and a photodiode that receives reflected light from the web and outputs a signal. When the web is irradiated with light, the intensity distribution with respect to the wavelength of the reflected light (hereinafter referred to as wavelength intensity distribution) is generally different between the ground and the mark, and the difference is expressed as the intensity difference of the output signal of the photodiode. . The mark sensor compares the output signal of the photodiode with a predetermined threshold value to determine the presence or absence of a mark (see, for example, Patent Document 1).

JP 05-016337 A

  In the mark sensor, when light having different wavelength intensity distributions is received, the intensity difference between the output signals of each light by the photodiode is preferably as large as possible. Thereby, the influence of noise of the output signal is reduced, and the presence / absence of a mark can be accurately determined. The present inventor has come to recognize that there is room for improvement in a structure that can realize such a requirement.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a light detection element, a mark, and the like that can easily generate an intensity difference in an output signal of each light when receiving light having different wavelength intensity distributions. An object of the present invention is to provide a mark determination method using a sensor and a light detection element.

  One embodiment of the present invention relates to a light detection element. The light detection element includes a light receiving element having a plurality of photoelectric conversion regions having different spectral sensitivity characteristics, an external terminal for outputting a signal from each of the plurality of photoelectric conversion regions, and between the plurality of photoelectric conversion regions and the external terminal. And a plurality of switches provided for each path connecting the two.

  One embodiment of the present invention relates to a mark sensor. The mark sensor is configured to detect the presence or absence of a mark provided on the web based on a light source that emits light to the web, a light detection element that has a light receiving element that receives light from the web, and a signal output from the light detection element. A mark determination unit for determining. The thing of the above-mentioned aspect is used for a photon detection element.

  One embodiment of the present invention relates to a mark determination method using a light detection element. The mark determination method includes a step of irradiating light to a range through which a mark provided on a traveling web passes, receiving light from the web by a light receiving element of a light detection element, and outputting a signal from an external terminal; Determining whether the signal intensity output from the terminal exceeds a predetermined threshold, and when the signal intensity does not exceed the predetermined threshold, the plurality of switches are switched on and off, and the signal is output again. The step and the step of determining whether or not a predetermined threshold is exceeded are repeated. The thing of the above-mentioned aspect is used for a photon detection element.

  According to the photodetector of an aspect of the present invention, when receiving light having different wavelength intensity distributions, an intensity difference can be easily generated in the output signal of each light.

It is a figure which shows the structure of the multicolor printing system in which the mark sensor which concerns on this embodiment is used. It is a figure which shows the structure of the mark sensor in which the photon detection element which concerns on this embodiment is used. It is a circuit diagram which shows the structure of the photon detection element concerning this embodiment. It is a figure which shows the spectral sensitivity characteristic of the light receiving element which concerns on this embodiment. It is a figure which shows the spectral sensitivity characteristic of a photon detection element, and the reflected light intensity distribution of a mark or a base | substrate at the time of an on-off state with a some switch. It is a figure which shows the spectral sensitivity characteristic of a photon detection element, and the reflected light intensity distribution of a mark or a base | substrate when a some switch is another on-off state. It is a figure which shows the flowchart of the mark determination method by the photon detection element which concerns on this embodiment.

  FIG. 1 shows a configuration of a multicolor printing system 60 in which a mark sensor 10 according to an embodiment of the present invention is used.

  The multicolor printing system 60 includes a plurality of printing units 61 and a control device 71. The printing unit 61 includes a plate cylinder 63, an impression cylinder 65, and a mark sensor 10. The web 50 is guided along a predetermined travel route by a guide roll 67, and a color pattern corresponding to the plate cylinder 63 is printed by the plate cylinder 63 and the impression cylinder 65. A predetermined mark is printed on the web 50 by the plate cylinder 63, and the mark is detected by the mark sensor 10. Based on the detection result of the mark sensor 10, the control device 71 determines the displacement of the printing position that occurs between the plate cylinders 63. When there is a shift in the printing position, the control device 71 increases or decreases the rotation amount of the plate cylinder 63 to eliminate the shift.

  FIG. 2 shows the configuration of the mark sensor 10. The mark sensor 10 includes a light source 11, a light detection element 30, and a mark determination unit 73. The light source 11 is a white light source. The light emitted from the light source 11 is applied to the web 50. The reflected light of the light irradiated on the web 50 is collected by the known optical system 13 and received by the light receiving element 31 of the light detecting element 30.

  FIG. 3 shows a circuit configuration of the light detection element 30. The light detection element 30 includes a light receiving element 31, current-voltage conversion circuits 33a to 33c, amplification circuits 35a to 35c, switches SW1 to SW3, an addition circuit 37, and an external terminal 39.

  The light receiving element 31 is an RGB photodiode. The light receiving element 31 has a plurality of photoelectric conversion regions 32a to 32c. FIG. 4 shows the spectral sensitivity characteristics of the light receiving element 31. The spectral sensitivity characteristics Sa to Sc of the regions 32a to 32c are different from each other. The first region 32a has a characteristic Sa having a peak wavelength λR in the red band, the second region 32b has a characteristic Sb having a peak wavelength λG in the green band, and the third region 32c has a peak in the blue band. It has a characteristic Sc having a wavelength λB. Each region 32a to 32c is grounded on the cathode side, converts the received light into a current signal, and outputs it to the anode side. This current signal has a magnitude obtained by integrating the product of the received light intensity (W) and the light receiving sensitivity (A / W) for each wavelength.

  Returning to FIG. 3, a first path 41a, a second path 41b, and a third path 41c are provided between the first area 32a, the second area 32b, and the third area 32c, respectively, with the external terminal 39. In the first path 41a, a first current-voltage conversion circuit 33a, a first amplifier circuit 35a, and a first switch SW1 are provided. The second path 41b is provided with a second current-voltage conversion circuit 33b, a second amplifier circuit 35b, and a second switch SW2. In the third path 41c, a third current-voltage conversion circuit 33c, a third amplifier circuit 35c, and a third switch SW3 are provided.

  The current-voltage conversion circuits 33a to 33c convert the current signals from the photoelectric conversion regions 32a to 32c into voltage signals and output the voltage signals. The amplifier circuits 35a to 35c amplify and output the voltage signals from the current-voltage conversion circuits 33a to 35c. The amplification circuits 35a to 35c amplify at the same rate for each of the paths 41a to 41c to such an extent that signal processing by the mark determination unit 73 is facilitated.

  The switches SW1 to SW3 switch presence / absence of electrical connection of the paths 41a to 41c. The switches SW <b> 1 to SW <b> 3 are manually switched on / off, but may be switched by the mark determination unit 73.

  The adder circuit 37 adds and outputs the voltage signals from the amplifier circuits 35a to 35c of the paths 41a to 41c. The external terminal 39 outputs a signal from the adder circuit 37 to the external mark determination unit 73.

  According to the light detection element 30 described above, only the signals of the specific photoelectric conversion regions 32a to 32c are output from the external terminal 39 to the mark determination unit 73 by switching the switches SW1 to SW3 on and off. For example, when the first switch SW1 is turned on and the second switch SW2 and the third switch SW3 are turned off, only the signal of the first region 32a is output. When the first switch SW1 and the second switch SW2 are turned on and the third switch SW3 is turned off, the signals of the first region 32a and the second region 32b are added by the addition circuit 37 and output.

  The mark determination unit 73 is included in the control device 71. The configuration of the mark determination unit 73 is realized by a CPU, memory, or other LSI of any computer in terms of hardware. The mark determination unit 73 determines the presence / absence of a mark on the web 50 based on a signal output from the light detection element 30. This process is performed by setting a predetermined threshold, comparing the signal intensity output from the light detection element 30 with the threshold, and determining that there is a mark when the signal intensity exceeds the threshold.

  FIG. 5 shows the spectral sensitivity characteristics of the light detection element 30 and the reflected light intensity distribution of the mark and the base. The spectral sensitivity characteristics when the second switch SW2 is turned on and the first switch SW1 and the third switch SW3 are turned off are shown. Only the signal of the second region 32b is output from the photodetecting element 30. Further, the wavelength intensity distribution Sn of the reflected light of the base and the wavelength intensity distribution Sm of the reflected light of the mark are indicated by a two-dot chain line. The peak wavelengths of these wavelength intensity distributions Sn and Sm are approximately the same from the peak wavelength of the spectral sensitivity characteristic Sb of the second region 32b, and the intensity distributions are approximately the same. At this time, the output of the light detection element 30 is proportional to the magnitude obtained by multiplying the multiplied value of the intensity of received light and the light reception sensitivity for each wavelength, so that an intensity difference between output signals hardly occurs between the ground and the mark.

  FIG. 6 shows spectral sensitivity characteristics when the switch SW1 of the light detection element 30 is turned on and the switches SW2 and SW3 are turned off. Only the signal of the first region 32 a is output from the light detection element 30. The peak wavelength of the mark wavelength intensity distribution Sm is closer to the peak wavelength of the spectral sensitivity characteristic Sa of the first region 32a than the underlying wavelength intensity distribution Sn. At this time, the output of the light detection element 30 is larger for the mark than for the ground, and the difference in output signal strength between the ground and the mark is large.

  FIG. 7 shows a flowchart of a mark determination method by the light detection element 30. The operator or mark determination unit 73 turns on only the switch SW1 of the light detection element 30. The light source 11 irradiates light to the range through which the mark of the web 50 passes. The light detection element 30 receives the light from the web 50 by the light receiving element 31, and outputs a signal from the external terminal 39 to the mark determination unit 73 (S12). The mark determination unit 73 determines whether the output signal intensity exceeds a predetermined threshold (S14). In steps S12 and S14, the time from the start of light reception may be measured, and after a predetermined time has elapsed, it may be determined whether the output signal stored within that time exceeds the threshold value.

  If the predetermined threshold is not exceeded (N in S14), the operator or mark determination unit 73 switches on only the switch SW2 (S16), and again outputs step S12 and whether the predetermined threshold is exceeded. The determination step S14 is repeated. If the predetermined threshold is not exceeded, only the switch SW3 is turned on, and steps S12 and S14 are repeated to complete the process. The process is also terminated if the predetermined threshold is exceeded (Y in S14).

  According to the light detection element 30 according to the present embodiment, when light having different wavelength intensity distributions is received, an intensity difference can be easily generated in the output signal of each light only by switching the switches SW1 to SW3 on and off. Thereby, the mark sensor 10 can accurately determine the presence or absence of a mark. Further, since signals from the photoelectric conversion regions 32a to 32c are added by the adder circuit 37 and then output to the external terminal 39, it is not necessary to add signals externally for the mark determination process, and the external structure is compact. Can be

  According to the mark determination method according to the present embodiment, the switches SW1 to SW3 necessary for accurately determining a predetermined mark can be set. In particular, if switching control of the switches SW1 to SW3 is performed by the mark determination unit 73, the setting can be automatically performed, and the work burden on the operator is reduced.

  Note that, as a method of causing an intensity difference in the output signal between the ground and the mark, for example, it is conceivable to use a plurality of light sources having different emission spectra and change the wavelength intensity distribution of the reflected light by switching the light sources. Compared with this method, the light detection element 30 according to the present embodiment does not need to be provided with a plurality of light sources, can simplify the hardware configuration including the optical system of the mark sensor 10, and can reduce the cost of the light detection element 30. There is an advantage that can be manufactured.

  As mentioned above, although this invention was demonstrated based on embodiment, embodiment shows only the principle and application of this invention. In the embodiment, many modifications and arrangements can be made without departing from the spirit of the present invention defined in the claims.

  In the above-described embodiment, the light receiving element 31 having the three photoelectric conversion regions 32a to 32c has been described, but the number of the photoelectric conversion regions may be two or more. The light receiving element 31 may be other than the RGB photodiode. The signals from the photoelectric conversion regions 32 a to 32 c may be output from the external terminal 39 without being added by the adder circuit 37. In this case, for the mark determination process, the external mark determination unit 73 adds signals from the photoelectric conversion regions 32a to 32c. The mark sensor 10 may detect the mark by receiving the transmitted light of the transparent web 50 in addition to the light detection element 30 receiving the reflected light of the web 50.

  In the above-described mark determination method, it is determined whether a predetermined threshold value is exceeded based on a signal output when only one of the switches SW1 to SW3 is on. However, two or more of the switches SW1 to SW3 are on. The determination may be made based on the signal at the time.

  Further, in the mark determination method described above, all the switches SW1 to SW3 are turned on, and steps S12 to S16 are executed when there is no difference in intensity in the output signal even when light having a different wavelength intensity distribution is received. You may make it do. As a result, an intensity difference can be stably generated in the output signal when light having a different wavelength intensity distribution is received while being used as the light detecting element 30 having sensitivity in a wide wavelength band.

10: Mark sensor, 30: Light detecting element, 31: Light receiving element, SW1 to SW3: Switch, 37: Adder circuit, 50: Web

Claims (4)

A light detection element used in a mark sensor of a multicolor printing system,
A light receiving element having a plurality of photoelectric conversion regions having different spectral sensitivity characteristics;
An external terminal for outputting a signal from each of the plurality of photoelectric conversion regions to the outside;
And a plurality of switches provided for each path connecting between the plurality of photoelectric conversion regions and the external terminal.   2. The photodetecting element according to claim 1, further comprising an addition circuit provided between the plurality of switches and the external terminal and adding signals from each of the plurality of photoelectric conversion regions. A light source that illuminates the web;
The photodetecting element according to claim 1 or 2, further comprising a light receiving element that receives light from the web.
A mark sensor, comprising: a mark determination unit that determines presence / absence of a mark provided on a web based on a signal output from the light detection element. Light is irradiated to the range where the mark provided on the traveling web passes, and the light from the web is received by the light receiving element of the light detecting element according to claim 1 or 2, and a signal is output from the external terminal. Steps,
Determining whether the signal intensity output from the external terminal exceeds a predetermined threshold,
When the signal strength does not exceed a predetermined threshold value, the steps of switching on and off the plurality of switches, outputting the signal again, and determining whether the predetermined threshold value is exceeded are repeated. A mark determination method using a light detection element.

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