U.S. patent application number 12/713681 was filed with the patent office on 2011-03-03 for light detection device and sheet processing apparatus including the same.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Seiji Ikari, Junji Miura.
Application Number | 20110052085 12/713681 |
Document ID | / |
Family ID | 43086122 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110052085 |
Kind Code |
A1 |
Ikari; Seiji ; et
al. |
March 3, 2011 |
LIGHT DETECTION DEVICE AND SHEET PROCESSING APPARATUS INCLUDING THE
SAME
Abstract
An exemplary aspect of the present disclosure, there is provided
a light detection device including a first detecting portion to
detect fluorescence from a first detection position on a conveyor
path along which a sheet is conveyed, a second detecting portion to
detect afterglow from a second detection position on the conveyor
path along which the sheet is conveyed, a lighting portion to apply
excitation light over a range including the first detection
position and not including the second detection position, a first
reference member which includes fluorescent material that emits
fluorescence by being excited by the lighting portion and which
emits reference light toward the first detecting portion, a second
reference member to emit reference light toward the second
detecting portion when the sheet is present at the second detection
position, the reference light not influencing a result of detection
by the second detecting portion, and a correction controller to
correct a result of detection by the first detecting portion based
on the reference light detected by the first detecting portion and
to correct a result of detection by the second detecting portion
based on the reference light detected by the second detecting
portion.
Inventors: |
Ikari; Seiji; (Kanagawa-ken,
JP) ; Miura; Junji; (Kanagawa-ken, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
Tokyo
JP
|
Family ID: |
43086122 |
Appl. No.: |
12/713681 |
Filed: |
February 26, 2010 |
Current U.S.
Class: |
382/224 ;
250/458.1; 250/559.1 |
Current CPC
Class: |
G01N 21/64 20130101;
G07D 7/12 20130101; G06K 9/00456 20130101 |
Class at
Publication: |
382/224 ;
250/458.1; 250/559.1 |
International
Class: |
G06K 9/62 20060101
G06K009/62; G01J 1/58 20060101 G01J001/58; G01N 21/86 20060101
G01N021/86 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 2009 |
JP |
2009-197190 |
Claims
1. A light detection device comprising: a first detecting portion
to detect fluorescence from a first detection position on a
conveyor path along which a sheet is conveyed; a second detecting
portion to detect afterglow from a second detection position on the
conveyor path along which the sheet is conveyed; a lighting portion
to apply excitation light over a range including the first
detection position and not including the second detection position;
a first reference member to emit reference light toward the first
detecting portion, the first reference member including fluorescent
material which emits fluorescence by being excited by the lighting
portion; a second reference member to emit reference light toward
the second detecting portion when the sheet is present at the
second detection position, the reference light not influencing a
result of detection by the second detecting portion; and a
correction controller to correct a result of detection by the first
detecting portion based on the reference light detected by the
first detecting portion and to correct a result of detection by the
second detecting portion based on the reference light detected by
the second detecting portion.
2. The light detection device according to claim 1, wherein the
second reference member is disposed to be separated from the second
detection position by a predetermined distance along an optical
path, and emits diffuse reference light.
3. The light detection device according to claim 2, wherein the
second reference member includes fluorescent material which emits
fluorescence by being excited by the lighting portion, and is
disposed at a position which the light emitted from the lighting
portion enters.
4. The light detection device according to claim 2, further
comprising: a light guide to receive the reference light emitted
from the first reference member, and to guide the received
reference light so that the received reference light enters the
second reference member, wherein the second reference member
diffusely reflects the reference light entering through the light
guide.
5. The light detection device according to claim 2, further
comprising: a light guide to receive the reference light emitted
from the first reference member, and to guide the received
reference light so that the received reference light enters the
second reference member; and a reflector to reflect incident light,
wherein the second reference member diffusely transmits the
reference light entering through the light guide, and the reflector
reflects the reference light diffused by the second reference
member and causes the reference light diffused by second reference
member to enter the second detecting portion.
6. The light detection device according to claim 2, wherein the
predetermined distance is set based on a detected transmittance of
the sheet and a detected intensity of light emitted by the second
reference member.
7. A sheet processing apparatus comprising: a conveyor path to
convey a sheet; a first detecting portion to detect fluorescence
from a first detection position on the conveyor path along which
the sheet is conveyed; a second detecting portion to detect
afterglow from a second detection position on the conveyor path
along which the sheet is conveyed; a lighting portion to apply
excitation light over a range including the first detection
position and not including the second detection position; a first
reference member to emit reference light toward the first detecting
portion, the first reference member including fluorescent material
which emits fluorescence by being excited by the lighting portion;
a second reference member to emit reference light toward the second
detecting portion when the sheet is present at the second detection
position, the reference light not influencing a result of detection
by the second detecting portion; a correction controller to correct
a result of detection by the first detecting portion based on the
reference light detected by the first detecting portion and to
correct a result of detection by the second detecting portion based
on the reference light detected by the second detecting portion; a
determination portion to determine whether or not the sheet
contains each of fluorescent printed information and phosphorescent
printed information, based on a fluorescent image detected by the
first detecting portion and an afterglow image detected by the
second detecting portion; and a classification processor to
determine a type of the sheet based on a result of the
determination by the determination portion and to classify the
sheet by type.
8. The sheet processing apparatus according to claim 7, wherein the
second reference member is disposed to be separated from the second
detection position by a predetermined distance along an optical
path, and emits diffuse reference light.
9. The sheet processing apparatus according to claim 8, wherein the
second reference member includes fluorescent material which emits
fluorescence by being excited by the lighting portion, and is
disposed at a position which the light emitted from the lighting
portion enters.
10. The sheet processing apparatus according to claim 8, further
comprising: a light guide to receive the reference light emitted
from the first reference member, and to guide the received
reference light so that the received reference light enters the
second reference member, wherein the second reference member
diffusely reflects the reference light entering through the light
guide.
11. The sheet processing apparatus according to claim 8, further
comprising: a light guide to receive the reference light emitted
from the first reference member, and to guide the received
reference light so that the received reference light enters the
second reference member; and a reflector to reflect incident light,
wherein the second reference member diffusely transmits the
reference light entering through the light guide, and the reflector
reflects the reference light diffused by the second reference
member and causes the reference light diffused by the second
reference member to enter the second detecting portion.
12. The sheet processing apparatus according to claim 8, wherein
the predetermined distance is set based on a detected transmittance
of the sheet and a detected intensity of light emitted by the
second reference member.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2009-197190, filed on
Aug. 27, 2009, the entire contents of all of which are incorporated
herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a light detection device
for detecting light from a sheet being conveyed, and a sheet
processing apparatus including the same.
BACKGROUND
[0003] Heretofore, sheet processing apparatuses for counting and
distinguishing various sheets such as banknotes have been brought
to practical use. A sheet processing apparatus takes in sheets
inserted in an insert portion one by one and conveys the sheets to
a light detection device. The light detection device detects light
from each of the sheets and acquires an image based on the detected
light. The sheet processing apparatus determines the type and
authenticity of the sheet based on the acquired image. The sheet
processing apparatus also determines whether or not the sheet can
be recirculated, based on the acquired image. The sheet processing
apparatus stacks the sheets in a state in which the sheets are
classified by type based on results of the determinations.
[0004] On sheets to be processed by the sheet processing apparatus,
there are printed fluorescent printed information (first printed
information) and phosphorescent printed information (second printed
information). The fluorescent printed information is information
printed in ink (fluorescent ink) containing fluorescent material.
The fluorescent material is excited by excitation light (e.g.,
ultraviolet rays) or the like emitted from an excitation light
source. The excited fluorescent material emits light
(fluorescence). When the irradiation with the excitation light is
interrupted, the fluorescent material stops emitting
fluorescence.
[0005] The phosphorescent printed information is information
printed in ink (phosphorescent ink) containing phosphorescent
material. The phosphorescent material is excited by excitation
light (e.g., ultraviolet rays) or the like emitted from an
excitation light source. The excited phosphorescent material emits
light. When the irradiation with the excitation light is
interrupted, the phosphorescent material emits light (afterglow)
which gradually attenuates with time.
[0006] Japanese Patent No. 3790931, for example, discloses a light
detection device including an excitation light source, a sensor for
detecting fluorescence, and a sensor for detecting
phosphorescence.
[0007] In general, a light detection device for detecting
fluorescence and phosphorescence includes a fluorescence detecting
portion on the upstream side of a conveyor path along which sheets
are conveyed. Further, the light detection device includes a
phosphorescence detecting portion downstream of the fluorescence
detecting portion.
[0008] The fluorescence detecting portion irradiates a sheet with
excitation light from an excitation light source to excite the
fluorescent and phosphorescent materials. The fluorescence
detecting portion detects fluorescence emitted from the excited
fluorescent material and reads fluorescent printed information.
[0009] The phosphorescence detecting portion detects afterglow
emitted from the phosphorescent material after interruption of the
irradiation with the excitation light by the fluorescence detecting
portion, and reads phosphorescent printed information.
[0010] The amount of light emitted by the excitation light source
changes due to aging. Also, the sensitivities of the sensors of the
detecting portions may change. For these reasons, light detection
devices have generally been brought to practical use, each of which
includes a fluorescent reference plate in the vicinity of a
detection position of a detecting portion.
[0011] In this case, the fluorescence detecting portion includes a
fluorescent glass as a fluorescent reference plate. The fluorescent
glass emits fluorescence as a detection reference toward a sensor.
The sensor and the fluorescent glass are disposed to face each
other across a conveyor path of a sheet processing apparatus. The
fluorescence detecting portion detects fluorescence emitted from
the fluorescent glass while no sheets are being conveyed. The
fluorescence detecting portion corrects the amount of light emitted
by a light emitting element or the sensitivity of the sensor based
on the value of the detected fluorescence.
[0012] However, light from an excitation light source does not
reach a detection position of a phosphorescence detecting portion.
Accordingly, if a fluorescent glass is disposed at the detection
position of the phosphorescence detecting portion, the fluorescent
glass is not excited. Thus, there has been the problem that
correction cannot be performed on a sensor of the phosphorescence
detecting portion.
SUMMARY
[0013] An object of the present invention is to provide a light
detection device in which correction can be performed on a
fluorescence detecting portion and a phosphorescence detecting
portion, and a sheet processing apparatus including this light
detection device.
[0014] An aspect of the present disclosure relates to a light
detection device containing a first detecting portion to detect
fluorescence from a first detection position on a conveyor path
along which a sheet is conveyed; a second detecting portion to
detect afterglow from a second detection position on the conveyor
path along which the sheet is conveyed; a lighting portion to apply
excitation light over a range including the first detection
position and not including the second detection position; a first
reference member to emit reference light toward the first detecting
portion, the first reference member including fluorescent material
which emits fluorescence by being excited by the lighting portion;
a second reference member to emit reference light toward the second
detecting portion when the sheet is present at the second detection
position, the reference light not influencing a result of detection
by the second detecting portion; and a correction controller to
correct a result of detection by the first detecting portion based
on the reference light detected by the first detecting portion and
to correct a result of detection by the second detecting portion
based on the reference light detected by the second detecting
portion.
[0015] Another aspect of the present disclosure relates to a sheet
processing apparatus containing: a conveyor path to convey a sheet;
a first detecting portion to detect fluorescence from a first
detection position on the conveyor path along which the sheet is
conveyed; a second detecting portion to detect afterglow from a
second detection position on the conveyor path along which the
sheet is conveyed; a lighting portion to apply excitation light
over a range including the first detection position and not
including the second detection position; a first reference member
to emit reference light toward the first detecting portion, the
first reference member including fluorescent material which emits
fluorescence by being excited by the lighting portion; a second
reference member to emit reference light toward the second
detecting portion when the sheet is present at the second detection
position, the reference light not influencing a result of detection
by the second detecting portion; a correction controller to correct
a result of detection by the first detecting portion based on the
reference light detected by the first detecting portion and to
correct a result of detection by the second detecting portion based
on the reference light detected by the second detecting portion; a
determination portion to determine whether or not the sheet
contains each of fluorescent printed information and phosphorescent
printed information, based on a fluorescent image detected by the
first detecting portion and an afterglow image detected by the
second detecting portion; and a classification processor to
determine a type of the sheet based on a result of the
determination by the determination portion and to classify the
sheet by type.
DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view showing an example of the
configuration of a sheet processing apparatus according to one
embodiment;
[0017] FIG. 2 is a schematic front view showing an example of the
configuration of the sheet processing apparatus shown in FIG.
1;
[0018] FIG. 3 is a block diagram showing the configuration of a
control system of the sheet processing apparatus shown in FIGS. 1
and 2;
[0019] FIG. 4 is a simplified diagram schematically showing the
configuration of a light detection device according to a first
embodiment;
[0020] FIG. 5 is a schematic diagram showing an example of disposed
positions of the portions shown in FIG. 4;
[0021] FIGS. 6A and 6B are schematic diagrams for explaining light
emitted from a second fluorescent reference plate shown in FIG.
4;
[0022] FIGS. 7A and 7B are schematic diagrams for explaining light
emitted from a second fluorescent reference plate shown in FIG.
4;
[0023] FIG. 8 is a graph for explaining the relationship between
light transmitted through a sheet and an elongation distance;
[0024] FIG. 9 is a simplified diagram for schematically showing the
configuration of a light detection device according to a second
embodiment; and
[0025] FIG. 10 is a simplified diagram for schematically showing
the configuration of a light detection device according to a third
embodiment.
DETAILED DESCRIPTION
[0026] Hereinafter, a light detection device according to a first
embodiment of the present invention and a sheet processing
apparatus including this light detection device will be described
in detail with reference to the drawings.
[0027] FIGS. 1 and 2 are views for explaining an example of the
configuration of a sheet processing apparatus 111 according to the
first embodiment of the present invention. The sheet processing
apparatus 111 inspects sheets, and bands sheets qualified for
recirculation.
[0028] As shown in FIG. 1, the sheet processing apparatus 111 has,
on the outside thereof, an insert portion 112, an operating portion
136, an operation/display panel 137, a door 138, a take-out port
139, and a keyboard 140.
[0029] The insert portion 112 is intended for the insertion of
sheets. The insert portion 112 receives a pile of sheets
collectively. The operating portion 136 receives various operation
inputs from an operator. The operation/display panel 137 displays
various operation guides, processing results, and the like to the
operator. Here, the operation/display panel 137 may be configured
as a touch screen. In this case, the sheet processing apparatus 111
detects various operation inputs based on buttons displayed on the
operation/display panel 137 and operations performed on the
operation/display panel 137 by the operator.
[0030] The door 138 is used for opening and closing an insert
cavity of the insert portion 112. The take-out port 139 is intended
for taking out sheets from a stacker stacked with sheets
disqualified for the recirculation by the sheet processing
apparatus 111. The keyboard 140 receives various operation inputs
from the operator.
[0031] As shown in FIG. 2, the sheet processing apparatus 111 has
therein, the insert portion 112, a take-out portion 113, an
absorption roller 114, a conveyor path 115, an inspection portion
116, gates 120 to 125, a rejection sheet conveyor path 126, a
rejection sheet stacker 127, stack/band portions 128 to 131 a
cutting portion 133, and a stacker 134. The sheet processing
apparatus 111 further includes a main controller 151 for
comprehensively controlling the operation of each portion of the
sheet processing apparatus 111.
[0032] The take-out portion 113 is provided above the insert
portion 112. The take-out portion 113 has the absorption roller
114. The absorption roller 114 is provided to be in contact with
the top, in the stacking direction, of a stack of sheets set in the
insert portion 112. Specifically, when the absorption roller 114
rotates, the sheets set in the insert portion 112 are taken into
the apparatus one by one from the top of the stack in the stacking
direction. The absorption roller 114 has the function of, for
example, taking out one sheet per revolution. Thus, the absorption
roller 114 takes out sheets at a constant pitch. Each of the sheets
taken in by the absorption roller 114 is guided to the conveyor
path 115.
[0033] The conveyor path 115 is a conveyor portion for conveying
the sheets to each portion of the sheet processing apparatus 111.
The conveyor path 115 includes a conveyor belt, a drive pulley, and
the like, which are not shown. In the conveyor path 115, the
conveyor belt is operated by an unillustrated drive motor. In the
conveyor path 115, the sheets taken in by the absorption roller 114
are conveyed by the conveyor belt at a constant speed. It should be
noted that in the following description, the side of the conveyor
path 115 closer to the take-out portion 113 is referred to as an
upstream side, and the side of the conveyor path 115 closer to the
stacker 134 is referred to as a downstream side.
[0034] The inspection portion 116 is provided along the conveyor
path 115 extending from the take-out portion 113. The inspection
portion 116 includes an image reader 117, an image reader 118, a
thickness inspection portion 119, and a light detection device 135.
The inspection portion 116 detects optical characteristic
information and magnetic characteristic information on a sheet.
Based on the information, the sheet processing apparatus 111
determines the type of the sheet. The sheet processing apparatus
111 also determines the degree of wear and soiling of the sheet.
The sheet processing apparatus 111 further determines the
orientation of the sheet in regard to the front and reverse sides.
The sheet processing apparatus 111 still further determines whether
the sheet is genuine or forged.
[0035] The image readers 117 and 118 are provided to face each
other across the conveyor path 115. The image readers 117 and 118
read images on both sides of the sheet being conveyed along the
conveyor path 115. Each of the image readers 117 and 118 includes a
CCD camera. The sheet processing apparatus 111 acquires pattern
images on the front and reverse sides of the sheet based on the
images captured by the image readers 117 and 118.
[0036] The image readers 117 and 118 temporarily respectively store
the read images in unillustrated memory in the inspection portion
116. In accordance with operation inputs, the images stored in this
memory are displayed on the operation/display panel 137 by the
sheet processing apparatus 111.
[0037] The thickness inspection portion 119 inspects the thickness
of the sheet being conveyed along the conveyor path 115. For
example, in the case where the detected thickness is not less than
a specified value, the sheet processing apparatus 111 detects a
double taking of sheets.
[0038] The light detection device 135 detects fluorescence and
afterglow from the sheet being conveyed along the conveyor path 115
to acquire fluorescent printed information and phosphorescent
printed information. The light detection device 135 will be
described in detail later.
[0039] The inspection portion 116 includes a magnetic sensor, which
are not shown, and the like. The magnetic sensor detects magnetic
characteristic information on the sheet.
[0040] The gates 120 to 125 are disposed in this order downstream
of the inspection portion 116 along the conveyor path 115. The
gates 120 to 125 are controlled by the main controller 151. The
main controller 151 controls the operation of the gates 120 to 125
based on results of inspections by the inspection portion 116.
Thus, the main controller 151 performs control so that the sheet
being conveyed along the conveyor path 115 may be conveyed to a
predetermined processing portion.
[0041] Through the gate 120 disposed immediately behind the
inspection portion 116, the rejection sheet conveyor path 126
branches off from the conveyor path 115. Specifically, the main
controller 151 switches opening and closing of the gate 120 so that
only illegal sheets, uninspectable notes and the like may be
conveyed to the rejection sheet conveyor path 126. Here, the
illegal sheets are sheets determined to be non-authorized sheets
(legal sheets) based on results of inspections by the inspection
portion 116, and the uninspectable notes are notes not inspectable
by the inspection portion 116.
[0042] At the end of the rejection sheet conveyor path 126, the
rejection sheet stacker (rejection portion) 127 is provided. The
rejection, sheet stacker 127 is stacked with the aforementioned
rejected sheets and uninspectable notes without any turn from the
state where the sheets and notes are taken out by the take-out
portion 113. The sheets stacked in the rejection sheet stacker 127
can be taken out through the take-out port 139.
[0043] At ends of paths branched off by the gates 121 to 124, the
stack/band portions 128 to 131 (collectively referred to as a
stack/band unit 132) are provided, respectively. In the stack/band
unit 132, sheets qualified for the recirculation are stacked to be
classified by type and orientation in regard to front and reverse
sides. The stack/band unit 132 bands and stores the stacked sheets
in bundles of a predetermined number each.
[0044] At the end of a path branched off by the gate 125, the
cutting portion 133 is disposed. The cutting portion 133 cuts
sheets and stores the cut sheets. It should be noted that the
sheets conveyed to the gate 125 are authorized sheets determined to
be unfit for recirculation. At the end of the other path branched
off by the gate 125, the stacker 134 is disposed. In the case where
a worn-note cutting mode is selected, the main controller 151
controls the gate 125 so that sheets may be conveyed to the cutting
portion 133. On the other hand, in the case where the worn-note
cutting mode is not selected, the main controller 151 controls the
gate 125 so that sheets may be conveyed to the stacker 134.
[0045] The main controller 151 counts sheets stacked in the
stack/band unit 132 and counts sheets cut by the cutting portion
133.
[0046] FIG. 3 is a block diagram for explaining an example of the
configuration of a control system of the sheet processing apparatus
111 shown in FIGS. 1 and 2. As shown in FIG. 3, the inspection
portion 116, a conveyor controller 152, a stack/band controller
153, the operation/display panel 137, the keyboard 140, and the
like are connected to the main controller 151, which
comprehensively controls the entire apparatus.
[0047] The main controller 151 is responsible for the overall
control of the sheet processing apparatus 111. The main controller
151 controls the conveyor controller 152 and the stack/band
controller 153 based on an operation signal inputted through the
operation/display panel 137 and results of inspections by the
inspection portion 116.
[0048] The inspection portion 116 includes the image readers 117
and 118, the thickness inspection portion 119, the light detection
device 135, sensors 154, and a CPU 155.
[0049] The image readers 117 and 118 read images on both sides of a
sheet being conveyed along the conveyor path 115. The thickness
inspection portion 119 inspects the thickness of the sheet being
conveyed along the conveyor path 115.
[0050] The light detection device 135 detects fluorescence and
afterglow from the sheet being conveyed along the conveyor path 115
to acquire fluorescent printed information and phosphorescent
printed information.
[0051] The sensors 154 are, for example, a magnetic sensor and the
like. The magnetic sensor detects magnetic characteristic
information from the sheet being conveyed along the conveyor path
115.
[0052] The CPU 155 determines the type, the degree of wear and
soiling, the orientation in regard to the front and reverse sides,
the authenticity, and the like of the sheet being conveyed along
the conveyor path 115 based on results of inspections by the image
readers 117 and 118, the thickness inspection portion 119, the
light detection device 135, the sensors 154, and the like.
[0053] The conveyor controller 152 controls the take-out portion
113, the conveyor path 115, the rejection sheet conveyor path 126,
and the gates 120 to 125 under the control of the main controller
151. Thus, the conveyor controller 152 controls the taking in and
conveyance of sheets. The conveyor controller 152 also performs a
classification process for classifying determined sheets by type.
In other words, the conveyor controller 152 functions as a
classification portion.
[0054] The stack/band controller 153 controls the rejection sheet
stacker 127 and the stack/band portions 128 to 131 under the
control of the main controller 151. Thus, the stack/band controller
153 controls the stacking and banding of sheets.
[0055] It is assumed that on sheets to be processed by the sheet
processing apparatus 111 according to this embodiment, fluorescent
printed information (first printed information) is printed in
fluorescent ink containing fluorescent material and phosphorescent
printed information (second printed information) is printed in
phosphorescent ink containing phosphorescent material, for
example.
[0056] Fluorescent and phosphorescent materials are excited by
excitation light such as light, heat, ultraviolet rays, or X-rays
from outside to emit light. The amounts of light emitted by
fluorescent and phosphorescent materials increase with increasing
excitation light irradiation time. The amounts of light emitted by
fluorescent and phosphorescent materials become saturated in the
case where excitation light irradiation time reaches emission
saturation time. Emission saturation time is the time required to
saturate the amount of light emitted by fluorescent or
phosphorescent material. Emission saturation time depends on
characteristics of material.
[0057] Fluorescent and phosphorescent materials transition to
non-emitting states when decay time has elapsed since emission
saturation. Decay time is the time it takes for fluorescent or
phosphorescent material to transition from a state in which an
emission amount is saturated to a non-emitting state. Decay time
also depends on characteristics of the material of fluorescent or
phosphorescent material.
[0058] The emission saturation time of fluorescent material is
shorter than that of phosphorescent material. The decay time of
fluorescent material is also shorter than that of phosphorescent
material.
[0059] Accordingly, the light detection device 135 of this
embodiment irradiates the fluorescent and phosphorescent materials
with excitation light until the amounts of light emitted by the
fluorescent and phosphorescent materials become sufficiently
saturated. When time corresponding to the decay time of the
fluorescent material has elapsed since the irradiation with the
excitation light has been interrupted, the fluorescent material
transitions to a state in which fluorescence is not emitted. By
detecting light with this timing, the light detection device 135
can detect only phosphorescence (afterglow) emitted by the
phosphorescent material.
[0060] FIG. 4 is an explanatory diagram schematically showing the
configuration of the light detection device 135 shown in FIGS. 2
and 3. As shown in FIG. 4, the light detection device 135 is
provided in the vicinity of the conveyor path 115 which includes a
drive pulley 1, a conveyor belt 2, and the like. Sheets P is
conveyed along the conveyor path 115 in the direction indicated by
arrow a.
[0061] The light detection device 135 includes a lighting portion
3, first and second detecting portions 4 and 5, an amp circuit 6, a
signal processor 7, a controller 8, a correction controller 9,
first and second fluorescent reference plates 10 and 11, and a
shield plate 12.
[0062] The lighting portion 3 emits excitation light, e.g.,
ultraviolet rays or the like. The lighting portion 3 applies the
excitation light to a sheet P being conveyed along the conveyor
path 115. The lighting portion 3 emits light over a range including
at least a detection position A of the first detecting portion
4.
[0063] The lighting portion 3 includes, for example, a fluorescent
tube outputting ultraviolet rays or a cold-cathode tube. The
lighting portion 3 can continuously emit ultraviolet rays by a
high-frequency voltage being applied thereto.
[0064] In recent years, the luminance of LED lamps have been
increased. Accordingly, a lighting device may be employed in which
LED lamps are arranged in an array along the conveyor path 115.
Alternatively, a lighting device may be employed which emits light
toward a detection position using a light source, such as a mercury
lamp, that emits light containing ultraviolet rays.
[0065] This embodiment is described by taking as examples
fluorescent material and phosphorescent material which emit light
by being irradiated with ultraviolet rays. However, the present
invention is not limited to this. For example, in the case where
fluorescent material and phosphorescent material which emit light
by being excited by infrared rays are detected, the lighting
portion 3 includes a lighting device which outputs infrared rays.
In other words, the lighting portion 3 is appropriately modified in
accordance with characteristics of substances to be detected.
[0066] Each of the first and second detecting portions 4 and 5
includes, for example, a CMOS or CCD line image sensor and a lens
for receiving light. Specifically, the first detecting portion 4
includes a lens 41 and a sensor 42. On the other hand, the second
detecting portion 5 includes a lens 51 and a sensor 52.
[0067] The lens 51 receives light from the predetermined detection
position A on the conveyor path 115. The lens 41 images the
received light onto the sensor 42. The sensor 42 converts the
received light into an electric signal. The lens 51 receives light
from a predetermined detection position B on the conveyor path 115.
The lens 51 images the received light onto the sensor 52. The
sensor 52 converts the received light into an electric signal.
[0068] In the case where the first and second detecting portions 4
and 5 perform color separation on the detected light, the first and
second detecting portions 4 and 5 include array sensors such as
color line image sensors. In the case where the first and second
detecting portions 4 and 5 do not need to perform color separation,
the first and second detecting portions 4 and 5 include monochrome
image sensors, photodiode arrays, or the like. In the case where
the first and second detecting portions 4 and 5 do not need to have
widths in the scanning directions, the first and second detecting
portions 4 and 5 may be formed by a single light receiving
element.
[0069] The first and second detecting portions 4 and 5 may include,
for example, back-thinned image sensors. The first and second
detecting portions 4 and 5 may further include TDI (Time Delay
Integration) image sensors or the like.
[0070] In the case where the first and second detecting portions 4
and 5 are formed by a single light receiving element, the first and
second detecting portions 4 and 5 may be formed by an avalanche
photodiode, a photomultiplier tube, or the like.
[0071] The first detecting portion 4 detects fluorescence from the
sheet P. The second detecting portion 5 detects afterglow from the
sheet P.
[0072] The amp circuit 6 amplifies signals detected by the first
and second detecting portions 4 and 5. The amp circuit 6 includes
an amplifier 61 for amplifying a signal detected by the first
detecting portion 4 and an amplifier 62 for amplifying a signal
detected by the second detecting portion 5. The gains of the
amplifiers are controlled by the correction controller 9. The amp
circuit 6 transmits amplified signals to the signal processor
7.
[0073] The signal processor 7 receives the signals transmitted from
the amp circuit 6. The signal processor 7 performs
analog-to-digital conversion (A/D conversion) of the received
signals. The signal processor 7 acquires image information as
results of the A/D conversion. In other words, the signal processor
7 samples the received signals to acquire image information.
[0074] The acquired image information corresponds to per-line light
detected by the first and second detecting portions 4 and 5. The
signal processor 7 performs the above-described processing for the
entire sheet P. Thus, the signal processor 7 acquires a fluorescent
image and an afterglow image of the sheet P.
[0075] The controller 8 is responsible for the overall control of
the light detection device 135. The controller 8 includes a CPU, a
buffer memory, a program memory, a nonvolatile memory, and the
like. The CPU performs various kinds of arithmetic processing. The
buffer memory temporarily stores results of arithmetic by the CPU.
The program memory and the nonvolatile memory stores various
programs executed by the CPU, control data, and the like. The
controller 8 can perform various kinds of processing by the CPU
executing programs stored in the program memory.
[0076] For example, the controller 8 controls the respective
timings with which the first and second detecting portions 4 and 5
detect light. The nonvolatile memory of the controller 8 stores
reference data beforehand. The controller 8 compares the image
information detected from the sheet P and the reference data stored
in the nonvolatile memory. The controller 8 determines, based on
the result of the comparison, whether or not the image information
detected from the sheet P contains fluorescent printed information
and phosphorescent printed information. In other words, the
controller 8 functions as a determination portion.
[0077] The correction controller 9 controls the respective gains of
the amplifiers 61 and 62 of the amp circuit 6. The correction
controller 9 controls the gain of the amplifier 61 in accordance
with the level of reference light emitted from the first
fluorescent reference plate 10. The correction controller 9 also
controls the gain of the amplifier 62 in accordance with the level
of reference light emitted from the second fluorescent reference
plate 11.
[0078] The light intensity of afterglow is weaker than that of
fluorescence. In other words, in the case where the gains of the
amplifiers 61 and 62 have the same value, a signal detected by the
second detecting portion 5 is weaker than a signal detected by the
first detecting portion 4. For this reason, the correction
controller 9 sets the gain of the amplifier 62 higher than the gain
of the amplifier 61. This enables the light detection device 135 to
obtain signals on comparable levels for fluorescence and
afterglow.
[0079] The first fluorescent reference plate 10 supplies the first
detecting portion 4 with reference light for use in correcting the
gain of the amplifier 61 of the amp circuit 6. In other words, the
first fluorescent reference plate 10 functions as a reference
member for supplying the first detecting portion 4 with the
reference light. The first fluorescent reference plate 10 is
disposed at a position facing the first detecting portion 4 across
the conveyor path 115. Further, the first fluorescent reference
plate 10 is disposed at least on an extension of a line connecting
the first detecting portion 4 and the detection position A.
[0080] The first fluorescent reference plate 10 includes, for
example, glass (fluoroglass) or the like containing fluorescent
material. For example, in the case where ultraviolet rays are
applied to fluoroglass, the fluorescent material contained in the
fluoroglass emits fluorescence. Specifically, when the excitation
light is applied to the first fluorescent reference plate 10, the
first fluorescent reference plate 10 emits fluorescence toward the
first detecting portion 4. In other words, when there is no sheet P
at the detection position A, at least part of the first fluorescent
reference plate 10 appears in an image captured by the first
detecting portion 4.
[0081] The second fluorescent reference plate 11 supplies the
second detecting portion 5 with reference light for use in
correcting the gain of the amplifier 62 of the amp circuit 6. In
other words, the second fluorescent reference plate 11 functions as
a reference member for supplying the second detecting portion 5
with the reference light. The second fluorescent reference plate 11
is disposed at a position facing the second detecting portion 5
across the conveyor path 115. Further, the second fluorescent
reference plate 11 is disposed at least on an extension of a line
connecting the second detecting portion 5 and the detection
position B. It should be noted that the second fluorescent
reference plate 11 is disposed to be separated from the detection
position B by a distance L. In other words, when there is a sheet P
at the detection position B, a space having the distance L exists
between the sheet P and the second fluorescent reference plate
11.
[0082] The second fluorescent reference plate 11 includes, for
example, glass (fluoroglass) or the like containing fluorescent
material. For example, in the case where ultraviolet rays are
applied to fluoroglass, the fluorescent material contained in the
fluoroglass emits fluorescence. Specifically, when the excitation
light is applied to the second fluorescent reference plate 11, the
second fluorescent reference plate 11 emits fluorescence toward the
second detecting portion 5. In other words, when there is no sheet
P at the detection position B, at least part of the second
fluorescent reference plate 11 appears in an image captured by the
second detecting portion 5.
[0083] The shield plate 12 blocks light emitted from the lighting
portion 3.
[0084] FIG. 5 is an explanatory diagram for explaining an example
of the disposed position of each portion. As described previously,
the first detecting portion 4 detects fluorescence. To detect
fluorescence, each portion is disposed so that light emitted from
the lighting portion 3 may enter at least the detection position A
of the first detecting portion 4.
[0085] When there is no sheet P at the detection position A, the
light emitted from the lighting portion 3 enters the first
fluorescent reference plate 10 disposed in the vicinity of the
detection position A. The fluorescent material contained in the
first fluorescent reference plate 10 is excited by the incident
light to emit light (reference light) toward the first detecting
portion 4.
[0086] The second detecting portion 5 detects phosphorescence
(afterglow). To detect afterglow, each portion is disposed so that
the light emitted from the lighting portion 3 may not enter at
least the detection position B of the second detecting portion 5.
Specifically, the shield plate 12 is disposed on a line connecting
the lighting portion 3 and the detection position B. The shield
plate 12 blocks the light which has been emitted from the lighting
portion 3 to enter the detection position B.
[0087] In the case where the second fluorescent reference plate 11
is disposed in the vicinity of the detection position B, the light
emitted from the lighting portion 3 does not enter the second
fluorescent reference plate 11. Accordingly, the second detecting
portion 5 cannot detect the reference light emitted from the second
fluorescent reference plate 11. For this reason, in this
embodiment, the second fluorescent reference plate 11 is disposed
to be separated from the detection position B by the distance
L.
[0088] In the case where the second fluorescent reference plate 11
is disposed as shown in FIG. 5, the light emitted from the lighting
portion 3 enters the second fluorescent reference plate 11 but does
not enter the detection position B. As a result, the second
fluorescent reference plate 11 can emit the reference light toward
the second detecting portion 5, which detects phosphorescence.
[0089] The above-described arrangement enables the first detecting
portion 4 to detect fluorescence from a sheet P, and enables the
second detecting portion 5 to detect phosphorescence
(afterglow).
[0090] In the case where each portion is disposed as shown in FIGS.
4 and 5, the second fluorescent reference plate 11 always emits
fluorescence. Specifically, the second fluorescent reference plate
11 emits fluorescence even when there is a sheet P at the detection
position B. Accordingly, part of the light emitted from the second
fluorescent reference plate 11 is transmitted through the sheet P
to enter the second detecting portion 5.
[0091] The light intensity of afterglow detected by the second
detecting portion 5 has a lower value than that of fluorescence
detected by the first detecting portion 4. Accordingly, in the case
where afterglow is detected, the influence of transmitted light is
larger compared to the case where fluorescence is detected.
[0092] In this embodiment, the second fluorescent reference plate
11 is disposed so that the second fluorescent reference plate 11,
as a light source, may be separated from the conveyor path 115 by
the distance (elongation distance) L. In other words, in this case,
a sheet P being conveyed along the conveyor path 115 and the second
fluorescent reference plate 11 are separated from each other by the
elongation distance L along the optical path.
[0093] FIGS. 6A and 6B are explanatory diagrams for explaining the
light emitted from the second fluorescent reference plate 11 shown
in FIG. 4. FIG. 6A is a view for explaining an example in which the
elongation distance L between the second fluorescent reference
plate 11 and the conveyor path 115 is short. On the other hand,
FIG. 6B is a view for explaining an example in which the elongation
distance L between the second fluorescent reference plate 11 and
the conveyor path 115 is long.
[0094] In the case where the fluorescent material of the second
fluorescent reference plate 11 is excited by the light emitted from
the lighting portion 3, the fluorescent material emits diffuse
light. The light emitted in a diffused state enters the sheet P
from the opposite side of the sheet P from the readout side to be
transmitted through the sheet P. The light intensity of the light
transmitted through the sheet P varies depending on the elongation
distance L between the second fluorescent reference plate 11 and
the sheet P. In other words, in the case where there is a sheet P
at the detection position B, the intensity of the light transmitted
through the detection position B on the sheet P to enter the second
detecting portion 5 varies depending on the elongation distance
L.
[0095] For example, in the example shown in FIG. 6A, the elongation
distance L is shorter compared to the example shown in FIG. 6B.
Accordingly, in the example shown in FIG. 6A, the intensity of the
light transmitted through the sheet P to enter the lens 51 is
higher compared to the example shown in FIG. 6B.
[0096] FIGS. 7A and 7B are explanatory diagrams for explaining the
light emitted from the second fluorescent reference plate 11 shown
in FIG. 4. FIG. 7A is a view for explaining an example in which the
elongation distance L between the second fluorescent reference
plate 11 and the conveyor path 115 is short. On the other hand,
FIG. 7B is a view for explaining an example in which the elongation
distance L between the second fluorescent reference plate 11 and
the conveyor path 115 is long.
[0097] When there is no sheet P at the detection position B, the
light emitted from the second fluorescent reference plate 11
directly enters the second detecting portion 5. In this case, since
the light is not transmitted through the sheet P, the light
intensity is not attenuated. As a result, the second detecting
portion 5 can detect light at almost equal levels in both the
examples shown in FIGS. 7A and 7B.
[0098] In other words, when light is detected by the second
detecting portion 5 in the state in which there is no sheet P at
the detection position B, the second detecting portion 5 detects
the second fluorescent reference plate 11 itself. Accordingly, the
light intensity of the light detected by the second detecting
portion 5 does not vary at least within the range of the focal
depth of the second detecting portion 5.
[0099] The light intensity of the light transmitted through a sheet
P is also influenced by the width of the second fluorescent
reference plate 11. The quantity of the fluorescent material
contained in the entire second fluorescent reference plate 11
varies depending on the width of the second fluorescent reference
plate 11 with respect to the conveying direction of the sheet
P.
[0100] For example, in the case where the width of the second
fluorescent reference plate 11 is large, the total quantity of
fluorescence emitted from the entire second fluorescent reference
plate 11 is large. In the case where the width of the second
fluorescent reference plate 11 is small, the total quantity of
fluorescence emitted from the entire second fluorescent reference
plate 11 is small. In other words, reducing the width of the second
fluorescent reference plate 11 can reduce the light transmitted
through a sheet P.
[0101] FIG. 8 is a graph for explaining the relationship between
the light transmitted through a sheet P and the elongation distance
L. FIG. 8 shows an example in which the intensity of the reference
light detected from the second fluorescent reference plate 11 by
the second detecting portion 5 in a state where there is no sheet P
at the detection position B is set as 100%.
[0102] Graph A shows an example in which the width of the second
fluorescent reference plate 11 with respect to the conveying
direction is 10 mm. On the other hand, graph B shows an example in
which the width of the second fluorescent reference plate 11 with
respect to the conveying direction is 5 mm.
[0103] The state of the phosphorescent printed information printed
on a sheet P varies due to soiling, aging, or the like. For
example, a change in the quantity of the phosphorescent material
applied as phosphorescent information causes a change in the light
intensity of afterglow emitted from the phosphorescent
material.
[0104] A standard value of the light intensity of the afterglow is
assumed to be 50% of the intensity of the reference light, and the
variation range of the light intensity of the afterglow is assumed
to be 50% of the intensity of the reference light. In this case,
the second detecting portion 5 detects the afterglow as light
having an intensity of 25% to 75% of the intensity of the reference
light.
[0105] Based on the above-described assumptions, if the light
intensity of the light transmitted through a sheet P is less than
approximately 10% of the intensity of the reference light, the
afterglow can be detected with high accuracy. It should be noted
that the range of 25% to 10% of the intensity of the reference
light is assumed to be a margin for detecting the afterglow with
high accuracy.
[0106] As shown in FIG. 8, in the case where the width of the
second fluorescent reference plate 11 with respect to the conveying
direction is 10 mm, if the elongation distance L is approximately
20 mm, the light intensity of the light transmitted through a sheet
P can be reduced to less than 10% of the intensity of the reference
light. On the other hand, in the case where the width of the second
fluorescent reference plate 11 with respect to the conveying
direction is 5 mm, if the elongation distance L is approximately 10
mm, the light intensity of the light transmitted through a sheet P
can be reduced to less than 10% of the intensity of the reference
light.
[0107] As described above, the light detection device 135 of this
embodiment includes, on the side of the second detecting portion 5
for detecting the afterglow, the second fluorescent reference plate
11 disposed to be separated from the conveyor path 115 by the
elongation distance L. The elongation distance L is set so that the
light from the lighting portion 3 on the first detecting portion 4
side may enter the second fluorescent reference plate 11 and that
the light emitted from the second fluorescent reference plate 11
may not influence the result of detection of the afterglow by the
second detecting portion 5.
[0108] Thus, the reference light can be supplied to the second
detecting portion 5. Also, in the case where the afterglow is
detected, the transmitted light can be prevented from influencing
the result of detection. As a result, it is possible to provide a
light detection device in which correction can be performed on a
fluorescence detecting portion and a phosphorescence detecting
portion, and a sheet processing apparatus including the light
detection device.
[0109] It should be noted that though the above-described
embodiment has been described with the width of the second
fluorescent reference plate 11 with respect to the conveying
direction being assumed to be 5 mm or 10 mm, the present invention
is not limited to this configuration. The second fluorescent
reference plate 11 may have any width as long as the width is at
least not less than the scanning width of the second detecting
portion 5.
[0110] The elongation distance L between the conveyor path 115 and
the second fluorescent reference plate 11 may be any distance as
long as the reference light does not influence the result of
detection by the second detecting portion 5. For example, the light
intensity of the reference light emitted from the second
fluorescent reference plate 11 differs depending on the material
and the like of the fluorescent material contained in the second
fluorescent reference plate 11. In other words, the elongation
distance L needs to be appropriately set in accordance with the
light intensity of the reference light emitted from the second
fluorescent reference plate 11.
[0111] Next, a second embodiment will be described. FIG. 9 is an
explanatory diagram for explaining an example of the configuration
of a light detection device 135 according to the second embodiment.
It should be noted that components similar to those in the first
embodiment are denoted by the same reference signs and will not be
further described in detail.
[0112] The light detection device 135 shown in FIG. 9 includes a
lighting portion 3, first and second detecting portions 4 and 5, an
amp circuit 6, a signal processor 7, a controller 8, a correction
controller 9, a fluorescent reference plate 10, a shield plate 12,
a reflection white plate 13, and a light guide plate 14.
[0113] The reflection white plate 13 is a reflecting diffuser which
diffuses and reflects incident light. The reflection white plate 13
is disposed to be separated from a conveyor path 115 by an
elongation distance L. In other words, the reflection white plate
13 is disposed to be separated from a detection position B on the
conveyor path 115 by the elongation distance L along the optical
path. The light guide plate 14 is a light guide which guides
incident light. The light guide plate 14 is disposed to face a
lower portion of the fluorescent reference plate 10. The light
guide plate 14 receives reference light emitted from the
fluorescent reference plate 10, and guides the received reference
light so that the received reference light may enter the reflection
white plate 13.
[0114] The lighting portion 3 applies light to the fluorescent
reference plate 10. The fluorescent reference plate 10 is excited
by the light to emit fluorescence as reference light. The light
guide plate 14 guides the fluorescence emitted from the fluorescent
reference plate 10 inside. The light guide plate 14 emits the light
guided inside toward the reflection white plate 13. The reflection
white plate 13 diffuses and reflects the incident fluorescence. The
fluorescence diffused and reflected by the reflection white plate
13 enters the second detecting portion 5. In this case, the
reflection white plate 13 functions as a reference member for
supplying the second detecting portion 5 with the reference
light.
[0115] In the above-described configuration, in the case where
there is no sheet P at the detection position B, the fluorescence
emitted from the fluorescent reference plate 10 is reflected by the
reflection white plate 13 to enter the second detecting portion 5.
In other words, the second detecting portion 5 can acquire the
reference light as a detection reference. As a result, the
correction controller 9 can control the gain of an amplifier 62.
Also, since the conveyor path 115 and the reflection white plate 13
are disposed to be separated from each other by the elongation
distance L, it is possible to reduce the influence of the light
emitted from the reflection white plate 13 on a result of detection
by the second detecting portion 5.
[0116] Next, a third embodiment will be described. FIG. 10 is an
explanatory diagram for explaining an example of the configuration
of a light detection device 135 according to the third embodiment.
It should be noted that components similar to those in the first
and second embodiments are denoted by the same reference signs and
will not be further described in detail.
[0117] The light detection device 135 shown in FIG. 10 includes a
lighting portion 3, first and second detecting portions 4 and 5, an
amp circuit 6, a signal processor 7, a controller 8, a correction
controller 9, a fluorescent reference plate 10, a shield plate 12,
a light guide plate 14, a transparence white plate 15, and a
reflection mirror 16.
[0118] The transparence white plate 15 is a translucent reflector
which diffuses and transmits incident light. The transparence white
plate 15 is disposed at an output end of the light guide plate 14.
The light guide plate 14 receives reference light emitted from the
fluorescent reference plate 10, and guides the received reference
light so that the received reference light may enter the
transparence white plate 15. The reflection mirror 16 is a
reflector which reflects light. The reflection mirror 16 is
disposed at such a position that the reflection mirror 16 can cause
light emitted from the transparence white plate 15 to enter the
second detecting portion 5.
[0119] The lighting portion 3 applies light to the fluorescent
reference plate 10. The fluorescent reference plate 10 is excited
by the light to emit fluorescence as reference light. The light
guide plate 14 guides the fluorescence emitted from the fluorescent
reference plate 10 inside. The light guide plate 14 guides the
light guided inside in the direction indicated by arrows G shown in
FIG. 10, and emits the light from the output end. The transparence
white plate 15 diffuses the light emitted from the output end of
the light guide plate 14. The reflection mirror 16 reflects the
light diffused by the transparence white plate 15 and causes the
light to enter the second detecting portion 5. In this case, the
transparence white plate 15 functions as a reference member for
supplying the second detecting portion 5 with the reference
light.
[0120] It should be noted that the reflection mirror 16 is disposed
to be separated from the transparence white plate 15 by a distance
L1. Further, the reflection mirror 16 is disposed to be separated
from the conveyor path 115 by a distance L2. In this case, the sum
of the distances L1 and L2 corresponds to the elongation distance L
of the first embodiment. Specifically, in this configuration, the
transparence white plate 15 as a reference member and a detection
position B on the conveyor path 115 are separated from each other
by the sum of the distances L1 and L2 along the optical path.
[0121] In the above-described configuration, in the case where
there is no sheet P at the detection position B, the fluorescence
emitted from the fluorescent reference plate 10 is reflected by the
reflection mirror 16 to enter the second detecting portion 5. In
other words, the second detecting portion 5 can acquire the
reference light as a detection reference. As a result, the
correction controller 9 can control the gain of an amplifier 62.
Also, the length of the optical path from the transparence white
plate 15 to the conveyor path 115 is L1+L2. Setting the distances
L1 and L2 at not less than predetermined lengths makes it possible
to reduce the influence of the light emitted from the transparence
white plate 15 on the result of detection by the second detecting
portion 5.
[0122] This invention is not limited to the above-described
embodiments themselves, but, in a practical phase, can be realized
by modifying components without departing from the spirit of the
invention. Moreover, various inventions can be formed using
appropriate combinations of some of the components disclosed in
each of the above-described embodiments. For example, in any of the
embodiments, some of all the components described therein may be
deleted. Furthermore, components of different embodiments may be
appropriately combined.
* * * * *