U.S. patent application number 13/951869 was filed with the patent office on 2014-01-30 for colorimetry apparatus and image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Tomoaki Nakai, Akihiko Uchiyama.
Application Number | 20140029963 13/951869 |
Document ID | / |
Family ID | 49995001 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140029963 |
Kind Code |
A1 |
Nakai; Tomoaki ; et
al. |
January 30, 2014 |
COLORIMETRY APPARATUS AND IMAGE FORMING APPARATUS
Abstract
The colorimetry apparatus includes a light source for emitting
light to a surface of a detected object, a diffraction grating for
spectrally separating, for each wavelength, the light emitted from
the light source and reflected by the detected object, and a line
sensor including multiple pixels, for receiving the light, which is
spectrally separated by the diffraction grating, for the each
wavelength by the multiple pixels. The light source and the line
sensor are arranged on the common substrate.
Inventors: |
Nakai; Tomoaki; (Numazu-shi,
JP) ; Uchiyama; Akihiko; (Mishima-shi, JP) |
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
49995001 |
Appl. No.: |
13/951869 |
Filed: |
July 26, 2013 |
Current U.S.
Class: |
399/39 ;
250/226 |
Current CPC
Class: |
G03G 15/01 20130101;
G01J 3/50 20130101; G01J 3/502 20130101; G03G 15/5062 20130101;
G01J 1/0488 20130101; G01J 3/18 20130101; G03G 2215/00257
20130101 |
Class at
Publication: |
399/39 ;
250/226 |
International
Class: |
G03G 15/01 20060101
G03G015/01; G01J 3/50 20060101 G01J003/50 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2012 |
JP |
2012-168501 |
Jul 16, 2013 |
JP |
2013-147644 |
Claims
1. A colorimetry apparatus, comprising: a light emission element
for emitting light to a surface of a detected material; a
diffraction grating for spectrally separating the light emitted
from the light emission element and reflected by the detected
material; and a light receiving element including multiple pixels,
for receiving spectral light, which is spectrally separated by the
diffraction grating, for the each wavelength by the multiple
pixels, wherein the light emission element and the light receiving
element are arranged on a common substrate.
2. A colorimetry apparatus according to claim 1, wherein the
diffraction grating and the light receiving element are arranged so
that an optical path of the spectral light received by the light
receiving element is positioned along a virtual plane parallel to
the surface of the detected material arranged at a preset
position.
3. A colorimetry apparatus according to claim 2, wherein a surface
of the common substrate on which the light emission element and the
light receiving element are arranged is perpendicular to the
virtual plane.
4. A colorimetry apparatus according to claim 1, wherein the common
substrate has a hole formed in a region between the light emission
element and the light receiving element.
5. A colorimetry apparatus according to claim 1, wherein a part of
the common substrate between the light emission element and the
light receiving element is made of a material that transmits less
light than another part of the common substrate.
6. A colorimetry apparatus according to claim 1, further comprising
a control unit, arranged on the common substrate, for controlling
the colorimetry apparatus.
7. An image forming apparatus for forming an image on a recording
material, the image forming apparatus comprising: an image forming
unit for forming an image on the recording material; a light
emission element for emitting light to a surface of the recording
material; a diffraction grating for spectrally separating, for each
wavelength, the light emitted from the light emission element and
reflected by the recording material; and a light receiving element
including multiple pixels, for receiving spectral light, which is
spectrally separated by the diffraction grating, for the each
wavelength by the multiple pixels; and a control unit for adjusting
an image formation condition of the image forming unit based on an
output from the light receiving element, wherein the light emission
element and the light receiving element are arranged on the common
substrate.
8. An image forming apparatus according to claim 7, wherein the
diffraction grating and the light receiving element are arranged so
that an optical path of the light spectrally separated by the
diffraction grating and received by the light receiving element is
situated along a virtual plane parallel to the surface of the
recording material arranged at a preset position.
9. An image forming apparatus according to claim 8, wherein a
surface of the common substrate on which the light emission element
and the light receiving element are arranged is perpendicular to
the virtual plane.
10. An image forming apparatus according to claim 7, wherein the
common substrate has a hole formed in a region between the light
emission element and the light receiving element.
11. An image forming apparatus according to claim 7, wherein a part
of the common substrate between the light emission element and the
light receiving element is made of a material that transmits less
light than another part of the common substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a colorimetry apparatus and
an image forming apparatus.
[0003] 2. Description of the Related Art
[0004] In recent years, a color image forming apparatus such as a
color printer and a color copier is required to output images with
higher image quality. In particular, stability of image gradation
and image color significantly affects the image quality. However,
change of environment such as temperature or humidity, or long-term
use of the color printer causes change of tint of an obtained
image. Therefore, in order to realize stable tint, it is necessary
to detect the tint of the image by using a colorimetry sensor and
to provide feedback for a process condition of the image forming
apparatus.
[0005] Conventionally, as one of devices for measuring tint
(chromaticity) of a color of a printed matter or an object, there
is used a colorimetry device. As a general colorimetry device,
there is a filter type colorimetry device in which white color
light is emitted to a detected object, and reflection light is
received by a light receiving sensor through an RGB color filter so
as to measure intensity of each color component. In addition, there
is known a spectral colorimetry device in which wavelength
dispersion of the reflection light is performed by using a
diffraction grating, a prism, or the like, then intensity is
detected for each wavelength by a line sensor, and spectral
reflectance of the detected object is determined through
calculation considering a wavelength distribution of the detected
dispersed light, a wavelength distribution of light from a light
source, spectral sensitivity of the sensor, and the like. The
spectral colorimetry device is advantageous in view of the accuracy
in colorimetry, and hence the spectral colorimetry device is used
in many cases as a colorimetry sensor that is used for control for
stabilizing tint of a color printer. Japanese Patent Application
Laid-Open No. 2009-008471 proposes a spectral colorimetry device
that can measure paper color information with high accuracy even if
the paper sheet is conveyed in a fluttering state. In addition,
Japanese Patent Application Laid-Open No. 2010-211055 proposes an
image forming apparatus that uses the spectral colorimetry device
to control a fixing condition with high accuracy even if a toner
adhering amount fluctuates.
[0006] However, the conventional spectral colorimetry device has
the following problems.
[0007] First, the spectral colorimetry device has high accuracy in
colorimetry, but cost thereof is high. In particular, if a distance
from the light source to the detected object is long, it is
necessary to increase a light emission amount in order to secure
intensity of light emitted to the detected object. As a result,
there are risks such as increase of cost for a circuit of supplying
a larger current and increase of cost of a light emission element.
In addition, as described above, if the distance from the light
source to the detected object is long, a size of the spectral
colorimetry device is increased. In this case, a size of the image
forming apparatus itself including the colorimetry device is
increased, and hence cost of the entire apparatus is increased.
[0008] In addition, in the spectral colorimetry device, the
wavelength dispersion of the reflection light is performed by using
the diffraction grating, the prism, or the like, and then the
intensity is detected for each wavelength by the line sensor.
Therefore, if a position of the line sensor is fluctuated by
thermal deformation of the spectral colorimetry device, detection
accuracy may be lowered. Here, a housing of the spectral
colorimetry device is usually made of a mold resin in view of
easiness of molding, cost, weight, and the like. Therefore, if an
ambient temperature rises during a period after the image forming
apparatus is produced until the image forming apparatus is
delivered to a user, the temperature of the housing of the spectral
colorimetry device also rises. As a result, even after returning to
room temperature, the thermal deformation (creep) of the device may
be fixed. In addition, if the image forming apparatus is an
electrophotographic image forming apparatus, heat generated in a
fixing process may be transferred to the spectral colorimetry
device so that thermal deformation is caused. A positional
fluctuation of the line sensor due to the thermal deformation is
insignificant, but the positional fluctuation may affect detection
accuracy of the spectral colorimetry device having a structure in
which the wavelength dispersion of the reflection light is
performed by using the diffraction grating, the prism, or the like,
and then the light is detected by the line sensor.
[0009] In addition, in order to arrange the spectral colorimetry
device in the image forming apparatus, it is necessary to secure a
space for the spectral colorimetry device as a matter of course.
However, if the spectral colorimetry device is large in size, it is
necessary to increase also a size of the image forming apparatus,
which may degrade a commercial value of the image forming
apparatus. Therefore, it is preferred that the spectral colorimetry
device have a smaller size.
[0010] However, the spectral colorimetry device needs the light
source, the diffraction grating or the prism, the line sensor, and
the like, and further needs an optical guide member for guiding the
reflection light to the diffraction grating or the prism, the line
sensor, and the like, and a lens or the like for collimating light.
Further, in order that the light subjected to the wavelength
dispersion by the diffraction grating or the prism can be
appropriately detected by the line sensor, the spectral colorimetry
device needs a certain extent of an optical path length, which is
one of factors that prevent downsizing of the spectral colorimetry
device.
SUMMARY OF THE INVENTION
[0011] It is an object of the present invention to reduce cost of a
colorimetry apparatus or to suppress lowering of detection accuracy
of the colorimetry apparatus.
[0012] In addition, it is another object of the present invention
to provide the following colorimetry apparatus.
[0013] That is, the colorimetry apparatus includes: a light
emission element for emitting light to a surface of a detected
material; a diffraction grating for spectrally separating, for each
wavelength, the light emitted from the light emission element and
reflected by the detected material for each wavelength; and a light
receiving element including multiple pixels, for receiving spectral
light, which is spectrally separated by the diffraction grating,
for the each wavelength by the multiple pixels. The light emission
element and the light receiving element are arranged on the same
substrate.
[0014] In addition, it is still another object of the present
invention to provide the following image forming apparatus.
[0015] That is, the image forming apparatus includes an image
forming unit for forming an image on a recording material; a light
emission element for emitting light to a surface of the recording
material; a diffraction grating for spectrally separating, for each
wavelength, the light emitted from the light emission element and
reflected by the recording material; and a light receiving element
including multiple pixels, for receiving spectral light, which is
spectrally separated by the diffraction grating, for the each
wavelength by the multiple pixels; and a control unit for adjusting
an image formation condition of the image forming unit based on an
output from the light receiving element. The light emission element
and the light receiving element are arranged on the same
substrate.
[0016] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIGS. 1A and 1B are explanatory diagrams illustrating a
schematic structure of a spectral colorimetry device according to a
first embodiment of the present invention.
[0018] FIG. 2 is a cross-sectional view illustrating a schematic
structure of an image forming apparatus to which the spectral
colorimetry device of the first embodiment is applied.
[0019] FIG. 3 is a schematic diagram illustrating a patch image for
measuring color that is formed on a recording material.
[0020] FIG. 4 is a block diagram illustrating an example of an
image processing operation in the image forming apparatus of the
first embodiment.
[0021] FIG. 5 is a schematic diagram of a spectral colorimetry
device of a comparative example.
[0022] FIGS. 6A and 6B are explanatory diagrams illustrating a
schematic structure of a spectral colorimetry device according to a
second embodiment of the present invention. Specifically, FIG. 6A
is a diagram illustrating an XY cross section of the spectral
colorimetry device according to the second embodiment of the
present invention, as viewed from a direction perpendicular to a
detected surface of a detected material. FIG. 6B is a diagram
illustrating an XZ cross section of the spectral colorimetry device
according to the second embodiment of the present invention, as
viewed from a front of the spectral colorimetry device.
[0023] FIG. 7 is a schematic diagram illustrating a substrate of a
spectral colorimetry device according to a third embodiment of the
present invention.
[0024] FIG. 8A is a diagram illustrating an XZ cross section of the
spectral colorimetry device of the first embodiment.
[0025] FIG. 8B is a diagram illustrating an XY cross section of the
spectral colorimetry device of the first embodiment.
[0026] FIGS. 9A, 9B, 9C, and 9D are diagrams illustrating a cross
section 9A, a cross section 9B, a cross section 9C, and a cross
section 9D of FIG. 8B, respectively.
[0027] FIG. 10A is a diagram illustrating a housing of the spectral
colorimetry device of the first embodiment in an assembled
state.
[0028] FIG. 10B is a diagram illustrating the housing of the
spectral colorimetry device of the first embodiment in an exploded
state before assembly.
[0029] FIG. 11A is an XY cross-sectional view of a specific
structure of the spectral colorimetry device of the second
embodiment as viewed from a lateral direction (Z direction).
[0030] FIG. 11B is an upper side cross-sectional view (XZ
cross-sectional view) of a specific structure of the spectral
colorimetry device of the second embodiment.
[0031] FIG. 11C is an XY cross-sectional view of a specific
structure of the spectral colorimetry device of the second
embodiment as viewed from the lateral direction (Z direction).
[0032] FIGS. 12A, 12B, 12C, and 12D are diagrams illustrating cross
sections 12A, 12B, 12C, and 12D of FIG. 11C, respectively.
[0033] FIG. 13A is a diagram illustrating a state where the housing
of the spectral colorimetry device is assembled.
[0034] FIG. 13B is a diagram illustrating a state before the
housing of the spectral colorimetry device is assembled.
DESCRIPTION OF THE EMBODIMENTS
[0035] Now, exemplary embodiments of the present invention are
described in detail with reference to the attached drawings. Note
that, dimensions, materials, shapes, relative positions of
components, and the like to be described in the embodiments may be
changed as appropriate depending on the structure of an apparatus
to which the present invention is applied, or various conditions.
Therefore, the scope of the present invention is not intended to be
limited only to those embodiments.
[0036] The present invention relates to an image forming apparatus
such as an inkjet or electrophotographic copier or printer, and
more particularly, to a colorimetry apparatus for measuring a color
of an image (a patch colorimetry) output by the image forming
apparatus.
First Embodiment
[0037] Now, a first embodiment of the present invention is
described.
[0038] FIG. 1A is an explanatory diagram illustrating a schematic
structure of a spectral colorimetry device 10 as a colorimetry
apparatus of this embodiment. Here, as illustrated in FIG. 1A, a
direction perpendicular to a detected surface (surface) of a
detected object (hereinafter referred to as a detected material) 14
is defined as a Z direction, a longitudinal direction of the
spectral colorimetry device 10 is defined as an X direction, a
height direction of the spectral colorimetry device 10 (front
direction of the apparatus) is defined as a Y direction. In other
words, FIG. 1A illustrates an XZ cross section of the spectral
colorimetry device 10.
[0039] The spectral colorimetry device 10 of this embodiment
includes a white color light source (hereinafter referred to as a
light source) 12 having a light emission wavelength distribution
over the entire visible light range, an emission-side light
condensing and guiding lens (hereinafter referred to as an emission
light guide) 19, an incident-side light condensing and guiding lens
(hereinafter referred to as an incident light guide) 17, a slit 22,
a diffraction grating (concave reflection diffraction grating) 18,
and a charge accumulation type line sensor (hereinafter referred to
as a line sensor) 11 having multiple pixels. Here, the light source
12 corresponds to a light emission element. In addition, the
diffraction grating 18 corresponds to a spectral unit. In addition,
the line sensor 11 corresponds to a light receiving element.
[0040] This embodiment has a feature in that the light source 12
and the line sensor 11 are mounted (arranged) on the same substrate
21 (surface of the substrate 21, on the same substrate). The
substrate 21 is suitably made of epoxy resin-impregnated paper or a
laminated glass fiber fabric impregnated with an epoxy resin. With
reference to FIGS. 8A, 8B, 9A, 9B, 9C, and 9D, a more specific
structure of the spectral colorimetry device 10 of this embodiment
is described. FIG. 8A illustrates an XZ cross section of the
spectral colorimetry device 10. FIG. 8B illustrates an XY cross
section of the spectral colorimetry device 10 as viewed from the Z
direction.
[0041] On the substrate 21, there is arranged a control and
operation unit 21c for controlling operation of the spectral
colorimetry device 10. The control and operation unit 21c includes
a circuit for controlling a light emission amount and a light
emission timing of the light source 12, and an operation circuit
for processing a signal output from the line sensor 11. The
spectral colorimetry device 10 includes a casing 10a and a lid 10b
constituting the housing. The emission light guide 19, the incident
light guide 17, the slit 22, the diffraction grating 18, and the
substrate 21 are fixed to the casing 10a of the housing at
respective positions.
[0042] Next, a method of positioning and fixing the emission light
guide 19, the incident light guide 17, the slit 22, and the
diffraction grating 18 to the casing 10a is described. FIGS. 9A,
9B, 9C, and 9D are diagrams illustrating a cross section 9A, a
cross section 9B, a cross section 9C, and a cross section 9D of
FIG. 8B, respectively. The cross section 9A illustrates a
relationship between the emission light guide 19 and the casing
10a. The emission light guide 19 is positioned so as to abut
against the casing 10a in the Y direction (direction of an arrow)
and is fixed in this state to the casing 10a with an ultraviolet
curing adhesive. Similarly, the incident light guide 17 in the
cross section 9B, the slit 22 in the cross section 9C, and the
diffraction grating 18 in the cross section 9D are positioned so as
to abut against the casing 10a in the Y direction and are fixed in
this state at the respective positions to the casing 10a with an
ultraviolet curing adhesive.
[0043] Next, with reference to FIGS. 10A and 10B, a relationship
among the casing 10a, the lid 10b, and the substrate 21 is
described in detail. FIGS. 10A and 10B are perspective views of the
housing. FIG. 10A illustrates a state where the housing of the
spectral colorimetry device is assembled. FIG. 10B illustrates an
exploded state before the housing of the spectral colorimetry
device 10 is assembled. Here, the emission light guide 19, the
incident light guide 17, the slit 22, and the diffraction grating
18, which are fixed to the inside, are not illustrated in the
diagrams. As understood from the diagrams, the lid 10b and the
substrate 21 are fixed to the casing 10a in the Z direction. The
lid 10b is positioned when the lid 10b is fitted to a groove formed
in the casing 10a and is fixed with an ultraviolet curing adhesive.
On the other hand, the substrate 21 is provided with a datum hole
21a serving as a reference for positioning in the X direction and
in the Y direction. The datum hole 21a is fitted onto a boss (not
shown) formed on the casing 10a so that the substrate 21 is
positioned in the X direction and in the Y direction. Further, a
notch portion 21b is formed in the substrate 21, and this portion
is fitted onto a protrusion (not shown) formed on the casing 10a to
serve as a rotation stopper about the Z axis for the substrate 21.
The substrate 21 is fixed to the casing 10a with an ultraviolet
curing adhesive.
[0044] Light 15 emitted from the light source 12 is condensed by
the emission light guide 19 on the emission side, and a direction
of the light 15 is changed so that the light 15 enters the detected
surface of the detected material 14 at an angle of approximately
45.degree. through an aperture 13. Here, the color of the detected
material 14 is measured at a preset position of the spectral
colorimetry device 10 (position opposed to the aperture 13 arranged
in the Z direction of the spectral colorimetry device 10 as
illustrated in an upper part of FIG. 1A).
[0045] The light 15 entering the detected material 14 at an angle
of approximately 45.degree. becomes scattered light (reflection
light) in accordance with an optical absorption characteristic of
the detected material 14. A part of scattered light 16 is received
by the incident light guide on the incident side to become
collimated light, and then a direction of the light is changed so
that the light enters the slit 22. Further, the scattered light 16
passes through the slit 22 and enters the diffraction grating 18.
The scattered light 16 entering the diffraction grating 18 is
reflected by the diffraction grating 18 and is then spectrally
separated by the diffraction grating 18 to become a spectral light
beam spectrally separated and condensed for each wavelength. The
line sensor 11 is arranged substantially on a tangent of a Rowland
circle (not shown) of the diffraction grating 18, and the spectral
light beam is received and detected by the pixels for each
wavelength.
[0046] In a case of the structure of this embodiment illustrated in
FIG. 1A, a center axis of the Rowland circle (not shown) is
orthogonal to the X direction axis and to the Z direction axis, and
is parallel to the detected surface of the detected material.
[0047] FIG. 1B is a schematic diagram illustrating the line sensor
11 of this embodiment.
[0048] As illustrated in FIG. 1B, in this embodiment, the line
sensor 11 is constituted of 134 pixels aligned in one direction,
which are necessary for detecting visible light having wavelengths
of approximately 350 nm to approximately 750 nm in units of
approximately 3 nm.
[0049] The line sensor 11 outputs (generates) a voltage signal
(electric signal) for each pixel in accordance with intensity of
the incident (received) dispersed light. Further, the output signal
is AD-converted by an AD converter (not shown) so that the
reflection light from the detected material 14 can be obtained as a
digital intensity signal for each pixel. The line sensor 11 of this
embodiment is a charge accumulation type line sensor and outputs a
voltage signal for each pixel in accordance with intensity of the
incident dispersed light during a predetermined accumulation
period. The accumulation period can be adjusted appropriately by
action of the control and operation unit 21c.
[0050] The digital intensity signal of each pixel is sent to the
control and operation unit 21c for the following operation. An
address number n (n=1 to 134) of each pixel of the line sensor 11
is associated with (namely, assigned with a value of) a
corresponding wavelength .lamda. in advance and is stored in a
memory unit (not shown). This value assigning work can be performed
by a conventionally known method by using a reference single
wavelength spectrum having a known wavelength when the sensor is
shipped, for example.
[0051] In this way, because each pixel is associated with the
wavelength .lamda., it is possible to obtain a wavelength-signal
intensity spectrum Oi(.lamda.) of the reflection light from the
detected material 14 based on the voltage signal output for each
pixel described above.
[0052] Using this, a spectral reflectance Or(.lamda.) of the
detected material can be determined by the following equation.
Or(.lamda.)={Oi(.lamda.)/Wi(.lamda.)}.times.Wr(.lamda.) Equation
(1)
In this equation, Wi(.lamda.) represents the wavelength-signal
intensity spectrum of the reflection light when the light source 12
emits light to a reference sample (usually, white color reference
sample) having a known spectral reflectance that is separately
measured. In addition, Wr(.lamda.) represents a spectral
reflectance of the reference sample itself.
[0053] Further, an operation unit (not shown) performs
interpolation operation of the spectral reflectance in the range
from 380 nm to 730 nm in units of 10 nm based on the obtained
spectral reflectance Or(.lamda.), and outputs the result to the
outside.
[0054] Now, there is described a case where a color of a
measurement object is measured by the spectral colorimetry device
10 of this embodiment.
[0055] First, the control and operation unit 21c replaces the
wavelength .lamda. indicated in Equation (1) with the pixel address
n, and calculates Oi(n)/Wi(n) generated for each pixel based on an
output signal Oi(n) of a white reference that has been measured in
advance and an output signal Wi(n) generated when the measurement
object is measured.
[0056] After that, a relationship of each pixel of the line sensor
11 associated by this correction method and a wavelength is read
out from the memory unit (not shown), and the pixel address n is
replaced with the wavelength .lamda. so that
Oi(.lamda.)/Wi(.lamda.) is obtained. Further, a value of
Wr(.lamda.) stored in the memory unit (not shown) is read out, and
the spectral reflectance Or(.lamda.) of the detected material can
be obtained in accordance with Equation (1).
[0057] The spectral colorimetry device 10 of this embodiment can be
applied to an electrophotographic color image forming apparatus,
for example. As an example thereof, there is described a case where
the spectral colorimetry device 10 is applied to a tandem color
image forming apparatus adopting an intermediate transfer belt.
[0058] FIG. 2 is a cross-sectional view illustrating a schematic
structure of an image forming apparatus to which the spectral
colorimetry device 10 of this embodiment is applied.
[0059] First, with reference to FIG. 2, operations of image forming
units of the image forming apparatus of this embodiment are
described. Here, structures and operations of individual image
forming units are substantially the same except that different
colors of toner (yellow (Y), magenta (M), cyan (C), and black (K))
are used. Thus, in the following description, unless it is
necessary to make specific distinctions, the suffixes Y, M, C, and
K each added to reference symbols of the components in FIG. 2 so as
to express corresponding colors are omitted so that the components
are collectively described.
[0060] The image forming unit of this embodiment is constituted of
members described below.
[0061] The members include a feed unit 44, a photosensitive member
for a station of each color (an image bearing member, hereinafter
referred to as a photosensitive drum) 31, a charging roller 32 as a
primary charging unit, an exposing light scanner 33, and a
developing device 38 as a developing unit. In addition, the members
include an intermediate transfer belt 37, a drive roller 41 for
driving the intermediate transfer belt, a tension roller 40, an
auxiliary roller 42, a primary transfer roller 34, a secondary
transfer roller 43, a fixing unit 51, a control unit 55 and a
controller unit 56 for controlling image formation operation of the
image forming unit.
[0062] The photosensitive drum 31 is formed of an organic
photoconductive layer applied around an outer periphery of an
aluminum cylinder and is rotated by a drive force transmitted from
a drive motor (not shown). The drive motor rotates the
photosensitive drum 31 in accordance with the image formation
operation in a clockwise direction in FIG. 2.
[0063] When the above-mentioned control unit 55 receives an image
signal (input signal), a recording material P is sent out by pairs
of feed rollers 45 and 46 from the feed unit 44 (such as a
cassette) to the inside of the image forming apparatus. After that,
the recording material P is temporarily nipped by a roller-like
synchronous rotation member, namely a pair of conveyance
(registration) rollers for synchronization between image formation
operation and conveyance of the recording material P as described
later, and the recording material P is stopped to wait.
[0064] On the other hand, the controller unit 56 causes the
exposing light scanner 33 to form an electrostatic latent image in
accordance with the received image signal on a surface of the
photosensitive drum 31 charged at a predetermined potential by
action of the charging roller 32.
[0065] The developing device 38 is a unit for visualizing the
electrostatic latent image and performs development of a yellow
(Y), magenta (M), cyan (C), or black (K) image for each station.
Each developing device includes a sleeve 35 to which a developing
bias is applied for visualizing the electrostatic latent image.
[0066] In this way, the electrostatic latent image formed on the
surface of each photosensitive drum 31 is developed as a single
color toner image by action of each developing device. The
photosensitive drum 31, the charging roller 32, and the developing
device 38 for each color constitute an integral structure as a
toner cartridge that is mounted to a main body of the image forming
apparatus in a removable manner.
[0067] The intermediate transfer belt 37 comes into contact with
each photosensitive drum 31 and rotates in synchronization with
rotation of each photosensitive drum 31 in a counterclockwise
direction in FIG. 2 when a color image is formed. The developed
single color toner images are sequentially transferred (primarily
transferred) by action of a primary transfer bias applied to each
primary transfer roller 34 so as to form a multicolor toner image
on the intermediate transfer belt 37.
[0068] After that, the multicolor toner image formed on the
intermediate transfer belt 37 is conveyed to a secondary transfer
portion (nip portion) formed between the drive roller 41 and the
secondary transfer roller 43.
[0069] At the same time, the recording material P waiting in the
state of being nipped between the pair of conveyance rollers 47 is
conveyed to the secondary transfer portion by action of the pair of
conveyance rollers 47 in synchronization with the multicolor toner
image on the intermediate transfer belt 37. Further, the multicolor
toner image on the intermediate transfer belt 37 is collectively
transferred (secondarily transferred) onto the recording material P
by action of a secondary transfer bias applied to the secondary
transfer roller 43.
[0070] The fixing unit 51 melts and fixes the transferred
multicolor toner image while conveying the recording material P,
and the fixing unit 51 includes a fixing roller 51a for heating the
recording material P, and a pressure roller 51b for bringing the
recording material P into press-contact with the fixing roller 51a.
The fixing roller 51a and the pressure roller 51b are each formed
into a hollow shape, and heaters 51ah and 51bh are respectively
provided inside. The recording material P bearing the multicolor
toner image is conveyed by the fixing roller 51a and the pressure
roller 51b, and heat and pressure are applied to the recording
material P so that the toner is fixed to the surface of the
recording material P.
[0071] The recording material P after fixing the toner image is
discharged to a discharge tray 52 by a pair of discharge rollers 50
so that the image formation operation is finished. Alternatively,
if image formation on the second side is performed, the recording
material P is switched back (to be conveyed backward) in a
discharge unit. If the image formation on the second side is
performed, the recording material P bearing the multicolor toner
image on the first side (on one side) passes through a duplex
conveyance path D by the switch back operation in the discharge
unit and is temporarily nipped by the pair of conveyance
(registration) rollers 47 again to stop and wait. After that, the
above-mentioned sequential image formation operation is carried out
so as to perform the image formation on the second side of the
recording material P.
[0072] A cleaning unit 48 removes toner remaining on the
intermediate transfer belt 37 (residual toner), and the residual
toner collected by the cleaning unit 48 is stored in a cleaner
container 49.
[0073] The spectral colorimetry device 10 of this embodiment is
arranged in a center position of the duplex conveyance path in a
longitudinal direction in order to measure a color of a toner patch
(a patch for colorimetry) formed on the recording material P as the
detected material. The longitudinal direction herein means a
direction orthogonal to the conveyance direction in an image
formation plane of the recording material P conveyed in the duplex
conveyance path (rotation axis direction of the photosensitive drum
31).
[0074] In the image forming apparatus of this embodiment, the
control unit 55 arranged in the image forming apparatus adjusts
image formation conditions of each image forming unit based on a
colorimetry result of the spectral colorimetry device 10. The
adjustment of image formation conditions means correction of image
data, and adjustment of an exposure light amount, the developing
bias, the transfer bias, and the like.
[0075] Now, colorimetry operation of a toner patch by the spectral
colorimetry device 10 is described. FIG. 3 is a schematic diagram
illustrating the patch image T for colorimetry formed on the
recording material P.
[0076] When the colorimetry operation of the toner patch is started
by the spectral colorimetry device 10, the patch image T for
colorimetry as illustrated in FIG. 3 is first formed on the
recording material P by the above-mentioned sequential image
formation operation. The recording material P after passing through
the fixing unit 51 is pulled into the duplex conveyance path D by
the switch back operation in the discharge unit. Then, the spectral
colorimetry device 10 arranged in the duplex conveyance path D
sequentially performs colorimetry of the patch image T for
colorimetry formed on the recording material P in synchronization
with conveyance of the recording material P. After that, the
recording material P after passing through the pair of conveyance
rollers 47 passes through the secondary transfer portion and the
fixing unit 51 so as to be discharged onto the discharge tray 52 by
the pair of discharge rollers 50.
[0077] This sequential image formation operation is controlled by
the control unit 55 arranged in the image forming apparatus.
[0078] Next, an example of image processing operation in the image
forming apparatus of this embodiment is described with reference to
a block diagram of FIG. 4.
[0079] The controller unit 56 and the control unit 55 of the image
forming apparatus are connected to each other via a video
interface, and the controller unit 56 is connected to a host
computer 57 of an external terminal or a network (not shown). A
storage unit of the controller unit 56 stores a color matching
table (CM) to be used for color conversion, a color separation
table (C1), and a color correction table (C2). In addition, the
control unit 55 includes a CPU 202 for processing image formation
and a colorimetry result from the spectral colorimetry device 10,
and a memory 203 for temporarily storing a measurement result.
[0080] When the image formation operation is started, the following
processing is performed.
[0081] First, using the color matching table (CM) prepared in
advance, the controller unit 56 converts an RGB signal indicating
the color of the image transmitted from the host computer or the
like into a device RGB signal (hereinafter referred to as DevRGB)
adapted to a color reproduction range of the color image forming
apparatus. Next, using the color separation table (C1) and the
color correction table (C2) described later, the DevRGB signal is
converted into a CMYK signal indicating toner material colors of
the color image forming apparatus. Further, using a density
correction table (D) for correcting a gradation and density
characteristic unique to each color image forming apparatus, the
CMYK signal is converted into a C'M'Y'K' signal corrected for the
gradation and density characteristic. After that, halftone
processing is performed so as to convert the C'M'Y'K' signal into a
C''M''Y''K'' signal. Then, using a PWM table (PW), the C''M''Y''K''
signal is converted into exposure times Tc, Tm, Ty, and Tk of the
exposing light scanners (33C, 33M, 33Y, and 33K) corresponding to
the C''M''Y''K'' signal. The PWM herein stands for pulse width
modulation.
[0082] The controller unit 56 controls the exposing light scanners
33 in accordance with the exposure times Tc, Tm, Ty, and Tk so as
to form the electrostatic latent images on the surfaces of the
photosensitive drums 31C, 31M, 31Y, and 31K, respectively. Thus,
the sequential image formation operation is performed as described
above.
[0083] In addition, in the colorimetry operation of the toner patch
image by the spectral colorimetry device 10, the patch image T for
colorimetry is formed on the recording material P in accordance
with multiple CMYK color patch data (CPD) stored in the controller
unit 56 as color patch data in advance. The patch image T for
colorimetry formed on the recording material (detected material)
undergoes the colorimetry by the spectral colorimetry device 10,
and the spectral reflectance Or(.lamda.) is read for each patch and
is output from the control and operation unit 21c.
[0084] The read spectral reflectance data is converted into a
chromaticity value (for example, CIEL*a*b*) by the control unit 55
and is sent to a color conversion unit of the controller unit 56.
Further, using a color management system (CMS) (not shown), the
chromaticity value is converted into CMYK data (CSD) depending on
the image forming apparatus. After that, the converted CMYK data
(CSD) and default color patch data (CPD) are compared so as to
generate the correction table (C2) for correcting a difference
between the converted CMYK data (CSD) and the default color patch
data (CPD).
[0085] Such processing is performed on every patch image T for
colorimetry after the colorimetry, but the patch image T for
colorimetry is not always required to include all colors that can
be reproduced by the image forming apparatus. For instance, it is
possible to create a mixed color gray patch so as to perform only
gray axis correction. For CMYK data that are not formed as the
patch image for colorimetry on the recording material P, it is only
necessary that interpolation processing be performed based on the
patch after the colorimetry so that the correction table (C2) is
generated. The correction table (C2) generated in this way is
revised and stored in the controller unit 56 together with the
color separation table (C1).
[0086] Next, a comparative example for clearly describing an effect
of this embodiment is described.
[0087] FIG. 5 is a schematic diagram illustrating a spectral
colorimetry device 310 of the comparative example. For convenience
of description, a similar component to that of this embodiment is
denoted by the same reference symbol.
[0088] In the comparative example, a substrate 24 on which the
light source 12 is mounted and a substrate 25 on which the line
sensor 11 is mounted are different substrates.
[0089] On the other hand, as described above, in the spectral
colorimetry device 10 of this embodiment, the light source 12 and
the line sensor 11 are mounted on the same substrate 21. Thus, it
is unnecessary to assemble the substrate 24 and the substrate 25
separately unlike the comparative example, and workability in
assembling the spectral colorimetry device 10 is improved. As a
result, it is possible to contribute to cost reduction.
[0090] In addition, as described above, the spectral colorimetry
device 10 has a problem in that detection accuracy is lowered due
to thermal deformation. This is caused by a fluctuation of the
position of, in particular, the line sensor 11 due to thermal
deformation (creep) of a mold resin that is suitably used for the
housing of the spectral colorimetry device 10. When the position of
the line sensor 11 fluctuates, association between a spectral
wavelength that is intended to be detected and each pixel of the
line sensor 11 is changed. As a result, the detection accuracy may
be lowered.
[0091] In this embodiment, the light source 12 and the line sensor
11 are mounted on the same substrate 21, and a size of the
substrate 21 of this embodiment is larger than a size of the
substrate 25 of the comparative example on which only the line
sensor 11 is mounted. The substrates and 25 are suitably made of
epoxy-resin impregnated paper or a laminated glass fiber fabric
impregnated with an epoxy resin, and an influence of the thermal
deformation (creep) is much smaller than that of the housing made
of a mold resin. Therefore, in order to suppress a fluctuation of
the position of the line sensor 11 due to the thermal deformation
in the spectral colorimetry device 10, the structure of this
embodiment is more advantageous than that of the comparative
example.
[0092] In this embodiment, the following effect is further
obtained.
[0093] As the mold resin that is suitably used for the housing,
there are polycarbonate, acrylonitrile-butadiene-styrene copolymer
(ABS), polyethylene, polypropylene, and the like. However, these
mold resins have smaller tensile elasticity and bending strength
than the epoxy resin-impregnated paper and the laminated glass
fiber fabric impregnated with an epoxy resin that are suitably used
for the substrate 21.
[0094] Therefore, when an external force is applied due to thermal
deformation or the like of the color image forming apparatus, the
substrate 21 provides a function as a reinforcing member. Thus, the
effect of suppressing a positional fluctuation of the line sensor
11 is larger as the size of the substrate 21 is larger as in this
embodiment. As a result, it is possible to prevent the detection
accuracy from being lowered.
[0095] In addition, if the substrate 24 on which the light source
12 is mounted and the substrate 25 on which the line sensor 11 is
mounted are different substrates as in the comparative example,
when the housing of the spectral colorimetry device 10 is deformed
thermally, positions of the substrate 24 and the substrate 25 may
be fluctuated. Therefore, positions of the light source 12 and the
line sensor 11 are fluctuated separately, and the detection
accuracy may be lowered more significantly.
[0096] On the other hand, in this embodiment, because the light
source 12 and the line sensor 11 are mounted on the same substrate
21, when the housing of the spectral colorimetry device 10 is
deformed thermally, the light source 12 and the line sensor 11
follow a fluctuation of the substrate 21. Therefore, in this
embodiment, decrease of the detection accuracy can be suppressed
more than in the case of the comparative example in which positions
of the light source 12 and the line sensor 11 are fluctuated
separately.
[0097] As described above, in this embodiment, because the light
source 12 and the line sensor 11 are mounted on the same substrate
21, it is unnecessary to prepare separate substrates for mounting
the light source 12 and the line sensor 11 separately, and hence
cost can be reduced. In addition, because the same substrate 21 is
used, it is sufficient to fix the single substrate to the housing
when assembling the spectral colorimetry device 10, and hence
workability of assembling can be improved. As a result, it is
possible to contribute to cost reduction. Further, because an
influence of the thermal deformation can be reduced, it is possible
to prevent the detection accuracy from being lowered.
[0098] Further, the spectral colorimetry device 10 is mounted on
the image forming apparatus, the output of the patch image for
colorimetry is read by the spectral colorimetry device 10 arranged
in the image forming apparatus, and a color measurement result is
fed back to the image formation condition. Thus, it is possible to
obtain an output (image) having good color reproducibility.
Second Embodiment
[0099] Next, a second embodiment of the present invention is
described with reference to FIGS. 6A and 6B. Note that, a similar
component to that of the first embodiment is denoted by the same
reference symbol, and description thereof is omitted.
[0100] FIGS. 6A and 6B are explanatory diagrams illustrating a
schematic structure of a spectral colorimetry device 210 of this
embodiment. Definitions of the X direction, the Y direction, and
the Z direction are the same as those in the first embodiment. FIG.
6A is a diagram illustrating an XY cross section of the spectral
colorimetry device 210 as viewed from a direction perpendicular to
the detected surface of the detected material (from top). In
addition, FIG. 6B is a diagram illustrating an XZ cross section of
the spectral colorimetry device 210 as viewed from the front of the
spectral colorimetry device 210.
[0101] This embodiment has a feature in that the diffraction
grating 18 and the line sensor 11 are arranged so that an optical
path of light that is spectrally separated by the diffraction
grating 18 and is received by the line sensor 11 (spectral light
beam) becomes substantially parallel to the detected surface
(surface) of the detected material 14. In other words, the center
axis of the Rowland circle (not shown) of the diffraction grating
18 is parallel to the Z axis and is orthogonal to the detected
surface (surface). Therefore, in this embodiment, the plane on
which the diffraction grating 18 and the line sensor 11 are
arranged (virtual plane) and the detected surface of the detected
material 14 are substantially parallel to each other. In addition,
in this embodiment, the surface of the substrate 21 on which the
light source 12 and the line sensor 11 are mounted and the line
sensor 11 are mounted) and the detected surface of the detected
material 14 are substantially perpendicular to each other.
[0102] In the spectral colorimetry device 210 of this embodiment,
the light 15 is emitted in the Y direction from the light source 12
on the substrate 21 substantially perpendicular to the detected
surface of the detected material 14. Here, the detected surface of
the detected material 14 is situated on the XY plane, and the
surface of the substrate 21 is situated on the XZ plane.
[0103] The light 15 emitted in the Y direction is condensed by an
emission light guide 27 on the emission side, and the direction of
the light 15 is changed to propagate on the XZ plane by the
emission light guide 27 so as to enter the detected material 14
parallel to the emission direction of the light source 12 (Y
direction) at an angle of approximately 45.degree.. The light 15
entering the detected material 14 at an angle of approximately
45.degree. becomes scattered light in accordance with the optical
absorption characteristic of the detected material 14. A part of
the scattered light 16 is received by an incident light guide 28 on
the incident side to become collimated light, and then the
direction thereof is changed to propagate on the XY plane so as to
enter the slit 22. Further, the scattered light 16 passes through
the slit 22, is spectrally separated by the diffraction grating 18,
and propagates along the XY plane so as to be detected by the line
sensor 11.
[0104] As described above, in this embodiment, the optical path of
the light spectrally separated by the diffraction grating 18 and
detected by the line sensor 11 and the detected surface of the
detected material 14 are situated on the XY plane so as to have a
substantially parallel relationship. On the other hand, the first
embodiment is different from this embodiment in that the optical
path of the light that is spectrally separated by the diffraction
grating 18 and is detected by the line sensor 11 is situated on the
XZ plane and is substantially perpendicular to the detected surface
of the detected material 14 situated on the XY plane. Here, in the
first embodiment, the surface of the substrate 21 and the detected
surface of the detected material 14 are substantially parallel to
each other.
[0105] With reference to FIGS. 11A, 11B, and 11C, a more specific
structure of the spectral colorimetry device 210 of this embodiment
is described. FIGS. 11A and 11C are XY cross-sectional views
illustrating a specific structure of the spectral colorimetry
device 210 as viewed from the lateral direction (Z direction). FIG.
11B is an upper side cross-sectional view (XZ cross-sectional view)
illustrating a specific structure of the spectral colorimetry
device 210.
[0106] As illustrated in FIGS. 11A, 11B, and 11C, the spectral
colorimetry device 210 includes a casing 210a and a lid 210b
constituting the housing. The emission light guide 27, the incident
light guide 28, the slit 22, the diffraction grating 18, and the
substrate 21 are fixed to the casing 210a of the housing at
respective positions.
[0107] Next, a method of positioning and fixing the emission light
guide 27, the incident light guide 28, the slit 22, and the
diffraction grating 18 to the casing 210a is described. FIGS. 12A,
12B, 12C, and 12D are diagrams illustrating cross sections 12A,
12B, 12C, and 12D of FIG. 11C, respectively. The cross section 12A
illustrates a relationship between the emission light guide 27 and
the casing 210a. The emission light guide 27 is positioned so as to
abut against the casing 210a in the Y direction (direction of an
arrow) and is fixed in this state to the casing 210a with an
ultraviolet curing adhesive. Similarly, the other components, that
is, incident light guide 28 (the cross section 12B), the slit 22
(cross section 12C), and the diffraction grating 18 (the cross
section 12D) are positioned so as to abut against the casing 210a
in the Y direction (direction of an arrow) and are fixed in this
state to the casing 210a with an ultraviolet curing adhesive.
[0108] Next, a relationship among the casing 210a, the lid 210b,
and the substrate 21 is described in detail. FIGS. 13A and 13B are
perspective views of the housing. FIG. 13A illustrates a state
where the housing of the spectral colorimetry device 210 is
assembled. FIG. 13B illustrates a state before the housing of the
spectral colorimetry device 210 is assembled. Here, the emission
light guide 27, the incident light guide 28, the slit 22, and the
diffraction grating 18, which are fixed to the inside, are not
illustrated in the diagrams. As understood from the diagrams, the
lid 210b fixed to the casing 210a in the Z direction and the
substrate 21 is fitted thereto in the Y direction. The lid 210b is
positioned when the lid 210b is fitted to a groove formed in the
casing 210a and is fixed with an ultraviolet curing adhesive. On
the other hand, the substrate 21 is provided with the datum hole
21a serving as a reference for positioning in the X direction and
in the Z direction. The datum hole 21a is fitted onto a boss (not
shown) formed on the casing 210a so that the substrate 21 is
positioned in the X direction and in the Z direction. Further, the
notch portion 21b is formed in the substrate 21, and this portion
is fitted onto a protrusion (not shown) formed on the casing 210a
to serve as a rotation stopper about the Y axis for the substrate
21. The substrate 21 is fixed to the casing 210a with an
ultraviolet curing adhesive.
[0109] Here, when the light subjected to the wavelength dispersion
by the diffraction grating 18 is detected by the line sensor 11, in
order to secure a wavelength resolution, a certain extent of
optical path length is necessary for the optical path from the
diffraction grating 18 to the line sensor 11.
[0110] In the structure of the first embodiment, the optical path
of the light that is spectrally separated by the diffraction
grating 18 and is detected by the line sensor 11 is situated on the
XZ plane and is substantially perpendicular to the detected surface
of the detected material 14. Therefore, in the direction
perpendicular to the detected surface of the detected material 14
(Z direction), it is necessary to set the optical path length from
the diffraction grating 18 to the line sensor 11 to a desired
length, and it may be difficult to reduce a size (dimension) of the
spectral colorimetry device 210. Here, in the following
description, the size of the spectral colorimetry device 210 in the
direction perpendicular to the detected surface of the detected
material 14 (Z direction) is referred to as height of the spectral
colorimetry device 210 (distance between two planes parallel to the
detected surface) for convenience of description.
[0111] In contrast, in this embodiment, as described above, the
optical path of the light that is spectrally separated by the
diffraction grating 18 and is detected by the line sensor 11 is
situated on the XY plane and is substantially parallel to the
detected surface of the detected material 14. Therefore, in this
embodiment, it is possible to set the height of the spectral
colorimetry device 210 smaller than that in the structure of the
first embodiment.
[0112] In the image forming apparatus of this embodiment, as
illustrated in FIG. 2, the spectral colorimetry device 210 is
arranged at a position opposed to the recording material P in the
duplex conveyance path. In this structure, the height of the
spectral colorimetry device 210 can be reduced, and hence the image
forming apparatus can be downsized. In addition, there is no risk
of interference between the spectral colorimetry device 210 and
another member such as the secondary transfer roller 43 so that
design flexibility can be enhanced.
[0113] In addition, in the first embodiment, the optical path of
the light that is spectrally separated by the diffraction grating
18 and is detected by the line sensor is situated on the XZ plane
and is substantially perpendicular to the detected surface of the
detected material 14. Therefore, when the optical path length from
the diffraction grating 18 to the line sensor 11 is set to a
desired length, the optical path length from the light source 12 to
the detected material 14 may be increased. In contrast, in this
embodiment, the height of the spectral colorimetry device 210 can
be set smaller than that in the first embodiment, and hence the
optical path length from the light source 12 to the detected
material 14 can be set smaller than that in the first
embodiment.
[0114] Compared with the first embodiment, the optical path length
from the light source 12 to the detected material 14 can be
decreased to 60% in this embodiment, and the light emission amount
of the light source 12 can be halved substantially. Therefore, in
this embodiment, it is unnecessary to increase the light emission
amount for securing the light amount emitted to the detected
material 14. Therefore, it is also unnecessary to supply a large
current, and hence cost increase of the circuit and the light
emission element can be suppressed. As a result, cost can be
reduced.
[0115] As described above, according to this embodiment, because
the substrate 21 on which the light source 12 is mounted and the
detected surface are substantially perpendicular to each other, it
is possible to obtain the effect that the height of the spectral
colorimetry device 210 in the direction perpendicular to the
detected surface can be reduced in addition to the effect of the
first embodiment. Further, because the optical path length from the
light source 12 to the detected material 14 can be reduced, it is
possible to reduce cost of the spectral colorimetry device 210.
[0116] Here, in this embodiment, the optical path of the light that
is spectrally separated by the diffraction grating 18 and is
detected by the line sensor 11 is situated on the XY plane and is
substantially parallel to the detected surface of the detected
material 14. However, the present invention is not limited thereto,
it is only necessary that the optical path be situated along the XY
plane (virtual plane parallel to the detected surface). In
addition, in this embodiment, the surface of the substrate 21 on
which the light source 12 and the line sensor 11 are mounted and
the detected surface of the detected material 14 are substantially
perpendicular to each other, but the present invention is not
limited thereto. In other words, the surface of the substrate 21
and the detected surface of the detected material 14 need not be
substantially perpendicular to each other, as long as the optical
path of the light that is spectrally separated by the diffraction
grating 18 and is received by the line sensor 11 to be detected by
the line sensor 11 is situated along the XY plane.
[0117] In addition, with the structure of this embodiment, among
sizes of the spectral colorimetry device 210, the height of the
spectral colorimetry device 210 (size in a direction perpendicular
to the detected surface of the detected material 14 (Z direction))
can be suppressed. In contrast, in order to suppress a size of the
colorimetry device 210 in a direction parallel to the detected
surface of the detected material 14 (Y direction) among the sizes
of the spectral colorimetry device 210, it is preferred to use the
structure of the first embodiment.
Third Embodiment
[0118] Next, a third embodiment of the present invention is
described. Here, a similar component to that of the first and
second embodiments is denoted by the same reference symbol, and
description thereof is omitted.
[0119] This embodiment has a feature in that a region of the
substrate 21 between the light source 12 and the line sensor 11 has
a light transmission reducing structure for reducing light
transmission (preventing a part of light emitted by the light
source 12 from entering the line sensor 11 through the substrate
21).
[0120] FIG. 7 is a schematic diagram illustrating the substrate 21.
The light source 12 and the line sensor 11 are mounted on the
substrate 21. In addition, a hole 26 is formed in a region of the
substrate 21 between the light source 12 and the line sensor 11. In
this embodiment, a slit is formed as the hole 26.
[0121] In this embodiment, as illustrated in FIG. 7, the light
source 12 and the line sensor 11 are arranged at the center of the
substrate 21 (center in the vertical direction in FIG. 7) on the
substrate 21 having a height (length in the vertical direction in
FIG. 7) of 15 mm, and a width (length in the horizontal direction
in FIG. 7) of 90 mm. Further, the hole 26 having a height of 13 mm
and a width of 2 mm is arranged at a center position of the
substrate 21 in the vertical direction in FIG. 7, which is a
position that is 5 mm apart from the light source 12 in a direction
toward the line sensor 11.
[0122] Thus, a part of light (stray light) emitted from the light
source 12 is less likely to enter the line sensor 11 through the
substrate 21. In this embodiment, the stray light that is emitted
from the light source 12 through the substrate 21 so as to enter
the line sensor 11 can be reduced by 98% with respect to the first
embodiment.
[0123] Here, if the line sensor 11 is influenced by the stray
light, the detection accuracy may be lowered. This is because the
line sensor 11 detects the stray light as a disturbance component
besides the light spectrally separated by the diffraction grating
18. In particular, when measuring a color of a toner patch having a
low brightness in which the reflection light from the detected
material becomes weaker, the decrease of the detection accuracy
becomes conspicuous. Therefore, it is desired to suppress the stray
light as much as possible.
[0124] Next, the reason why the stray light can be reduced in this
embodiment is described in detail.
[0125] The substrate 21 is suitably made of epoxy resin-impregnated
paper or a laminated glass fiber fabric impregnated with an epoxy
resin. Therefore, the substrate 21 has a structure that transmits
light well.
[0126] Therefore, if a part of the light emitted from the light
source 12 is reflected without entering the emission light guide 19
or 27 on the emission side and enters the substrate 21, this light
propagates through the substrate 21 and is detected by the line
sensor 11 as stray light. In addition, if a part of the light
output from the emission light guide 19 or 27 on the emission side
does not propagate toward the aperture 13 but is reflected in the
spectral colorimetry device 10 or 210 so as to enter the substrate
21, this light propagates through the substrate 21 and is detected
by the line sensor 11 as stray light.
[0127] In this embodiment, because the hole 26 is formed as the
light transmission reducing structure in the region between the
light source 12 and the line sensor 11, the stray light propagating
through the substrate 21 can be reduced so that the detection
accuracy can be improved.
[0128] Further, the light transmission reducing structure is not
limited to this structure but may be a structure in which at least
a part of a region of the substrate 21 between the light source 12
and the line sensor 11 is formed of a member made of a material for
reducing light transmission so that the stray light is reduced. In
addition, the hole 26 described above may be formed so that the
stray light is further reduced.
[0129] As the material used for the substrate 21 for reducing light
transmission, it is preferred to use a mixture of an epoxy resin
and a coloring agent such as carbon powder or graphite powder. In
addition, it is also preferred to use ceramics such as alumina or
aluminum nitride for the substrate 21.
[0130] As described above, according to this embodiment, because
the light transmission reducing structure is arranged in the region
of the substrate 21 between the light source 12 and the line sensor
11, it is possible to obtain the effect of suppressing lowering of
the detection accuracy by the stray light in addition to the effect
of the embodiments described above.
[0131] According to the present invention, it is possible to
provide the colorimetry apparatus in which cost is reduced and
lowering of the detection accuracy is suppressed. In addition, it
is possible to provide the colorimetry apparatus that can realize
downsizing of the apparatus main body.
[0132] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0133] This application claims the benefit of Japanese Patent
Application Nos. 2012-168501, filed Jul. 30, 2012, and 2013-147644,
filed Jul. 16, 2013, which are hereby incorporated by reference
herein in their entirety.
* * * * *