U.S. patent application number 09/988770 was filed with the patent office on 2002-03-14 for density checking apparatus for tobacco flavor-tasting article or component of tobacco flavor-tasting article.
Invention is credited to Ishikawa, Yoshiaki, Kida, Shinzo.
Application Number | 20020030820 09/988770 |
Document ID | / |
Family ID | 15367541 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020030820 |
Kind Code |
A1 |
Kida, Shinzo ; et
al. |
March 14, 2002 |
Density checking apparatus for tobacco flavor-tasting article or
component of tobacco flavor-tasting article
Abstract
In an optical density checking apparatus, a 0.7-.mu.m first
light beam not transmitted through shredded leaf tobacco and a
1.3-.mu.m second light beam transmitted through the shredded leaf
tobacco, which are from first and second light sources, are
synthesized, and an obtained synthetic light beam is applied to a
tobacco rod. The projected light quantities, reflected light
quantities, and passing light quantities of the first and second
light beams are measured by a composite light-receiving element,
projected light quantity control circuit, and arithmetic circuit.
The arithmetic circuit calculates the transmitted light quantity of
the second light beam transmitted through the shredded leaf tobacco
on the basis of the projected light quantities, reflected light
quantities, and passing light quantities of the first and second
light beams, and calculates the density of the shredded leaf
tobacco on the basis of the transmitted light quantity.
Inventors: |
Kida, Shinzo; (Sumida-ku,
JP) ; Ishikawa, Yoshiaki; (Sumida-ku, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
15367541 |
Appl. No.: |
09/988770 |
Filed: |
November 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09988770 |
Nov 20, 2001 |
|
|
|
PCT/JP00/07455 |
Oct 25, 2000 |
|
|
|
Current U.S.
Class: |
356/432 |
Current CPC
Class: |
G01N 21/25 20130101;
Y10S 131/905 20130101; G01N 21/5907 20130101; Y10S 131/908
20130101; Y10S 131/906 20130101; A24C 5/3412 20130101 |
Class at
Publication: |
356/432 |
International
Class: |
G01N 021/59 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 1999 |
JP |
11-144671 |
Claims
What is claimed is:
1. An apparatus directed to as a test target a rod-like
flavor-tasting article or a component thereof having an aggregate
of a large number of small pieces, to optically check the density
of the small pieces, comprising: a first light source configured to
emit a first light beam formed of light with a first wavelength not
substantially transmitted through the small pieces; a second light
source configured to emit a second light beam formed of light with
a second wavelength substantially transmitted through the small
piece; an optical system configured to synthesize the first and
second light beams and to irradiate the test target with an
obtained synthetic light beam; a first measurement unit configured
to measure first and second projected light quantities respectively
corresponding to the first and second light beams included in the
synthetic light beam before applied to the test target; a second
measurement unit configured to measure first and second reflected
light quantities respectively corresponding to the first and second
light beams included in the synthetic light beam reflected by a
surface of the test target; a third measurement unit configured to
measure first and second passing light quantities respectively
corresponding to the first and second light beams included in the
synthetic light beam passing through the test target; and an
arithmetic circuit configured to calculate a transmitted light
quantity of the second light beam transmitted through the small
pieces on the basis of the first and second projected light
quantities, first and second reflected light quantities, and first
and second passing light quantities, and to calculate the density
of the small pieces on the basis of the transmitted light
quantity.
2. The apparatus according to claim 1, wherein the second
measurement unit measures the first and second reflected light
quantities by receiving and detecting both the first and second
light beams included in the synthetic light beam reflected by the
surface of the test target.
3. The apparatus according to claim 1, wherein the second
measurement unit measures one of the first and second reflected
light quantities by receiving and detecting one of the first and
second light beams included in the synthetic light beam reflected
by the surface of the test target, and measures the other one of
the first and second reflected light quantities by calculation with
a premise that the other one of the first and second reflected
light quantities can be obtained with the same reflectance as that
of one of the reflected light quantities.
4. The apparatus according to claim 1, further comprising a
detection circuit configured to calculate a fluctuation value as a
difference between a reference value representing the density of
the small pieces and a measurement value of the density of the
small pieces which is obtained by the arithmetic circuit, and a
control circuit configured to control an amount of the small pieces
to be introduced into the test target in a manufacturing system for
the test target on the basis of the fluctuation value.
5. The apparatus according to claim 4, further comprising an
integrating circuit configured to calculate an average value of
fluctuation values of a plurality of test targets obtained with the
detection circuit and to transmit the average value to the control
circuit.
6. The apparatus according to claim 4, further comprising a
comparative determination circuit configured to compare the
fluctuation value and a threshold value and to determine whether
the test target is defective or not.
7. The apparatus according to claim 1, wherein the small pieces are
shredded leaf tobacco, and the first and second wavelengths are 0.5
.mu.m to 0.8 .mu.m and 1.2 .mu.m to 1.4 .mu.m, respectively.
8. The apparatus according to claim 1, wherein each of the first
and second light beams comprises a laser light beam.
9. The apparatus according to claim 8, wherein at least one of the
first to third measurement units has a composite light-receiving
element configured to receive and detect the first and second light
beams on one optical path.
10. The apparatus according to claim 1, wherein the synthetic light
beam applied from the optical system to the test target comprises a
parallel light beam.
11. The apparatus according to claim 1, wherein the first
measurement unit measures the first and second projected light
quantities by receiving and detecting the first and second light
beams included in a beam portion separated from the synthetic light
beam between the optical system and the test target.
12. The apparatus according to claim 1, further comprising a
mirror, which is disposed between the optical system and the test
target, and has a mirror surface facing the test target to be
inclined with respect thereto and a hole matching with an optical
axis of the optical system, wherein the synthetic light beam from
the optical system passes through the hole as a convergent light
beam with a focal point falling on the hole and is thereafter
applied to the test target, and the synthetic light beam reflected
by the surface of the test target is reflected by the mirror and is
introduced to the second measurement unit.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation Application of PCT Application No.
PCT/JP00/07455, filed Oct. 25, 2000, which was not published under
PCT Article 21(2) in English.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a checking apparatus
directed to as a test target a rod-like flavor-tasting article or a
component thereof having an aggregate of a large number of small
pieces, such as shredded leaf tobacco, to optically check the
density of the small pieces. This checking apparatus can be used
in, e.g., a system that manufactures a tobacco rod by wrapping
shredded leaf tobacco with a wrapper, to feedback-control the
amount of shredded leaf tobacco introduced to the tobacco rod and
to eliminate a defective tobacco rod.
[0004] 2. Description of the Related Art
[0005] In a process of manufacturing a flavor-tasting article such
as a cigarette, tobacco rod, or tobacco filter, or a component of
the same, to know whether the product is defective or not, the
density of each constituent member of the flavor-tasting article
must be checked. For example, in a system for manufacturing a
tobacco rod by wrapping shredded leaf tobacco with a wrapper, an
optical density checking apparatus is used to obtain the packed
state of the shredded leaf tobacco in the tobacco rod. As a
checking apparatus of this type, Jpn. Pat. Appln. KOKOKU
Publication No. 8-2288 (corresponding to U.S. Pat. Nos. 4,805, 641
and 4,986,285) discloses an apparatus for optically checking the
density of a tobacco strand by using a light beam within a range of
ultraviolet rays to infrared rays.
[0006] The present inventor checked the density of a tobacco rod by
using a checking apparatus of the type disclosed in the above
reference. The correlation between the light attenuation ratio and
the weight of the shredded leaf tobacco was not accurately obtained
depending on the characteristics of the shredded leaf tobacco in
the tobacco rod. This problem may be posed because the following
several important factors are not sufficiently considered.
[0007] First, the water contained in the shredded leaf tobacco
largely influences the correlation between the light attenuation
ratio and the weight of the shredded leaf tobacco. When the
light-emitting element is an LED, the emitted light is not a
single-wavelength light, but its wavelength band is wide, and
accordingly the ratio of light attenuation caused by the shredded
leaf tobacco changes depending on the wavelength. Because light is
transmitted through the clearance of the packed shredded leaf
tobacco or along the surface of the wrapper of the rod (which is
influenced by circumferential change of the tobacco rod), the
quantity of light coming incident on the light-receiving element is
larger than that calculated considering the quantity of light
actually attenuated by the shredded leaf tobacco. Furthermore, a
measurement error occurs due to the dark current of the
light-receiving element.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention has been made in view of the problems
of the prior art described above, and has as its object to provide
a density checking apparatus which is directed to as a test target
a rod-like flavor-tasting article or a component thereof having an
aggregate of a large number of small pieces, such as shredded leaf
tobacco, and which can optically check the density of the small
pieces at high precision.
[0009] According to the first aspect of the present invention,
there is provided an apparatus directed to as a test target a
rod-like flavor-tasting article or a component thereof having an
aggregate of a large number of small pieces, to optically check the
density of the small pieces, comprising:
[0010] a first light source configured to emit a first light beam
formed of light with a first wavelength not substantially
transmitted through the small pieces;
[0011] a second light source configured to emit a second light beam
formed of light with a second wavelength substantially transmitted
through the small piece;
[0012] an optical system configured to synthesize the first and
second light beams and to irradiate the test target with an
obtained synthetic light beam;
[0013] a first measurement unit configured to measure first and
second projected light quantities respectively corresponding to the
first and second light beams included in the synthetic light beam
before applied to the test target;
[0014] a second measurement unit configured to measure first and
second reflected light quantities respectively corresponding to the
first and second light beams included in the synthetic light beam
reflected by a surface of the test target;
[0015] a third measurement unit configured to measure first and
second passing light quantities respectively corresponding to the
first and second light beams included in the synthetic light beam
passing through the test target; and
[0016] an arithmetic circuit configured to calculate a transmitted
light quantity of the second light beam transmitted through the
small pieces on the basis of the first and second projected light
quantities, first and second reflected light quantities, and first
and second passing light quantities, and to calculate the density
of the small pieces on the basis of the transmitted light
quantity.
[0017] According to the second aspect of the present invention, in
the apparatus according to the first aspect, the second measurement
unit measures the first and second reflected light quantities by
receiving and detecting both the first and second light beams
included in the synthetic light beam reflected by the surface of
the test target.
[0018] According to the third aspect of the present invention, in
the apparatus according to the first aspect, the second measurement
unit measures one of the first and second reflected light
quantities by receiving and detecting one of the first and second
light beams included in the synthetic light beam reflected by the
surface of the test target, and measures the other one of the first
and second reflected light quantities by calculation with a premise
that the other one of the first and second reflected light
quantities can be obtained with the same reflectance as that of one
of the reflected light quantities.
[0019] According to the fourth aspect of the present invention, the
apparatus according to any one of the first to third aspects
further comprises a detection circuit configured to calculate a
fluctuation value as a difference between a reference value
representing the density of the small pieces and a measurement
value of the density of the small pieces which is obtained by the
arithmetic circuit, and a control circuit configured to control an
amount of the small pieces to be introduced into the test target in
a manufacturing system for the test target on the basis of the
fluctuation value.
[0020] According to the fifth aspect of the present invention, the
apparatus according to the fourth aspect further comprises an
integrating circuit configured to calculate an average value of
fluctuation values of a plurality of test targets obtained with the
detection circuit and to transmit the average value to the control
circuit.
[0021] According to the sixth aspect of the present invention, the
apparatus according to the fourth or fifth aspect further comprises
a comparative determination circuit configured to compare the
fluctuation value and a threshold value and to determine whether
the test target is defective or not.
[0022] According to the seventh aspect of the present invention, in
the apparatus according to any one of the first to sixth aspects,
the small pieces are shredded leaf tobacco, and the first and
second wavelengths are 0.5.mu.m to 0.8 .mu.m and 1.2 .mu.m to 1.4
.mu.m, respectively.
[0023] According to the eighth aspect of the present invention, in
the apparatus according to any one of the first to seventh aspects,
each of the first and second light beams comprises a laser light
beam.
[0024] According to the ninth aspect of the present invention, in
the apparatus according to the eighth aspect, at least one of the
first to third measurement units has a composite light-receiving
element configured to receive and detect the first and second light
beams on one optical path.
[0025] According to the 10 th aspect of the present invention, in
the apparatus according to any one of the first to ninth aspects,
the synthetic light beam applied from the optical system to the
test target comprises a parallel light beam.
[0026] According to the 11 th aspect of the present invention, in
the apparatus according to any one of the first to 10th aspects,
the first measurement unit measures the first and second projected
light quantities by receiving and detecting the first and second
light beams included in a beam portion separated from the synthetic
light beam between the optical system and the test target.
[0027] According to the 12 th aspect of the present invention, the
apparatus according to any one of the first to 11th aspect further
comprises a mirror, which is disposed between the optical system
and the test target, and has a mirror surface facing the test
target to be inclined with respect thereto and a hole matching with
an optical axis of the optical system, wherein the synthetic light
beam from the optical system passes through the hole as a
convergent light beam with a focal point falling on the hole and is
thereafter applied to the test target, and the synthetic light beam
reflected by the surface of the test target is reflected by the
mirror and is introduced to the second measurement unit.
[0028] The embodiments of the present invention include inventions
at various stages, and various types of inventions can be extracted
from appropriate combinations of a plurality of disclosed
constituent elements. For example, when an invention is extracted
by omitting several ones from all constituent elements shown in the
embodiments, to practice the extracted invention, the omitted
portions are compensated for by known conventional technique.
[0029] According to the present invention, in an optical density
checking apparatus directed to as a test target a rod-like
flavor-tasting article or a component thereof having an aggregate
of a large number of small pieces, such as shredded leaf tobacco,
when the first light beam not substantially transmitted through the
small pieces and the second light beam substantially transmitted
through the small pieces are used, the density of the small pieces
can be checked at high precision.
[0030] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0031] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0032] FIG. 1 is a view showing an apparatus for checking the
density of shredded leaf tobacco in a tobacco rod according to an
embodiment of the present invention;
[0033] FIG. 2 is a view showing a model wherein a wall-like test
target made of an aggregate of a large number of small pieces SP is
irradiated with an infrared laser beam G1 to measure the density of
the small pieces SP;
[0034] FIG. 3 is a view showing a model wherein a rod-like test
target made of an aggregate of a large number of small pieces SP is
irradiated with an infrared laser beam G1 to measure the density of
the small pieces SP;
[0035] FIG. 4 is a side view showing a composite light-receiving
element that receives and detects two light beams with different
wavelengths on one optical path; and
[0036] FIG. 5 is a view showing an apparatus for checking the
density of shredded leaf tobacco in a tobacco rod according to
another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Embodiments of the present invention will be described with
reference to the accompanying drawings. In the following
description, constituent elements having substantially the same
functions and arrangements are denoted by the same reference
numerals, and a repetitive description is made when necessary.
[0038] FIG. 1 is a view showing an apparatus for checking the
density of shredded leaf tobacco in a tobacco rod according to an
embodiment of the present invention.
[0039] As shown in FIG. 1, this checking apparatus has first and
second light sources 12 and 14 formed of laser diodes for emitting
first and second light beams B1 and B2, respectively. The first
light beam B1 of the first light source 12 is formed of a laser
beam with a single first wavelength of 0.7 .mu.m. The first
wavelength is selected from the range of 0.5 .mu.m to 0.8 .mu.m so
the first light beam B1 is substantially transmitted through a
wrapper WP of a tobacco rod TR serving as a test target but is not
substantially transmitted through shredded leaf tobacco LS which is
an aggregate of a large number of small pieces. The second light
beam B2 of the second light source 14 is formed of a laser beam
with a single second wavelength of 1.3 .mu.m. The second wavelength
is selected from the range of 1.2 .mu.m to 1.4 .mu.m so the second
light beam B2 is substantially transmitted through the wrapper WP
and shredded leaf tobacco LS without being substantially influenced
by water of the shredded leaf tobacco LS.
[0040] The first and second light beams B1 and B2 emitted from the
first and second light sources 12 and 14 are synthesized by a half
mirror 16. A first synthetic portion C1 synthesized toward the
tobacco rod TR as the test target, i.e., the synthetic light beam,
is shaped to a parallel light beam CB with a width of about 5 mm
(with respect to the diameter of 6 mm to 10 mm of the tobacco rod
TR) through a correction lens 18 and collimator lens 22, and is
applied to the tobacco rod TR.
[0041] A second synthetic portion C2 of the first and second light
beams B1 and B2, which is separated from the first synthetic
portion C1 by the half mirror 16, is further split by a half mirror
24, and is guided to first and second light-receiving elements 26
and 28. A 0.7-.mu.m light filter 32 and 1.3-.mu.m light filter 34
are disposed at the input sides of the first and second
light-receiving elements 26 and 28 in order that only light
originated from the first and second light beams B1 and B2 become
incident on the first and second light-receiving elements 26 and
28.
[0042] The received light quantities of the first and second
light-receiving elements 26 and 28 are measured by a projected
light quantity control circuit 36, so that the first and second
projected light quantities of the first and second light beams B1
and B2 included in the parallel light beam CB are monitored. The
projected light quantity control circuit 36 calculates the first
and second projected light quantities of the first and second light
beams B1 and B2 included in the parallel light beam CB, and
feedback-controls outputs from the first and second light sources
12 and 14 so that the first and second projected light quantities
are constant. The first and second projected light quantities of
the first and second light beams B1 and B2 included in the parallel
light beam CB are transmitted from the projected light quantity
control circuit 36 to an arithmetic circuit 48 (to be described
later).
[0043] The reflected light of the parallel light beam CB, which is
reflected by the surface of the tobacco rod TR, i.e., the surface
of the wrapper WP, is focused on a pair of third light-receiving
elements 42, disposed above and under the tobacco rod TR, through
condenser lenses 44. In this embodiment, since 1.3-.mu.m light
filters 46 are disposed between the third light-receiving elements
42 and condenser lenses 44, only the reflected light of the second
light beam B2 become incident on the third light-receiving elements
42.
[0044] The received light quantities of the pair of third
light-receiving elements 42 are measured by the arithmetic circuit
48. The arithmetic circuit 48 calculates the first and second
reflected light quantities of the first and second light beams B1
and B2 included in the parallel light beam CB reflected by the
surface of the tobacco rod TR. The received light quantities of the
third light-receiving elements 42 are only that of the reflected
light of the second light beam B2. However, the arithmetic circuit
48 calculates the first and second reflected light quantities on
the premise that the first light beam B1 is also reflected with the
same reflectance as that calculated from the reflected light of the
second light beam B2. Instead of this arrangement, a
light-receiving element for receiving the reflected light of the
first light beam B1 may be further disposed in addition to the
third light-receiving elements 42 for receiving the reflected light
of the second light beam B2.
[0045] The transmitted light of the parallel light beam CB, which
is transmitted through the tobacco rod TR, is focused on a half
mirror 54 by a condenser lens 52 while including light that has
detoured along the surface of the tobacco rod TR, and is split by
the half mirror 54. The split light beams are guided to fourth and
fifth light-receiving elements 56 and 58. A 0.7-.mu.m light filter
62 and 1.3-.mu.m light filter 64 are disposed at the input sides of
the fourth and fifth light-receiving elements 56 and 58 in order
that only light originated from the first and second light beams B1
and B2 become incident on the fourth and fifth light-receiving
elements 56 and 58.
[0046] The received light quantities of the fourth and fifth
light-receiving elements 56 and 58 are also measured by the
arithmetic circuit 48. The arithmetic circuit 48 calculates the
first and second passing light quantities of the first and second
light beams B1 and B2 included in the parallel light beam CB
passing through the tobacco rod TR. Since the first light beam B1
with the wavelength of 0.7 .mu.m is not substantially transmitted
through the shredded leaf tobacco LS, light becoming incident on
the fourth light-receiving element 56 is the synthesis of light
passing through the clearance of the shredded leaf tobacco LS and
light detouring along the surface of the tobacco rod TR. Since the
second light beam B2 with the wavelength of 1.3 .mu.m is
substantially transmitted through the shredded leaf tobacco LS,
light becoming incident on the fifth light-receiving element 58 is
the synthesis of light transmitted through the shredded leaf
tobacco LS, light passing through the clearance of the shredded
leaf tobacco LS, and light detouring along the surface of the
tobacco rod TR.
[0047] The arithmetic circuit 48 amplifies light reception quantity
signals corresponding to the first and second projected light
quantities, first and second reflected light quantities, and first
and second passing light quantities, and calculates the density of
the shredded leaf tobacco LS in the tobacco rod TR on the basis of
the signals. This algorithm will be described first with reference
to FIGS. 2 and 3 showing simplified models.
[0048] FIG. 2 is a view showing a model wherein a wall-like test
target made of an aggregate of a large number of small pieces SP is
irradiated with an infrared laser beam G1 to measure the density of
the small pieces SP. In this case, in an ideal state, the basic
relationship between the projected light quantity and transmitted
light quantity (passing light quantity=transmitted light quantity
in this case) of the laser beam G1 is expressed by the following
equation:
J=I.multidot.exp(-.SIGMA.(.mu.i.multidot.xi))
[0049] where
[0050] I: the projected light quantity of the laser beam G1;
[0051] J: the transmitted light quantity of the laser beam G1;
[0052] .mu.i: the transmission coefficient of the small pieces SP;
and
[0053] xi: the thickness of the small pieces SP
[0054] However, when the density of the shredded leaf tobacco is to
be measured by irradiating a rod-like test target such as a tobacco
rod with an infrared laser beam, a decrease in incident light
quantity caused by light reflected by the surface of the tobacco
rod, an increase in passing light quantity caused by light
detouring along the surface of the tobacco rod, and noise included
in the passing light quantity caused by light passing through the
shredded leaf tobacco must be considered. FIG. 3 is a view showing
a model wherein a rod-like test target made of an aggregate of a
large number of small pieces SP is irradiated with an infrared
laser beam G1 to measure the density of the small pieces SP. In the
model shown in FIG. 3, when the above factors are considered, the
relationship between the projected light quantity and passing light
quantity of the laser beam G1 is expressed by the following
equation:
I.sub.0-I.sub.2I.sub.3=(I-I.sub.1).multidot.exp(-.SIGMA.(.mu.i.multidot.xi-
)) (1)
[0055] where
[0056] I: the projected light quantity of the laser beam G1;
[0057] I.sub.0: the passing light quantity of the laser beam
G1;
[0058] I.sub.1: the reflected light quantity of the laser beam
G1;
[0059] I.sub.2: the detouring light quantity of the laser beam
G1;
[0060] I.sub.3: the quantity of light passing through the small
pieces SP of the laser beam G1;
[0061] .mu.i: the transmission coefficient of the small pieces SP;
and
[0062] xi: the thickness of the small pieces SP
[0063] In the case of the tobacco rod TR, the transmission
coefficient pi of each piece of the shredded leaf tobacco LS can be
known in advance. A total thickness .SIGMA.xi of the shredded leaf
tobacco LS is closely related to the packing density of the
shredded leaf tobacco, and the transmission coefficient .mu.i of
the shredded leaf tobacco is substantially constant. Therefore,
even in the apparatus shown in FIG. 1, if values corresponding to
I, I.sub.0, I.sub.1, I.sub.2, and I.sub.3 in equation (1) are
measured, the total thickness of the shredded leaf tobacco LS in
the transmission path of the parallel light beam CB can be
obtained. Once the total thickness is obtained, the packing density
of the shredded leaf tobacco LS can be calculated at high precision
by multiplying it by a predetermined coefficient.
[0064] In the apparatus shown in FIG. 1, what corresponds to the
laser beam G1 of the model shown in FIG. 3 is the second light beam
B2 included in the parallel light beam CB emerging from the
collimator lens 22. More specifically, I of equation (1)
corresponds to the projected light quantity (calculated by the
projected light quantity control circuit 36) of the second light
beam B2 included in the parallel light beam CB emerging from the
collimator lens 22. I.sub.1 of equation (1) corresponds to the
reflected light quantity (received by the third light-receiving
elements 42) of the second light beam B2 included in the parallel
light beam CB reflected by the surface of the tobacco rod TR.
I.sub.0 of equation (1) corresponds to the passing light quantity
(received by the fifth light-receiving element 58) of the second
light beam B2 included in the parallel light beam CB passing
through the tobacco rod TR.
[0065] I.sub.2 and I.sub.3 of equation (1) each correspond to part
of the passing light quantity of the second light beam B2 included
in the parallel light beam CB passing through the tobacco rod TR.
Hence, I.sub.2 and I.sub.3 cannot be directly measured in the
apparatus shown in FIG. 1. In the present invention, however, the
total noise light quantity I.sub.2+I.sub.3 of light detouring along
the surface of the tobacco rod and light passing through the
shredded leaf tobacco, which concern the second light beam B2, can
be estimated from the net projected light quantity and passing
light quantity of the first light beam B1.
[0066] More specifically, the arithmetic circuit 48 calculates the
net projected light quantities of the first and second light beams
B1 and B2. The net projected light quantities can be obtained by
subtracting the reflected light quantities of the first and second
light beams B1 and B2 included in the parallel light beam CB
reflected by the surface of the tobacco rod TR, from the projected
light quantities of the first and second light beams B1 and B2
included in the parallel light beam CB emerging from the collimator
lens 22. The projected light quantities of the first and second
light beams B1 and B2 are calculated by the projected light
quantity control circuit 36 on the basis of light received by the
first and second light-receiving elements 26 and 28. The reflected
light quantities of the first and second light beams B1 and B2 are
calculated by the arithmetic circuit 48 on the basis of light
received by the third light-receiving elements 42.
[0067] Subsequently, the ratios (attenuation ratios) of the passing
light quantities of the first light beams B1 and B2 to the net
projected light quantities are calculated. The passing light
quantities of the first light beams B1 and B2 are calculated by the
arithmetic circuit 48 on the basis of light received by the fourth
and fifth light-receiving elements 56 and 58. As described above,
since the first light beam B1 with the wavelength of 0.7 .mu.m is
not substantially transmitted through the shredded leaf tobacco LS,
light becoming incident on the fourth light-receiving element 56 is
the synthesis of light passing through the clearance of the
shredded leaf tobacco LS and light detouring along the surface of
the tobacco rod TR. Since the second light beam B1 with the
wavelength of 1.3 .mu.m is substantially transmitted through the
shredded leaf tobacco LS, light becoming incident on the fifth
light-receiving element 58 is the synthesis of light transmitted
through the shredded leaf tobacco LS, light passing through the
clearance of the shredded leaf tobacco LS, and light detouring
along the surface of the tobacco rod TR.
[0068] Subsequently, the total noise light quantity of the light
detouring along the surface of the tobacco rod and the light
passing through the shredded leaf tobacco, which concern the second
light beam B2, is estimated from the net projected light quantity
and passing light quantity of the first light beam B1. The total
noise light quantity is subtracted from the passing light quantity
of the second light beam B2, thereby obtaining the transmitted
light quantity of the second light beam B2 transmitted through the
shredded leaf tobacco LS.
[0069] For example, assume that the attenuation ratio, i.e.,
(passing light quantity)/(net projected light quantity), of the
first light beam B1 is 10%, and that the attenuation ratio, i.e.,
(passing light quantity)/(net projected light quantity), of the
second light beam B2 is 30%. In this case, it is estimated that, of
the attenuation ratio 30% of the second light beam B2, 10% is
originated from the light detouring along the surface of the
tobacco rod and the light passing through the shredded leaf
tobacco, and 20% is originated from the light transmitted through
the shredded leaf tobacco LS. In other words, the net light
quantity, i.e., the transmitted light quantity, corresponding to
I.sub.0-I.sub.2-I.sub.3 of equation (1) can be obtained by
subtracting the attenuation ratio of the first light beam B1 from
that of the second light beam B2.
[0070] The arithmetic circuit 48 calculates .SIGMA.xi from the net
projected light quantity (I-I.sub.1) and transmitted light quantity
(I.sub.0-I.sub.2-I.sub.3) calculated in this manner and the
transmission coefficient ui of the shredded leaf tobacco LS input
in advance, and multiplies it by a predetermined coefficient, thus
calculating the density of the shredded leaf tobacco LS in the
tobacco rod TR. The arithmetic circuit 48 includes an integrating
circuit for integrating the signal for a time of 100 .mu.S to 1 mS,
so the adverse influence of noise that can be generated momentarily
in the detection signal is removed.
[0071] A density signal Y calculated by the arithmetic circuit 48
and representing the density of the shredded leaf tobacco LS is
transmitted to a weight fluctuation detection circuit 72. The
weight fluctuation detection circuit 72 calculates as a fluctuation
value .alpha. a difference (X-Y) between a weight reference signal
X as the reference value of the density of the shredded leaf
tobacco LS and the density signal Y calculated by the arithmetic
circuit 48. The weight reference signal X is a voltage
corresponding to the transmission amount of light which attenuates
when standard packing determined in accordance with the type of
tobacco is performed.
[0072] The fluctuation value a calculated by the weight fluctuation
detection circuit 72 is transmitted to an integrating circuit 73.
The integrating circuit 73 calculates an average fluctuation value
am of several hundred tobacco rods TR by integrating the
fluctuation values .alpha. for a long period of time. The average
fluctuation value am calculated by the integrating circuit 73 is
transmitted to a weight control circuit 74 added to a manufacturing
system 80 for the tobacco rod TR. The weight control circuit 74
controls the amount of shredded leaf tobacco LS to be packed in
each tobacco rod TR in the manufacturing system 80 for the tobacco
rod TR on the basis of the average fluctuation value .alpha.m.
[0073] The fluctuation value a calculated by the weight fluctuation
detection circuit 72 is also transferred to a comparative
determination circuit 76. The comparative determination circuit 76
compares a preset threshold signal .beta. as the threshold of the
fluctuation value .alpha. with the fluctuation value a calculated
by the weight fluctuation detection circuit 72, and determines
whether the tobacco rod TR is defective or not. If it is determined
that the tobacco rod TR is defective (.beta.<.alpha.), an
elimination signal .gamma. is transmitted from the comparative
determination circuit 76 to an elimination circuit 78. The
elimination circuit 78 eliminates the tobacco rod TR determined
defective from the manufacture line on the basis of the elimination
signal .gamma..
[0074] FIG. 5 is a view showing an apparatus for checking the
density of shredded leaf tobacco in a tobacco rod according to
another embodiment of the present invention. The basic concept of
this embodiment is the same as that of the embodiment shown in FIG.
1. Hence, a description of the second embodiment will be made
mainly on the difference from the embodiment shown in FIG. 1.
[0075] As shown in FIG. 5, this checking apparatus has a mounting
block 90 for mounting a tobacco rod TR as a test target therein.
The mounting block 90 is formed of a metal solid body with
cylindrical holes 92 and 94 in two directions perpendicular to each
other. One hole 92 is formed coaxially with the optical axis of a
parallel light beam CB (synthesis light beam) for check. The inner
surface of the hole 92 is mirror-finished in order to prevent light
absorption. A cylinder lens 96 and collimator lens 98 are disposed
at the input and output sides, respectively, of the hole 92. The
other hole 94 is formed as a hole where the tobacco rod TR is to be
inserted. The diameter of the hole 94 is selected such that no
clearance is substantially formed when the tobacco rod TR is
inserted in the hole 94.
[0076] This checking apparatus also has first and second light
sources 12 and 14 formed of laser diodes for respectively emitting
first and second light beams B1 and B2. The wavelengths of the
first and second light beams B1 and B2 are selected to satisfy the
conditions described with reference to the apparatus shown in FIG.
1. More specifically, the wavelengths of the first and second light
beams B1 and B2 are set at, e.g., 0.7 .mu.m and 1.3 .mu.m,
respectively, as described above.
[0077] The first and second light beams B1 and B2 from the first
and second light sources 12 and 14 are synthesized by a half mirror
prism 17a to form a synthetic light beam B12. The synthetic light
beam B12 is switched by a prism 17b toward the mounting block 90,
and is shaped to a convergent light beam through cylinder lenses
19a and 19b and a collimator lens 22. The focal point of the
convergent light beam is set to fall on a center hole 45a of a
mirror 45 disposed immediately before the mounting block 90. The
mirror 45 is arranged such that its mirror surface is inclined with
respect to the mounting block 90 so as to face it at an angle of,
e.g., 45.degree., and that its center hole 45a is coaxial with the
optical axis.
[0078] A beam splitter 25 is disposed between the collimator lens
22 and mirror 45, and splits the synthetic light beam B12. A beam
portion separated from the check beam portion of the synthetic
light beam B12 by the beam splitter 25 is guided to a composite
light-receiving element 27. The composite light-receiving element
27 is an element for receiving and detecting two light beams with
different wavelengths on one optical path, and in this case is set
to match the wavelengths of the first and second light beams B1 and
B2. The composite light-receiving element will be described later
in detail.
[0079] The received light quantity of the composite light-receiving
element 27 is measured by a projected light quantity control
circuit 36, so the first and second projected light quantities of
the first and second light beams B1 and B2 included in the
synthetic light beam B12 are monitored. The projected light
quantity control circuit 36 calculates the first and second
projected light quantities, feedback-controls outputs from the
first and second light sources 12 and 14, and transmits the first
and second projected light quantities to an arithmetic circuit
48.
[0080] The check beam portion of the synthetic light beam B12
passes through the center hole 45a of the mirror 45, is shaped to a
parallel light beam by the cylinder lens 96 at the input side of
the mounting block 90, and is applied to the tobacco rod TR. The
light reflected by the surface of the tobacco rod TR is reflected
by the mirror 45 and is guided to a composite light-receiving
element 43 through aspherical condenser lenses 47a and 47b. The
composite light-receiving element 43 can also receive and detect
the first and second light beams B1 and B2 of the reflected light
on one optical path. The received light quantity of the composite
light-receiving element 43 is measured by the arithmetic circuit
48, so the first and second reflected light quantities of the first
and second light beams B1 and B2 are monitored.
[0081] The check beam portion passing through the tobacco rod TR is
shaped to a converging light beam by the collimator lens 98 at the
output side of the mounting block 90, and is guided to a composite
light-receiving element 57. The composite light-receiving element
57 can also receive and detect the first and second light beams B1
and B2 of the passing light on one optical path. The received light
quantity of the composite light-receiving element 57 is measured by
the arithmetic circuit 48, so the first and second passing light
quantities of the first and second light beams B1 and B2 are
monitored.
[0082] The arithmetic circuit 48 calculates the density of shredded
leaf tobacco LS in the tobacco rod TR by using the first and second
projected light quantities, first and second reflected light
quantities, and first and second passing light quantities of the
first and second light beams B1 and B2 which are obtained in this
manner. Control operation from a weight fluctuation detection
circuit 72 to an elimination circuit 78 or manufacturing system 80
is completely the same as that described with reference to the
apparatus shown in FIG. 1.
[0083] In this embodiment, the algorithm used for calculation of
the density of the shredded leaf tobacco LS is basically the same
as that described with reference to the embodiment shown in FIG. 1.
Note that in the embodiment shown in FIG. 1, the first reflected
light quantity of the first light beam B1 is calculated on the
basis of the second reflected light quantity of the second light
beam B2, whereas in the second embodiment, it is measured by
actually receiving and detecting the first reflected light quantity
of the first light beam B1. Accordingly, in this embodiment, if the
test target has different reflectances depending on the
wavelengths, no error is caused.
[0084] FIG. 4 is a side view showing a composite light-receiving
element 100 used as each of the composite light-receiving elements
27, 43, and 57. As shown in FIG. 4, the composite light-receiving
element 100 has light-receiving portions 102 and 104 disposed at
two different levels perpendicular to an optical axis OA of an
incident light beam. The light-receiving portions 102 and 104 are
formed of different semiconductor light-receiving elements. The
primary (upper) light-receiving portion 102 detects the first light
beam B1 with a short wavelength (0.7 .mu.m in this case), and the
secondary (lower) light-receiving portion 104 detects the second
light beam B2 with a long wavelength (1.3 .mu.m in this case) which
can pass through the primary light-receiving portion 102. A Peltier
element 106 for cooling the light-receiving portions 102 and 104 is
disposed on the inner surface of the housing of the composite
light-receiving element 100.
[0085] In this manner, when a composite light-receiving element
that can receive and detect the first and second light beams B1 and
B2 on one optical path is used, a great advantage can be obtained
in terms of cost and space. Concerning this point, each of the
first and second light beams B1 and B2 from the first and second
light sources 12 and 14 is a laser light beam and accordingly has a
single wavelength. Therefore, even if processing such as wavelength
separation is not performed before the light is received, the
composite light-receiving element will not detect light in which
the wavelengths of the first and second light beams B1 and B2 are
mixed. When the light-receiving portions 102 and 104 are cooled by
the Peltier element 106, temperature drift or noise caused by
overheat of the light-receiving portions 102 and 104 can be
prevented.
[0086] The preferred embodiments of the present invention have been
described with reference to the accompanying drawings. Note that
the present invention is not limited to the above arrangements.
Various types of modifications and changes within the scope of the
technical concept described in the claims may be anticipated by a
person skilled in the art. It is to be understood that these
modifications and changes belong to the technical range of the
present invention.
[0087] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *