U.S. patent application number 14/242339 was filed with the patent office on 2014-07-31 for fluorescence observation system and set of filters.
This patent application is currently assigned to CARL ZEISS MEDITEC AG. The applicant listed for this patent is CARL ZEISS MEDITEC AG. Invention is credited to Roland GUCKLER, Helge JESS.
Application Number | 20140211306 14/242339 |
Document ID | / |
Family ID | 45494928 |
Filed Date | 2014-07-31 |
United States Patent
Application |
20140211306 |
Kind Code |
A1 |
JESS; Helge ; et
al. |
July 31, 2014 |
FLUORESCENCE OBSERVATION SYSTEM AND SET OF FILTERS
Abstract
A set of filters for fluorescence observation comprises an
illumination light filter and an observation light filter, wherein
the following is holds: .intg. S T L ( r -> ) T O ( r -> ) r
-> r .intg. S T L ( r -> ) T O ( r -> ) r = R -> and (
3 ) W -> - R -> .ltoreq. 0.2 ; ( 4 ) ##EQU00001## wherein:
.lamda. designates the wavelength, T.sub.L(.lamda.) is the
transmission characteristic of the illumination light filter,
T.sub.O(.lamda.) is the transmission characteristic of the
observation light filter, and A.sub.1, A.sub.2 are numbers between
0 and 1, {right arrow over (r)} is a coordinate in the CIE xy
chromaticity diagram of the CIE 1931 XYZ color space, S is a line
called the spectral locus in the CIE xy chromaticity diagram of the
CIE 1931 XYZ color space, and {right arrow over (W)} is the white
point in the CIE xy chromaticity diagram of the CIE 1931 XYZ color
space.
Inventors: |
JESS; Helge; (Oberkochen,
DE) ; GUCKLER; Roland; (Aalen-Dewangen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CARL ZEISS MEDITEC AG |
Jena |
|
DE |
|
|
Assignee: |
CARL ZEISS MEDITEC AG
Jena
DE
|
Family ID: |
45494928 |
Appl. No.: |
14/242339 |
Filed: |
April 1, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13205847 |
Aug 9, 2011 |
8730601 |
|
|
14242339 |
|
|
|
|
61371885 |
Aug 9, 2010 |
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Current U.S.
Class: |
359/385 ;
359/885 |
Current CPC
Class: |
G01J 3/0235 20130101;
G02B 5/288 20130101; G02B 21/0076 20130101; G02B 21/16 20130101;
G01J 3/4406 20130101; G01N 21/6447 20130101; G02B 21/06 20130101;
G01N 21/64 20130101; G01N 21/6458 20130101; G02B 5/20 20130101 |
Class at
Publication: |
359/385 ;
359/885 |
International
Class: |
G02B 21/06 20060101
G02B021/06; G02B 5/20 20060101 G02B005/20; G01N 21/64 20060101
G01N021/64 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2010 |
DE |
10 2010 033 825.7 |
Claims
1. A set of filters comprising an illumination light filter and an
observation light filter; wherein a transmission characteristic of
the illumination light filter is a sum of a first partial
characteristic and a second partial characteristic; wherein a
transmission characteristic of the observation light filter is a
sum of the third partial characteristic and a fourth partial
characteristic; wherein the first partial characteristic has, at
wavelengths below a threshold wavelength, at least one wavelength
range in which the transmission has values greater than a first
value; wherein the second partial characteristic has, at
wavelengths above the threshold wavelength, at least one second
wavelength range in which the transmission has values less than a
second value and greater than a third value, wherein the
transmission of the illumination light filter has, between the
first wavelength range and the second wavelength range, values less
than a fourth value; wherein the third partial characteristic has,
at wavelengths above the threshold wavelength, at least one third
wavelength range in which the transmission has values greater than
the first value; wherein the fourth partial characteristic has, at
wavelengths below the threshold wavelength, at least one fourth
wavelength range in which the transmission has values less than the
second value and greater than the third value; and wherein the
fourth value is less than the third value, the third value is less
than the second value and the second value is less than the first
value.
2. The set of filters according to claim 1, wherein: 0 .ltoreq. 1
300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 3 ( .lamda. ) .lamda.
< A 1 and ( 1 ) 2 A 1 < 1 300 nm .intg. 400 nm 700 nm T L (
.lamda. ) T O ( .lamda. ) .lamda. < A 2 ; ( 2 ) ##EQU00008##
wherein: .lamda. designates the wavelength, T.sub.1(.lamda.) is the
first partial characteristic, T.sub.2(.lamda.) is the second
partial characteristic, T.sub.3(.lamda.) is the third partial
characteristic, T.sub.L(.lamda.)=T.sub.1(.lamda.)+T.sub.2(.lamda.)
is the transmission characteristic of the illumination light
filter, T.sub.O(.lamda.) is the transmission characteristic of the
observation light filter, and A.sub.1, A.sub.2 are numbers between
0 and 1.
3. The set of filters according to claim 1, wherein: 0 .ltoreq. 1
300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 3 ( .lamda. ) .lamda.
< A 1 ; ##EQU00009## 2 A 1 < 1 300 nm .intg. 400 nm 700 nm T
L ( .lamda. ) T O ( .lamda. ) .lamda. < A 2 ; ##EQU00009.2## A 1
< 1 300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 4 ( .lamda. )
.lamda. < 0.5 A 2 ; ##EQU00009.3## and ##EQU00009.4## A 1 < 1
300 nm .intg. 400 nm 700 nm T 2 ( .lamda. ) T 3 ( .lamda. ) .lamda.
< 0.5 A 2 ; ##EQU00009.5## wherein .lamda. designates the
wavelength, T.sub.1(.lamda.) is the first partial characteristic,
T.sub.2(.lamda.) is the second partial characteristic,
T.sub.3(.lamda.) is the third partial characteristic,
T.sub.4(.lamda.) is the fourth partial characteristic,
T.sub.L(.lamda.)=T.sub.1(.lamda.)+T.sub.2(.lamda.) is the
transmission characteristic of the illumination light filter,
T.sub.O(.lamda.)=T.sub.3(.lamda.)+T.sub.4(.lamda.) is the
transmission characteristic of the observation light filter, and
A.sub.1, A.sub.2 are numbers between 0 and 1.
4. A fluorescence observation system comprising: a light source for
illuminating an object; observation optics for imaging the object;
an illumination light filter disposed in an illumination beam path
between the light source and the object; and an observation light
filter disposed in a beam path of the observation optics; wherein a
transmission characteristic of the illumination light filter is a
sum of a first partial characteristic and a second partial
characteristic; wherein a transmission characteristic of the
observation light filter is a sum of a third partial characteristic
and a fourth partial characteristic; wherein the first partial
characteristic has, at wavelengths below a threshold wavelength, at
least one wavelength range in which the transmission has values
greater than a first value; wherein the second partial
characteristic has, at wavelengths above the threshold wavelength,
at least one second wavelength range in which the transmission has
values less than a second value and greater than a third value,
wherein the transmission of the illumination light filter has,
between the first wavelength range and the second wavelength range,
values less than a fourth value; wherein the third partial
characteristic has, at wavelengths above the threshold wavelength,
at least one third wavelength range in which the transmission has
values greater than the first value; wherein the fourth partial
characteristic has, at wavelengths below the threshold wavelength,
at least one fourth wavelength range in which the transmission has
values less than the second value and greater than the third value,
wherein the transmission of the observation light filter has,
between the fourth wavelength range and the third wavelength range,
values which are smaller than the fourth value; and wherein the
fourth value is less than the third value, the third value is less
than the second value and the second value is less than the first
value.
5. The fluorescence observation system according to claim 4,
wherein: 0 .ltoreq. 1 300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T
3 ( .lamda. ) .lamda. < A 1 ; ##EQU00010## 2 A 1 < 1 300 nm
.intg. 400 nm 700 nm T L ( .lamda. ) T O ( .lamda. ) .lamda. < A
2 ; ##EQU00010.2## A 1 < 1 300 nm .intg. 400 nm 700 nm T 1 (
.lamda. ) T 4 ( .lamda. ) .lamda. < 0.5 A 2 ; ##EQU00010.3## and
##EQU00010.4## A 1 < 1 300 nm .intg. 400 nm 700 nm T 2 ( .lamda.
) T 3 ( .lamda. ) .lamda. < 0.5 A 2 ; ##EQU00010.5## wherein
.lamda. designates the wavelength, T.sub.1(.lamda.) is the first
partial characteristic, T.sub.2(.lamda.) is the second partial
characteristic, T.sub.3(.lamda.) is the third partial
characteristic, T.sub.4(.lamda.) is the fourth partial
characteristic, T.sub.L(.lamda.)=T.sub.1(.lamda.)+T.sub.2(.lamda.)
is the transmission characteristic of the illumination light
filter, T.sub.O(.lamda.)=T.sub.3(.lamda.)+T.sub.4(.lamda.) is the
transmission characteristic of the observation light filter, and
A.sub.1, A.sub.2 are numbers between 0 and 1.
6. A method of performing a fluorescence observation, wherein the
method comprises: filtering of an illumination light beam directed
to an object using an illumination light filter, and filtering of
light emanating from the object using an observation light filter;
wherein a transmission characteristic of the illumination light
filter is a sum of a first partial characteristic and a second
partial characteristic; wherein a transmission characteristic of
the observation light filter is a sum of a third partial
characteristic and a fourth partial characteristic; wherein the
first partial characteristic has, at wavelengths below a threshold
wavelength, at least one wavelength range in which the transmission
has values greater than a first value; wherein the second partial
characteristic has, at wavelengths above the threshold wavelength,
at least one second wavelength range in which the transmission has
values less than a second value and greater than a third value,
wherein the transmission of the illumination light filter has,
between the first wavelength range and the second wavelength range,
values less than a fourth value; wherein the third partial
characteristic has, at wavelengths above the threshold wavelength,
at least one third wavelength range in which the transmission has
values greater than the first value; wherein the fourth partial
characteristic has, at wavelengths below the threshold wavelength,
at least one fourth wavelength range in which the transmission has
values less than the second value and greater than the third value,
wherein the transmission of the observation light filter has,
between the fourth wavelength range and the third wavelength range,
values which are smaller than the fourth value; and wherein the
fourth value is less than the third value, the third value is less
than the second value and the second value is less than the first
value.
7. The method according to claim 6, wherein 0 .ltoreq. 1 300 nm
.intg. 400 nm 700 nm T 1 ( .lamda. ) T 3 ( .lamda. ) .lamda. < A
1 ; ##EQU00011## 2 A 1 < 1 300 nm .intg. 400 nm 700 nm T L (
.lamda. ) T O ( .lamda. ) .lamda. < A 2 ; ##EQU00011.2## A 1
< 1 300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 4 ( .lamda. )
.lamda. < 0.5 A 2 ; ##EQU00011.3## and ##EQU00011.4## A 1 < 1
300 nm .intg. 400 nm 700 nm T 2 ( .lamda. ) T 3 ( .lamda. ) .lamda.
< 0.5 A 2 ; ##EQU00011.5## wherein .lamda. designates the
wavelength, T.sub.1(.lamda.) is the first partial characteristic,
T.sub.2(.lamda.) is the second partial characteristic,
T.sub.3(.lamda.) is the third partial characteristic,
T.sub.4(.lamda.) is the fourth partial characteristic,
T.sub.L(.lamda.)=T.sub.1(.lamda.)+T.sub.2(.lamda.) is the
transmission characteristic of the illumination light filter,
T.sub.O(.lamda.)=T.sub.3(.lamda.)+T.sub.4(.lamda.) is the
transmission characteristic of the observation light filter, and
A.sub.1, A.sub.2 are numbers between 0 and 1.
Description
FIELD
[0001] The present invention relates to a fluorescence observation
system, a method for performing a fluorescence observation and a
set of filters which can be used in such system and method.
BACKGROUND
[0002] Fluorescence observation is used in many fields of
engineering, biology and medicine in order to visibly discriminate
between different structures of an object. Herein, an illumination
light filter is disposed in a beam path between an illumination
light source and an object to be observed, wherein the illumination
light filter allows substantially only light to traverse the filter
which can excite a fluorescence of a fluorescent dye. An
observation light filter is disposed in a beam path of imaging
optics, wherein the observation light filter allows only
fluorescent light to traverse the filter whereas light which can
traverse the illumination light is substantially not allowed to
traverse the observation light filter. Fluorescent structures of
the object can be perceived as bright regions in an image which is
observed with the eye by viewing into the observation optics or
which is recorded by a camera via the observation optics, and
non-fluorescing structures of the object remain dark such that
structures contained in the non-fluorescing regions cannot be
perceived.
[0003] It is desirable that also non-fluorescent regions of the
object can be seen in the image in order to be able to better
determine a position of fluorescent structures relative to the
non-fluorescent structures. In this respect, U.S. Pat. No.
6,212,425 B1 suggests to adjust transmission characteristics of the
illumination light filter and of the observation light filter
relative to each other such that both the fluorescent structures of
the object emitting the fluorescent light and non-fluorescent
structures reflecting light are visible downstream of the
observation light filter.
[0004] It has been found that non-fluorescent regions of an object
are not satisfactorily visible with such adjustment of the
illumination light filter and the observation light filter.
SUMMARY
[0005] Accordingly, it is desirable to provide a set of filters, a
fluorescence observation system and a method for performing a
fluorescence observation allowing to better perceive
non-fluorescent regions of an object.
[0006] The present invention has been accomplished taking the above
problems into consideration.
[0007] The present invention provides sets of filters, fluorescence
observation systems and methods allowing to observe fluorescent and
non-fluorescent regions of an object.
[0008] According to embodiments, an illumination light filter has a
transmission characteristic depending on the wavelength of the
light which is a sum of a first partial characteristic and a second
partial characteristic, wherein the first partial characteristic
has a first wavelength range at wavelength below a threshold
wavelength in which the transmission has values greater than a
first value, and wherein the second partial characteristic has a
second wavelength range at wavelengths above the threshold
wavelength, in which the transmission has values less than a second
value and greater than a third value, wherein the transmission of
the illumination light filter has values less than a fourth value
at wavelengths between the first wavelength range and the second
wavelength range.
[0009] The threshold wavelength is a wavelength determined based on
a used fluorescence process and separates wavelengths used for
exciting the fluorescence process from wavelengths used for
detecting the fluorescence process. In certain embodiments, the
threshold wavelength is selected such that it is greater than a
maximum of the excitation spectrum of the used fluorescence process
and less than a maximum of an emission spectrum of the used
fluorescence process. It is, however, possible to deviate from such
selection, and the threshold wavelength can be selected to be less
than the wavelength of the maximum of the excitation spectrum or
greater than the wavelength of the maximum of the excitation
spectrum, since excitation and emission spectra of fluorescence
processes overlap in practice.
[0010] The first partial characteristic of the transmission
characteristic of the illumination light filter has a function of
supplying fluorescence excitation light to the object. For this
purpose, the first partial characteristic has, in the first
wavelength range below the threshold wavelength, values of
transmission which are greater than the first value, wherein the
first value is selected to be as high as possible when designing
the filter. Exemplary values are greater than 0.75 or 0.9. A value
of 1.0 can be a target for optimization, wherein such value can be
only approximately reached in practice.
[0011] The second partial characteristic of the transmission
characteristic of the illumination light filter has a function of
supplying a certain amount of light to the object which is not used
for exciting the fluorescence but for making non-fluorescent
structures of the object visible. Since this light has wavelengths
above the threshold wavelength, it can traverse the observation
light filter when it is reflected by the object such that
non-fluorescent structures of the object can be perceived due to
such light.
[0012] Since fluorescent light generated by a fluorescent object
typically has a low intensity, it is desirable that an intensity
with which non-fluorescent regions of the object can be perceived
in the fluorescent image is not substantially greater than the
intensity with which the fluorescent regions are perceived since
the fluorescent regions are otherwise outshined by the
non-fluorescent regions. For that reason, it may be advantageous
that the amount of light supplied to the object via the second
partial characteristic is limited by selecting the transmission of
the illumination light filter in the second wavelength range to be
smaller than the second value and greater than the third value.
Herein, the second value is less than the first value, such that
the maximum transmission in the second wavelength range is
significantly less than the maximum transmission in the first
wavelength range. However, the maximum transmission in the second
wavelength range is greater than the third value, wherein the third
value represents a significant transmission rather than a
transmission which is very small and which is present in wavelength
ranges of the transmission characteristic of the filter in which
the filter should preferably transmit no light at all. Such low
transmission values are provided, for example, between the first
wavelength range and the second wavelength range where the
transmission is less than the fourth value, wherein the fourth
value represents a transmission of the filter such that the filter
transmits preferably no light at all at these wavelengths.
[0013] Summarized, the illumination light filter may have the
following properties: the filter transmits a significant amount of
light of plural wavelength ranges which are separated from each
other, wherein at least one of the plural wavelength ranges is
located below the threshold wavelength and allows a large amount of
light to traverse, whereas at least one of the plural wavelength
ranges is located above the threshold wavelength and allows to
traverse a relatively low but still significant amount of
light.
[0014] According to certain embodiments, the first value can be
0.50 and/or the second value can be 0.01, the third value can be
0.0005 and/or the fourth value can be 0.0002.
[0015] According to some embodiments, the observation light filter
may have a transmission characteristic which is a sum of a third
partial characteristic and a fourth partial characteristic.
However, the fourth partial characteristic is optional, such that
the transmission characteristic of the observation light filter can
be completely represented by a characteristic which is illustrated
in more detail as the third partial characteristic below.
[0016] The third partial characteristic has at least one wavelength
range at wavelengths above the threshold wavelength in which the
transmission has values which are greater than the first value. The
third partial characteristic has a function of allowing both the
fluorescent light and that light which serves to perceive the
non-fluorescent regions to traverse the filter. The light which
serves to perceive the non-fluorescent regions was allowed to reach
the object due to the second partial characteristic of the
illumination light filter, for example. Since intensities of
fluorescent light are typically low, maximum values of the
transmission in the third wavelength range are as high as possible.
For example, such maximum values are greater than the first value
illustrated above. As a result, both fluorescent structures of the
object and non-fluorescent structures of the object can be
perceived. This is achieved by supplying a significant amount of
light having wavelengths such that it does not necessarily excite
the fluorescence is supplied to the object and allowed to traverse
the observation light filter together with the fluorescence light.
Such property may be represented by the following formulas:
0 .ltoreq. 1 300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 3 (
.lamda. ) .lamda. < A 1 and ( 1 ) 2 A 1 < 1 300 nm .intg. 400
nm 700 nm T L ( .lamda. ) T O ( .lamda. ) .lamda. < A 2 ; ( 2 )
##EQU00002##
[0017] wherein: [0018] .lamda. designates the wavelength, [0019]
T.sub.1(.lamda.) is the first partial characteristic, [0020]
T.sub.2(.lamda.) is the second partial characteristic, [0021]
T.sub.3(.lamda.) is the third partial characteristic, [0022]
T.sub.L(.lamda.)=T.sub.1(.lamda.)+T.sub.2(.lamda.) is the
transmission characteristic of the illumination light filter,
[0023] T.sub.O(.lamda.) is the transmission characteristic of the
observation light filter, and [0024] A.sub.1, A.sub.2 are numbers
between 0 and 1.
[0025] Formula (1) shows that a spectral overlap between the first
partial characteristic of the illumination light filter for
supplying fluorescence excitation light to the object and the third
partial characteristic of the observation light filter for allowing
fluorescence light to traverse may have a value A.sub.1.
[0026] Formula (2) shows that a significant amount of light which
is not fluorescence light and may thus be used to observe
non-fluorescent regions of the object may traverse the combination
of the illumination light filter and the observation light
filter.
[0027] According to certain embodiments, A.sub.2 can be 0.1, or
A.sub.2 can be 0.05, or A.sub.2 can be 0.01, or A.sub.2 can be
0.005.
[0028] In embodiments in which the transmission characteristic of
the observation light filter is the sum of the third partial
characteristic and the fourth partial characteristic, the fourth
partial characteristic has, at wavelength below the threshold
wavelength, a fourth wavelength range in which the transmission has
values which are less than the second value and greater than the
third value. The fourth partial characteristic has a function of
allowing light to traverse the filter which is not fluorescence
light and which may thus be used to perceive non-fluorescent
objects. Since this light should not outshine the fluorescences,
the amount of light which can traverse the observation light filter
due to the fourth partial characteristic is limited by selecting
maximum values of the transmission in the fourth wavelength range
such that they are smaller than the second value which is
significantly smaller than the first value which may represent a
transmission optimized for maximal transmission. On the other hand,
the amount transmitted by the observation light filter below the
threshold wavelength should still be significant. For that reason,
the maximum value of the transmission in the fourth wavelength
range is greater than the third value which is significantly
greater than the fourth value which represents a transmission which
is intended to substantially prevent transmission.
[0029] With such arrangement, there is provided light for observing
non-fluorescent regions of the object from at least two different
wavelength ranges, mainly the light which is not fluorescence light
and which is supplied to the object due to the second partial
characteristic of the illumination light filter and which traverses
the observation light filter due to the third partial
characteristic, and light which is supplied to the object due to
the first partial characteristic of the illumination light filter
and which traverses the observation light filter due to the fourth
partial characteristic. These two wavelength ranges for observing
non-fluorescent regions of the object have a spectral distance from
each other. This spectral distance achieves an advantage in that
the non-fluorescent regions do not appear monochromatic. Moreover,
non-fluorescent regions can be perceived in plural spectral ranges,
resulting in that different structures in the non-fluorescent
regions of the object can be better perceived as compared to a
monochromatic perception.
[0030] Herein, it is possible that the second partial
characteristic of the illumination light filter and the fourth
partial characteristic of the observation light filter allow the
transmission of light in plural spectral ranges which are separated
from each other. These spectral ranges can be selected such that
the light available for the observation of non-fluorescent regions
originates from plural spectral ranges which can be selected such
that a mixture of the light is nearly white light. A
non-fluorescent white surface can be perceived as a white surface
through the system of the illumination light filter and the
observation light filter, accordingly.
[0031] According to some embodiments, a set of filters comprises an
illumination light filter and an observation light filter,
[0032] wherein a transmission characteristic of the observation
light filter has, at wavelength below a threshold wavelength, at
least one wavelength range in which a transmission has values which
are greater than a first value, and the transmission characteristic
of the illumination light filter has, at wavelength above the
threshold wavelength, at least one wavelength range in which the
transmission has values which are less than a fourth value;
[0033] wherein a transmission characteristic of the observation
light filter has, at wavelength above the threshold wavelength, at
least one wavelength range in which the transmission has values
greater than the first value, and the transmission characteristic
of the observation light filter has, below the threshold
wavelength, at least one wavelength range in which the transmission
has values which are smaller than the fourth value;
[0034] wherein
2 A 1 < 1 300 nm .intg. 400 nm 700 nm T L ( .lamda. ) T O (
.lamda. ) .lamda. < A 2 , ( 2 ) .intg. S T L ( r -> ) T O ( r
-> ) r -> r .intg. S T L ( r -> ) T O ( r -> ) r = R
-> and ( 3 ) W -> - R -> .ltoreq. 0 , 2 ; ( 4 )
##EQU00003##
[0035] wherein: [0036] .lamda. designates the wavelength, [0037]
T.sub.L(.lamda.) is the transmission characteristic of the
illumination light filter, [0038] T.sub.O(.lamda.) is the
transmission characteristic of the observation light filter, [0039]
A.sub.1, A.sub.2 are numbers between 0 and 1, [0040] {right arrow
over (r)} is a coordinate in the CIE xy chromaticity diagram of the
CIE 1931 XYZ color space, [0041] S is a line called the spectral
locus in the CIE xy chromaticity diagram of the CIE 1931 XYZ color
space, and [0042] {right arrow over (W)} is the white point in the
CIE xy chromaticity diagram of the CIE 1931 XYZ color space.
[0043] As already illustrated above, formula (2) shows that a
significant amount of light which is not fluorescence light and
which may serve for observing non-fluorescent regions of the object
may traverse the combination of the illumination light filter and
the observation light filter.
[0044] Formula (3) shows that the light which traverses the
combination of the illumination light filter and the observation
light filter and which is not fluorescence light belongs to
different spectral ranges and that its spectral intensities are
adjusted such that its mixture is nearly white light.
[0045] For defining these properties, reference is made to the CIE
1931 XYZ color space. This color space has a chromaticity diagram
in which a red portion of a light is represented by the coordinate
x and the green portion of light is represented by the coordinate
y, wherein a blue portion z of the light fulfills x+y+z=1. A
horseshoe-shaped curved line called the spectral locus of the
CIE-chromaticity diagram represents the pure spectral colors. The
white point has the coordinates x=1/3, y=1/3.
[0046] The integrals of the formula (3) are calculated along the
line S which is the spectral locus line in the in the CIE xy
chromaticity diagram of the CIE 1931 XYZ color space. Formula (3)
represents a determination of a center of gravity of the light
intensities on the spectral locus line, wherein a weighting is
performed with the product T.sub.LT.sub.O which represents the
transmission through the combination of the illumination light
filter and the observation light filter. The result of the
determination of the center of gravity is the vector {right arrow
over (R)} in the CIE xy chromaticity diagram of the CIE 1931 XYZ
color space.
[0047] Formula (4) shows that a distance between the result {right
arrow over (R)} of the determination of the center of gravity and
the white point {right arrow over (W)} in the CIE xy chromaticity
diagram of the CIE 1931 XYZ color space is less than a
predetermined value and is, thus, close to the white color.
[0048] According to further embodiments, the sets of filters
illustrated above are integrated with a fluorescence observation
system comprising a light source for illuminating the object.
Herein, the transmission characteristics of the filters can be
adjusted such that a spectrum of the light generated by the light
source is taken into account. For example, this can be achieved by
replacing the product T.sub.LT.sub.O in the above formulas by a
product I.sub.QT.sub.LT.sub.O, wherein I.sub.Q represents the
spectral distribution of the light of the light source.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] The forgoing as well as other advantageous features of the
disclosure will be more apparent from the following detailed
description of exemplary embodiments of the disclosure with
reference to the accompanying drawings. It is noted that not all
possible embodiments of the present disclosure necessarily exhibit
each and every, or any, of the advantages identified herein.
[0050] FIG. 1 is a schematic illustration of a fluorescence
observation system;
[0051] FIGS. 2a to 2d are graphs for schematically illustrating a
set of filters for fluorescence observation; and
[0052] FIG. 3 shows a representation of the chromaticity diagram of
the CIE xy chromaticity diagram of the CIE 1931 XYZ color space in
which properties of the set of filters illustrated with reference
to FIGS. 2a to 2d are shown.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0053] In the exemplary embodiments described below, components
that are alike in function and structure are designated as far as
possible by alike reference numerals. Therefore, to understand the
features of the individual components of a specific embodiment, the
descriptions of other embodiments and of the summary of the
disclosure should be referred to.
[0054] An embodiment of a fluorescence observation system is
illustrated with reference to a surgical microscope below. However,
embodiments of the fluorescence observation system are not limited
to surgical microscopes and comprise any type of fluorescence
observation system in which illumination light directed to an
object is filtered with an illumination light filter and in which
light emerging from the object is filtered with an observation
light filter.
[0055] Referring to FIG. 1, a fluorescence observation system or
microscope 1 comprises microscopy optics 3 including an objective
lens 5 having an optical axis 7. An object 9 to be observed is
located in an object plane of the objective lens 5. Light emerging
from the object 9 is formed into an image side beam 11 by the
objective lens 5, wherein two zoom systems 12, 13 are located in
the beam 11 and spaced apart from the optical axis 7. The zoom
systems 12, 13 select two partial beams 14 and 15 from the beam 11
and supply the partial beams 14, 15 to oculars 16, 17 via
deflecting prisms (not shown). A user looks into the oculars with
his left eye 18 and right eye 19 in order to perceive a magnified
representation of the object 9.
[0056] A semi-transparent mirror 21 maybe located in the partial
beam 15 in order to supply a portion of the light as a beam 23 to a
camera system 24. The camera system 24 may comprise one camera or
plural cameras. In the illustrated embodiment, the camera system 24
comprises a camera 32 receiving light of the beam 23 having
traversed a semi-transparent mirror 25 via camera adapter optics
31, and a camera 55 receiving light of the beam 23 reflected from
the semi-transparent mirror 25 via a filter 57 and camera adapter
optics 53. The filter 57 can be a fluorescence light filter which
transmits only fluorescence light of a fluorescent dye contained in
the object 9. Thus, the camera 32 can detect a normal light image
of the object 9, whereas the camera 55 can detect a fluorescence
light image of the object 9. Images of the cameras 32 and 55 are
supplied to a controller 35 via data connections 33 and 65,
respectively, and can be stored in a memory 95 of the
controller.
[0057] Similarly, a semi-transparent mirror 37 can be located in
the other partial beam 14 in order to reflect a partial beam 39
which is supplied to a camera 43 via camera adapter optics 41 such
that the camera 43 may also detect a normal light image, wherein
detected images of the camera 43 are transmitted to the controller
35 via a data connection 45.
[0058] A display 69 is connected to the controller 35 via a data
connection 67, and an image displayed on the display 69 is
projected into the beam path of the ocular 17 via projection optics
70 and a further semi-transparent mirror 68 located in the partial
beam 15, such that the user may directly perceive both the image
displayed on the display 69 and the image of the object with his
eye 19. The controller 35 may, for example, project data or images
of the object detected by the cameras 32, 55 and 43, or generated
by an analysis of the detected images.
[0059] The controller 35 may also supply the images detected by the
cameras to a head mounted display 49, wherein the head mounted
display includes two displays 51, 52 for the right and left eyes,
respectively, of the user.
[0060] The microscope 1 further comprises an illumination system 63
for generating an illumination light beam 81 directed to the object
9. For this purpose, the illumination system 63 comprises a broad
band light source, such as, for example, a halogen lamp or a Xenon
lamp 71, a reflector 72 and a collimator 73 for generating a
collimated light beam 74 which may be directed onto an entrance end
76 of a fiber bundle 77 by one or more lenses 75, in order to
couple light emitted by the lamp 71 into the fiber bundle 77. The
light is transported to a location close to the object 9 by the
fiber bundle 77 and is emitted from the fiber bundle 77 at an exit
end 78 of the bundle 77 and is collimated by collimating optics 79
to provide the illumination light beam 81 directed to the object
9.
[0061] The illumination system 63 further comprises a filter plate
83 including an illumination light filter 84 for fluorescence
observation and an illumination light filter 85 for normal light
observation. An actuator 87 controlled by the controller 35 is
provided in order to selectively locate the illumination light
filter 84 for fluorescence light observation or the illumination
light filter 85 for normal light observation in the beam 74 as
indicated by an arrow 88. The illumination light filter 84 for
fluorescence light observation is located in the beam 74 if a
fluorescence is to be excited in the object to be observed, while
the illumination light filter 85 for normal light observation is
located in the beam 74 if the object 9 is to be observed under
normal light, such as white light. The illumination light filter 85
can be configured such that, for example, it does not allow
infrared light or near infrared light generated by the lamp 71 to
be transmitted, in order to avoid an unnecessary warming of the
object 9, while shorter wavelengths are transmitted.
[0062] The selective arrangement of the illumination light filters
84 and 85, respectively, in the beam 74 can be controlled by the
user via an input device, such as a button 79.
[0063] An observation light filter 91 for fluorescence observation
is located in each of the partial beams 15 and 14, wherein an
actuator 93 controlled by the controller 35 is provided to
selectively remove the observation light filters 91 from the
partial beams 14 and 15 as indicated by an arrow 94.
[0064] The observation light filters 91 are placed in the beam
paths 14, 15 if the illumination light filter 84 for fluorescence
observation is arranged in the beam 74, and they are removed from
the beam paths 14, 15 if the illumination light filter 85 for
normal light observation is arranged in the beam 74. For this
purpose, the controller 35 may operate the actuator 93 together
with the actuator 87 upon actuation of the input device 97 by the
user.
[0065] In the illustrated embodiment, the illumination light filter
for fluorescence observation and the observation light filter 91
for fluorescence observation are inserted into or removed from the
beam path by actuators controlled by the controller. It is,
however, also possible that the filters are mounted on filter
holders which are directly operated by the hand of the user in
order to insert the filters into and remove the filters from the
beam paths. The illumination light filter and the observation light
filter for fluorescence observation each have transmission
characteristics adapted to a fluorescent dye having a fluorescence
which is desired to be observed. A plurality of fluorescent dyes
are known, and sets of filters including an illumination light
filter and an observation light filter can be provided for each of
these fluorescent dyes as will be illustrated in more detail below.
The fluorescent dyes which can be used with these sets of filters
are only limited in that the fluorescence light of these dyes
should include wavelength of visible light in order to allow
structures of the object 9 containing the fluorescent dye to be
perceived with the human eye. Properties of the sets of filters
will be illustrated below with reference to an exemplary set of
filters including illumination light filters and observation light
filters which are designed to observe the fluorescence of the
fluorescent dye fluorescein. For this purpose, reference is made to
FIGS. 2a to 2d.
[0066] FIG. 2a is a schematic illustration of a graph 101 of the
excitation spectrum of fluorescein and a graph 103 of the emission
spectrum of fluorescein in a normalized representation. The maximum
of the excitation spectrum 101 has a wavelength of about 485 nm,
and the maximum of the emission spectrum 103 has a wavelength of
about 514 nm, wherein the graphs of the excitation spectrum 101 and
of the emission spectrum 103 overlap.
[0067] FIG. 2b is a schematic illustration of a graph of a
transmission characteristic 105 of the illumination light filter in
a logarithmic scale of the ordinate in a wavelength range from 380
nm to 780 nm. This is the wavelength range of visible light
relevant for illustrating the properties of the set of filters. The
threshold wavelength is designated with reference numeral 107 in
FIG. 2b. In the illustrated example, the threshold wavelength 107
is selected such that it is located between the maximum of the
excitation spectrum 101 and the maximum of the fluorescence
spectrum 103. Such selection is, however, not required. It is also
possible to select the threshold wavelength such that it is smaller
than the wavelength of the maximum of the excitation spectrum 101
or greater than the wavelength of the maximum of the fluorescence
spectrum 103, as long as the excitation spectrum 101 and the
fluorescence spectrum 103, respectively, have an intensity value at
the threshold wavelength 107 which is significantly greater than
zero.
[0068] The transmission characteristic 105 is the sum of two
partial characteristics I and II defined within the full range from
380 nm to 780 nm. The partial characteristic I has, at wavelengths
below the threshold wavelength 107, a wavelength range 109 in which
the transmission has values greater than a value L1. The partial
characteristic I has a function of allowing fluorescence excitation
light to traverse the illumination light filter in order to excite
the fluorescence of the fluorescent dye. The transmission of the
filter within the wavelength range 109 is selected to be as high as
possible in order to achieve a high efficiency. The value L1
represents a transmission value which can be achieved, for example,
if the filter is optimized for a high transmission in this
wavelength range. In the illustrated example, the value of L1 is
0.6.
[0069] The partial characteristic II includes, at wavelengths above
the threshold wavelength, at least one second wavelength range in
which the transmission has values which are less than a second
value L2 and greater than a value L3. The partial characteristic II
has a function of allowing light to traverse the illumination light
filter which is used for illuminating the object such that its
non-fluorescent regions can be perceived rather than for exciting
the fluorescence. Since the non-fluorescent regions should not
outshine the fluorescent regions and since the fluorescence
typically has a low intensity, the illumination light is
transmitted with a relatively low intensity by the illumination
light filter due to the partial characteristic II. This is the
reason why the maximum of the partial characteristic II is less
than the value L2 which is smaller than the value L1 which is
exceeded by the transmission characteristic in those wavelength
ranges in which a transmission as high as possible is desired. The
value L2 is 0.1 in the illustrated embodiment. However, the
transmission provided by the partial characteristic II is higher
than the value L3, which is significantly higher than the value L4.
The transmission is below the value L4 within lowest wavelength
ranges in which it is desired that the illumination light filter
substantially blocks the illumination light. The value L3 is 0.0002
and the value L4 is 0.00005 in the illustrated embodiment.
[0070] A transmission characteristic 113 of the observation light
filter is schematically shown in FIG. 2c. The transmission
characteristic 113 is again a sum of two partial characteristics
III and IV. The partial characteristic III has, at wavelengths
above the threshold wavelength 107, at least one wavelength range
115 in which the transmission has values greater than the value L1.
The partial characteristic III has a function of allowing both
fluorescence light and illumination light to traverse the
observation light filter, which light has reached the object due to
the partial characteristic II of the illumination light filter.
This is the reason why both fluorescent regions and non-fluorescent
regions of the object can be perceived. The fluorescent regions can
be perceived since the fluorescent light can traverse the
observation light filter due to the partial characteristic III, and
the non-fluorescent regions can be perceived since light having
reached the object due to the partial characteristic II can
traverse the observation light filter.
[0071] The partial characteristic IV includes, at wavelengths below
the threshold wavelength 107, at least one wavelength range 117 in
which the transmission has values which are smaller than the value
L2 and greater than the value L3. The partial characteristic IV has
a function of allowing light, which reaches the object due to the
partial characteristic I of the illumination light filter and which
is reflected from or scattered at the object, to traverse the
observation light filter in order to make non-fluorescent regions
of the object visible. Similar to the partial characteristic II of
the illumination light filter, the partial characteristic IV of the
observation light filter has maximum transmissions which are
smaller than the value L2 and greater than the value L3 in order to
avoid outshining of the fluorescent regions. The value L3 is
significantly greater than the value L4, wherein the transmission
characteristic 113 is below the value L4 in those wavelength ranges
in which the transmission of light through the observation light
filter should be blocked.
[0072] Optical filters having properties as schematically
illustrated in FIGS. 2b and 2c can be manufactured, for example, by
evaporating multi-layers of dielectric materials on a glass
substrate, wherein suitable layer compositions and thicknesses can
be determined using mathematical simulation methods as known in the
field of optical engineering. Moreover, each of the observation
light filter and the illumination light filter can be provided by
of two or more separate filters which are together disposed in the
optical beam path and provide properties of the whole filter. For
example, the illumination light filter may be provided by two
suitably selected high pass filters and two suitably selected low
pass filters.
[0073] FIG. 2d schematically shows the product of the transmission
characteristic 105 of the illumination light filter and the
transmission characteristic 113 of the observation light filter.
This product shows significant intensities in three wavelength
ranges, mainly in the wavelength range 117 in which the partial
characteristic IV of the observation light filter is significantly
transmitting, in the wavelength range 115 in which the partial
characteristic II of the illumination light filter is significantly
transmitting, and in a region around the threshold wavelength 107
in which the transmission is represented by a line 123. The
transmission represented by the line 123 results from a spectral
overlap of a shoulder 125 of the transmission characteristic I and
a shoulder 127 of the transmission characteristic III of the
observation light filter. It is possible that the shoulders 125 and
127 are intentionally provided in order to provide light for the
observation of non-fluorescent regions of the object. It is also
possible that the spectral overlap is inevitable in practice since
arbitrarily steep edges of the transmission characteristics cannot
be achieved due to technical limitations in the manufacture of the
filters.
[0074] The intensity of the light traversing the set of filters due
to the overlap between the shoulders 125 and 127 is
0 .ltoreq. 1 300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 3 (
.lamda. ) .lamda. < A 1 and ( 1 ) ##EQU00004##
[0075] and is zero, if no overlap is present, or less than the
value A.sub.1, if some overlap is present.
[0076] The intensity of the light which traverses the set of
filters due to the partial characteristic IV in the wavelength
range 117 is represented by the formula
A 1 < 1 300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 4 (
.lamda. ) .lamda. < 0.5 A 2 ( 2 ) ##EQU00005##
[0077] and is greater than A.sub.1 and less than 0.5 A.sub.2.
Similarly, the intensity which traverses the set of filters due to
the partial characteristic II is represented by the formula
A 1 < 1 300 nm .intg. 400 nm 700 nm T 1 ( .lamda. ) T 3 (
.lamda. ) .lamda. < 0.5 A 2 ( 3 ) ##EQU00006##
[0078] wherein this intensity is again greater than the intensity
caused by the overlap 123 and less than 0.5 A.sub.2.
[0079] FIG. 2 shows that light from at least two different
wavelength ranges significantly contributes to the perception of
non-fluorescent regions of the object. This has an advantage in
that the non-fluorescent regions of the object do not appear
monochrome and that non-fluorescent white regions of the object
appear to be nearly white.
[0080] The widths and the amounts of the values of the partial
characteristic II in the wavelength range 111 and of the partial
characteristic IV in the wavelength range 117 define the amounts of
light in the various wavelength ranges and are available for
observing non-fluorescent regions of the object. In the
illustration of FIG. 2d, the available light has a higher spectral
power density in the wavelength range from 485 nm to 505 nm due to
the partial characteristic IV than in the relatively broader
wavelength range from 620 nm to 700 nm due to the partial
characteristic II. The spectral distribution of the available light
for visualizing non-fluorescent regions of the object is selected
such that a non-fluorescent white surface of the object possibly
generates a white color impression for the user as illustrated with
reference to FIG. 3 below.
[0081] FIG. 3 is a schematic representation of the CIE-chromaticity
diagram of the CIE-1931 color space in which the line called the
spectral locus carries reference numeral S and in which the white
point carries the reference numeral W. A rectangle IV in FIG. 3
designates that region of the spectral locus line S in which the
transmission of the partial characteristic IV of the observation
light filter has values greater than L3, while a rectangle II
designates that region of the spectral locus line S in which the
partial characteristic II of the illumination light filter has
values greater than L3. Light for observing non-fluorescent regions
is provided in the portions II and IV of the spectral locus line,
accordingly. A center of gravity of the portion IV is designated by
reference numeral 131 in FIG. 3, and a center of gravity of the
portion II is designated by reference numeral 133 in FIG. 3. The
centers of gravity and weights of the portions IV and II are
selected such that the light of these portions adds up to form a
mixture of light close to the white point W. This mixing of light
is represented in FIG. 3 by arrows 135.
[0082] The properties of the transmission characteristics of the
illumination light filter and the observation light filter
illustrated above are represented by the following formulas (3) and
(4):
.intg. S T L ( r -> ) T O ( r -> ) r -> r .intg. S T L ( r
-> ) T O ( r -> ) r = R -> and ( 3 ) W -> - R ->
.ltoreq. 0.2 ; ( 4 ) ##EQU00007##
[0083] wherein: [0084] .lamda. designates the wavelength, [0085]
T.sub.L(.lamda.) is the transmission characteristic of the
illumination light filter, [0086] T.sub.O(.lamda.) is the
transmission characteristic of the observation light filter, and
[0087] {right arrow over (r)} is a coordinate in CIE xy
chromaticity diagram of the CIE 1931 XYZ color space, [0088] S is a
line called the spectral locus line in CIE xy chromaticity diagram
of the CIE 1931 XYZ color space, and [0089] {right arrow over (W)}
is the white point in CIE xy chromaticity diagram of the CIE 1931
XYZ color space.
[0090] The integral in the enumerator of formula (3) is taken along
the spectral locus line S. Due to the term {right arrow over
(r)}dr, a determination of a center of gravity is performed in the
coordinates of the color space using a weighting T.sub.L({right
arrow over (r)})T.sub.O({right arrow over (r)}). The integral in
the denominator of formula (3) is also taken along the spectral
locus line S. This integral is used for normalization such that the
value {right arrow over (R)} represents the center of gravity of
the function T.sub.L({right arrow over (r)})T.sub.O({right arrow
over (r)}) along the spectral line S.
[0091] The formula (4) indicates that this center of gravity {right
arrow over (R)} has a distance from the white point {right arrow
over (W)} in CIE xy chromaticity diagram of the CIE 1931 XYZ color
space of less than 0.2. According to other embodiments, the
distance can be less than 0.15 or less than 0.1. This means that
the light available for observing a white non-fluorescent object
generates a nearly white impression.
[0092] The design of the set of filters as illustrated above with
reference to FIGS. 2a to 2d has a further advantage in that red
light above 620 nm is also available for the observation of
non-fluorescent regions due to the partial characteristic II. This
allows blood, which may be present on the object, to be perceived
with its natural color without disturbing the observation of the
fluorescence of the fluorescent dye fluorescein in the green
spectral range.
[0093] In the context of using the fluorescent dye fluorescein it
may be useful to select the threshold wavelength 107 from within a
range from 510 nm to 540 nm, and in particular from within a range
from 520 nm to 530 nm, to select the wavelength of the wavelength
range 111 from within a range from 600 nm to 750 nm, and to select
the wavelengths of the wavelength range IV from within a range from
475 nm to 515 nm.
[0094] In the context of using the fluorescent dye hypericin, it
may be useful to select the threshold wavelength from within a
range from 575 nm to 610 nm, and in particular from within a range
from 585 nm to 600 nm, to select the wavelength of the wavelength
range 111 from within a range from 610 nm to 750 nm, and to select
the wavelengths of the wavelength range 117 from within a range
from 420 nm to 560 nm. Herein, the wavelength range 117 may in
particular comprise two portions, namely a first portion between
420 nm and 490 nm, and a second portion between 510 nm and 560
nm.
[0095] In the context of using the fluorescent dye or a precursor
of 5ala (protoporphyrin IX), it may be useful to select the
threshold wavelength from within a range from 580 nm to 620 nm, to
select the wavelength of the wavelength range 111 from within a
range from 610 nm to 750 nm, and to select the wavelengths of the
wavelength range 117 from within a range from 420 nm to 560 nm.
Herein, the wavelength range 117 may in particular comprise two
portions, namely a first portion between 420 nm and 490 nm, and a
second portion between 510 nm and 560 nm.
[0096] The present disclosure illustrates certain exemplary
embodiments wherein it is evident that many alternatives,
modifications and variations will be apparent to those skilled in
the art. Therefore, the exemplary embodiments illustrated in this
disclosure are intended to be illustrative and not limiting in any
way. Various changes may be made without departing from the spirit
and scope of the present disclosure as defined in the following
claims.
* * * * *