Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2001-03-07
2004-02-17
Strecker, Gerard R. (Department: 2862)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C356S139070, C356S153000, C359S368000, C372S009000
Reexamination Certificate
active
06693272
ABSTRACT:
This application claims the benefit of Japanese Patent applications Nos. 2000-063984 and 2000-127242 which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light path deviation detecting apparatus for detecting deviations (shift and tilt) of a detection target light path, and to a confocal microscope mounted with this light path deviation detecting apparatus.
2. Related Background Art
A confocal microscope is superior to a general microscope in terms of its resolution and other various performances, and is used widely in industrial and biological fields.
FIG. 7
is a diagram showing a laser scan type confocal microscope as this type of confocal microscope.
Referring to
FIG. 7
, a light source
11
emits linearly polarized laser beams. A beam expander
12
expands a beam diameter of the laser beam. The laser beam with the expanded beam diameter travels straight through a polarized beam splitter
13
and reaches a ¼ wavelength plate. The ¼ wavelength plate
14
transforms the laser beam into circularly polarized light and emits the same polarized light to a scan unit
15
.
This scan unit
15
scans the laser beam in two-dimensional directions by use of a biaxial mirror drive mechanism. An objective lens
18
converges the scan light at an observation point on a sample
19
.
The scan light reflected by the sample
19
becomes reversely circularly polarized light. The reversely circularly polarized light travels tracing back the objective lens
18
and the scan unit
15
, and arrives at the ¼ wavelength plate
14
.
The ¼ wavelength plate
14
transforms the circularly polarized light into rectilinearly polarized light of which the polarizing direction is orthogonal to the direction when illuminating, and emits the linearly polarized light to the polarized beam splitter
13
. The polarized beam splitter
13
reflects the linearly polarized light. A condenser lens
21
converges the reflected linearly polarized light at a pinhole
23
of a light shielding plate
22
. A photoelectric detecting device
24
receives the light penetrating this pinhole
23
.
An A/D converter
25
converts an output of luminance of the photoelectric detecting device
24
into a digital signal.
A CPU
26
takes in the digital signal from the A/D converter
25
with a sampling clock synchronizing with the scan operation of the scan unit
15
, and generates an image of the sample
19
. This image is properly displayed on a display
27
.
By the way, in this type of confocal microscope, an exit position and an exit angle of the laser beam fluctuates due to a change in characteristic of the light source and to a positional change of the internal optical element when switching a wavelength (in the case of the light source capable of switching the wavelength such as a titanium/sapphire laser).
FIG. 8A
is a diagram showing a state drawn by a dotted line, wherein a shift occurs on the light path of the light source
11
for the reason given above. If such a shift occurs, the laser beam for the illumination deviates from a range of an entrance pupil
17
of an objective lens
18
. As a result, a quantity of the illumination light upon the sample
19
decreases, resulting in an inconvenience such as a decrease in S/N ratio of the sample image.
Further,
FIG. 8B
shows a state indicated by a dotted line, wherein a tilt occurs in the light path of the light source
11
. If such a tilt occurs, an illumination point on the sample
19
shifts. As a result, an observation point on the sample, which is in an optical conjugate relationship with the pinhole
23
, is not sufficiently illuminated with the laser beam. Further, in the worst case, the converging position completely deviates from the pinhole
23
with the result that no image is obtained.
The prior art confocal microscope does not include a device for detecting the exit position and the exit angle of the laser beam. Therefore, the operator often continues to use the confocal microscope while being unaware of the above inconvenience. Further, the operator, even if aware of the inconvenience described above, must request a service center for maintenance each time because of providing no contrivance for precisely calibrating the light path deviation.
Moreover, some of the confocal microscopes have a plurality of light sources. In this type of confocal microscope having the plurality of light sources, it is difficult and intricate to adjust the laser beams of each light source exactly onto the same optical axis.
SUMMARY OF THE INVENTION
It is a primary object of the present invention, which was devised under such circumstances, to provide a light path deviation detecting apparatus capable of detecting light path deviation categorized distinctively into a shift or a tilt.
It is another object of the present invention to provide a light path deviation detecting apparatus capable of enhancing an accuracy of detecting the light path deviation by effectively reducing stray light generated inside.
It is still another object of the present invention to provide a confocal microscope capable of detecting light path deviations categorized distinctively into a shift or a tilt.
It is a further object of the present invention to provide a confocal microscope capable of automating correction of a deviation of an illumination light path.
It is still a further object of the present invention to provide a confocal microscope capable of easily executing calibrating the light paths of a plurality of light sources.
The light path deviation detecting apparatus and the confocal microscope, which accomplishes the above object, will hereinafter be described in a way of giving the corresponding components the same numerals as those in the embodiment. Note that the corresponding components are given herein for reference but do not any limitation to the present invention.
According to a first aspect of the present invention, as shown in
FIG. 1
, a light path deviation detecting apparatus for detecting a deviation of a detection target light path (which may be a light path deviation between, e.g., a fiducial light path and the detection target light path), comprises a diverging element (
51
,
52
) for diverging the detection target light path into at least two light paths, and light detecting devices (
53
,
54
,
55
,
26
), of which light receiving surfaces are disposed spaced light path lengths different from each other from respective diverging destinations of the diverging means, for detecting respectively light receiving positions on the light receiving surfaces. The light detecting devices detect a tilt of the detection target light path from a difference between the light receiving positions detected respectively by the light detecting devices.
FIG. 9
shows one example, wherein the light receiving surfaces of the light detecting devices are disposed spaced light path lengths different from each other from the respective diverging destinations.
FIGS. 10A and 10B
imaginarily show a state where the light receiving surfaces A, B shown in
FIG. 9
are disposed equally on the detection target light path. The principle on the above geometry will hereinafter be explained by use of the imaginary light path shown in
FIGS. 10A and 10B
.
Referring first to
FIG. 10A
, a tilt (with an elevation angle &thgr;, and a rotational angle &psgr;) occurs in the detection target light. This beam of detection target light reaches at first a light receiving position Pa of the light receiving surface A. Thereafter, the detection target light travels forward only a light path length difference &Dgr;L in the direction (defined by the elevation angle &thgr; and the rotary angle &psgr;), and arrives at a light receiving position Pb of the light receiving surface B.
Therefore, a deviation width between the two light receiving positions Pa and Pb is equal to (&Dgr;L·tan &thgr;). The light path length difference &Dgr;L of these parameters is already known, and hence the elevation angle &thgr; of the tilt can
Adachi Akira
Aoshima Mikio
Uchida Tadashi
Nikon Corporation
Strecker Gerard R.
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