Autofocus apparatus
US008492693B2
(12) United States Patent
(10) Patent No.:
Brooker
(54)
(75)
(45) Date of Patent:
AUTOFOCUS APPARATUS
Inventor:
US 8,492,693 B2
Jeffrey S. Brooker, Oak Hill, VA (US)
Jul. 23, 2013
2004/0135061 A1
7/2004 Kreh
2005/0121596 A1
6/2005 Kam et al.
2009/0021724 A1 *
1/2009 Mahadevan'lansen
et al.
(73) Assignee: Thorlabs, Inc., Newton, NJ (US)
(*)
Notice:
............................. .. 356/73
FOREIGN PATENT DOCUMENTS
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
W0
Zoos/029506
3/2008
OTHER PUBLICATIONS
U.S.C. 154(b) by 313 days.
(21)
International Search Report and Written Opinion for corresponding
International Application No. PCT/US20l0/05298l mailed Jan. 20,
Appl, NO; 12/906,086
201 l.
(22) Filed:
Oct. 16, 2010
* cited by examiner
(65)
Prior Publication Data
US 2011/0090562 A1
Apr. 21, 2011
Primary Examiner * Seung C Sohn
(74) Attorney, Agent, or Firm * Graham Curtin, P.A.
Related US. Application Data
(60)
Provisional application No. 61/252,263, ?led on Oct.
(57)
16’ 2009'
An autofocus apparatus includes, in one embodiment, a light
(51)
Int. Cl.
G02B 7/04
G02B 27/64
(52)
source; a s P litter; a ?ber o P tic circulator; an o P tical collima
tor; a balance detector; and a microprocessor. The ?ber optic
circulator couples one of the split light signals at a ?rst port,
to the optical collimator at a second port, and to the balance
(2006 01)
(200601)
(200601)
G02B 27/40
U 5 Cl
'
detector at the third port. The optical collimator directs the
U'SI;C '
58
250/201 4
F 1d
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"""
"""""""" "
through a Dichroic mirror and a microscope objective. The
assl “ugh/263:2 214 1 214 R_ 356/73
balance detector uses another one of the split light signals as
' ’
1,
1
_
?l f
ee app lcanon
' ’
’356/479’
h h,
e or Comp ete Seam
an input, and converts a light signal, re?ected off of a sub
strate the sample is placed on, into an analog voltage signal.
lstory'
The microprocessor processes the output of the balance
References Cited
detector and position feedbacks from an adjustable micros
copy stage to generate a command for moving the position of
the adjustable microscopy stage to achieve a desired focus.
U.S. PATENT DOCUMENTS
5,654,799 A
6,900,943 B2
light beam from the ?ber optic circulator onto a sample
'
"""""""" "
(56)
ABSTRACT
8/1997 Chase et a1.
5/2005 Andersen et al.
200
11 Claims, 3 Drawing Sheets
LIGHT SOURCE
K
110
2 Axis Stage
with position feedback
240\
PD Detector
Optical Output
Voltage Output
Microprocessor
A/D converter
Position Feedback
ZAxis drive
195
198
US. Patent
Jul. 23, 2013
Sheet 1 of3
US 8,492,693 B2
LIGHT SOURCE
100
122
Z
T
Splitter
110
xi 8
‘I24
195
with sol/2min izgjback
] 98
1
Objective
1 50
A
1 60
—-
130
IV
Dichroic
_
COllimator '1 mlrror
1 Circulator
I |ir\|n(;r3i1rag|
140
3
i 70
Path
\
Balance
Detector
RF Output)
Microprocessor
/.-'|
Position
Converter
Feedback 0 utput
FIG. I
I
I
ZAXIS drlVe
US. Patent
Jul. 23, 2013
2001
Sheet 2 of3
US 8,492,693 B2
LIGHT SOURCE
Z Axis Stage
with position feedback
240\
PD Detector
Optical Output
Voltage Output D
Microprocessor
/—'|
€AID
Position
converter
Feedback Output
FIG. 2
ZA ' d '
X's We K- I
US. Patent
Jul. 23, 2013
Sheet 3 of3
Signal
Voltage
US 8,492,693 B2
/
/\ 1/
,/
\J
Stage Position
FIG. 3
\
US 8,492,693 B2
1
2
AUTOFOCUS APPARATUS
uses the ?rst portion of the light signal as an input; and a
microprocessor for processing the analog voltage signal from
CROSS-REFERENCE TO RELATED
APPLICATIONS
the balance detector.
In another embodiment of the present invention, an auto
This application claims the bene?t of US. Provisional
Application No. 61/252,263 ?led on Oct. 16, 2009, the con
tents of Which are herein incorporated by reference.
includes: a light source; an ?ber optic circulator having a ?rst
focus microscope apparatus is provided. The apparatus
port, second port and a third port; Wherein the light signal in
the ?ber optic circulator travels only from the ?rst port to the
second port and from the second port to the third port;
Wherein the ?ber optic circulator couples to a light signal
FIELD OF THE INVENTION
output of the light source at the ?rst port; an optical collimator
for directing a light output from the second port of the ?ber
optic circulator onto a sample through a Dichroic mirror and
a microscope objective, Wherein the sample is placed on an
adjustable microscopy stage; a photodiode detector for con
verting a light signal, re?ected off of a substrate that the
The invention generally relates to a microscopy apparatus,
and more particularly to techniques for automatically adjust
ing the position of a stage for attaining proper focus.
BACKGROUND
sample is placed on, into an analog voltage signal, Wherein
the re?ected light signal is captured by the microscope objec
As With all optical systems, microscopes suffer from
diminished depth of ?eld as the magni?cation and the NA
(numerical aperture) of the imaging lens (objective)
20
increases. When using a microscope, the user is responsible
tive and sent to the photodiode detector through the Dichroic
mirror, the optical collimator, and into the second port and out
of the third port of the ?ber optic circulator; and a micropro
for attaining proper focus of the sample by moving the sample
cessor for processing the analog voltage signal from the pho
relative to the objective. When microscopy is automated and
todiode detector.
In yet another embodiment of the present invention, a
the user is no longer involved in looking at each image, a
method of auto focusing is required. In the related art, tech
25
method for operating a microscopy apparatus is provided.
niques that achieve automatic focus by gauging the distance
The method includes the steps: illuminating a light beam to a
betWeen the front lens and the bottom of the container (e. g.,
slide, Well plate, etc.) are described. Such techniques are
based on re?ecting a beam of light off of the ?rst surface and
splitter for splitting the light beam into a ?rst portion of a light
signal and a second portion of a light signal; inputting the ?rst
portion of the light signal to a balance detector; coupling an
?ber optic circulator to the second portion of the light signal
measuring the re?ection. The de?ciency of such techniques,
30
hoWever, is that if the container that the sample is on has an
at a ?rst port, to an optical collimator at a second port, and to
inconsistent thickness, as in most plastics, then the resulting
35
a balance detector at the third port, Wherein the light signal in
the ?ber optic circulator travels only from the ?rst port to the
second port and from the second port to the third port; direct
ing a light beam from the second port of the ?ber optic
circulator onto a sample by the light collimator through a
Dichroic mirror and a microscope objective, Wherein the
sample is placed on an adjustable microscopy stage; captur
40
tive and sending to the balance detector through the optical
image can be off in focus the amount of the deviation of the
substrate.
Cellular imaging relies on the groWth of cells on the bottom
of a glass or plastic substrate. The cells groW parallel to the
surface and secrete proteins that cause them to adhere to the
substrate. In order to maintain the groWth of the cells, nutrient
rich liquid medium is added to feed the cells and maintain
proper physiological conditions. In this scenario, the surface
ing the re?ected light beam signal by the microscope obj ec
collimator and into the second port and out of the third port of
of the plastic is covered in an aqueous solution, Which can be
used to detect the position of the cells. The index of refraction
the ?ber optic circulator; converting the light signal re?ected
change betWeen the plastic and the liquid can be located using
a loW noise, high sensitivity re?ected light setup.
voltage signal by the balance detector; and processing the
off of a substrate that the sample is placed on, into an analog
45
SUMMARY
output of the balance detector.
The present invention may be realiZed as an autofocus
microscopy apparatus in one embodiment. The microproces
In an embodiment of the present invention, an autofocus
sor may generate a command for moving the position of the
microscope apparatus is provided. The apparatus includes: a
light source; a splitter for splitting a light beam illuminated by
adjustable microscopy stage to achieve a desired optical
focus, based on the output of the balance detector and position
50
the light source to a ?rst portion of a light signal and a second
feedbacks from the adjustable microscopy stage.
portion of a light signal; an ?ber optic circulator having a ?rst
port, second port and a third port; Wherein the light signal in
the ?ber optic circulator travels only from the ?rst port to the
second port and from the second port to the third port;
Wherein the ?ber optic circulator couples to the second por
tion ofthe light signal at the ?rst port; an optical collimator for
directing a light output from the second port of the ?ber optic
In another embodiment, the present invention may be real
iZed as a tracking device. The microprocessor may continu
ously monitor the analog voltage signal and generate a com
55
circulator onto a sample through a Dichroic mirror and a
microscope objective, Wherein the sample is placed on an
adjustable microscopy stage; a balance detector for convert
ing a light signal, re?ected off of a substrate that the sample is
placed on, into an analog voltage signal, Wherein the re?ected
60
voltage signal and seeks to change the distance betWeen the
sample and the microscope objective to maximize the voltage
from the detector, or maintain the voltage at a speci?ed point.
In another embodiment, the microprocessor may deter
mine the position of the sample based on the analog voltage
signal and position feedbacks.
light signal is captured by the microscope objective and sent
to the balance detector through the Dichroic mirror, the opti
cal collimator, and into the second port and out of the third
port of the ?ber optic circulator; Wherein the balance detector
mand in order to maintain a speci?c distance from the sample,
or Wherein the microprocessor continuously monitors the
BRIEF DESCRIPTION OF THE DRAWINGS
65
FIG. 1 is a diagram of an autofocus apparatus designed in
accordance With an embodiment of the invention.
US 8,492,693 B2
3
4
FIG. 2 is a diagram of an autofocus apparatus designed in
accordance With another embodiment of the invention.
FIG. 3 is a plot of signal voltage as a function of stage
signal from the objective 160 into an analog voltage signal
that is then converted to a digital signal by the A/ D converter
in the microprocessor 180.
The microprocessor 180, based on the value of the digital
position.
signal and position feedbacks, moves the microscopy stage
along the Z axis by commanding the controller 190. As shoWn
in FIG. 1 for example, the sample 195 is placed on the micros
copy stage 198 having an adjustable position along the
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS
This disclosure describes the best mode or modes of prac
Z-axis, thereby alloWing adjustment of the separation
ticing the invention as presently contemplated. This descrip
betWeen the sample 195 and objective 160 to maintain focus.
The microprocessor 180 also records the voltage values mea
sured by the balance detector 140 as Well as the position of the
adjustable microscopy stage at different distances betWeen
tion is not intended to be understood in a limiting sense, but
provides an example of the invention presented solely for
illustrative purposes by reference to the accompanying draW
ings to advise one of ordinary skill in the art of the advantages
and construction of the invention. In the various vieWs of the
draWings, like reference characters designate like or similar
parts. It is to be noted that all ?ber optic systems can be
the sample 195 and the objective 160. The voltage signal
peaks are analyZed and then the microscopy stage 198 is
commanded to move, by the controller 190, to the position of
the voltage signal peak that best correlates to the desired
optical focus. FIG. 3 shoWs an example plot of the voltage
replaced With free space equivalents.
FIG. 1 shoWs an exemplary and non-limiting diagram of an
autofocus apparatus 100 designed in accordance With an
embodiment of the invention. The apparatus 100 includes at
least a light source 110, a ?ber optic splitter 120, a balance
detector 140, a ?ber optic circulator 130, an optical collimator
150, a microprocessor 180, and a controller 190. The light
source 110 could include, but not be limited to, a laser diode,
for example. Other light sources are contemplated.
20
25
In accordance With principles of the invention, light illu
minated by the light source 110 is ?ber coupled or focused
into the ?ber optic splitter 120 Which directs a ?rst portion
122 of the original light into one of the ports of the balance
30
FIG. 2 shoWs an exemplary diagram of an autofocus appa
ratus 200 implemented in accordance With another non-lim
iting embodiment of the invention. In this embodiment the
apparatus 200 does not include a ?ber optic splitter and a
simple photodiode detector 240 is used instead of a balance
detector. Light illuminated by the light source 110 is ?ber
coupled or focused into the ?rst port (1) of the ?ber optic
circulator 130. The light travels in the circulator 130 and
outputs at the second port (2), Where the light signal is
focused into a beam by the collimator 150. Light signal
obtained back from the collimator 150 is input into the circu
lator 130 at the second port (2) and is output at the third port
(3). The output from the circulator 130 is fed into the photo
diode detector 240. The photodiode detector 240 converts the
detector 140. In one embodiment of the invention the Wave
length of the light source 110 is a 1310 nm. Other values are
contemplated. The ?ber optic circulator 130 comprises a ?rst
port (1), a second port (2) and a third port (3). The second
portion 124 output from the splitter 120 is fed into the ?rst
port (1) of the ?ber optic circulator 130. The second portion
124 is signi?cantly greater than the ?rst portion 122 (for
example, 99% versus 1%). The light travels in the circulator
130 and outputs at the second port (2), Where the light signal
signal peaks against the position of the microscopy stage.
35
light signal into a voltage signal output. The implementation
illustrated in FIG. 2 is e?icient When a time course of the
change in the light intensity is longer than the period of time
40
for the movement of the stage.
It should be appreciated by one of ordinary skill in the art
that the autofocus mechanisms illustrated in FIGS. 1 and 2 are
designed as a loW background high sensitivity detector using
is collimated into a beam by the collimator 150. It should be
noted that a light signal can travel in the circulator 130 only
a ?ber optic circulator. The addition of the circulator to the
from the ?rst port (1) to the second port (2) and to third port
the sample from being visible to the detector. This means of
(3).
light path prevents the light that is being sent from the laser to
45
designed to only re?ect Wavelengths above a prede?ned
Wavelength and pass anything beloW. In an exemplary
embodiment the prede?ned Wavelength is 1300 nm. The light
beam travels through the microscope objective 160 and is
The autofocus system of the present invention is particu
larly suited for high content screening and biological imag
50
copy stage. The light re?ects off of the plastic or glass sub
strate that the sample 195 is placed on, is captured by the
objective 160, and then sent back into the ?ber by the colli
than With current solutions. Some of the cell-based as says that
55
balance detector 140 circuitry the signal from the objective
160 is electronically divided by the signal from the ?rst por
tion 122 of the original light provided by the splitter 120, thus
cancelling out any change in the light source intensity over
time. The balance detector 140 further converts the corrected
are supported include, but are not limited to, nuclear-cyto
plasmic translocation, plasma membrane translocation, pro
tein expression, lipid droplet formation, DNA content, cell
toxicity, cell viability (apoptosis/necrosis) and others.
The light signal from the collimator 150 is input into the
circulator 130 at the second port (2) and is output at the third
port (3), as the light travels only in one direction through the
circulator 130. The output from the circulator 130 is fed into
another one of the ports of the balance detector 140. In the
ing. In one embodiment, the autofocus could be used With an
automated ?uorescence microplate imaging system that is
designed to enable investigators to develop cell-based assays
faster, at higher spatial resolution, and more economically
focused on the sample 195 placed on an adjustable micros
mator 150. If the sample 195 is not contained in a glass or
plastic substrate, the re?ection can come from the sample 195
itself.
illumination reduces the background signal to the detector, by
the amount of blocking that the circulator provides. In one
embodiment the blocking is better than 45 db.
The beam re?ects off of a Dichroic mirror 170, Which is
As shoWn in FIG. 1, position feedback is facilitated using,
60
in one embodiment, linear encoder scales embedded Within
the stage construction. While linear encoder scales are
described herein, other positioning means are contemplated.
One non-limiting example is for microscopy Where the
stage is used to either position any part of a microscope With
65
respect to a sample, or a sample With respect to a microscope.
One example of this application is shoWn in connection With
FIGS. 1-2 herein. Another non-limiting example includes
US 8,492,693 B2
6
5
a microprocessor for processing the analog voltage signal
machine vision inspection, or non contact-based dimensional
inspection. Other industries and applications are contem
from the photodiode detector.
plated.
2. The apparatus of claim 1, Wherein a time course of the
It is contemplated that the position of the sample may
change in the light intensity of the light source is longer than
change over time. It may be desirable to keep track of the
position of the sample in order to maintain focus. In an
embodiment of the present invention, the system can be real
iZed as a tracking device. Using the principles of the present
invention, the tracking device can maintain a speci?c distance
the period of time for the movement of the adjustable micros
copy stage.
3. The apparatus of claim 1, Wherein the microprocessor
generates a command for moving the position of the adjust
able microscopy stage to achieve a desired optical focus
betWeen the device and the sample by tracking the signal
voltage and continuously adjusting the Z-position. When the
position of the sample 195 changes, the re?ected light signal
based on voltage signal peaks measured by the photodiode
detector.
4. The apparatus of claim 1, Wherein the microprocessor
continuously monitors the voltage signal and generates a
command for moving the position of the adjustable micros
received by the balance detector 140 or the photodiode detec
tor 240 changes. As a result, microprocessor 180 detects a
change in the voltage signal from the balance detector 140 or
the photodiode detector 240. Microprocessor 180 generates a
corresponding movement command in order to receive the
same voltage from the detector, and thus maintains the same
distance betWeen the objective 160 and the sample 195.
The present invention can be used as a metrology tool.
copy stage in order to maintain a speci?c distance betWeen the
sample and the microscope objective.
20
maintain a speci?c distance betWeen the sample and the
Speci?cally, the invention provides a good non-contact tech
nique for measurement and distance gauging.
In another embodiment of the present invention, the system
can be realiZed as a distance measuring device. In this case,
there is no need to issue any movement command. The
microscope objective.
6. The apparatus of claim 1, Wherein the microprocessor
determines the position of the sample based on the analog
25
re?ected light signal received by the balance detector 140 or
the photodiode detector 240 is used to generate an analog
voltage signal.As shoWn in FIG. 3, the voltage depends on the
position of the stage. Microprocessor 180 analyZes the volt
age signal and position feedbacks from the stage and thus
determines the position of the sample.
7. A method for automatically operating an autofocus
coupling an ?ber optic circulator to a light signal output of
30
second port, and to a photodiode detector at the third
35
40
foreseen, may nonetheless represent equivalents thereto.
What is claimed is:
45
1. An autofocus apparatus, comprising:
a light source;
an ?ber optic circulator having a ?rst port, second port and
a third port; Wherein the light signal in the ?ber optic
circulator travels only from the ?rst port to the second
port and from the second port to the third port; Wherein
into an analog voltage signal, Wherein the re?ected light
signal is captured by the microscope objective and sent
to the photodiode detector through the Dichroic mirror,
the optical collimator, and into the secondport and out of
the third port of the ?ber optic circulator; and
travels only from the ?rst port to the second port and
from the second port to the third port;
directing a light beam from the second port of the ?ber
optic circulator onto a sample by the light collimator
through a Dichroic mirror and a microscope objective,
Wherein the sample is placed on an adjustable micros
copy stage;
capturing the re?ected light beam signal by the microscope
objective and sending to the photodiode detector
through the optical collimator and into the second port
and out of the third port of the ?ber optic circulator;
converting the light signal re?ected off of a substrate that
the sample is placed on, into an analog voltage signal by
the photodiode detector; and
processing the output of the photodiode detector.
8. The method of claim 7, Wherein a time course of the
50
the ?ber optic circulator couples to a light signal output
of the light source at the ?rst port;
an optical collimator for directing a light output from the
second port of the ?ber optic circulator onto a sample
through a Dichroic mirror and a microscope objective,
Wherein the sample is placed on an adjustable micros
copy stage;
a photodiode detector for converting a light signal,
re?ected off of a substrate that the sample is placed on,
a light source at a ?rst port, to an optical collimator at a
port, Wherein the light signal in the ?ber optic circulator
ticular embodiment, but it is to be construed With references
to the appended claims so as to provide the broadest possible
interpretation of such claims in vieW of the prior art and,
therefore, to effectively encompass the intended scope of the
invention. Furthermore, the foregoing describes the invention
in terms of embodiments foreseen by the inventor for Which
an enabling description Was available, notWithstanding that
insubstantial modi?cations of the invention, not presently
voltage signal from the photodiode detector and position
feedbacks received from the adjustable microscopy stage.
apparatus, the method comprising:
While the present invention has been described at some
length and With some particularity With respect to the several
described embodiments, it is not intended that it should be
limited to any such particulars or embodiments or any par
5. The apparatus of claim 1, Wherein the microprocessor
continuously monitors the voltage signal and generates a
command for moving the position of the objective in order to
change in the light intensity of the light source is longer than
the period of time for the movement of the adjustable micros
copy stage.
9. The method of claim 7, further comprising generating a
command for moving the position of the adjustable micros
55
copy stage to achieve a desired optical focus based on voltage
signal peaks measured by the photodiode detector.
10. The method of claim 7, further comprising continu
ously monitoring the voltage signal and generating a com
mand for moving the position of the adjustable microscopy
60
stage in order to maintain a speci?c distance betWeen the
sample and the microscope objective.
1 1. The method of claim 7, further comprising determining
the position of the sample based on the analog voltage signal
from the photodiode detector.
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