U.S. patent application number 11/118487 was filed with the patent office on 2005-09-01 for method of aligning optical system using a hologram and apparatus therefor.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Kim, Tae-hee.
Application Number | 20050190680 11/118487 |
Document ID | / |
Family ID | 36123484 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050190680 |
Kind Code |
A1 |
Kim, Tae-hee |
September 1, 2005 |
Method of aligning optical system using a hologram and apparatus
therefor
Abstract
A method of aligning an optical system and an optical system
incorporating the method. A hologram element is installed in the
optical system so that test beams diffracted by the hologram
element travel along a same optical path as test beams incident on
the optical system. Alignment errors in the optical system are
measured using interference patterns formed on an image surface by
test beams returned from the optical system and reference beams. At
least one optical element of the system is aligned using
measurements calculated from the interference patterns. The optical
system may provide for temporarily installing the hologram element
to perform the measurements or the optical system may be
constructed with a hologram formed on any optical element which may
require alignment. A direction and a magnitude of any misalignment
are determinable based on an appearance of the pattern and a number
of circles in the pattern, respectively.
Inventors: |
Kim, Tae-hee; (Gyeonggi-do,
KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Kyungki-do
KR
|
Family ID: |
36123484 |
Appl. No.: |
11/118487 |
Filed: |
May 2, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11118487 |
May 2, 2005 |
|
|
|
10246541 |
Sep 19, 2002 |
|
|
|
Current U.S.
Class: |
369/112.12 |
Current CPC
Class: |
G02B 27/62 20130101;
G02B 5/32 20130101; G01B 11/272 20130101 |
Class at
Publication: |
369/112.12 |
International
Class: |
G11B 007/00; G11B
007/135 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2001 |
KR |
2001-61641 |
Claims
What is claimed is:
1. An optical system comprising at least one optical element having
a hologram for diffracting light beams on a same optical path as
light beams transmitted or reflected by the at least one optical
element.
2. The optical system of claim 1, wherein the hologram is a
computer-generated hologram.
3. An optical system comprising: a barrel; and at least one optical
element having a hologram element formed thereon, wherein: the at
least one optical element is placed in a predetermined position of
the barrel so that test beams diffracted by the hologram element
travel along a same optical path as test beams incident on the
optical system.
4. The optical system of claim 3, wherein the hologram element is a
computer-generated hologram element.
5. An optical system comprising: a barrel; and at least one optical
element mounted in the barrel, wherein: the barrel further
comprises a unit in which to place a hologram element in a
predetermined position of the barrel.
6. The optical system of claim 5, wherein the hologram element
enables measurement of a manufacturing condition of the barrel.
7. The optical system of claim 5, wherein the hologram element
assists in an alignment of the optical element.
8. The optical system of claim 5, wherein the hologram element is a
computer-generated hologram element.
9. An optical system, comprising: a barrel; and at least one
optical element mounted in the barrel, the at least one optical
element having a computer generated hologram written on a
peripheral area of the optical element.
10. The optical system of claim 9, wherein the computer generated
hologram is ring shaped.
11. The optical system of claim 9, wherein the computer generated
hologram is fan shaped.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of Ser. No. 10/246,541
which claims the benefit of Korean Application No. 2001-61641 filed
Oct. 6, 2001, in the Korean Industrial Property Office, the
disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of aligning an
optical system and an apparatus therefor, and more particularly, to
a method of and an apparatus for easily aligning an optical system
using a computer-generated hologram (CGH) and aligning
elements.
[0004] 2. Description of the Related Art
[0005] In general, an alignment of an optical system is achieved by
aligning optical elements of the optical system and mechanically
adjusting positions of the optical elements so that the optical
system has an image quality within a prescribed tolerance. The
conventional technique for aligning the optical system does not
directly measure errors of the optical system, but measures light
intensity representing the image quality to realign the optical
elements where the image quality deviates from a tolerance
limit.
[0006] In the conventional method of aligning the optical system,
an additional unit is necessary to measure the image quality and
the optical system is realigned by measuring the image quality and
indirectly calculating the alignment errors of the optical system.
Thus, it is difficult to accurately calculate the alignment errors
and errors may occur in realigning the optical system.
[0007] In the conventional technique, optical elements are aligned
through mechanical manipulation, which results in a slack alignment
of the optical elements, and an additional alignment unit is
necessary to perform the alignment. Thus, the configuration of the
conventional apparatus becomes complicated and the manufacturing
cost increases.
SUMMARY OF THE INVENTION
[0008] To solve the above-described problems, it is an object of
the present invention to provide a method of precisely aligning an
optical system in real time and in an accurate manner by removing
errors occurring through mechanical manipulation of optical
elements of the optical system, and associated aligning
elements.
[0009] Additional objects and advantages of the invention will be
set forth in part in the description which follows, and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
[0010] Accordingly, to achieve the above and other objects, there
is provided a method of aligning an optical system. An optical
element and a hologram element are installed in a barrel. Alignment
errors of the optical element are measured from interference
patterns formed on an image surface by reference beams and test
beams. The optical element is aligned to remove the alignment
errors.
[0011] The hologram element is a computer-generated hologram
element which is manufactured according to the tolerance of the
optical system so that test beams travel in a same optical path as
an incident path.
[0012] The barrel may further include a unit for installing the
computer-generated hologram element.
[0013] The optical element may be installed in front of the
computer-generated hologram element, wherein the test beams
transmitted through the optical element are reflected on the
computer-generated hologram element and travel on the same optical
path.
[0014] Alternatively, the optical element may be installed after
the computer-generated hologram element, wherein the test beams
transmitted through the computer-generated hologram element are
perpendicularly reflected on an incident surface of the optical
element and travel on the same optical path.
[0015] The alignment errors of the optical element are measured
from errors of the interference patterns with respect to null
interference patterns.
[0016] To achieve the above and other objects, there is provided an
optical system comprising at least one optical element with a
hologram for diffracting test beams on the same optical path.
[0017] The hologram may be a computer-generated hologram.
[0018] To achieve the above and other objects, there is provided a
method of aligning an optical system. An optical element with a
hologram is aligned in a barrel so that test beams travel on the
same optical path as an incident path. Alignment errors of the
optical element are measured from interference patterns formed by
reference beams and the test beams. The optical element is aligned
to remove the alignment errors.
[0019] The hologram may be a computer-generated hologram.
[0020] The alignment errors of the optical element are measured
from errors of the interference patterns with respect to null
interference patterns.
[0021] To achieve the above and other objects, there is provided a
method of testing a barrel. A hologram element is placed in a
predetermined position of the barrel and a predetermined lens is
installed in a designated position of an optical element. A
manufacturing condition of the barrel is measurable from
interference patterns formed by reference beams and test beams.
[0022] The hologram element is manufactured according to the
tolerance of an optical element so that the test beams travel in
the same optical path as an incident path.
[0023] The hologram element may be a computer-generated hologram
element.
[0024] The barrel may include a unit for installing the
computer-generated hologram element.
[0025] The predetermined lens may be a spherical lens for measuring
the manufacturing condition of the barrel.
[0026] Where the predetermined lens is installed in front of the
computer-generated hologram element, the test beams transmitted
through the predetermined lens are reflected along the same optical
path as an incident path.
[0027] Where the predetermined lens is installed after the
computer-generated hologram element, the test beams transmitted
through the computer-generated hologram are perpendicularly
reflected on an incident surface of the predetermined lens and
travel on the same optical path as an incident path.
[0028] The manufacturing condition of the barrel is measurable from
errors of the interference patterns with respect to null
interference patterns.
[0029] An optical system according to the present invention
includes at least one optical element with a hologram element
placed in a predetermined position of a barrel so that test beams
travel on the same optical path as an incident path.
[0030] The hologram element may be a computer-generated hologram
element.
[0031] To achieve the above and other objects, there is provided an
optical system comprising at least one optical element with a unit
for placing a hologram element in a predetermined position of a
barrel.
[0032] The hologram element measures a manufacturing condition of
the barrel or aligns the at least one optical element.
[0033] The hologram element may be a computer-generated hologram
element.
[0034] The present invention provides a method of aligning an
optical system using a computer-generated hologram in real time and
in an accurate manner and a measured manufacturing condition of a
barrel. Also, the present invention provides an optical element
which is directly aligned and simultaneously used by writing a
hologram directly on the optical element, and a method of aligning
the optical system.
[0035] Alignment errors of the optical system include a defocus
error, a decenter error, a tip error, and a tilt error. The defocus
error occurs where light rays are bent toward an optical axis by
more or less than a correct amount as in focusing or defocusing the
system. The decenter error occurs where the center of the optical
element is not aligned with the optical axis of the system. The tip
error occurs where the optical element is inclined on an X-axis.
The tilting error occurs when the optical element is inclined on a
Y-axis.
[0036] The alignment of the optical system represents the
arrangement of optical elements constituting the optical system
without the defocus, decenter, tip and tilt errors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The above object and advantages of the present invention
will become more apparent by describing in detail preferred
embodiments thereof with reference to the attached drawings in
which:
[0038] FIG. 1 is a schematic view of an optical projection system
using a method of aligning an optical system according to a first
embodiment of the present invention;
[0039] FIG. 2 is another schematic view of the optical projection
system using a method of aligning the optical system according to a
second embodiment of the present invention;
[0040] FIG. 3 is a schematic view of an interferometer useable in
the method of aligning the optical system according to the
embodiments of the present invention;
[0041] FIG. 4 is a schematic view illustrating a method of testing
a barrel according to the present invention;
[0042] FIG. 5 is a schematic view illustrating another method of
testing a barrel according to the present invention;
[0043] FIG. 6 is a schematic view illustrating an optical system
and a method of aligning the optical system according to a first
embodiment of the present invention;
[0044] FIG. 7 is schematic view illustrating another optical system
and a method of aligning the optical system according to a second
embodiment of the present invention;
[0045] FIG. 8 is a view showing interference patterns resulting
from alignment or manufacturing errors;
[0046] FIG. 9 is view showing interference patterns resulting from
decentering errors in a first direction; and
[0047] FIG. 10 is a view showing interference patterns resulting
from decentering errors in a second direction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] Reference will now be made in detail to the present
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to like elements throughout. Embodiments of a method
of aligning an optical system, an optical system having aligned
elements, and a method of testing a barrel according to the present
invention will be described in detail.
[0049] FIG. 1 is a schematic view of an optical projection system
using a method of aligning an optical system having a hologram
element, i.e., a computer-generated hologram (CGH) element,
according to a first embodiment of the present invention. FIG. 3
shows a more detailed view of a Fizeau interferometer.
[0050] Referring to FIGS. 1 and 3, in an embodiment of an optical
system, a method of aligning the optical system, and a method of
testing a barrel according to the present invention, a Fizeau
interferometer 31 forms test beams 1 and reference beams 3 from a
light source 41. An optical projection system 35 has optical
elements on which the test beams 1 transmitted through the Fizeau
interferometer 31 are incident.
[0051] Alternatively, another type of interferometer may be used as
the interferometer 31. Also, the present invention is described
with reference to a method of aligning an optical projection system
but the principles thereof may be applied to an alignment of
another type of optical system.
[0052] The Fizeau interferometer 31 is positioned in front of the
optical projection system as shown in FIG. 1 and generates the test
beams 1 and the reference beams 3 necessary for the method of
aligning the optical system and the method of testing a barrel.
[0053] The test beams 1 emitted from the Fizeau interferometer 31
are incident on the optical projection system 35 which is
positioned rearward of the Fizeau interferometer 31. Here, the
optical elements which are components of the optical system are
lenses or mirrors, but not a CGH.
[0054] Referring to FIG. 3, the Fizeau interferometer 31 includes a
light source 41, a condensing lens 42, a filter 43, a beam splitter
45, and a collimating lens 47. The condensing lens 42 condenses
beams generated from the light source 41. The filter 43 transmits
only ones of the specific wavelengths of the incident beams. The
beam splitter 45 splits an optical path into two optical paths so
that some of the incident beams, the reference beams 3 travel
toward an image surface 49 and the test beams 1 travel toward the
optical projection system 35. The collimating lens 47 collimates
the test beams 1. The light source 41 may generate laser beams,
some of which are the test beams 1 and some of which are the
reference beams 3.
[0055] The condensing lens 42 condenses the laser beams generated
by the light source 41 and transmits the condensed laser beams to
the beam splitter 45. The filter 43 is positioned on an optical
path between the condensing lens 42 and the beam splitter 45 and is
adapted to transmit only incident beams having optimum light
intensity within a predetermined frequency range.
[0056] The beam splitter 45 changes the optical path of the
reference beams 3 of the incident beams to an angle of 90.degree.
so that the reference beams 3 travel toward the image surface 49
and transmits the test beams 1, without alteration of the optical
path, toward the optical projection system 35.
[0057] The collimating lens 47 collimates the test beams 1
transmitted through the beam splitter 45. Also, a lens (not shown)
is positioned in front of the collimating lens 47 to assist in
making the test beams 1 transmitted through the collimating lens 47
into convergent light beams.
[0058] The test beams 1 are transmitted to the optical projection
system 35 through the Fizeau interferometer 31, are reflected by an
optical element or a CGH element of the optical projection system
35, and are incident again on the Fizeau interferometer 31. The
beam splitter 45 changes the optical path of the reflected test
beams 1 incident again on the Fizeau interferometer 31 to an angle
of 90.degree. so that the reflected test beams 1 travel toward the
image surface 49 and form interference patterns with the reference
beams 3 on the image surface 49.
[0059] Referring to FIG. 2, in the optical projection system using
the optical system, the method of aligning the optical system, and
the method of testing the barrel according to the present
invention, convergent light beams may be used rather than
collimated light beams as the test beams transmitted through the
Fizeau interferometer 31. The convergent light beams may be formed
by positioning an optical lens in front of the collimating lens 47
of the Fizeau interferometer 31, as described above. The structure
and function of the optical system 35 shown in FIG. 2 are the same
as the structure and function of the optical system 35 described
with reference to FIG. 1.
[0060] FIGS. 4 and 5 are schematic views illustrating a method of
testing a barrel to measure the manufacturing condition of the
barrel in which an optical element is installed. Referring to FIGS.
4 and 5, in the method of testing the barrel according to
embodiments of the present invention, a hologram element, i.e., a
CGH element 33, is manufactured to reflect test beams 1 along an
optical path which is the same as an optical path of incident test
beams 1. The CGH element 33 is placed in a predetermined position
of a barrel 37. In the embodiment shown in FIG. 4, a predetermined
lens 32 is installed in a designated position of an optical
element, and the manufacturing condition of the barrel 37 is
measured from interference patterns formed by the reference beams 3
and the reflected test beams 1 emitted from the predetermined lens
32. In the embodiment shown in FIG. 5, a predetermined lens 34 is
installed in a designated position of another optical element, and
the manufacturing condition of the barrel 37 is measured from the
interference patterns formed by the reference beams 3 and the test
beams 1 reflected by the predetermined lens 34 and emitted from the
CGH element 33. The CGH element 33 is manufactured in consideration
of a tolerance limit of image quality.
[0061] As shown in FIG. 4, the predetermined lens 32 is
manufactured to the same size as a diameter and a thickness of an
edge of an optical element which will be installed in the barrel 37
and is designed to have an optimum curvature radius so that beams
are incident on an accurate predetermined position of the CGH
element 33. The predetermined lens 32 is manufactured in
consideration of each optical element and is installed in a
designated position where optical elements are placed to measure
the manufacturing condition of the barrel 37.
[0062] The CGH element 33 is manufactured so as to reflect the test
beams 1 transmitted from the predetermined lens 32 so that the test
beams 1 travel inversely with respect to optical path where the
predetermined lens 32 is positioned in front of the CGH element
33.
[0063] Where the predetermined lens 34 is positioned after the CGH
element 33 as shown in FIG. 5, the CGH element 33 is manufactured
so that the test beams 1 are transmitted to the CGH 33, reflected
on a mirror 36, are perpendicularly incident and reflected on an
incident surface of the predetermined lens 34, and travel inversely
with respect to the optical path, and transmitted to the
interferometer 31 through the CGH element 33.
[0064] The CGH element 33 may be ring-shaped or fan-shaped
depending on the optical path of the test beams 1 transmitted
through the predetermined lens 32. The barrel 37 may include an
additional unit so as to install the CGH element 33.
[0065] Referring to FIG. 4, the predetermined lens 32 is specially
manufactured to measure the manufacturing condition of the barrel
37. Also, the predetermined lens 32 is placed in a designated
position of each optical element that will be positioned in front
of a hologram element, i.e., the CGH element 33, to retransmit the
test beams 1 reflected by the CGH element 33 to the Fizeau
interferometer 31.
[0066] Referring to FIG. 5, the predetermined lens 34 is placed in
a designated position of each optical element after the CGH element
33. The test beams 1 transmitted through the CGH element 33 are
perpendicularly incident, are reflected on an incident surface of
the predetermined lens 34 according to the reflection law, change
direction to an inverse direction, and are thus transmitted to the
Fizeau interferometer 31.
[0067] As described above, the test beams 1 which are incident on
the Fizeau interferometer 31 from the optical projection system 35
form interference patterns with the reference beams 3 on the image
surface 49. If these interference patterns are null interference
patterns, the barrel 37 is determined to be manufactured to a
design parameter. If the interference patterns are not null
interference patterns, the barrel 37 is determined not to be
manufactured to the design parameter. Manufacturing errors of the
barrel 37 are correctable based on shapes of the interference
patterns.
[0068] FIG. 6 is a schematic view illustrating an optical system 35
in which a hologram element, i.e., a CGH element, is additionally
installed and a method of aligning the optical system according to
an embodiment of the present invention. Referring to FIG. 6, the
optical system according to the embodiment of the present invention
includes at least one optical element 32a on which test beams 1 are
incident from an interferometer 31 and a barrel 37 having a
hologram element. The hologram element is a CGH element 33. To
install the CGH element 33, an additional unit may be prepared in
the barrel 37.
[0069] Referring to FIG. 6, in the method of aligning the optical
system, a hologram element, i.e., the CGH element 33, is
manufactured to reflect test beams 1 along a same optical path as
an incident path of the test beams 1. Optical elements 32a and 34a
are installed in the barrel 37 and alignment errors of the optical
elements 32a and 34a are measurable from interference patterns
formed by reference beams 3 (FIG. 3) and test beams 1 transmitted
through the optical element 32a and reflected by the CGH element 33
or transmitted through the CGH element 33 and reflected by the
optical elements 34a. Finally, the optical elements 32a and 34a are
aligned to remove the alignment errors. The CGH element 33 is
manufactured in consideration of a tolerance limit of image
quality.
[0070] The CGH element 33 used in the method of aligning the
optical system according to the embodiment of the present invention
is manufactured by the same method as the CGH element 33 in the
method of testing the barrel. In other words, the CGH element 33 is
manufactured so that the CGH element 33 is written in a position
where test beams 1 transmitted through the optical elements 32a and
34a are incident. Light beams transmitted through the optical
element 32a positioned in front of the CGH element 33 are reflected
along the same optical path, and light beams transmitted through
the optical element 34a positioned behind the CGH element 33 are
reflected along the same optical path.
[0071] Alignment errors of the optical system are measurable after
the optical elements 32a and 34a are both arranged in the barrel 37
or after the optical elements 32a and 34a are separately
installed.
[0072] Similar to the method of testing the barrel, in the method
of aligning the optical system where the CGH element 33 is
additionally installed, alignment errors of the optical system are
measurable from errors of the reference patterns with respect to
null interference patterns formed by the reference beams 3
generated from the interferometer 31 and the test beams 1 returned
from the optical system 35.
[0073] FIG. 7 is a schematic view illustrating an optical system
using optical elements on which a CGH is written, according to the
embodiment of the present invention, and a method of aligning the
optical system. Referring to FIG. 7, holograms 30a and 30b are
written directly on optical elements 32b and 34b, respectively. The
holograms may be computer-generated holograms.
[0074] The CGH 30a and the CGH 30b which are designed through
computer simulation are written on the optical elements 32b and
34b, respectively, so that the test beams 1 are incident on the
optical elements 32b and 34b and are reflected in the same optical
path as the incident path. The CGH 30a and the CGH 30b may be
written around the respective peripheral areas of the optical
elements 32b and 34b so as not to degrade the quality of an image
formed by beams transmitted through the optical elements 32b and
34b.
[0075] Referring to FIG. 7, in the method of aligning the optical
system according to the embodiment of the present invention, a
hologram is formed on the optical elements 32b and 34b so that the
test beams 1 travel in the same optical path as the incident path.
The optical elements 32b and 34b are arranged in the barrel 37, and
alignment errors of the optical elements 32b and 34b are measured
from interference patterns which are formed on the image surface 49
by the reference beams 3 and the test beams 1 transmitted through
the optical elements 32b and 34b. Finally, the optical elements 32b
and 34b are aligned to remove the alignment errors. The hologram
formed on each optical element may be a CGH.
[0076] The test beams 1 are incident on and reflected by the
respective CGH formed on the optical elements 32b and 34b, change
optical paths to an inverse direction of the incident direction,
and interfere with the reference beams 3 of the interferometer 31
shown in FIG. 3 to form an interference pattern on the image
surface 49.
[0077] As described above, where the test beams 1 and the reference
beams 3 form a null interference pattern in the method of aligning
the optical system in which the CGH is additionally installed or in
the method of testing the barrel, the optical system is determined
to be correctly aligned. However, where another type of
interference pattern is formed, alignment errors are determined to
occur in the optical system.
[0078] Manufacturing errors of the barrel or alignment errors of
the optical system contribute to the defocus, tip, tilt, or
decenter errors of the optical system. FIGS. 8 through 10
illustrate interference patterns formed on the image surface 49 by
the errors. Errors may be calculated by equation 1 which is
applicable to all of the above-described errors.
.DELTA.E=.lambda./2.times.(number of interference patterns) (1)
[0079] Referring to FIG. 8, it can be seen that a number of
interference patterns increases with an increase in the error. The
errors shown, g.sub.-2 and g.sub.-1, indicate that the optical
elements are close to the X-axis direction of the interferometer,
while the + errors shown, g.sub.+1 and g.sub.+2, indicate the
opposite.
[0080] A null interference pattern go shown in FIG. 8 is formed
where optical system alignment errors or barrel test errors do not
occur. The shape of the circle of the null interference pattern
g.sub.0 represents the shape of the image surface, which means that
an interference pattern is not formed.
[0081] Interference patterns g.sub.+1 and g.sub.+2 are created
where the optical system alignment errors or the barrel test errors
are in a +error direction. Where errors occur, interference
patterns increase by one or by two, and circles of the interference
patterns become larger and spread out in a form of waves.
[0082] If two circles occur as in the interference pattern g.sub.+1
of FIG. 8, an error .DELTA.E determined according to equation 1
equals .lambda., where .lambda. is the wavelength of the beam. In
the same manner, if three circles occur as in the interference
pattern g.sub.-2 shown in FIG. 8, the error .DELTA.E determined
according to equation 1 is 1.5 .lambda.. The black and white colors
of interference patterns corresponding to the -error are
interchanged with the black and white colors of the interference
patterns corresponding to the +error direction.
[0083] FIGS. 9 and 10 show interference patterns created where
decentering error occurs in the method of aligning the optical
system or the method of testing the barrel. Referring to FIG. 9,
where the center of the optical axis of the optical element moves
upward on the Z-axis, as shown in FIG. 9, an interference pattern
g.sub.+1 is created in the +error direction. Where the center of
the optical axis of the optical element moves downward on the
Z-axis, as shown in FIG. 9, an interference pattern g.sub.-2 is
created in the -error direction.
[0084] Referring to FIG. 10, where the center of the optical axis
of the optical element moves along the Y-axis in a positive
direction, as shown in FIG. 10, an interference pattern g.sub.+1 is
created in the +error direction. Where the center of the optical
axis of the optical element moves along the Y-axis in a negative
direction, as shown in FIG. 10, an interference pattern g.sub.-2 is
created in the -error direction.
[0085] If tip or tilting error occurs in the method of aligning the
optical system or the method of testing the barrel, the
interference patterns shown in FIG. 9 are created. The errors can
be calculated from equation 1 according to the number of
interference patterns, as described above.
[0086] In the method of aligning the optical system and the method
of testing the barrel according to the embodiment of the present
invention, the manufacturing condition of the barrel or the
alignment errors of the optical system are measurable in real time
and in an accurate manner using a CGH.
[0087] In particular, in the optical system and the method of
aligning the optical system according to the present invention, the
CGH is not installed as an additional element, but the CGH is
directly written on the optical element to simplify the
configuration of the optical system. Also, since the CGH which is
written directly on one or more elements of the optical system
becomes a part of the optical system as sold, errors are prevented
from initially occurring and the CGH may be used by a customer to
aid in any realignment of the optical system without adding another
element to the system.
[0088] As described above, the method of aligning the optical
system or the method of testing the barrel may be applied to an
optical system easily and accurately measure alignment or
manufacturing errors of the optical system in real time.
[0089] Also, the aligned optical elements and the method of
aligning the optical system allow measuring the alignment errors in
optical systems in real time and in an accurate manner. Further,
since an additional unit is unnecessary for the CGH, the
configuration of the optical system is simplified and errors are
remarkably reduced.
[0090] Although a few embodiments of the present invention have
been shown and described, it would be appreciated by those skilled
in the art that changes may be made in these embodiments without
departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.
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