JP3294374B2 - How to collect reflected light - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a multiple pass optical system.
The present invention relates to a matrix system, and more particularly to a method for collecting reflected light in a multiple reflection optical device used for analyzing components of a gas such as a gas.

[0002]

2. Description of the Related Art Conventionally, in this type of technology, a gas component is analyzed by transmitting a laser beam into a housing of a cell into which a gas to be analyzed is inserted and analyzing the wavelength intensity after the transmission. Have been. In order to perform this analysis, it is necessary to realize an optical path (transmitted light path) as long as possible in the housing.

Classically, White has developed a system using multiple mirrors to lengthen the transmitted light path, but this system is still inadequate.

[0004] Recently, there is a technique disclosed in Japanese Patent Publication No. 4-6894. The technique relates to a multiple-pass optical matrix system having the configuration of the device shown schematically in FIG. 7 and the operation described below with reference to FIG.

First, in FIG. 7, the system has a housing 4 formed in a cylindrical cell. One end of the housing 4 in the longitudinal direction is adjacent to the main field mirror 24 and the main field mirror 24. An auxiliary field mirror 25 is provided, while a pair of four objective mirrors 39, 4 having the same radius of curvature are provided on the other end of the housing 4 in the longitudinal direction.
0, 41, 42 are installed via the mount 34 so as to face the field mirrors 24, 25. Main field mirror 24
Is the same as the curvature of the objective mirror, and its center of curvature is 4
The center of symmetry of the objectives coincides with the longitudinal axis of the housing 4. In the multiple reflection optical device configured as described above, the light beam emitted from the light source is projected into the housing 4 from the entrance opening 2 provided on the field mirror side, and the objective mirrors 39, 40, 41, and 42 and the field mirror. After repeating the reflection a plurality of times between any one set of 24 and 25,
Finally, the light is emitted from the exit opening 27 formed on the entrance opening 2 side, and the wavelength intensity of the light flux exiting the exit opening 27 is examined. The reflection effect in the housing 4 in the multiple reflection system will be described below with reference to the image matrix of FIG.

A light beam emitted from the light source is passed through one of the four objective mirrors 39 through an entrance opening 2 formed at one longitudinal end of a housing 4 provided in the cell. The main field mirror 24 reflected from the first objective mirror 39
To form a first spot at one end of an image matrix formed thereon. Further, the light beam is directed from the first spot of the main field mirror 24 to another second objective mirror 40, reflected therefrom, and reflected back to the first objective mirror 39 via the main field mirror 24. Such a first
While alternately repeating the reflection between the objective mirror 39 and the field mirror 24 and between the second objective mirror 40 and the field mirror 24 a plurality of times, the reflected light flux is formed in the image matrix formed on the main field mirror 24. When reaching one end row including one spot, it is arranged adjacent to the main field mirror 24 on the entrance opening 2 side via the first objective mirror 39, and has the same curvature as that of each objective mirror. And passes through an auxiliary field mirror 25 having a center of curvature coinciding with the symmetry point of the first and third objective mirrors 39,41. Then, the light beam reflected from the auxiliary field mirror 25 is directed to the third objective mirror 41 here,
The third objective 41 passes through the main field mirror 24 again, from which it is directed to the last fourth objective 42. After the above reflections have been repeated a plurality of times again, the final reflection by the first objective mirror 39 in the housing 4 leaves the system through the outlet opening 27 containing a spot corresponding to an odd number of round trips of the housing 4. .

[0007]

However, when the above-mentioned conventional system is used in an environment where extremely strong vibrations are generated, such as an airplane in flight, the optical path is distorted due to cell distortion of the multiple reflection optical device. It fluctuates and the transmitted light cannot be collected stably at the sampling port. In addition, when moving while sampling the atmosphere in an airplane in flight, since it is moving at high speed, it is difficult to perform data sampling again at a specific point, and mistakes in sampling transmitted light are not allowed.

Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-reflection optical device in which a gas to be measured is inserted even if the cell is distorted due to vibration or the like. It is an object of the present invention to provide a method capable of stably collecting light without reflecting the position of a light beam reflected from a predetermined position.

[0009]

To achieve SUMMARY OF to the above objects, according to a first embodiment of how to collect the reflected light of the present invention, the circle
At one end of a cylindrical housing provided in a cylindrical cell
Are paired horizontally, extending along the longitudinal axis of the housing.
A main field mirror that stands vertically so as to be orthogonal to
Auxiliary field of view also standing vertically adjacent to one side of the field mirror
And a mirror above the auxiliary field mirror.
An entrance window for introducing light from a source into the housing is formed.
On the other hand, the other end of the housing is provided with the
Vertical axis defined with reference to the longitudinal axis of the jing and
Be mechanically mounted on a holder with a horizontal axis
Depending on the vertical and horizontal axes.
4 pieces that are rotatable and have the same radius of curvature
The main field mirror is provided with the objective mirror.
Curvature equal to the radius of curvature of the housing and the longitudinal axis of the housing
Along with a center of curvature that coincides with the center of interest of the objective.
And the auxiliary field mirror has a radius of curvature of the objective mirror.
Equal curvature and one point of symmetry of the first and third objectives
With a matching center of curvature, and introduced from the entrance window.
The speed of light is the
By repeating reflection with the field mirror,
The length of the housing on the field mirror and the auxiliary field mirror
Vertical and horizontal directions based on the hand axis
Image matrix consisting of multiple spots arranged in a circle
Optical multi-path optical
・ In the method of collecting reflected light in the matrix system
There are, the light beam from the light source is the passed to the first objective of the <br/> objectives through the entrance window, the first is the light beam
Reflected from the objective mirror and passed through a first spot in the bottom row of a column vertically aligned with one end of an image matrix formed on the main field mirror, and a first spot on the main field mirror The light beam reflected from the first objective mirror was directed to a second objective mirror which is in a diagonal positional relationship with the first objective mirror, and the light beam reflected from the second objective mirror was directed to the main field mirror. Thereafter, the reflected light is again reflected to the first objective mirror, and a plurality of reflections between the first objective mirror and the main field mirror and between the second objective mirror and the main field mirror are alternately performed. after repeating times, the light beam reaches the column of the one end comprising the first spot of the image matrix formed on the main viewing mirror, the reflected light beam in the column of the one side end first One spot on the auxiliary field mirror through the objective mirror Then, the light is reflected from the auxiliary field mirror to a third objective mirror adjacent to the second objective mirror in a horizontal direction and to the first objective mirror in a vertical direction. after being passed to the third objective again from the main viewing mirror, there from with the third objective lens is reflected towards the fourth objective in the diagonal positional relationship is reflected by the fourth objective After the luminous flux is directed to the main field mirror, it is reflected back from the main field mirror to the third objective mirror, and between the third objective mirror and the main field mirror and the fourth objective mirror. The reflection between the main field mirror and the main field mirror is alternately repeated a plurality of times, and then, the reflection between the first and second objective mirrors and the main field mirror is alternately repeated a plurality of times again. and a fourth objective reflections between the said main field mirror Mutually repeated a plurality of times, and are to exit to the outside of the housing end of the light flux becomes passing through the longitudinal end exit window side formed of said housing in the housing,
At the same by a reflected light beam directed to the spot where the light beam to be the last pass is equivalent to the even-numbered maximum number of reciprocating in the image matrix, wherein the said reflection light beam toward the spots corresponding to the round-trip-numbered even-< The last reflected light beam performed through the third objective mirror,
The reflected light flux exits the housing through the exit window formed in the auxiliary field mirror.

According to a second aspect, in the image matrix according to the first aspect, in the vertical direction,
If each spot arranged in the horizontal direction so as to be orthogonal to the arranged column is a row, the number of rows is odd, so that
The centers of curvature of the four objective mirrors projected onto the main field mirror surface are adjusted.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings (FIGS. 1 to 6).

FIG. 1 shows a multi-reflection optical device (multi-pass optical device) used for implementing the method for collecting reflected light according to the present invention.
FIG. 8 is a schematic perspective view of an optical system (optical matrix system) , which is almost the same as the conventional one shown in FIG. 7 except for a position where an exit window for a reflected light beam is formed. Therefore,
Detailed description of the device is omitted. Set in a cylindrical cell
At one end of the hollow cylindrical housing 120, a horizontal
Orthogonal to the longitudinal axis of the housing 120 extending in the direction
Main field mirror 111 which stands vertically so that
An auxiliary field mirror that stands vertically adjacent to one side of the mirror 111
112 and a light flux from a light source (not shown).
) Is introduced into the housing 111.
It is formed above the auxiliary field mirror 112. Meanwhile, Howe
The other end of the jing 120 has a longitudinal axis of the housing 111.
Horizontal axis 123 and vertical axis 1 defined with reference to the line
24 (see FIG. 2).
By doing so, these horizontal axis 123 and vertical
Vertical and horizontal around axis 124
4 pieces that are rotatable and have the same radius of curvature
Of objective mirrors 113, 114, 115, 116
I have. The main field mirror 111 has a curvature equal to the radius of curvature of each objective mirror.
The center of interest of each objective along the ratio and the longitudinal axis of the housing
And the auxiliary field mirror 11
2 is a curvature equal to the radius of curvature of each objective and the first objective and
And a center of curvature coincident with the symmetry point of the third objective mirror.
You. The speed of light introduced from the entrance window 117 is focused on each objective mirror.
Incident / anti-reflective between field mirror 111 and auxiliary field mirror 112
The main field mirror 111 and the auxiliary
Of the housing 120
Vertical (row) and horizontal defined relative to axis
A plurality of input / reflection points (hereinafter referred to as
Image matrix consisting of
(See FIG. 4). Code 11
Reference numeral 8 denotes an exit window formed in the auxiliary field mirror 112 .

Further, objective mirrors 113, 114, 115, 1
In FIG. 2, reference numeral 16 denotes a mechanically mounted holder. Reference numerals 121 and 122 denote adjustment knobs for rotating the objective mirror in the horizontal and vertical directions, respectively. The direction of reflection of the light beam to the light source is determined.

By fixing the adjustment knob 122 and adjusting the 121, the four objective mirrors rotate around the horizontal axis 123. By fixing the adjustment knob 121 and adjusting the 122, the four objective mirrors are rotated. The mirror rotates about a vertical axis 124.

The center of curvature of the auxiliary field mirror 112 is the center of symmetry (the point of symmetry) of the first and third objective mirrors 113 and 115.

Further, objective mirrors 113, 114, 115,
By adjusting the reflection angle of 116 with adjustment knobs (not shown) provided respectively, the field mirrors 111 and 11 are adjusted.
Since the number of arrangements of the image matrix formed on 2 is determined, and the four objective mirrors are rotated around the horizontal axis 123, the horizontal reflection angle of the light flux to the field mirrors 111 and 112 changes. In the image matrix
The number of rows of spots arranged in the horizontal direction increases or decreases. On the other hand, by rotating the four objective mirrors around the vertical axis 124, the vertical reflection angle of the light flux to the field mirrors 111 and 112 changes. Vertically aligned spots in the image matrix
The number of rows in the unit increases or decreases.

FIG. 3 shows the main field mirror 111 and the auxiliary field mirror 11.
2 shows an image matrix representing the spot of the illuminated light beam. With reference to this, the reflection operation of the light beam in the multiple reflection optical device of the present invention will be described. (1) Reference numeral 0 denotes an incident position of a light beam incident from the incident window 117. The incident light beam is reflected via the first objective mirror 113 to the first spot 1 of the image matrix formed on the main field mirror 111. Passed. (2) Subsequently, the light is reflected from the first spot 1 formed on the main field mirror 111, travels toward the second objective mirror 114, is reflected via the objective mirror 114, and is now reflected on the main field mirror 111. 2 Passed to spot 2. (3) The luminous flux reflected from the second spot 2 passes through the first objective mirror 113 again to the third spot 3 on the main field mirror 111.
Passed through. (4) The luminous flux reflected from the third spot 3 again passes through the second objective mirror 114 to the fourth spot 4 on the main field mirror 111.
Passed through. (5) The light beam reflected from the fourth spot 4 is the first objective mirror 1
13 again passes to the next spot. The respective reflections between the first objective mirror 113 and the main field mirror 111 and between the second objective mirror 114 and the main field mirror 111 are alternately repeated a plurality of times to form an image matrix on the main field mirror 111. After moving to the spot 7 in the rightmost column and the bottom row, the beam is moved from there to the spot 8 in the leftmost column and the top row via the second objective mirror 114. (6) Subsequently, the light beam reflected from the spot 8 passes through the first objective mirror 113 to the lowest spot 9 on the auxiliary field mirror 112. (7) The luminous flux reflected from the spot 9 is directed to the third objective mirror 115, and passes therethrough to the spot 10 on the main field mirror 111. (8) The luminous flux reflected from the spot 10 is newly directed to the fourth objective mirror 116, and is again passed through the spot in the rightmost column and the bottom row 11 of the image matrix of the main field mirror 111. As described above, this spot 11 is the same as the spot 7 four round trips before, and the two spots overlap. This spot overlap also occurs in other spots except for the spot in the top row and the row containing the exit window. The reflection between the third objective mirror 115 and the main field mirror 111 and the reflection between the fourth objective mirror 116 and the main field mirror 111 are alternately repeated a plurality of times, and thereafter, the first and second objective mirrors 111 and 111 are again turned on. The reflection between 114 and the main field mirror 111 is alternately repeated a plurality of times.
The reflection between the objective mirrors 115 and 116 and the main field mirror 111 is alternately repeated a plurality of times to increase the number of spots formed in the plane of the field mirrors 111 and 112 while the spots in the image matrix are changed to the main field mirror 111. Is moved to the vicinity of the horizontal axis in the middle part of. (9) Then, the reflected light beam is finally reflected by the third objective mirror 115, and is emitted from the emission window 118 (see FIG. 1) including the reflected light beam spot corresponding to the even-numbered round trip.

The reason that the method of collecting reflected light according to the present invention takes out the final reflected light beam from the exit window including the reflected light beam spot corresponding to the even number of round trips is due to the relative position between the incident light beam and the field mirrors 111 and 112 due to vibration or the like. If the position and the relative position of the center of curvature projected on the main field mirror 111 of each of the objective mirrors 113 to 116 do not change, even if the reflected light beam spot on the field mirror corresponding to the odd number of round trips is shifted, the even number This is because the reflected light beam spot on the field mirror corresponding to the round trip cannot be deviated. The reason for this will be described with reference to FIG.

In FIG. 5, when a light beam incident from an entrance window 117 is reflected by a first objective mirror 113 (not shown) and forms an image on a spot 1 (odd number) on a main field mirror 111,
For example, the center of curvature A of the objective mirror 113 projected on the main field mirror 111 due to distortion of the apparatus due to horizontal vibration.
Is shifted to the right by Δα to become A ′, the image forming position of the spot 1 on the main field mirror 111 is 2Δα
Only to the right to the 1 'position. Subsequently, a light beam emitted from the spot 1 ′ shifted by 2Δα projects a center of curvature B onto the main field mirror 111 (not shown).
When the spot 2 (even number) is again imaged on the main field mirror 111 after being reflected by the
, The offset is canceled, and the imaging position of the spot 2 is not shifted regardless of whether the apparatus is distorted due to vibration. In the subsequent reflection, the odd-numbered and even-numbered round trips are merely repeated alternately. Also,
The same is true even if the reflection is transferred to the third and fourth objective mirrors.

In the arrangement and arrangement of the image matrix shown in FIG. 3, (a) the position of the incident light beam 0 at the entrance window 117 and the position of the incident light beam passing therethrough via the first objective mirror 113 onto the main field mirror 111. The point of symmetry A with respect to one spot 1 (the center of curvature of the first objective mirror 113), (b) the first spot 1, and the main field mirror 11 therefrom via the second objective mirror 114
1, a point of symmetry B (center of curvature of the second objective mirror 114) with the second spot 2 passed through the uppermost row of the rightmost column, and (c) the lowermost spot 9 on the auxiliary field mirror 112; From the leftmost column on the main field mirror 111 via the third objective mirror 115 and the point of symmetry with the spot 10 passed through the second row (third objective 1
(D) the point of symmetry between the spot 10 and the spot 11 passing therethrough through the fourth objective mirror 116 to the bottom rightmost column on the main field mirror 111 via the fourth objective mirror 116 (fourth center). The center of curvature (D) of the objective mirror 116 is determined. However, since the dimensions of the housing 120 formed in the multiple reflection optical device are limited in advance, the field mirror 111 installed therein is set. , 112 are also limited. Under such a limitation, in order to stably collect the reflected light beam, the emitted light beam from the housing 120 should be a reflected light beam corresponding to an even number of round trips, and furthermore, in order to realize a transmitted light path as long as possible, aberration After setting a spot interval larger than the diameter of the light beam on the field mirror including the light beam and the like, the number of spot rows in the image matrix is changed to the field mirrors 111 and 112.
4 are projected onto the main field mirror 111 so that the number of rows of spots is the largest odd number of 3 or more that can be inside the field mirrors 111 and 112. It is necessary to determine the centers of curvature A, B, C, and D of the objective mirror. The reason will be described with reference to FIGS.

FIG. 6 (a) shows that the number of columns of spots formed on the surfaces of the field mirrors 111 and 112 is n, the number of rows is 2m, which is an even number, and the emission window of the light beam is the maximum number of even numbers. An example of the image matrix in the case of performing is shown. As can be seen from this example, in the case of even-numbered rows, no spot image is seen in the second row from the top,
Each of the first and second rows has only one reflection. Then, if the number of spots in this example is calculated, it becomes as follows.

{2 × (2m−2) × (n−1) − (n−1)} (number in area X) + (2m−2) ······················· (Number in area Y) + (n-1) ... (number in area Z) = (2m-2) x (2n-1) (1) In FIG. 6B, in the odd-numbered (2m-1) -row image matrix in which the number of rows is smaller than that of FIG. An example in the case where the maximum number is set is shown. As can be seen from this example, in the case of an odd-numbered row, reflection occurs only once in each of the top row and the center row. The number of spots in this case is calculated by the following equation.

{2 × (2m−2) × (n−1) − (n−1)} (the number in the area X ′) + (2m−2) ······················ (Number in area Y ') + (n-1) ... (number in area Z') = (2m- 2) × (2n−1) (2) As is apparent from the above equations (1) and (2), when the light flux is collected at the even-numbered maximum number, the case where the rows of the image matrix are even-numbered rows and There is no difference in the number of spots from the case of the odd-numbered row, which is one less row. Therefore, the odd-numbered row matrix shown in FIG. 6B is more efficiently used to mount the field mirror than the even-numbered row matrix in which the second row from the top is wasted as shown in FIG. 6A. Available.

FIG. 4 shows that the above-mentioned reflection is repeated plural times,
It is a figure showing the image matrix of the example emitted from the spot corresponding to the 8th round trip.

[0025]

As described above, according to the present invention, the light beam is reciprocated up to the maximum even number of times between the opposing objective mirror and the field mirror, so that the position of the light beam at the exit port due to vibration or the like can be determined. In addition to allowing the offset to be offset, the transmitted light path of the light flux in the gas detection housing is also provided with a length that does not matter at all in use, so that it is subjected to strong vibration, for example, in an aircraft in flight. Even in an environment, the reflected light beam can be reliably collected at a predetermined exit window of the housing. Thereby, there is a specific effect that stable gas analysis can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a multiple reflection optical device for implementing the method of the present invention.

FIG. 2 is a schematic perspective view showing a holder on which four objective mirrors are mechanically mounted so as to be adjustable in angle.

FIG. 3 is a diagram showing an image matrix representing spots of a light beam applied to a field mirror and an auxiliary field mirror.

FIG. 4 is a diagram showing an image matrix in a method of collecting reflected light emitted from a spot corresponding to a 78th round trip.

FIG. 5 is an explanatory diagram showing a relationship between a deviation of a center of curvature of each objective mirror and a deviation of each spot on a field mirror.

FIG. 6 shows an image matrix (a) of an even-numbered row when the emission window is set to a spot position corresponding to the maximum number of even-numbered round trips, and an image matrix (b) of an odd-numbered row one less than the even-numbered row. FIG.

FIG. 7 is a schematic perspective view showing a conventional multiple reflection optical device.

FIG. 8 is a diagram illustrating an example of an image matrix according to a conventional method of collecting reflected light.

[Explanation of symbols]

 0 Incident position of light beam 111 Main field mirror 112 Auxiliary field mirror 113 First objective mirror 114 Second objective mirror 115 Third objective mirror 116 Fourth objective mirror 117 Incident window 118 Exit window 120 Housing 121 Horizontal axis adjustment knob 122 Vertical Axes adjusting knob 123 Horizontal axis 124 Vertical axis A, A 'Center of curvature of first objective mirror B, B' Center of curvature of second objective mirror C, C 'Center of curvature of third objective mirror D, D' Fourth objective Center of curvature of mirror Δα, 2Δα Shift width 2m, 2m-1 Number of rows n Number of columns X, Y, Z, X ', Y', Z 'Area

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04 G01J 3 / 26 G01N 21/00-21/01 G01N 21/17-21/61

Claims (2)

(57) [Claims] (1)Cylindrical how to be installed in a cylindrical cell
One end of the jing extends along the longitudinal axis of the housing.
The main body that stands vertically perpendicular to the horizontal direction
A field mirror, and also vertically standing adjacent to one side of the main field mirror
An auxiliary field mirror to be installed, and
The light flux from the light source is guided into the housing above the field mirror.
An entrance window is formed, while the other end of the housing
The side is defined with respect to the longitudinal axis of the housing.
Mechanically mounted on a holder with vertical and horizontal axes
These vertical axes and the water
Each piece is rotatable about a flat axis and equal to each other.
Four objective mirrors having a radius of curvature are provided,
The field mirror has a curvature equal to the radius of curvature of the objective and the
Coincides with the center of interest of the objective along the longitudinal axis of the jing
And the auxiliary field mirror has the following curvature center.
A curvature equal to the radius of curvature of the objective mirror, the first objective mirror and the third
Having a center of curvature corresponding to the symmetry point of the objective mirror,
The speed of light introduced from the entrance window is determined by the objective mirror and the main field of view.
Repeating reflection between a mirror and said auxiliary field mirror
Thereby, on the main field mirror and the auxiliary field mirror,
Vertical defined with respect to the longitudinal axis of the housing
From multiple spots aligned horizontally and horizontally
To form an image matrix
In the Chipas Optical Matrix System
A method of collecting reflected light, Said The luminous flux from the light sourceSaidThrough the entrance windowSaidObjective mirror
And the light flux is reflected from the first objective mirror to form the main field of view.
Perpendicular to one side of the image matrix formed on the mirror
directionThrough the first spot in the bottom row of the column
And the light flux reflected from the first spot on the main field mirror
However, this time, a second diagonal positional relationship with the first objective mirror is established.
The light beam directed to the objective mirror and reflected from the second objective mirror is directed to the main field mirror.
After being cut off, it is reflected back to the first objective mirror,
Between the first objective mirror and the main field mirror and
The reflection between the second objective mirror and the main field mirror is changed.
After a number of repetitions of one another, the luminous flux forms on the main field mirror.
DoneSaidThe first spot of the image matrix
includingSaidReaching the one end row, the reflected light flux in the one end row passes through the first objective mirror
SaidPassing through one spot on the auxiliary field mirror, and subsequently from the auxiliary field mirror with the second objective mirror horizontally
Direction and perpendicular to the first objective mirror
Is reflected to an adjacent third objective mirror, and furthermore, the light beam is again reflected from the third objective mirror by the main field of view.
After passing through the mirror, from there the diagonal position with respect to the third objective
Reflected towards the fourth objective in the relationship,The The light beam reflected by the fourth objective mirror is transmitted to the main field mirror.
And then from there again to the third objective
Reflected by the third objective mirror and the main field mirror.
And between the fourth objective mirror and the main field mirror.
Again alternately, a plurality of times, and then again, the first and second objective mirrors and the main field of view.
The reflection between the mirror and the mirror is alternately repeated a plurality of times.
Alternately repeating the reflection between a plurality of times, and
The last luminous flux in the housing is the housing
Through the exit window formed on one side in the longitudinal direction
Out of the housingHave been,Thereby The last passing light beam is the image
Equivalent to the largest even number of round trips in the matrix
Reflected light beam toward the spot
The reflected luminous flux toward the spot corresponding to the round trip ofSaid
The last reflected beam performed through the third objective,
The reflected light flux is emitted from the auxiliary field mirror.
Characterized in that it is taken out of the housing through a window
How to collect reflected light. Wherein in said image matrix, before
When each spot arranged in the horizontal direction so as to be orthogonal to the column arranged in the vertical direction is defined as a row, the four projections on the main field mirror surface are performed such that the number of rows is odd. 2. The method for collecting reflected light according to claim 1, wherein a center of curvature of each of the objective mirrors is adjusted.