JPH06500405A - dynamic shearing interferometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] dynamic shearing interferometer Enter into This patent application was filed by James G.A. Snyder on dynamic lateral shearing. Interferometer, Joint Pending Application No. 657, filed February 19, 1991. 289, and by James J. Snyder on dynamic shearing drying. Joint Pending Application No. 701,4 filed May 14, 1991 entitled Intervention No. 05, a continuation-in-part application, both of which are incorporated herein by reference.

Koyu Emperor! amount A company like Zygo & Wyco used for testing optical properties? Modern commercially available interferometers are typically Fizeau or Twyman-Green ( Michelson). Both types of test interferometers generate emissions within the instrument. The resulting parallel laser beam is split into two beams, one of which presents the reference surface. If the other beam is perfect, the outgoing beam will overlap the wavefront of the reference beam. Pass through test optics installed in such a way that they fit properly. The two beams are The fringes of a certain height are combined using a beam splinter, and the resulting fringes are A contour plot of the transmitted wavefront is shown. The striped pattern is a two-dimensional detector array ( For example, the light is captured by a COD camera) and analyzed by a computer. It provides details of the various parameters of the element's work and the distortions it causes. Ru. Although these instruments are well suited for measuring the quality of optical components, they It is not possible to directly measure the wavefront of the waveform. Additionally, the test wavefront is significantly different from the reference wavefront. If the spacing between the stripes reaches the pixel size everywhere, then When , the instrument cannot correctly interpret the stripe pattern. of different types Interferometers are available from Wyco to directly measure the wavefront of nearly parallel laser beams. Wear. The interferometer is a self-referencing muff bar tender with equal optical path lengths. Ru. In this interference needle, the reference beam is focused using a pinhole spatial filter. In other words, all wavefront aberrations are removed and the remaining spherical waves are made parallel by the lens. Te The source and reference beams have the same total distance before recombining at the beam splitter. , so that a laser source with a short interference length can be used. Self The self-referenced Pine Hearts Ender fringe pattern is similar to the fringe pattern produced by other forms of interferometer. are essentially similar to turns and are recorded and interpreted in the same way. As desired, Tests that would have produced a collimated output beam if the test optics had been perfect To measure optical elements by measuring the wavefront of the beam from the optical element For example, if the test lens is driven by a point source located at its focal point, If the illumination is made with It will be.

Instead of measuring the location of fringe extrema in an interference pattern, current commercially available interferometer systems The system has a different overall phase shift between the reference beam and the test beam. Store a sequence of interferograms that are each identical except for . Between irradiations The phase shift of changes the optical delay, e.g. by moving the reference mirror into the wavelength section. Therefore, it is corrected. Tests related to the starting phase at each pixel and therefore to the reference beam The pixel-by-pixel wavefront deviation of the beam, if the phase shift is known exactly For example, it can be calculated from the sequence of intensities measured at each pixel. This technique The technique is called phase-shift interferometry and provides a substantially better signal-to-nozzle ratio in phase measurements. and also provides a uniform grid of phase data that is independent of the number of fringes. . However, this requires moving the mirror to a precisely calculated distance between exposures. This adds significantly to the complexity and cost of the equipment. Actuation typically uses piezoelectric transducers This has disadvantages of hysteresis effects and non-linearity, and is difficult to implement. It's expensive.

Mechanical stability combined with optical complexity and requirements for scanning reference mirrors Commercial interferometers are expensive (approximately $100,000) and require precise control due to Requires a controlled laboratory environment. As a result, they are difficult for potential users to try. They tend to be located at specific optical testing centers that bring optical elements for testing. Ru.

Another type of interferometer is the transverse shearing plate interferometer. This device is typically Consists of an uncoated glass plate with a flat surface. Some finished products are parallel planes , and some develop a small angle (V-shape) between the surfaces.

Compared to most other interferometers, shearing interferometers are very compact; They are self-referential, and the interfering rays travel along a common or nearly common path, so Therefore, they are relatively insensitive to alignment, vibration, or air turbulence. this These features facilitate the use of shearing interferometers for laboratory and industrial applications. do.

A transverse shearing interferometer is generally used to measure the wavefront shape of a laser beam. It will be done. If the shearing plate is V-shaped, the horizontal shearing interference needle is - It is called an interferometer, and uses the appropriate direction of this V-shape to measure the wavelength and wavelength of the laser beam. It can be used to measure the shape of a wavefront.

A shearing interferometer is placed at an angle with respect to a characteristic incident beam and This results in two reflections of the beam. One reflection is from the front surface of the glass plate and the other from the rear. From the surface. (Another compound reflection also occurs between the surfaces before they exit the front surface.) occurs in However, these variously reflected beams are different from the two fundamental beams mentioned above. is also much lower in intensity and will therefore be ignored in the following analysis. ) these front and The two reflected beams from the rear surface interfere where they overlap. non-normal incidence For light, the reflected beams are laterally displaced from each other, resulting in fringes in the overlapping areas. The pattern is due to interference of the wavefront along with its own shearing deformation. obtained The constant slope of the fringe is analyzed to determine the fringe phase, which corresponds to the one-dimensional derivative of the wavefront. wave The shape of the surface is found by integrating the wavefront derivative along the shearing direction. A screen or other flat opaque surface placed in the path of the reflected beam The lateral of direction.

It indicates the lateral displacement of the optical axes of the two beams, referred to here as the deviation “S”. cormorant. The value of the deviation can be calculated directly from these parameters.

These principles of a transverse shearing interferometer are illustrated in Figure IB, which shows the optical element under test. Transverse shearing with laser source III producing a beam 113 of incidence on the child 114 The top view arrangement of the plate interferometer is shown.

Beam 113 exits the optic nearly parallel but slightly diverging and is sheared. incident on the recording plate 115. The beam incidence on the shearing plate creates a virtual image source. The divergence is shown exaggerated for ease of illustration. The outer edge of the incident beam is Reflects from the front surface of the shearing plate at points 117 and 119.

The outer edge of the incident beam is reflected from the back surface at points 121 and 123. Partially The superimposed reflected beams move from the shearing plate in the direction of arrow 125. , appears to come from two different virtual sources, one at point 127 and the other at point 129. . These two virtual image sources have a lateral split, 81 lateral displacement, and also an axial , with l called the axial delay. See Figure IB for geometry details. You can see more clearly. Shearing interference with refractive index n and thickness t With respect to the meter, the deviation of the two sources caused by the reflection of the incident beam at an angle θ is s=2*dl+kcosθ where di is shown in Figure IB. From Shell's law, Solving for sinθ=n*d 1/(t”+(1lz)+ytdl) di-t*sin θ/(n"-5in" θ)I72. Therefore two reflections The deviation between the beams is 3-t*5in2θ/(n"-5in"θ)1' .

Similarly, the axial delay l is 1=2*n*d2 d3 d2=n+kdl/sinθ, and d3=2*dl *sin θ.

Therefore, the axial delay is t=zt* (n"Sin"θ) It is.

FIG. Figure IA shows a theoretical superposition of the two reflected beams of Figure IA; front surface The beam reflected from is shown in FIG. 2 by circle 133 on surface 131 and The beam reflected from the surface is indicated by circle 135. The circles of the two beams are horizontal The center is shifted by a distance of directional shift S. Region 137 is the overlap of reflected beams. This is the area of alignment and interference. The laser beam is theoretically parallel without including any aberrations. If it is close, the interference region is as shown schematically in FIG. There will be some transition from dark to dark, but will show parallel alternating light and dark bands. right. (For the first row, the fringe pattern is sinusoidal in intensity.) Although the above analysis is for the case of a shearing plate with parallel surfaces, those skilled in the art will notice that similar results hold for V-shaped plates.

A good treatment of transverse shearing interferometers is given by John John of York, New York. Published by Willy & Sons, edited by Daniel Malacara Collected books Optical Schoff 108-141 of the original author and add it here as a reference. As seen in this referenced publication , the incident beam, and the use of an interferometer to emit, transmit, or manipulate the beam. Considerable information can be predicted about any device used to

However, in order to determine the time and date, the known transverse shearing interference needle requires even higher For wavefront analysis, which is inherent in Fizeau or Twyman-Green interferometers did not offer the possibility of

What is needed is a complex amplitude (field amplitude and field amplitude) of the laser beam wavefront. In order to characterize the laser, the profile can be measured (both phase and phase). An inexpensive, easy-to-use interference that can convert measurements into parameters commonly used in It is a total. No matter how good these parameters are (no matter how well the laser beam is focused) Beam quality characteristics, e.g. M2 and Strehl ratio, that describe the Other parameters related to aberrations, e.g. Zernissoke polynomials and Seidel aberrations Contains coefficients. Interferometers are also used for simple and conventional measurements of aberrations in optical elements and systems. need to be provided for.

Lord Kai ■dan! According to a preferred embodiment of the invention, the wavefront analysis interferometer completely characterizes the laser wavefront ( i.e., to measure complex field amplitudes) or to test optical elements or systems. Rugged enough to operate in standard factory environments Provide what is. This instrument is a transverse wavefront shearing phase shift interferometer. Ru. Due to its simplicity, it is inherently mechanically stable and relatively inexpensive. easy It has a sensitivity that can be adjusted to Even steep wavefronts that produce extremely high linear densities can be directly measured.

In a preferred embodiment, the interferometer is configured by reflecting an incident beam of electromagnetic radiation into two parts. consists of a shearing element for amplitude division, with each section substantially parallel to the other. have a wavefront with a direction of propagation, such that the two parts produce interference fringes between them. are arranged relative to each other in a direction transverse to the direction of the incident beam; and around an axis transverse to the incident beam and by a small amount to support the Consists of a mounting element for rotating the shearing element.

In a preferred embodiment, the shearing element includes a shearing plate with a flat surface and is transparent. Consists of materials. The optical delay of the interferometer is determined by attaching the shearing plate of the interferometer to the mounting element. by rotating through a small angle relative to the incident light beam.

In a preferred embodiment, the attachment element includes a thermally driven wire, which is driven by thermal expansion of the wire. resistance to rotate the shearing plate in relation to a part of the mounting element. Therefore, self-calibrate. The desired phase shift depends on the amount of rotation of the shearing plate. Given.

Plate 1 Scream Emperor 11 Doctor Figure IA shows a shearing plate placed at an angle with a laser source during testing. is a plan view of the optical element and display surface of , and illustrates the principle of transverse shearing interferometer. shows.

Figure IB shows the geometry of the various rays that cross and reflect from the shearing plate. It is a sectional view of the shearing plate of IA.

FIG. 2 is a diagram of the interference pattern produced by the arrangement of the elements of FIG.

FIG. 3 is an enlarged view of a dynamic transverse shearing interferometer according to a preferred embodiment of the present invention.

FIG. 4 is an assembly diagram of the interferometer of FIG. 3.

Figure 5 shows how a personal interferometer is used to characterize the wavefront of an optical element under test. FIG. 2 is a diagram showing typical measurement equipment.

Figure 6 shows how to rotate the shearing plate of a personal interferometer in a calibrated manner. FIG.

Figure 7 shows how to rotate the shearing plate of a personal interferometer in a calibrated manner. FIG. 3 is a schematic diagram of an alternative drive device.

Figure 8 shows an example of the present invention designed to measure wavefront properties along two axes simultaneously. FIG. 6 is a schematic diagram of a part of an alternative example.

Part 9 is an interferometer invented by Bo to continuously measure wavefront characteristics along two axes. FIG. 2 is a schematic diagram of the device.

Good morning, my father-in-law.

Figure 3 shows the dynamic lateral noring equation that can be used to study wavefront profiles. An enlarged view of the traverse meter 11 is shown. Interferometer 11 can also be made of other materials. However, the ring structure 15 is typically constructed from black anodized aluminum. attached to the uncoated plane parallel, hereafter referred to as etalon 13. Contains a glass plate (i.e. shearing plate).

The mounting ring has a front half 37 that houses the etalon 13 and a threaded mounting hole. Mounting post 17 adjustable by the day, e.g. industry standard stainless steel 172 inch It is partially separated into a rear half 35 which is mounted on a 1.27 cm (1.27 cm) post.

The mounting post is a stable base assembly that is a commercially available rotating stage. 19. Since the base assembly is a rotating stage, Contains an angular gradient so that the angular rotation of the interferometer can be accurately measured with respect to the

As can be seen in more detail in Figure 4, the mounting ring is centered along the vertical axis. Two pairs of stress relief drill holes 20 and 2 are cut through the ring at 1. Partially separated, with cuts 28 and 29 ending in 22 and 23 A saw cut with a zero width of about 1 no. 16 inches (0.16 co+) is preferred. in pairs The uncut areas between the drilled holes are located along the vertical diameter of the etalon. forming an integral pair of bending hinges 25 and 27.

The bending hinge provides a frictionless connection between the etalon and its mounting ring with respect to the base assembly. Allow a small amount of rotation. The incident beam is tested using this motion, as described next. The angle of incidence of the beam can be varied, thereby changing the combined interferometer fringe pattern to be scanned. cause a phenomenon.

In a preferred embodiment, the mounting ring has a length of approximately 1.375 inches (3.5 cm). 3 inch (7,62co+) schedule 80.6061-T6 aluminum It consists of a single piece of aluminum pipe. In nominal dimensions, this pipe is 2. It has a standard inner diameter of 9 inches (7,37 cn+).

Adapted to a 3 inch diameter etalon with a thickness of 172 inches (1.27 cm) 0.550 inch (1.40 cm) is generally preferred, but 1. 3.01 to 3.02 inches on one side, slightly deeper than 72 inches (1,27 cm). Mill to provide an inch (7.65 to 7.67 cm) opening. this also provides an area 30 for an etalon near the center of the pipe. Etalon is a region 30, attached to the front half 37 and held by two studs 42 and 44. It is held in place by two tabs 38 and 40. In a preferred example, drill hole 2 0 to 23 have a diameter of 378 inches (0,95 cm) and are placed next to each other in pairs. The center spacing between holes is approximately 0.438 inches (1,11 cm) with bending stress A separation distance between the edges of the hole of approximately 1/16 inch (0,26 cm) relative to the hole. leave.

Those skilled in the art will know that these dimensions are the desired elastic constants of the bending hinge and the ring used. I will admit that it can vary considerably depending on the material.

The etalon in the preferred embodiment has nominal dimensions of 3 inches in diameter and 172 inches in thickness. It is a K-7 glass plate. Other materials can also be used, such as fused silica.

The etalon in the preferred embodiment has a lambda at 633 nanometers with a 3 inch aperture. The flatness characteristic is equal to or less than /10. In a preferred embodiment, the remaining V The glyphs are specified in lambda/10 or less at 633 nanometers. Those skilled in the art should understand this Their specification is chosen to obtain the desired accuracy in determining the wavefront profile. , and will admit that other particularizations give different accuracy measures.

In FIG. 5, personal interference is used to determine the wavefront characteristics of the optical element 311 under test. A typical measurement configuration for using the meter is shown. The device has optical elements that do not contain aberrations. Then, provide the laser 309 with a beam passing through an optical element that is approximately parallel. adjusted accordingly. A personal interferometer is placed in the beam emerging from the optical element and The interferometer stage rotates to reflect the beam back toward the light source. Using the rotary stage of the traverse meter, a deviation of the reflected beam with a beam diameter of approximately 173 is given. To do this, rotate the incident angle of the laser beam. Accurate angle of incidence is read from the stage and enters computer 315. The user then inputs the laser wavelength into the computer. 174 waveform using the wavelength, angle of incidence, and etalon thickness and refractive index. Determine the exact incremental etalon rotation required to change the interference phase by . Determining the amount of etalon rotation required to change the phase by the 174 waveform. pre-calibrate instruments or use algorithms to perform such calculations analytically. This can be done by using rhythm. (The calibration approach is quite simple. A pure, necessarily parallel beam is used to illuminate the interferometer, resulting in a single interference pattern. rotate the etalon so that it varies by the stripes of and is therefore identical to the one before rotation, Then, divide the rotation angle into four parts. ) The user then starts the measurement process. This way When performing the following steps, use the CCD camera 317 and frame grabber 319 to Grab one frame of video stored in your computer. Etalon next? bending hinges by precise amounts to impart a 174 wavefront shift in the reflected beam. Rotate the etalon around the cage. Save one frame of the video again and Continue until all four frames of O are stored. The stored video data is Processed using standard algorithms to generate images at the starting phase and at each pixel in the frame. gives the fringe contrast (adjustment depth) of the interferogram.

The fringe pattern intensity distribution is expressed by the following equation.

1 (x, y) - = A (x, y) A'' (x + s, y) = : A (x = s + y ) i”+: A(x, y+) j j A(x+s, y): CO5φ A (x, y) in the t (x + y) formula is the complex field vibration at the point (X, y). S is the width and S is the offset, which is assumed to be along the X direction. Striped phase, φ.

(x, y) is shifted in steps of Pi/2 as described above, and at each pixel The measured intensity is varied sinusoidally by the last term in the equation. 4 types of measurements The sequence of values is analyzed using fast Fourier transform or other computational methods, and the The amplitude and phase of the last term can be determined.

At each pixel along the shift (x) direction, a wavefront phase, φ(x, y) is generated. Then, the fringe phase is processed using standard algorithms.

The phase information is then converted into a wavefront profile map shown on display 321.

Additionally, other parameters may be further calculated as is known in the art. For example, RMS error, peak-to-trough error, etc.

Fringe amplitude at each vixel,! A(x, y): i A(x+s, y): Should It is a product of the magnitude of the field amplitude of the two beams that are connected to each other. Each column of pixels The fringe amplitude data along the The size of the field near the wavefront i A (x, y)! decide Ru. This data is used when matching the wavefront phase at each pixel and φ(X, Y). , the complete composite field distribution A(x, i=t A(x, y): exp(iφ(x, y)) is given.

The composite field amplitude is completely characterized by the electromagnetic field (with the exception of polarization) at the measurement plane. So, using basic optical principles, we can measure the field or intensity at other points along the propagation path. can be calculated directly.

For example, the far-field divergence of the beam or the intensity distribution at the focal point of the lens can be determined by fast Fourier It can be calculated by the product method of converted and measured composite field amplitudes. far The field divergence or focal intensity distribution is determined by the beam quality it (sometimes M2 parameter). to determine standard beam properties such as It can be compared with calculated values for an ideal beam.

Angular motion resulting in controlled rotation by bending hinges is preferred in the California ThermX, available from Blue Sky Research, San Joes, CA. Provided by (registered trademark) translator. This ThermX) Lance The rotor is connected under tension between the front half 37 and rear half 35 of the ring structure 15. It includes a wire 31 (FIG. 4). TherwX translator driver below The electrical circuit, called a , includes control electronics that heat the wire, It is included in the puff cage 49. The wire is typically continuous to control its length. heats up, but also continuously cools down to its surrounding environment by heat radiation and convection do. (ThermX) The lansulator and driver are further detailed below. right. ) The wire 31 is attached to two threaded stands 41 and 43 (Fig. 4). These are electrically isolated from the ring and are connected to the rear of the interferometer ring structure. ThermX translator driver installed inside the puff cage 49 The two power wires 45 and 47 are connected to each other. driver puff cage 49 is separated from the ring structure 15 on a spacer such as spacer 51 and The shield 53 is assembled between the ring and the driver, and heat from the driver is transferred to the etalon. so as not to affect the thermal stability of The driver puff cage can also be installed elsewhere. Although other preferred configurations include, for example, in the base, the attachment shown in FIG. This has the advantage that the power wire can be shortened. The advantages of base mounting for drive packages are Generating transmission of the incident beam is an advantage for using high power lasers. This is likely due to the thermal excursion of the etalon due to heat from the circuit elements. will minimize the impact.

The nut engages the threaded studs 41 and 43, and the initial tension is applied to the bending hinge. used to apply force and in turn against each other without reducing the gap between the cuts 28. Apply pressure to the front and rear sides of the splint ring structure. The initial displacement is approximately 0 ．． 11, which results in an initial angular displacement of the etalon of approximately 0.14 degrees.

When the wire 31 is heated or cooled, it is logical that it is proportional to its length and its thermal expansion coefficient. expand or contract imaginatively. The front half 37 holding the etalon is therefore required to achieve a rotation of the fringe by 1/4 for the frame according to the initial displacement angle It rotates around the bending hinge in relation to the rear half 35 by a small angle.

A DC electric FA (not shown in the figure) is attached to the built-in Therm Powered by The current supplied by NtA is the length of the wire small around the vertical axis defined by the bending hinge of the ring structure. Displace the etalon at a different angle. This small angular displacement is the front of the etalon and Changes the axial delay of light reflected from the rear surface.

Those skilled in the art will appreciate that systems for varying the relative separation of the front and rear halves of the ring structure 15 will be apparent to those skilled in the art. The stem is not required for the Therm You will understand that it may be a system. For example, a stack of piezoelectric crystals Or even a monitor drive screw can be used. However, Therm X) Lancetrator is a non-displacement system for such moderately small displacements. Always easier and more elegant to perform.

Therm+X) lancerator and The basic component of the drive system is the resistance wire 31. Wires especially have large thermal expansion selected to have both high temperature coefficient and high temperature coefficient of resistance. wire under tension is maintained, the length of which defines a controlled interval. of the wire at temperature T (C) The length is L=Lo+a, *L*T −= Lo(1+a LoT) (a LoT<4) In the formula, Lo is the length at 0°C, and a is the coefficient of thermal expansion. wire resistance teeth R=R6+a, l*R*T'Ro (1+a, water T) (a R* T<<1) In the formula, Ro is the resistance at 0° C., and ae is the temperature coefficient of resistance. child These two parts can be combined to give the resistance as a function of length, R”Ro(1+a**L/al*Lo-am/a+-) and depending on the length of the resistor The change is dRR0*a.

given by.

An electric current passes through the wire, heating it and stretching it, which causes a controlled period of increase the distance. The temperature of the wire and therefore its length is determined by sensing the resistance of the wire. be monitored. Since thermal expansion and resistance changes are largely a function of temperature repeatability, The change in wire resistance gives an accurate measurement of the change in wire length. most other Unlike a transducer, the Ther+wX wire system uses the same simple element to drive the and position sensors.

FIG. 6 shows an electrical schematic diagram of the ThermX drive device. As is already clear, The The rmX drive is specifically designed for the calibrated Move the personal interferometer etalon in very precise increments to perform phase shifts It is a precision microtranslator suitable for In this preferred example, the Connect the stone bridge 205 to a resistor, which is a Thera+X drive resistor wire (31). Formed from resistor R111, and resistors R211, R311, and R411 . For best results, these resistances are all approximately equal, approximately 2 ohms. good In the case in point, the requirements for wire 31 are a resistivity of 24 ohms/linear foot, or Resistance wire stub rom 61 with a coefficient of linear expansion of 15.6 parts/million/°C A match was made using 0.364 WG (0,005 inch diameter). This wire is It has a resistance thermal coefficient of 400ppm/”c.Resistors R211, R311 and The requirements for R411 and R411 are a resistivity of 32 ohms/linear foot, and 5 Matched using 800.36 AWG wire with resistance thermal coefficient of ppm/’C Ta. These wires are manufactured by California Fine Works in Grover, California. Available from Iya Company. Of course, other wires can also be used depending on the desired temperature characteristics. can be used.

Bridge 205 is used to sense the resistance of ThermX drive wire R111 and the resistance is directly proportional to the length of the wire to the first order of magnitude. master oshi The AC signal from the regulator 209 drives the bridge via amplifier A4 while D C current is wire I? Computerized wJt source 217 to adjust the length of 111 given from. Capacitor C1 is used for DC isolation. Yellowtail The edge imbalance is detected by the differential amplifier A3, and the phase discrimination amplifier 213 It amplifies the AC imbalance and its amplitude is proportional to the length of the wire RILL. Next The phase discrimination amplifier feeds back the position signal to the computer 215, and 217 and thus control the length of the wire.

In an alternative embodiment, the Wheatstone bridge balance is heated by a DC'r wire. Sensing is done using four currents. In this alternative embodiment, the error signal is It is divided and normalized by pressure.

An example of this embodiment is shown in detail in FIG. Here, the ThermX drive resistor is represented by R1 and is typically about 2 ohms.

R2 is a matching resistor to R1, which is also typically about 2 ohms. Ru. The other side of the bridge is represented by resistors R3 and R4, which are typical are much larger, for example both about IK ohms. Resistor R5 is at trim potential It acts as a differential meter and has a resistance of approximately 100 ohms in this example. A7 is an instrumentation amplifier , i.e. has good common mode rejection, and in this example the analog device Select AD624, which is available from Amazon. DIV normalizes the error signal. It is a divider for In this example, select the appropriate choice for the divider DIV. is typically an AD633, also available from Analog Devices. A1 has a gain of about 1000, DIV has a gain of about 10, and Brifji The quiescent current through is approximately 0.2A. 11 is an integrator, here an operational amplifier , A8 together with capacitor C2 and resistor R7.

In operation, the Vlgy is the drive for the 71 nodes. (Vl changes to R5 Since we track v2 which is set as is equal *) By setting Vmzy, the drive passing through the bridge The current is connected to a Therx resistor R1 so that the voltage R1 varies in a calibrated manner. changing its resistance (i.e., R1 tracks V IEF) Can be done. DIV is useful for evaluating the signal from amplifier A7, and integrator ■1 gives an error signal to

Those skilled in the art will appreciate that many modifications can be made to the described embodiments that are within the spirit and scope of the invention. would appreciate being able to do that.

For example, FIG. 8 shows an interferometer system using two shearing plates 91 and 93. The wavefront shape can be measured simultaneously along two orthogonal axes. I can do it. In this configuration, the first plate 91 is aligned in one axis, namely the vertical axis. Orient and rotate around the second plate by its ThermX drive. The ThermX drive system is mounted around an orthogonal axis shown schematically as horizontal axis 95 Rotate to match the orientation depending on the location. In this example, the output from the optical element under test is The light is incident on the first plate and, as before, the front and rear surfaces of plate 91. It gives an interference pattern from the light reflected from the surface, and the light is COD or COD as shown in Figure 5. or other devices. Plate 91, however, transmifcidin, so that a significant portion of the light passes through the second plate. It is sent to be incident on rate 93. Plate 93 is then dried relative to the orthogonal axis. This can also be detected as described above.

Another approach to measuring wavefront shape along two orthogonal axes is shown in Figure 9. Ru. In this embodiment, the light incident from the optical element under test is directed to the image rotation device 10. 01 and then sends the light to an interferometer. With this system, one axis The wavefront shape is measured along the and measure the wavefront shape around the orthogonal axis. Those skilled in the art can also measure the fringe phase by The phase shift method described above can be used for V-shaped shearing plates as well. Therefore, the above analysis can be applied to phiso-interferometers, as described in U.S. Pat. As stated in No. 4,173.442 (herein incorporated by reference) , the laser wavelength can be measured from the fringe phase. Therefore, as an alternative embodiment , the laser wavelength can be measured using the interferometer according to the present invention.

There are many other changes that can be made to each component as well.

For example, the dimensions and materials of the etalon can vary widely, and the structure of the base and ring The mechanical configuration of can be varied and can be varied in many dimensions. Electricity and and control circuit for the preferred circuit configuration for the ThermX drive device. It can be designed to be completed. Interferometer embodiments also reflect the spirit and scope of the invention. The shearing plate can be attached to the support with bibofts and the drive device is provided to rotate the shearing plate. Also, those skilled in the art can You will notice that choosing to use a rotation simplifies the calculations. However, other rotation angles also There is also no inherent reason why it cannot be used. Then, pin the shearing plate into the support. There are many different ways in which the bot can rotate the plate sufficiently. It can take many shapes as well. For example, a drive device that can be implemented is Engage the driven part on the housing for the motor and shearing plate. A drive cam can be incorporated to Similarly, according to the claims that follow. Without departing from the spirit and scope of the invention, which is limited only by There are other examples of changes.

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Claims (28)

[Claims] 1. The incident beam is made of a transparent material and enters two substantially parallel interfering parts. A system with a flat surface oriented to reflect the beam and produce amplitude splitting. a shearing plate; a mounting device for supporting said shearing plate; and said for rotating said shearing plate about an axis parallel to one of said planes; for determining the characteristics of an incident beam of electromagnetic radiation containing an actuating device coupled to an attachment device; equipment. 2. Further, for determining the rotational position of said shearing plate in relation to the mounting device. 2. The apparatus of claim 1, further comprising a detection device for detecting a second object. 3. and a controller for controlling the actuating device in response to the output from the sensing device. 3. The device of claim 2, comprising a computer device. 4. Furthermore, the mounting device is held in a rotating manner and the rotation angle of the mounting device is measured. 2. The apparatus of claim 1, further comprising a stage apparatus for controlling the image. 5. a wire having a length between a first end and a second end; a retaining device for attaching the first end and the second end so as to retain the first end and the second end; a driving device for changing the temperature of the wire; a driving device for measuring the resistance of the wire; a detection device for receiving a signal from the detection device and responding to the signal from the drive device; a feedback device for controlling the wire to give a calibrated change in the length of the wire; Place A translator consisting of. 6. The incident beam is made of a transparent material and enters two substantially parallel interfering parts. A system with a flat surface oriented to reflect the beam and produce amplitude splitting. a shearing plate; a mounting device for supporting said shearing plate; and said shearing plate in relation to a mounting device about an axis parallel to one of said faces; The translation device includes a translation device for rotating; a wire having a length between a first end and a second end; a retaining device for attaching the first end and the second end so as to hold the first end and the second end together; a driving device for changing the temperature of the wire; a driving device for measuring the resistance of said wire; Detection device; receives a signal from the detection device and moves the drive device in response to the signal; Feedback device for controlling to give calibrated changes in wire length including Device for determining the characteristics of an incident beam of electromagnetic radiation. 7. Furthermore, the mounting device is held in a rotating manner and the rotation angle of the mounting position is measured. 7. The apparatus according to claim 6, further comprising a stage apparatus for controlling. 8. two substantially parallel planes transposed with respect to each other transversely in the direction of the incident beam Shearing device for amplitude division by reflection of an incident beam of electromagnetic radiation into parts ; a mounting device for supporting said shearing device; and an axis perpendicular to the incident beam. an actuation device for rotating the shearing device relative to the incident beam about the Place Interferometer including. 9. Furthermore, the mounting device is held in a rotating manner and the rotation angle of the mounting device is measured. 9. The interferometer according to claim 8, further comprising a stage device for controlling the interferometer. 10. Furthermore, a stripe for detecting a stripe pattern produced by the shearing device. 9. An interferometer according to claim 8, including a detection device. 11. further rotating the shearing device by a plurality of angular increments about the axis; claim 10, further comprising a computer device for providing a signal to said actuating device to Interferometer as described. 12. The computer device processes the fringe pattern to determine the fringe phase at each increment. 12. The interferometer of claim 11, wherein the interferometer is processed. 13. the computer device determines a wavefront phase profile for the incident beam; 13. The interferometer of claim 12, wherein the fringe phase is processed at each increment for the purpose of determining the fringe phase. 14. Further, the operation is performed to cause rotation of the shearing device about the axis. the rotation of said shearing device about said axis in order to provide a signal to said shearing device; to collect data from said fringe detection device and to collect data from said data. Claim 10, further comprising a computer device for determining wavefront characteristics for the beam. interferometer. 15. of the two parts, each part having a wavefront with a direction of propagation substantially parallel to the other; are displaced in relation to each other laterally in the direction of the incident beam so as to produce interference fringes between for dividing the amplitude by reflection of the incident beam of electromagnetic radiation into said two parts. shearing device; supporting said shearing device and around an axis perpendicular to the incident beam; An interferometer system including a mounting device for rotating said shearing device by a small amount. . 16. Furthermore, a fringe detection for detecting interference fringes caused by the shearing device. 16. The interferometer system of claim 15, comprising an apparatus. 17. Furthermore, the shearing device can be adapted to different angles of orientation and rotation around the axis. determining a wavefront profile based on the interference fringes detected by the corresponding fringe detection device; 17. The interferometer system of claim 16, including a computer device for. 18. Furthermore, the fringes are used to determine the wavefront amplitude profile for the incident beam. includes computer equipment for processing information from the detection equipment, thereby 17. The interferometer system of claim 16, wherein the interferometer system determines a complex amplitude of a wavefront of the incident beam. 19. The computer device is a Fourier and calculates the composite amplitude by at least 19. The interferometer system of claim 18, wherein the interferometer system transforms to determine one of the two. a) far-field intensity distribution of the wavefront for the incident beam; b) the incident beam Focal spot intensity distribution for . 20. The computer device performs at least one of the following on the incident beam: 20. The interferometer system of claim 19. a) M2; b) Strehl ratio. 21. Furthermore, the fringe detection is performed to determine the wavefront phase profile for the incident beam. 17. The apparatus of claim 16, comprising a computer device for processing information from the output device. Interference system. 22. The computer device determines at least one of the following characteristics of the incident beam: 22. The interferometer system of claim 21, wherein the interferometer system processes the wavefront phase profile to determine Mu. a) Zzernik polynomial coefficient b) Seidel aberration. 23. Claim wherein the wavefront phase profile is used to calculate laser wavelength. Interferometer system according to 21. 24. from an optical system in which the incident beam is to determine optical properties. 16. The interferometer system of claim 15, which radiates. 25. Furthermore, the electric current from the incident beam that is not reflected by the shearing device is a second shearing device arranged to receive a portion of the magnetic radiation; The shearing device of 2 is used to divide the amplitude into two parts by reflection of said part. and each part has a wavefront with a direction of propagation substantially parallel to each other, and the two parts the minutes are mutually transverse to the direction of the incident beam so as to produce interference fringes between them. Relevantly replaced; supporting the second shearing device; and supporting the second shearing device around a second axis. a second mounting device for rotating the shaft by a small amount; If a request is made that is not parallel to the axis of rotation of the ringing device or not parallel to the direction of the incident beam, 16. The interferometer system according to claim 15. 26. Furthermore, the optical axis of the incident beam is adjusted before entering the shearing device. 16. An image rotation device as claimed in claim 15, including an image rotation device for rotating said incident beam about said image rotation device. Interferometer system. 27. The computer device is used to determine the fringe contrast for each increment. 12. The interferometer of claim 11, wherein the interferometer processes the fringe pattern. 28. The computer device processes the fringe pattern to determine a wavefront amplitude profile. 12. The interferometer according to claim 11, wherein the interferometer processes a .