A large-angle Fizeau interferometer wavelength measurement device

Abstract

This invention discloses a large-angle Fizeau interferometer wavelength measurement device, comprising an optical fiber port, an off-axis parabolic mirror, a Fizeau interferometer, a cylindrical mirror, and a linear CCD array, all coaxially arranged along the main optical path. A laser beam is incident through the optical fiber port onto the off-axis parabolic mirror for collimation, resulting in parallel light with a specific spot size. The collimated light is then incident on the Fizeau interferometer, and the light reflected from the Fizeau interferometer passes through the cylindrical mirror onto the linear CCD array, forming interference fringes. The cylindrical mirror vertically constricts the interference fringes reflected from the Fizeau interferometer, increasing the intensity of the final interference fringes incident on the linear CCD array. The Fizeau interferometer used in this invention avoids the influence of reflected light from unwanted reflective surfaces on the final interference fringes, improving the final wavelength measurement accuracy. The Fizeau interferometer composed of angled wedge-shaped window mirrors eliminates the need for coating, resulting in a wide usable wavelength range.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and specifically to a large-angle Fizeau interferometer wavelength measurement device. Background Technology

[0002] With the increasing sophistication of optical research, our applications of light are becoming more and more widespread. Laser wavelength, as a reference value for measurement, is widely used in measurements of length, speed, angle, flatness, straightness, and perpendicularity, and is a crucial measurement parameter in precision metrology, precision machinery, and microelectronics industries. Accurate wavelength measurement is also a key technology for traceability of measurement values. The instrument used to accurately measure laser wavelength is called a wavelengthmeter, and most wavelengthmeters utilize interferometry to measure laser wavelength. Based on different interferometric devices, wavelengthmeters are broadly classified into three types: Michelson interferometer, FP interferometer, and Fizeau interferometer.

[0003] Traditional Michelson and FP interferometers have low measurement accuracy, while multibeam Fizeau interferometers can achieve high-precision wavelength measurement quickly and efficiently. A typical Fizeau interferometer uses a wedge-shaped interference module composed of two parallel glass plates. Whether interference fringes are collected at the transmission or reflection end, reflected light from the parallel plate surfaces, which do not participate in the main interference, will affect the final interference fringes, thus reducing wavelength measurement accuracy. Summary of the Invention

[0004] In view of this, in order to solve the above-mentioned problems in the prior art, the present invention proposes a wavelength measurement device for a large-angle Fizeau interferometer, which can eliminate the error influence of useless reflected light on the final interference fringes and improve the final measurement accuracy of wavelength.

[0005] The present invention solves the above problems through the following technical means:

[0006] A large-angle Fizeau interferometer wavelength measurement device includes an optical fiber port, an off-axis parabolic mirror, a Fizeau interferometer, a cylindrical mirror, and a linear CCD array, which are placed coaxially along the main optical path.

[0007] The laser beam is collimated by an off-axis parabolic mirror through the fiber optic port, which collimates the scattered light emitted from the fiber optic port into parallel light with a certain spot size. The collimated light is then incident on a Fizeau interferometer, and the light reflected from the Fizeau interferometer is incident on a linear CCD through a cylindrical mirror to form interference fringes. The cylindrical mirror then vertically contracts the interference fringes reflected from the Fizeau interferometer, increasing the intensity of the interference fringes that are finally incident on the linear CCD.

[0008] Preferably, the Fizeau interferometer includes two wedge-shaped window mirrors with large angles, namely a first wedge-shaped window mirror and a second wedge-shaped window mirror.

[0009] The first and second inclined surfaces of the first wedge-shaped window mirror have a large angle between them, and the third and fourth inclined surfaces of the second wedge-shaped window mirror also have a large angle between them, the same as the wedge angle of the first wedge-shaped window mirror. This large angle is 15° to 35°. The second and third inclined surfaces of the first and second wedge-shaped window mirrors have a small angle, which is 1 to 3 arcmin. When collimated light is incident on the Fizeau interferometer, the first inclined surface of the first wedge-shaped window mirror reflects the collimated light from one direction, while the second inclined surface of the first wedge-shaped window mirror reflects the collimated light from the opposite direction. The third inclined surface of the second wedge-shaped window mirror reflects the collimated light in the same direction as the light reflected by the second inclined surface of the first wedge-shaped window mirror, and the fourth inclined surface of the second wedge-shaped window mirror reflects the collimated light in the same direction as the light reflected by the first inclined surface of the first wedge-shaped window mirror. This avoids the reflected light from the first and fourth inclined surfaces of the first and second wedge-shaped window mirrors participating in the interference.

[0010] Preferably, the large angle is 20°.

[0011] Preferably, the wavelength measurement process of the Fizeau interferometer is as follows: a beam with wavelength λ s When standard light is incident, a set of fringes with a spacing of Δx is obtained. s Interference fringes; the wavelength of the light to be measured is λ u The spacing of the interference fringes produced when incident on the Fizeau interferometer is Δx u The following relationship exists: λ s =2nα·Δx s , λ u =2nα·Δx u The initial measurement value of the wavelength is obtained: λ u =Δx u / Δx s ·λ s ; n is the air refractive index, α is the angle between the second and third inclined planes; in the interference fringe pattern of the laser under test obtained on the linear CCD, at the first minimum intensity, the following relationship holds: ΔL=m·λ u m is the order of the interference fringe, ΔL is the optical path difference, ΔL = 2nd, and d is the minimum thickness of the wedge; m = ΔL / λ u The interference fringe order m is calculated and rounded. Let the first pixel of the linear CCD be x0, and the distance from x0 to the minimum value of the first fringe be l. The final measured wavelength of the laser is calculated using the following formula: λ uf =ΔL / (m+l / Δx) u ).

[0012] Preferably, the large-angle Fizeau interferometer wavelength measurement device further includes a plane mirror, which is disposed between the off-axis parabolic mirror and the Fizeau interferometer to reflect the collimated light into the Fizeau interferometer.

[0013] Preferably, the fiber optic port is located at the focal point of the off-axis parabolic mirror.

[0014] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0015] 1. The collimating device, the off-axis parabolic mirror, and the Fizeau interferometer used in the large-angle Fizeau interferometer wavelength measurement device of this invention can both be used within a very wide wavelength range.

[0016] 2. The Fizeau interferometer used in the large-angle Fizeau interferometer wavelength measurement device of the present invention avoids the influence of reflected light generated by unwanted reflective surfaces on the final interference fringes, further improving the final measurement accuracy of wavelength.

[0017] 3. The design of the Fizeau interferometer composed of angled wedge-shaped window mirrors successfully avoids the common practice of coating the window mirrors in Fizeau interferometers, which would reduce the usable wavelength range. This design avoids coating, thus making the usable wavelength range very wide. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the large-angle Fizeau interferometer wavelength measurement device of the present invention;

[0020] Explanation of reference numerals in the attached figures:

[0021] 1. Fiber optic port; 2. Off-axis parabolic mirror; 3. Plane mirror; 4. Fizeau interferometer; 41. First wedge window mirror; 42. Second wedge window mirror; 411. First inclined plane; 412. Second inclined plane; 421. Third inclined plane; 422. Fourth inclined plane; 5. Cylindrical mirror; 6. Linear CCD array. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, this invention provides a large-angle Fizeau interferometer wavelength measurement device, comprising an optical fiber port 1, an off-axis parabolic mirror 2, a plane mirror 3, a Fizeau interferometer 4, a cylindrical mirror 5, and a linear CCD array 6, all arranged coaxially along the main optical path; all optical elements are coaxial and at the same height relative to the instrument base plane. The positional relationship of the above parts is as follows: laser light is incident on the off-axis parabolic mirror 2 through the optical fiber port 1 for collimation, and the collimated light is then incident on the Fizeau interferometer 4 through the plane mirror 3. The light reflected from the Fizeau interferometer 4 is incident on the linear CCD array 6 through the cylindrical mirror 5 to form interference fringes.

[0024] The fiber optic port 1 is located at the focal point of the off-axis parabolic mirror 2.

[0025] The off-axis parabolic mirror 2 is a wide-band, high-reflectivity off-axis parabolic mirror that collimates the scattered light emitted from the fiber port 1 into parallel light with a certain spot size, and then incident on the Fizeau interferometer 4 through the plane mirror 3.

[0026] The cylindrical mirror 5 reduces the interference fringes reflected by the Fizeau interferometer 4 in the vertical direction, thereby increasing the light intensity of the interference fringes that are finally incident on the linear CCD array 6.

[0027] The Fizeau interferometer 4 consists of two wedge-shaped window mirrors 41 and 42 with large angles. The first inclined surface 411 and the second inclined surface 412 in the first wedge-shaped window mirror 41 have a certain large angle between them. The third inclined surface 421 and the fourth inclined surface 422 in the second wedge-shaped window mirror 42 also have a large angle with the same wedge angle as the first wedge-shaped window mirror 41. The large angle is 15° to 35°, preferably about 20°. The second inclined surface 412 in the first wedge-shaped window mirror 41 and the third inclined surface 421 in the second wedge-shaped window mirror 42 have a certain small angle with each other. The small angle is about 1 to 3 arcmin. Collimated light is incident from mirror 3 into Fizeau interferometer 4, as shown in Figure (1). The first inclined surface 411 on the first wedge window mirror 41 reflects the collimated light from one direction, while the second inclined surface 412 on the first wedge window mirror 41 reflects the collimated light from the opposite direction. The third inclined surface 421 on the second wedge window mirror 42 reflects the collimated light from the same direction as the light reflected by the second inclined surface 412 in the first wedge window mirror 41, and the fourth inclined surface 422 on the second wedge window mirror 42 reflects the collimated light from the same direction as the light reflected by the first inclined surface 411 in the first wedge window mirror 41. This avoids the reflected light from the first inclined surface 411 in the first wedge window mirror 41 and the fourth inclined surface 422 in the second wedge window mirror 42 from participating in the interference.

[0028] The Fizeau interferometer measures wavelength based on the following principle: a beam with wavelength λ... s When standard light is incident, a set of fringes with a spacing of Δx is obtained. s Interference fringes; the wavelength of the light to be measured is λ u The spacing of the interference fringes produced when incident on the interferometer is Δx u The following relationship exists: λ s =2nα·Δx s , λ u =2nα·Δx u This allows us to obtain the initial measurement value of the wavelength, λ. u =Δx u / Δx s ·λ s Where n is the refractive index of air, and α is the angle between the second inclined plane 412 and the third inclined plane 421. In the interference fringe pattern of the laser under test obtained on the linear CCD 6 array, at the first minimum intensity, the following relationship holds: ΔL=m·λ u Where m is the order of the interference fringe, ΔL is the optical path difference, ΔL = 2nd, and d is the minimum thickness of the wedge. m = ΔL / λ u The interference order m is calculated and rounded. Let the first pixel of the linear CCD 6 be x0, and the distance from x0 to the minimum value of the first fringe be l. The final measured wavelength of the laser can be calculated using the following formula: λ uf=ΔL / (m+l / Δx) u ).

[0029] The collimating device, the off-axis parabolic mirror, and the Fizeau interferometer used in the large-angle Fizeau interferometer wavelength measurement device of this invention can both be used within a very wide wavelength range.

[0030] The Fizeau interferometer used in the large-angle Fizeau interferometer wavelength measurement device of this invention avoids the influence of reflected light from unwanted reflective surfaces on the final interference fringes, further improving the final measurement accuracy of the wavelength.

[0031] The design of the Fizeau interferometer, which consists of angled wedge-shaped window mirrors, successfully avoids the need for coating the window mirrors in typical Fizeau interferometers, as coating would reduce the usable wavelength range. This design avoids coating, thus making the usable wavelength range very wide.

[0032] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A wavelength measurement device for a large-angle Fizeau interferometer, characterized in that, It includes fiber optic ports, off-axis parabolic mirrors, Fizeau interferometers, cylindrical mirrors, and linear CCD arrays, all placed coaxially along the main optical path. The laser beam is collimated by being incident on an off-axis parabolic mirror through the fiber optic port, which collimates the scattered light emitted from the fiber optic port into parallel light with a certain spot size. Collimated light is incident on the Fizeau interferometer, and the light reflected from the Fizeau interferometer is incident on the linear CCD through a cylindrical mirror to form interference fringes. The cylindrical mirror reduces the interference fringes reflected from the Fizeau interferometer in the vertical direction, increasing the light intensity of the interference fringes that are finally incident on the linear CCD. The Fizeau interferometer includes two wedge-shaped window mirrors with large angles: a first wedge-shaped window mirror and a second wedge-shaped window mirror. The first and second inclined surfaces of the first wedge-shaped window mirror have a large angle between them, and the third and fourth inclined surfaces of the second wedge-shaped window mirror also have a large angle between them, the same as the wedge angle of the first wedge-shaped window mirror. This large angle is 15° to 35°. The second and third inclined surfaces of the first and second wedge-shaped window mirrors have a small angle, which is 1 to 3 arcmin. When collimated light is incident on the Fizeau interferometer, the first inclined surface of the first wedge-shaped window mirror reflects the collimated light from one direction, while the second inclined surface of the first wedge-shaped window mirror reflects the collimated light from the opposite direction. The third inclined surface of the second wedge-shaped window mirror reflects the collimated light in the same direction as the light reflected by the second inclined surface of the first wedge-shaped window mirror, and the fourth inclined surface of the second wedge-shaped window mirror reflects the collimated light in the same direction as the light reflected by the first inclined surface of the first wedge-shaped window mirror. This avoids the reflected light from the first and fourth inclined surfaces of the first and second wedge-shaped window mirrors participating in the interference.

2. The wavelength measurement device for a large-angle Fizeau interferometer according to claim 1, characterized in that, The large angle is 20°.

3. The wavelength measurement device for a large-angle Fizeau interferometer according to claim 1, characterized in that, The Fizeau interferometer measures wavelength as follows: a beam with wavelength λ... s When standard light is incident, a set of fringes with a spacing of Δx is obtained. s Interference fringes; the wavelength of the light to be measured is λ u The spacing of the interference fringes produced when incident on the Fizeau interferometer is Δx u The following relationship exists: λ s =2nα·Δx s , λ u =2nα·Δx u The initial measurement value of the wavelength is obtained: λ u =Δx u / Δx s ·λ s ; n is the air refractive index, α is the angle between the second and third inclined planes; in the interference fringe pattern of the laser under test obtained on the linear CCD, at the first minimum intensity, the following relationship holds: ΔL=m·λ u m is the order of the interference fringe, ΔL is the optical path difference, ΔL = 2nd, and d is the minimum thickness of the wedge; m = ΔL / λ u The interference fringe order m is calculated and rounded; let... The first pixel of the linear CCD is x0, and the distance from x0 to the minimum value of the first fringe is l. The final measured wavelength of the laser is calculated by the following formula: λ uf =ΔL / (m+l / Δx) u ).

4. The wavelength measurement device for a large-angle Fizeau interferometer according to claim 1, characterized in that, The large-angle Fizeau interferometer wavelength measurement device also includes a plane mirror, which is disposed between the off-axis parabolic mirror and the Fizeau interferometer to reflect the collimated light into the Fizeau interferometer.

5. The wavelength measurement device for a large-angle Fizeau interferometer according to claim 1, characterized in that, The fiber optic port is located at the focal point of the off-axis parabolic mirror.

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