CN115248083A - Method and device for making reference light vertically incident on detection surface in coherent detection light path - Google Patents
Method and device for making reference light vertically incident on detection surface in coherent detection light path Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
- G01J2009/0211—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods for measuring coherence
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Abstract
The invention discloses a method and a device for making reference light vertically incident on a detection surface in a coherent detection light path, and the method for making the reference light vertically incident on the detection surface in the coherent detection light path is characterized in that: in a coherent detection light path, a beam of light is incident into a beam splitting prism in parallel through beam expanding collimation, and then is split into two beams of light by the beam splitting prism, wherein one beam of light is used as reference light and is reflected to an adjusting CCD (charge coupled device), and then is reflected by the adjusting CCD and then is incident to a detection surface of the detection CCD through the beam splitting prism; the other beam of light is used as detection light and is incident on the pyramid prism through the beam splitter prism, is reflected to the neutral attenuation piece through the pyramid prism to weaken the light intensity of the other beam of light, and is reflected to a detection surface on the detection CCD through the beam splitter prism; at this time, the direction of the CCD is adjusted, a fringe pattern generated on a detection surface of the detection CCD is observed, and when only one coarse fringe appears on the fringe pattern, the reference light is vertically incident on the detection surface. The invention can make the reference light vertically incident on the detection surface by adjustment, and has the advantage of convenient adjustment.
Description
Technical Field
The invention relates to the technical field of digital holography, in particular to a method and a device for enabling reference light to vertically enter a detection surface in a coherent detection light path.
Background
In the digital holography, a photoelectric sensing device (such as CCD or CMOS) is used for replacing a dry plate to record a hologram, then the hologram is stored in a computer, and the computer is used for simulating an optical diffraction process to realize holographic reconstruction and processing of a recorded object.
Coherence of light means that the two light waves (light waves) are transmitted with the same phase difference, have the same frequency, or have identical waveforms. The two beams can generate stable interference (i.e. constructive interference and destructive interference) in the propagation process. In reality, however, perfect coherent light energy does not exist, and coherence is usually used to describe the coherent performance of light, including temporal coherence and spatial coherence. The laser light emerging from the laser is generally very coherent. This combination of lasers after beam splitting can produce stable coherent fringes. Coherence has a more general physical meaning, and represents the correlation (correlation) of two waves, or sets of waves.
The detection of optical signals is divided into direct detection and heterodyne detection. The direct detection is a detection mode of directly demodulating an optical signal containing information by using a photoelectric conversion function of a photoelectric detector, and responds to light intensity information of the signal. The direct detection mode has simple system structure, reliability and easy realization, and is widely applied to the aspects of optical communication, laser ranging, laser radar, infrared detection, imaging and the like. Optical heterodyne detection is optical frequency coherent detection, is realized based on the principle that coherent reference light and incident signal light are mixed on a photosensitive surface, and is particularly suitable for optical frequency modulation and phase modulation systems.
Compared with direct detection, optical heterodyne detection has the characteristics of high conversion gain, good filtering performance, good space and polarization discrimination capability and the like, and can respond to amplitude, frequency and phase information of signals. Therefore, the optical heterodyne detection has wide application prospect in the fields of weak signal detection side, optical communication, optical radar, remote sensing technology and spectroscopy. Therefore, in an optical experiment, it is important that the reference light can be vertically incident on the detection plane so that the detection plane can better receive information.
Disclosure of Invention
The invention aims to provide a method and a device for enabling reference light to vertically enter a detection surface in a coherent detection light path. The invention can make the reference light vertically incident on the detection surface by adjustment, and has the advantage of convenient adjustment.
The technical scheme of the invention is as follows: in the coherent detection light path, a beam of light is incident into a beam splitting prism in parallel through beam expanding collimation, and then is split into two beams of light by the beam splitting prism, wherein one beam of light is reflected to an adjusting CCD (charge coupled device) as reference light, and then is reflected by the adjusting CCD and then is incident to a detection surface of the detection CCD through the beam splitting prism; the other beam of light is used as detection light and is incident on the pyramid prism through the beam splitter prism, is reflected to the neutral attenuation piece through the pyramid prism to weaken the light intensity of the other beam of light, and is reflected to a detection surface on the detection CCD through the beam splitter prism; at this time, the direction of the CCD is adjusted, a fringe pattern generated on a detection surface of the detection CCD is observed, and when only one coarse fringe appears on the fringe pattern, the reference light is vertically incident on the detection surface.
In the method for making the reference light vertically enter the detection surface in the coherent detection optical path, the coherent detection optical path is a michelson interference optical path.
In the method for making the reference light vertically incident on the detection surface in the coherent detection light path, the adjustment CCD is arranged on the adjustment frame, and the adjustment of the adjustment CCD direction is performed by the adjustment frame.
In the method for making the reference light vertically enter the detection surface in the coherent detection light path, the pyramid is used to ensure the adjustment precision and ensure that the detection light returns strictly according to the original path.
The device for the method for enabling the reference light to vertically enter the detection surface in the coherent detection light path comprises a light source, wherein the output end of the light source is connected with a beam expander, and the beam expander is connected with a beam splitter prism through a collimating lens; the two sides of the beam splitter prism are respectively provided with an adjusting CCD and a detecting CCD, and the beam splitter prism is sequentially connected with a neutral attenuation sheet and a pyramid prism along the emission direction of the detecting light; the adjusting CCD is arranged on the adjusting frame.
Compared with the prior art, the invention uses two CCD devices of the detection CCD and the adjustment CCD, and then the interference fringe pattern generated by the detection CCD can be observed by adjusting the direction of the adjustment CCD, and when a thick fringe appears in the image, the detection light is vertically incident. Because the reference light does not have the deviation of angle that vertical incidence CCD detecting surface can appear, cause the measurement of light path inaccurate, and when reference light is perpendicular to CCD detecting surface incidence, then the probe light can coincide with the reference light to know that the reference light is vertical incidence. Furthermore, because the reference light reflected by the adjusting CCD is weaker, if one light beam is very strong and the other light beam is very weak, the generated interference fringes are not obvious, and the contrast is very weak, so the invention weakens the detection light reflected by the pyramid prism through arranging the neutral attenuation sheet, ensures that the interference fringes are more obvious, the contrast is higher, and is easy to observe. The invention adopts the pyramid prism as the prism of the corner reflector, the pyramid prism is a backward reflector, the operation principle is that internal reflection exists on the surfaces of three mutually orthogonal prisms, so that the direction of a reflected beam is nominally parallel to the direction of an incident beam-the precision is only limited by the precision of the direction of a reflecting surface, therefore, the invention can ensure that the detection light returns according to the original path by using the pyramid prism.
Drawings
FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention.
The symbols in the drawings are: 1. a light source; 2. a beam expander; 3. a collimating lens; 4. a beam splitting prism; 5. adjusting the CCD; 6. detecting the CCD; 7. a neutral damping sheet; 8. a corner cube prism; 9. and (4) an adjusting frame.
Detailed Description
The invention is further described with reference to the following figures and examples, which are not to be construed as limiting the invention.
The embodiment is as follows: the method for enabling reference light to vertically enter a detection surface in a coherent detection light path comprises the coherent detection light path, wherein the coherent detection light path is a Michelson interference light path, the device part of the coherent detection light path comprises a laser light source 1, the output end of the light source 1 is connected with a beam expander 2, the beam expander 2 is connected with a beam splitter prism 4 through a collimating lens 3, the beam splitter prism 4 adopts a non-polarizing beam splitter prism 4 (BS), and the beam splitter prism 4 can customize beam splitting proportion, namely adjust the proportion of transmission and reflection, such as 5 beam splitting, 6 beam splitting, 10. The transmission and reflection of the beam splitter prism 4 are mainly due to the fact that one end of the surface of the prism is plated with a non-polarization film, and therefore the original polarization state cannot be changed on the two sides; an adjusting CCD5 and a detecting CCD6 are respectively arranged on two sides of the beam splitter prism 4, and the beam splitter prism 4 is sequentially connected with a neutral attenuation sheet 7 and a pyramid prism 8 along the emission direction of the detection light; the adjusting CCD5 is arranged on an adjusting frame 9. The adjustment frame 9 is a common rotatable device, commercially available. The beam is expanded by a beam expander 2, collimated by a collimating lens 3, and parallelly incident into a beam splitter prism 4, and then split into two beams by the beam splitter prism 4, wherein one beam is firstly reflected to an adjusting CCD5 as reference light, and then reflected by the adjusting CCD5 and then incident to a detection surface of a detection CCD6 through the beam splitter prism 4; the other beam of light as detection light is transmitted through the beam splitter prism 4 and is incident on the pyramid prism 8, is reflected to the neutral attenuation piece 7 through the pyramid prism 8 to weaken the light intensity of the other beam of light, and is reflected to the detection surface on the detection CCD6 through the beam splitter prism 4; at this time, the direction of the CCD5 is adjusted by the adjusting frame 9, a fringe pattern generated on the detection surface of the detection CCD6 is observed, and when only one thick fringe appears on the fringe pattern, the reference light is perpendicularly incident on the detection surface to be adjusted.
The invention uses two CCD devices of a detection CCD6 and an adjustment CCD5, and then the interference fringe pattern generated by the detection CCD6 can be observed by adjusting the direction of the adjustment CCD5, and when a thick fringe appears in the image, the detection light is vertically incident. The reference light is not vertically incident on the CCD detection surface, so that the angle deviation can be generated, the measurement of a light path is inaccurate, and when the reference light is vertically incident on the CCD detection surface, the detection light can be superposed with the reference light, so that the reference light is known to be vertically incident. Furthermore, because the reference light reflected by the adjusting CCD5 is weak, if one light beam is strong and the other light beam is weak, the generated interference fringes are not significant, and the contrast is weak, so the detection light reflected by the pyramid prism 8 is weakened by arranging the neutral attenuation sheet 7, the interference fringes are more obvious, the contrast is higher, and the observation is easy. The invention uses the cube-corner prism 8 as the prism of the angular reflector, the cube-corner prism 8 is a kind of backward reflector, its operating principle is that there is internal reflection on the three mutually orthogonal prism surfaces, cause the direction of the reflected beam to be nominally parallel to direction of the incident beam-the precision is only limited by the precision of the direction of the reflecting surface, therefore the invention uses the cube-corner prism 8 to ensure that the detecting light returns according to the original way.
Claims (5)
1. The method for making the reference light vertically incident on the detection surface in the coherent detection light path is characterized in that: in a coherent detection light path, parallelly irradiating a beam of light into a beam splitter prism through beam expanding collimation, dividing the beam of light into two beams of light by the beam splitter prism, reflecting one beam of light as reference light onto an adjusting CCD (charge coupled device), reflecting the reference light by the adjusting CCD, and irradiating the reference light onto a detection surface of the detecting CCD through the beam splitter prism; the other beam of light is used as detection light and is incident on the pyramid prism through the beam splitting prism, is reflected to the neutral attenuator through the pyramid prism to weaken the light intensity of the other beam of light, and is reflected to the detection surface on the detection CCD through the beam splitting prism; at this time, the direction of the CCD is adjusted, a fringe pattern generated on a detection surface of the detection CCD is observed, and when only one coarse fringe appears on the fringe pattern, the reference light is vertically incident on the detection surface.
2. The method of claim 1, wherein the reference light is incident on the detection plane perpendicularly in the coherent detection light path, and the method further comprises: the coherent detection light path is a Michelson interference light path.
3. The method of claim 1, wherein the reference light is incident on the detection plane perpendicularly in the coherent detection light path, and the method further comprises: the adjusting CCD is arranged on the adjusting frame, and the direction of the adjusting CCD is adjusted through the adjusting frame.
4. The method of claim 1, wherein the reference light is incident on the detection plane perpendicularly in the coherent detection light path, and the method further comprises: the pyramid is used for ensuring the adjustment precision and ensuring that the detection light strictly returns according to the original path.
5. The apparatus for coherent detection of optical path according to any of claims 1-4, wherein the reference light is incident on the detection plane perpendicularly, and the apparatus comprises: the device comprises a light source (1), wherein the output end of the light source (1) is connected with a beam expander (2), and the beam expander (2) is connected with a beam splitter prism (4) through a collimating lens (3); an adjusting CCD (5) and a detecting CCD (6) are respectively arranged on two sides of the beam splitter prism (4), and a neutral attenuation sheet (7) and a pyramid prism (8) are sequentially connected to the beam splitter prism (4) along the emission direction of the detection light; the adjusting CCD (5) is arranged on the adjusting frame (9).
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| CN202210030096.0A CN115248083A (en) | 2022-01-12 | 2022-01-12 | Method and device for making reference light vertically incident on detection surface in coherent detection light path |
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Citations (9)
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| CN2916623Y (en) * | 2006-07-05 | 2007-06-27 | 中国科学院上海光学精密机械研究所 | Frequency domain optical coherence tomography device for full-depth detection |
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2022
- 2022-01-12 CN CN202210030096.0A patent/CN115248083A/en active Pending
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