CN101191970B - Ultrafast Optical Parametric Image Enlargement Method and Device - Google Patents

Abstract

A method and its apparatus for amplifying ultrafast optical parametric image includes such steps as multiplying the frequency of infrared light emitted from laser YDFL by optical waveguide PPLN to generate frequency-multiplied light, using the generated frequency-multiplied light as the pump light of optical parametric amplifier, and using the residual infrared light as signal light. The signal light irradiates a target object through the dichroic mirror, is imaged by the confocal imaging system, and is injected into the optical parameter amplifier through the dichroic mirror; the pumping light is reflected to the delay line after passing through the dichroic mirror, is adjusted to be synchronous with the signal light, and then is reflected to the optical parametric amplifier through the dichroic mirror. The pumping light output by the optical parametric amplifier is reflected by the dichroic mirror; the signal light and the idle frequency light output by the optical parametric amplifier penetrate through the dichroic mirror and are imaged on the CCD camera through the lens. The invention solves the technical problems of limited detection depth or lower spatial resolution in the background technology. The invention has compact structure, can continuously and rapidly carry out multi-frame imaging amplification on the target, and ensures that a plurality of frames are superposed and averaged.

Description

Ultrafast Optical Parametric Image Enlargement Method and Device

technical field

The invention relates to a method and equipment for zooming in on an ultrafast light parameter image.

Background technique

Optical coherence tomography technology is relatively mature in the field of biomedicine. It uses ballistic photon imaging, and the detection depth is limited, only 1-2mm. It is impossible to obtain images with the thickness of biological tissues on the order of several mm or even cm.

Using snake photon imaging, the detection depth of biological tissue can be increased to centimeter level, but the spatial resolution is low.

Contents of the invention

The object of the present invention is to provide an ultrafast optical parametric image amplification method and its equipment, which solve the technical problems of limited detection depth or low spatial resolution in the background art.

Technical solution of the present invention is:

An ultrafast optical parametric image amplification method, which is special in that the implementation steps of the method include:

(1) Light source: the infrared light emitted by the laser YDFL is frequency-multiplied by the optical waveguide PPLN, and the frequency-doubled light generated is used as the first pump light PR1 of the optical parametric amplifier OPA, and the remaining infrared light is used as the first signal light SR1;

(2) The first pump light PR1 and the first signal light SR1 are phase-separated after passing through the first dichroic mirror D1:

(2.1) The first signal light SR1 is irradiated to the target object 0 through the first dichroic mirror D1, and after being imaged by the confocal imaging system CF, it is injected into the optical parametric amplifier OPA through the second dichroic mirror D2;

(2.2) The first pump light PR1 is reflected to the delay line VDL after passing through the first dichroic mirror D1, adjusted to be synchronized with the first signal light SR1 through the delay line VDL, and then reflected by the second dichroic mirror D2 and injected into the optical parametric amplifier OPA ;

(3) The output light amplified by the optical parametric amplifier OPA is divided into three parts: one is the second signal light SR2 for amplifying the image, the other is the idler light R, and the third is the remaining second pump light PR2;

(4) The second pump light PR2 amplified and output by the optical parametric amplifier OPA is reflected after passing through the third dichroic mirror D3;

The second signal light SR2 and the idler light IR of the enlarged image amplified and output by the optical parametric amplifier OPA pass through the third dichroic mirror D3 and are imaged on the CCD camera C through the imaging lens L.

A device for realizing the above ultrafast optical parametric image amplification method, which is special in that it includes a light source, the light source is composed of an optical waveguide PPLN coupled with a laser YDFL; the output optical path of the optical waveguide PPLN is provided with a first two-color mirror DI; the reflection light path of the first dichroic mirror D1 is provided with a delay line VDL, the output light path of the delay line VDL is provided with a second dichroic mirror D2, and the reflection light path of the second dichroic mirror D2 is not provided with An optical parametric amplifier OPA, the optical parametric amplifier OPA is arranged on the rear focal plane of the confocal imaging system CF; the first dichroic mirror D1 transmission optical path is provided with a target object 0, and the target object 0 is simultaneously located in the confocal imaging On the front focal plane of the system CF; an imaging lens L is arranged on the image plane at the double focal length of the confocal imaging system CF, and a CCD camera C is arranged on the image plane at the double focal length of the imaging lens L.

The above laser YDFL is preferably a high repetition rate, high power ytterbium-doped fiber laser.

The above-mentioned optical waveguide PPLN is preferably a frequency doubling device using a periodically poled lithium niobate crystal as a frequency doubling crystal.

The above-mentioned confocal imaging system CF is a confocal imaging system composed of two convex lenses.

The above-mentioned optical parametric amplifier OPA is preferably an optical parametric amplifier using a BBO crystal as a nonlinear crystal.

The present invention has the following advantages:

1. Compact structure and small volume.

2. Stable performance and high reliability.

3. Low power consumption, high power and high efficiency.

4. It can continuously and quickly zoom in on multiple images of the target, so that multiple images can be reconstructed and averaged, and the influence of random photon noise is small.

5. The signal-to-noise ratio can be kept unchanged in the optical parametric image amplification process, that is, the image signal can be amplified without noise.

6. Facilitate the acquisition of high-speed images.

7. The obtained optically enlarged image of the target: high signal-to-noise ratio, high spatial and temporal resolution, and high sensitivity.

Description of drawings

FIG. 1 is a schematic diagram of the structure and principle of the optical parametric image amplification system of the present invention.

Explanation of reference numbers:

YDFL-laser, PPLN-optical waveguide, D1-first dichroic mirror, 0-target object, CF-confocal imaging system, D2-second dichroic mirror, VDL-delay line, OPA-optical parametric amplifier, D3-third Dichroic mirror, L-imaging lens, C-CCD camera; PR1-first pump light, SR1-first signal light, PR2-second pump light, SR2-second signal light, IR-idler light; 01 - object plane, I1 - image plane, I2 - image plane, FT - Fourier plane.

light frequency. Optical parametric amplifiers can amplify weak optical image signals by being pumped by ultrafast pulses. The method of image enhancement using optical parametric amplifiers is called optical parametric image amplification. The magnified image and the co-E image produced by optical parametric image amplification are twin images, which can be applied to the related fields of quantum images. Optical parametric image amplification can be used as a front-end receiver for lidar detection, amplifying weak optical image signals from a distance. Optical parametric image amplification amplifies the weak optical image signal and increases the intensity of the image without changing the signal-to-noise ratio of the image, that is, without introducing noise. For the detection of target objects with low damage threshold value, the method of optical parametric image amplification can be used to detect, which can not only compensate the resolution and signal-to-noise ratio lost due to too weak signal, but also achieve non-damage detection of target objects. Using optical parametric image amplification as the time gate and snake-shaped photon imaging, according to the difference in the time when photons arrive at the detector after passing through the scattering medium, the optical parametric amplifier OPA is used to parametrically amplify the photons arriving at different times, which can obtain low noise and high gain. and higher resolution images. The optical parametric amplifier OPA is used as an ultrafast time gate, which can expose the imaging within ps time, so it can be used for space and time imaging in the ultrafast field. Optical parametric image amplification is used to image and analyze the transmitted light of biological tissue, and the temporal and spatial resolution information of biological tissue morphology and structure can be obtained.

Referring to accompanying drawing 1, the implementation steps of the ultrafast optical parametric image amplification method embodiment of the present invention are as follows:

(1) light source: the infrared light of the input s=1050nm sent by the laser YDFL is frequency-multiplied by the optical waveguide PPLN, and the generated frequency-multiplied light of the input p=525nm is used as the first pumping light PR1 of the optical parametric amplifier OPA; The remaining infrared light of λs=1050nm is used as the first signal light SR1.

(2) The first pump light PR1 and the first signal light SR1 are phase-separated after passing through the first dichroic mirror D1:

(2.1) The first signal light SR1 is irradiated to the target object 0 through the first dichroic mirror D1, and after being imaged by the confocal imaging system CF, it is injected into the optical parametric amplifier OPA through the dichroic mirror D2.

(2.1) The first pump light PR1 is reflected to the delay line VDL after passing through the first dichroic mirror D1, adjusted to be synchronized with the first signal light SR1 through the delay line VDL, and then reflected by the second dichroic mirror D2 and injected into the optical parametric amplifier OPA . The delay line VDL is used to adjust the first pump light PR1 arriving at its BBO crystal at different times to make it phase-matched with the first signal light SR1, then the optical parametric amplifier OPA can select different photons passing through the target object 0 to amplify.

(3) The output light after being amplified by the optical parametric amplifier OPA is divided into three parts: the first is the second signal light SR2 of the enlarged image, the second is the idler light IR of λi=525nm, and the third is the remaining second pump Puguang PR2.

(4) The second pump light PR2 amplified and output by the optical parametric amplifier OPA passes through the third dichroic mirror D3 and is reflected off. The second signal light SR2 and the idler light IR of the enlarged image amplified and output by the optical parametric amplifier OPA pass through the third dichroic mirror D3 and are imaged on the CCD camera C through the imaging lens L.

Referring to accompanying drawing 1, the ultrafast optical parametric image amplification device of the present invention mainly includes a light source. The light source is composed of optical waveguide PPLN coupled with laser YDFL. The light source has simple structure and good stability. The laser YDFL is a high repetition rate, high power ytterbium-doped fiber laser with a pulse width of 200ps, a central wavelength of 1050nm, a single pulse energy of 60μJ, and a repetition rate of 3Khz. The first dichroic mirror D1 is arranged on the output optical path of the optical waveguide PPLN. The optical waveguide PPLN uses periodically poled lithium niobate crystal as the frequency doubling device of the frequency doubling crystal. The delay line VDL is arranged on the reflection optical path of the first dichroic mirror D1, and the second dichroic mirror D2 is arranged on the output optical path of the delay line VDL. The optical parametric amplifier OPA is arranged on the reflection optical path of the second dichroic mirror D2 and on the rear focal plane of the confocal imaging system CF. Optical parametric amplifier OPA is based on BBO crystal as nonlinear crystal optical parametric amplifier. The optical parametric amplifier OPA is a key device for optical parametric image enhancement. The BBO crystal is used as the nonlinear crystal of the optical parametric amplifier OPA. By controlling the azimuth of the BBO crystal, the phase matching of the optical parametric amplifier OPA can be adjusted. The optical parametric amplifier OPA has a wide phase matching range, a large nonlinear coefficient, and a high damage threshold, and can selectively amplify different spatial frequency ranges of the image. When fully phase-matched, the optical parametric amplifier OPA amplifies the low-frequency range of the image and acts as a low-pass filter. When there is a certain amount of phase mismatch, the optical parametric amplifier OPA amplifies the high-frequency range of the image, and is used as a high-pass filter for edge enhancement of the image. The gain of the signal light is phase-sensitive, and no white radiation noise is generated during the amplification process, which can realize the noise-free amplification of the image, that is, the signal-to-noise ratio remains unchanged during the amplification process. The target object 0 is set on the transmission light path of the first dichroic mirror D1, and is located on the front focal plane of the confocal imaging system CF. The confocal imaging system CF is a confocal imaging system composed of two convex lenses, that is, the distance between the two convex lenses is the sum of the focal lengths of the two convex lenses. The focal length of the two convex lenses is f=12cm, and the distance between the two convex lenses is 24cm. The imaging lens L is set on the image plane at the double focal length of the confocal imaging system CF, and the CCD camera C is set on the image plane at the double focal length of the imaging lens L.

Claims (5)

1. an ultrafast light parametric image amplification method, is characterized in that, the realization step of this method comprises: (1) Light source: The infrared light emitted by the laser is frequency-multiplied by the optical waveguide, and the frequency-doubled light generated is used as the first pump light of the optical parametric amplifier, and the remaining infrared light is used as the first signal light; (2) The first pump light and the first signal light are phase-separated after passing through the first dichroic mirror: (2.1) The first signal light is irradiated to the target object O through the first dichroic mirror, and after being imaged by the confocal imaging system, it is injected into the optical parametric amplifier through the second dichroic mirror; (2.2) The first pumping light is reflected to the delay line after passing through the first two-color environment, adjusted to be synchronized with the first signal light through the delay line, and then injected into the optical parametric amplifier after being reflected by the second two-color environment; (3) The output light amplified by the optical parametric amplifier is divided into three parts: one is the second signal light for amplifying the image, the other is idler light, and the third is the remaining second pump light; (4) The second pump light amplified and output by the optical parametric amplifier is reflected after passing through the third dichroic environment; the second signal light and idler light of the enlarged image amplified and output by the optical parametric amplifier pass through the third dichroic mirror , imaged on the CCD camera C through the imaging lens L. 2. A device for realizing the ultrafast optical parametric image amplification method described in claim 1, characterized in that it comprises a light source, which is composed of an optical waveguide coupled with a laser; the output optical path of the optical waveguide is provided with a first A dichroic mirror; a delay line is arranged on the reflection optical path of the first dichroic mirror, a second dichroic mirror is arranged on the output optical path of the delay line, an optical parametric amplifier is arranged on the reflection optical path of the second dichroic mirror, the The optical parametric amplifier is arranged on the rear focal plane of the confocal imaging system, and the first dichroic mirror transmission optical path is provided with a target object O, and the target object O is simultaneously located on the front focal plane of the confocal imaging system; An imaging lens L is arranged on the image plane at the double focal length of the confocal imaging system, and a CCD camera C is arranged on the image plane at the double focal length of the imaging lens L. 3 . The ultrafast optical parametric image amplification device according to claim 2 , wherein the optical waveguide uses a periodically poled lithium niobate crystal as a frequency doubling device. 4. The ultrafast optical parametric image magnification device according to claim 3, characterized in that: said confocal imaging system is a confocal imaging system composed of two convex lenses. 5. The ultrafast optical parametric image amplification device according to claim 4, characterized in that: said optical parametric amplifier is a nonlinear crystal optical parametric amplifier with BBO crystal.

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