CN205514536U - Frequency domain optics chromatographic device that is concerned with - Google Patents

Abstract

The utility model discloses a frequency domain optics chromatographic device that is concerned with belongs to terahertz relevant tomographic image technical field now, and the relevant chromatographic device speed of current optics is slow, with high costs, the utility model discloses a frequency domain optics chromatographic device that is concerned with owing to need not refer to the along -track scanning of mirror, has accelerated formation of image speed including mercury lamp, the beam splitter, the automatically controlled two -dimensional translation table who is used for across -track scanning, the objective table that is used for placing the sample, reference mirror, diffraction grating, automatically controlled one -dimensional translation platform, the detector that produce THz greatly. Mode with the scanning of dot matrix CCD replaces area array CCD, has reduced the cost of system's device. And this structure adopts the wide range mercury lamp can reach 100 mu m as light source, vertical imaging resolution.

Description

A frequency domain optical coherence tomography device

technical field

The utility model belongs to the technical field of terahertz coherence tomography, and more specifically relates to a frequency-domain optical coherence tomography device.

Background technique

Optical coherence tomography (Optical Coherence Tomography, OCT), as a new optical tomography technology, uses a longer wavelength light source, and is widely used in clinical Widely used in medical field.

The traditional OCT technology is time-domain OCT, which is characterized by the need for depth scanning of the reference arm, corresponding to different depths of the sample. Deep scanning limits the acquisition speed of time-domain OCT, which affects its wider application.

The recently emerging frequency-domain OCT technology uses area array CCD for data acquisition, and obtains all the information in a depth direction inside the sample by collecting interference spectrum and Fourier transform. The high price restricts the further development of the system.

Utility model content

Aiming at the defects of slow imaging speed and high cost in the prior art, the purpose of this utility model is to solve the above technical problems.

To achieve the above purpose, the utility model provides a frequency-domain optical coherence tomography device, which includes a high-stability medium-pressure mercury lamp generating THz, a beam splitter, and an electronically controlled two-dimensional translation stage for lateral scanning , the stage used to place the sample, the reference mirror, the diffraction grating, the electronically controlled one-dimensional translation stage, and the detector;

The outgoing light of the mercury lamp passes through the sample arm and the reference arm respectively through the beam splitter, and is received by the detector after passing through the diffraction grating after interference;

The sample arm includes an electronically controlled two-dimensional translation stage for the lateral scanning and the stage for placing the sample, which is used to inject light into the sample and reflect it back;

the reference arm includes the reference mirror for reflecting light and interfering with light passing through the sample arm;

The detector is located on the electronically controlled one-dimensional platform.

Preferably, the device further includes a lock-in amplifier for amplifying the detection signal output by the detector; a computer for recording the output signal of the lock-in amplifier; and controlling the electronically controlled two-dimensional translation stage and the electronic Controller for one-dimensional translation stage.

Preferably, the device further includes an aperture stop, the aperture stop is located before the beam splitter on the optical path, and is used to control the spot size and increase the interference contrast;

Preferably, the beam splitter is made of a metal grating made on a Mylar film, and its transmission-reflection ratio is 4:1;

Generally speaking, compared with the prior art, the above technical solutions conceived by the utility model can achieve the following beneficial effects:

(1) Compared with the traditional time-domain optical coherence tomography technology, this structure greatly speeds up the imaging speed because it does not need the longitudinal scanning of the reference mirror. The area array CCD is replaced by the dot matrix CCD scanning method, which reduces the cost of the system device. Moreover, the structure uses a broad-spectrum mercury lamp as a light source, and the longitudinal imaging resolution can reach 100 μm.

Description of drawings

Fig. 1 is a schematic diagram of a frequency-domain optical coherence tomography system;

Figure 2 is a graph of the mercury lamp output spectrum.

detailed description

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

In order to solve the shortcomings of the existing technology, the utility model provides a frequency-domain optical coherence tomography system and method, which can realize high-precision three-dimensional image reconstruction of the sample to be tested by using the weak coherence principle of broadband terahertz. At the same time, since the frequency-domain OCT system does not need to move the reference mirror for axial scanning, it can obtain all the depth data at one time, so the imaging speed is accelerated. Experimental results show that the longitudinal resolution of terahertz coherence tomography is less than 100 μm. This technology has a good application prospect in the field of high-precision terahertz nondestructive detection, and provides a new experimental method for the field of terahertz nondestructive detection.

The frequency-domain optical coherence tomography system and method of the utility model include a high-stability medium-pressure mercury lamp 1 generating THz, a first gold-plated off-axis parabolic mirror 2 and a second gold-plated off-axis parabolic mirror with focusing and collimating functions 3. Aperture stop 4 to control the size of the light spot entering the interferometer and increase the interference contrast, chopper 5 to periodically modulate the THz wave emitted by the high-stability medium-pressure mercury lamp for detection by the detector, and beam splitter 6 It is composed of a metal grating made on Mylar film, and its transmission-reflection ratio is 4:1. The third gold-plated off-axis parabolic mirror 8 located on the reference arm 7 to focus the reference light, and the gold-plated height on the reference arm Anti-mirror 9, the fourth gold-plated off-axis parabolic mirror 11 on the sample arm 10 to focus and collimate the sample light, and the electronically controlled two-dimensional translation stage 12 for lateral scanning on the sample arm, consisting of a piece of aluminum plated The stage 14 for placing the sample 13 made of a high reflection mirror, the diffraction grating 16 at the receiving end 15 that diffracts the signal after the light interference from the sample arm 10 and the reference arm 7, passes through the focusing lens 17 to diffract the The light is converged, received by the Golay dot matrix detector 18 placed on the electronically controlled one-dimensional translation platform 19, and the lock-in amplifier 20 that amplifies the detection signal output by the Golay dot matrix detector 18 records the output signal of the lock-in amplifier. A computer 21, and a controller 22 for controlling the electronically controlled two-dimensional translation stage 12 at the sample arm and the electronically controlled one-dimensional translation stage 19 at the receiving end.

Below in conjunction with accompanying drawing, the specific embodiment of the present utility model is described in further detail.

Step 1: Initialize the electronically controlled two-dimensional translation stage to the initial point of lateral scanning, and initialize the electronically controlled one-dimensional translation stage to perform lateral scanning along the diffraction spot. At the same time, the high-stability mercury lamp 1 outputs THz waves covering the frequency range of 1THz-20THz. After passing through the gold-plated off-axis parabolic mirrors 2 and 3, the aperture diaphragm 4 and the chopper 5, it is incident on the beam splitter 6, and is divided into reference light and sample light. The reference light is incident on the gold-plated high reflection mirror 9 through the gold-plated off-axis parabolic mirror 8 and is reflected back, and is incident on the beam splitter again through the gold-plated off-axis parabolic mirror. At the same time, the sample light enters the sample through the gold-plated off-axis parabolic mirror 11 and is reflected back, and then enters the beam splitter again through the gold-plated off-axis parabolic mirror 11. It is necessary to ensure that the incident light emitted by the light source and the reference light reflected by the reference arm are safe to the sample. The sample light reflected back by the arms is focused at the same point on the beam splitter.

Step 2: According to the principle of Michelson interferometer, the sample light and reference light re-passed through the beam splitter meet the coherence condition, and generate an interference signal containing the internal structure information of the sample. The composite light is divided into monochromatic light by the diffraction grating 16, and passed through the focusing lens 17 The focused spectrum is scanned and detected by the Golay lattice detector 18 along the vertical direction of the optical axis, and the optical signal is converted into an electrical signal containing the internal structure information of the sample.

Step 3: Perform lock-in amplification processing on the electric signal through the lock-in amplifier 20 and collect it by the computer. In this way, a depth imaging is completed, and then the electronically controlled two-dimensional translation stage is used to scan the surface of the sample in two dimensions, and finally the three-dimensional imaging of the sample is completed.

Step 4: Perform relevant data processing on the 3D data collected by the computer, and perform 3D reconstruction in combination with relevant software.

According to the interference theory of weakly coherent light, the coherence length of the radiation source Where λ ₀ is the central wavelength of the radiation source, and Δλ is the spectral width of the radiation source. Interference between the two beams occurs only when the optical path difference between the reference arm and the sample arm is less than the coherence length. In order to achieve high-precision longitudinal imaging, the light source used is required to have a short coherence length, that is, a wide radiation spectrum. The terahertz radiation source selected in the experiment is a high-stability mercury lamp, and its output spectrum is shown in Figure 2. The output frequencies are mainly concentrated in 1THz-10THz and 11THz-20THz.

Frequency-domain OCT has the largest depth of detection due to its characteristics. If the virtual image position of the reference mirror is located on the sample surface, then the period of the cosine function corresponding to the depth d _i is π/ _ni d _i , and the total number of interference fringes M _i contained in Δk _FWHM is: can get Therefore, it can be seen that all scattering points in the axial depth of the sample have different total numbers of interference fringes, and the deepest part in the axial direction corresponds to the highest frequency. In this system, the number of sampling points is N by setting the sampling interval of the lattice detector. Due to the symmetry of the interference spectrum, the maximum number of interference fringes that can be detected is N/2, thus obtaining the maximum frequency domain OCT system The imaging depth d is: where n is the average refractive index of the sample, and Δλ is the spectral width.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and modifications made within the spirit and principles of the present utility model Improvements and the like should all be included within the protection scope of the present utility model.

Claims (4)

1. a domain optical coherence chromatographic apparatus, described device include produce the mercury lamp of THz, beam splitter, for transversal scanning Automatically controlled two-dimension translational platform, for placing the object stage of sample, reference mirror, diffraction grating, automatically controlled one-dimensional translation stage, detection Device；

The emergent light of described mercury lamp respectively by sample arm and reference arm, passes through described diffraction grating through interfering through beam splitter again Received by described detector afterwards；

Described sample arm includes the automatically controlled two-dimension translational platform for described transversal scanning and the described object stage for placing sample, For light being incided described sample interior and reflecting；

Described reference arm includes described reference mirror, for carrying out reflecting and doing with by the light of described sample arm by light Relate to；

Described detector is positioned in described automatically controlled one-dimensional platform.

2. device as claimed in claim 1, it is characterised in that described device also includes the detection letter exporting described detector Number it is amplified the lock-in amplifier processed；Record the computer of described lock-in amplifier output signal；And control described automatically controlled Two-dimension translational platform and the controller of described automatically controlled one-dimensional translation stage.

3. device as claimed in claim 1, it is characterised in that described device also includes that aperture diaphragm, described aperture diaphragm exist Before being positioned at described beam splitter in light path, it is used for controlling spot size size and increasing interference contrast.

4. device as claimed in claim 1, it is characterised in that beam splitter is by the metal grating made on Mylar thin film Constituting, its Transflective ratio is for 4:1.