CN102353451A - Secondary acousto-optic tunable filter hyperspectral imaging method and device - Google Patents

Abstract

The invention relates to a secondary acousto-optic tunable filter hyperspectral imaging method and device, which can capture high-resolution spectral images of the target to be measured in the visible light and near-infrared bands, and realize the identification and analysis of the shape and characteristics of the target. It belongs to the technical field of optical remote sensing imaging. The present invention is characterized in that the optical imaging technology is organically combined with the secondary acousto-optic tunable filter part, wherein two acousto-optic tunable filters are used as spectroscopic elements for spectral imaging, and two acousto-optic tunable filters In series on the optical structure, its transmission spectrum is multiplied, and compared with the spectral imaging system of a single Acousto-optic Tunable Filter (AOTF), the resolution of the system is 4 times higher than that of it. The secondary acousto-optic tunable filter hyperspectral imaging technology and device have the advantages of high spectral resolution, small size, light weight, fast spectral scanning speed, and wide tuning range. It can be obtained in the fields of remote sensing science, agricultural census, and geographic information acquisition. Wide range of applications.

Description

Secondary acousto-optic tunable filter hyperspectral imaging method and device

technical field

The invention relates to a secondary acousto-optic tunable filter hyperspectral imaging method and device. The device can acquire image data and spectral data of a target at the same time, and can be used in fields such as remote sensing science, agricultural census, and geographic information acquisition to realize target detection. The identification and analysis of morphology and characteristics belong to the field of optical remote sensing imaging technology.

Background technique

Remote sensing technology is mainly used in geographic surveys, resource dynamic monitoring, and general surveys of agricultural production, including acquisition of target information, remote sensing image processing, and analysis of target characteristics.

The hyperspectral imaging system is an important means for humans to observe and understand the world. The traditional hyperspectral imaging system relies on mechanical tuning technology to scan the target. Its complex structure and large volume restrict the rapid development of hyperspectral imaging technology. and widely used. The secondary filtering acousto-optic tunable hyperspectral imaging technology solves this technical problem.

The secondary acousto-optic tunable filter hyperspectral imaging device of the present invention is composed of a light source, an imaging part, a secondary acousto-optic tunable filter part, a BCCD and a PC control part.

The light source uses sunlight as a common light source, which is more convenient in terms of light extraction.

The imaging optics part is composed of three non-center obscuring front telescopes. The telescopic system of the imaging system can converge the light energy in the distance, and then the converged light beam is incident on the secondary acousto-optic imaging system in a quasi-parallel direction by the telecentric optical path. tune filter section. Using two AOTFs as secondary acousto-optic tunable filter components, the reflected beam of the light source irradiating the target to be measured is incident on AOTF ₁ , and is split by AOTF ₁ , and its +1 order diffracted beam enters AOTF ₂ as its incident light, and passes through AOTF ₂ splits the light again, and the +1-order diffracted light beam of AOTF ₂ is finally incident on the BCCD, so as to achieve higher resolution, and then use the BCCD to obtain the image information of the target. The spectral imaging part based on the secondary filter device can change the radio frequency signal input by its computer according to the application requirements, and then flexibly adjust the spectral resolution to improve the spectral resolution of the imaging system under the premise of ensuring a good signal.

The device has the advantages of no moving parts, small size, light weight, high resolution, high signal-to-noise ratio, fast tuning and scanning speed, and good wavelength stability. AOTF is suitable for online and on-site spectral image acquisition, and can be applied to all-round product quality inspection.

The device uses BCCD as the image receiving system, BCCD is also called back-illuminated CCD, and its advantages are that the noise is small and the response spectrum range is better than that of the commonly used front-illuminated CCD.

The invention is a novel imaging technology integrating optics, spectroscopy, precision machinery, electronic technology and computer technology. The basic technology and devices involved are mature, and the invention can be realized.

Contents of the invention

A secondary acousto-optic tunable filter hyperspectral imaging method and device. The device is composed of a light source, a secondary acousto-optic tunable filter part, a BCCD imaging part, and a PC control and management part. The present invention uses the secondary acousto-optic tunable filter part as the core component of the spectroscopic part, and according to the principle of acousto-optic interaction, relies on the flexible change of ultrasonic frequency to select the central light wavelength, so that the two AOTFs have a certain wavelength difference. A suitable wavelength difference can be obtained at the balance point, and high resolution can be obtained.

When the light source shines on the object, the reflected light of the object enters the imaging system, and the binary optical lens is used as the imaging part. It combines the off-axis three-mirror system with the zoom system with the binary optical lens. This group of lenses Consisting of three quadratic aspherical front-facing telescopes without central obscuration, it not only improves the light-gathering capability of multi-spectral imaging, but also facilitates the miniaturization and light weight of the system. Such an imaging system can collimate and focus the beam into the secondary filtering section.

The main components of the secondary filtering part of the present invention are two AOTFs, AOTF consists of a uniaxial birefringent crystal (the material usually used is TeO ₂ ), a piezoelectric transducer bonded to one side of the uniaxial crystal, and an AOTF acting on The high-frequency signal source of the piezoelectric transducer is composed. AOTF utilizes the Bragg diffraction effect on the light incident in the propagation medium when the sound wave propagates in the anisotropic medium, that is, splits the incident multi-spectrum, when the incident angle of the ultrasonic wave input by the piezoelectric transducer (PZT) Timing, corresponding to a certain ultrasonic frequency value, the only incident light is diffracted, blocking other parts of the light, to achieve the spectroscopic effect. When the ultrasonic frequency is changed, the wavelength of light diffracted by the acousto-optic tunable filter will also change correspondingly, thus playing the role of spectral scanning. During the working process, the computer controls the driver, adjusts the driver to select the RF signals loaded on the two AOTFs, and provides two sets of RF signals with the same spectral range and different wavelengths to the AOTF, so that AOTF ₁ and AOTF ₂ produce a wavelength difference to meet the secondary filtering In order to obtain a narrower spectral width and improve the resolution of spectral imaging.

The diffracted monochromatic beam is focused on the BCCD, which is located in the focal plane of the imaging and beam-splitting sections. The optical signal filtered by the AOTF irradiates the BCCD, modulates the ultrasonic frequency loaded on the AOTF, and obtains the spectral image cube data of the object. When the beam passes through the secondary filtering part, the narrower spectral width is the corresponding weakening of the optical signal. The traditional CCD cannot achieve the ideal imaging effect. Therefore, the BCCD used in this patent has low noise and its operating temperature can be controlled. Has a high transfer efficiency. BCCD converts the optical signal from the secondary filter device into an electrical signal, and then transmits the electrical signal to the interface circuit, and the interface circuit transmits the signal to the PC control part, self-checks whether its work is normal, and finally the data processing of the PC control part Software and image analysis software to identify the target to be tested.

The time resolution and spatial resolution of the secondary acousto-optic tunable filter hyperspectral imaging method and device are higher than that of the single-acousto-optic tunable filter spectral imaging technology, which can realize fast and high-precision spectral image data acquisition.

Description of drawings

Accompanying drawing 1 is the functional block diagram of secondary acousto-optic tunable filter hyperspectral imaging device;

Accompanying drawing 2 is a schematic diagram of the acousto-optic adjustable secondary filter;

Accompanying drawing 3 is the flowchart of the secondary acousto-optic tunable filter hyperspectral imaging system.

Detailed ways

Step 1: Start the computer, open the control and management software. The system completes the self-test;

Step 2: Select the target and adjust the optical system so that the system can image clearly;

Step 3: According to the spectral range and spectral accuracy to be measured, two sets of ultrasonic frequencies are given;

Step 4: Obtain a clear, high-resolution spectral image of the target;

Step 5: Store and analyze the spectral image.

Claims (7)

1. adjustable filtering ultra-optical spectrum imaging method of secondary acousto-optic and device, its characteristics are: be made up of light source, imaging moiety, the secondary acousto-optic is adjustable filtering part, BCCD and PC control section.

2. imaging moiety according to claim 1 is characterized in that: the reflected light of target to be measured is converged collimation incide in the secondary filtering device, make transmitted light satisfy filtering part incident demand, to improve the spectrum and the image resolution ratio of spectrum imaging system.

3. the adjustable filtering part of secondary acousto-optic according to claim 1; It is characterized in that: form by two acousto-optic tunable filters (AOTF); Piezoelectric transducer loads the ultrasonic signal of different frequency on each acousto-optic tunable filter, make it produce wavelength difference.

4. according to said two acousto-optic tunable filters of claim 3, it is characterized in that: the reflected light of target to be measured is incided AOTF ₁, it tells+and 1 order diffraction light enters into AOTF ₂, through AOTF ₂Beam split once more, its AOTF ₂+ the inciding among the BCCD of 1 order diffraction light.

5. ultrasonic signal according to claim 3 is characterized in that: the relation that is carried in two ultrasonic frequencies on the AOTF is by spectral range to be measured and the spectral resolution decision of drafting.As tuning AOTF ₂The time, AOTF ₁Diffraction light centre wavelength value fix, make it produce central wavelength difference.

6. acousto-optic tunable filter according to claim 3 is characterized in that: TeO is partly adopted in the adjustable beam split of acousto-optic ₂As analyzing crystal, piezoelectric transducer is at TeO ₂One end of crystal provides ultrasound wave, TeO ₂The other end of crystal adds foamed sound absorber, and ultrasound wave is propagated to go the form of ripple in crystal.

7. BCCD according to claim 1 and PC control section; It is characterized in that: two groups of ultrasonic frequencies that computer control is corresponding with required wavelength with the output of management system; Act on piezoelectric transducer; The AOTF beam split; Obtain the spectrum picture of target to be measured; BCCD gathers image information, and last computing machine carries out data processing to the spectral information of target to be measured, has realized the analysis to the spectrum picture characteristic of target to be measured.

Images