CN102507019A - Hartmann wavefront sensor based on micro-scanning for image quality detection - Google Patents

Abstract

The invention belongs to the field of optical detection, and relates to a Hartmann sensor. The Hartmann sensor comprises an optical path shrinkage system, a micro-scanning device, a micro lens array, a CCD (Charge Coupled Device) detector, a digital image processor and a wavefront processor. The micro-scanning device is placed between a parallel optical tube and the micro lens array; through a micro-scanning operation, the detected wavefront 4-frame image is acquired by a CCD; a single-frame image is reconstructed through the digital image processor; and centroid calculation and wavefront reconstruction are carried out through the wavefront processor. According to the Hartmann sensor provided by the invention, the image quality detection precision of the Hartmann sensor can be improved, and the application range of the Hartmann sensor is enlarged.

Description

Hartmann wave front sensor is used in picture element detection based on micro scanning

Technical field

The present invention relates to a kind of Wavefront sensor that picture element detects, particularly a kind of Hartmann wave front sensor of being used for based on micro scanning.

Background technology

Adaptive optical technique is to adopt Wavefront sensor to measure the position phase of incident light, the wave front aberration of wave-front corrector real-Time Compensation incident light in real time; Make incident light output plane ripple behind wave-front corrector, and complete ADAPTIVE OPTICS SYSTEMS is made up of three parts such as Wavefront detecting, wavefront correction, wave front restoration and control computing generally.Because Hartmann wave front sensor has the advantage of real-time and good stability, ADAPTIVE OPTICS SYSTEMS generally adopts this sensor measurement wavefront.Traditional Hartmann wave front sensor principle light path is seen Fig. 1.

The accuracy of detection that improves Hartmann sensor is exactly to improve the centroid detection precision of Hartmann sensor, and the centroid detection precision of sensor is inseparable with the performance that it is positioned at the ccd detector of locating the focal plane.The Hartmann sensor that the micro scanning device is introduced that the present invention proposes will make moderate progress to the systematic error that is caused by CCD in the detection of Hartmann sensor wavefront, reduces the requirement to CCD, thereby obtains more accurate wavefront reconstruction data.

Summary of the invention

Technical solution of the present invention: detect based on the picture element of micro scanning and to use Hartmann wave front sensor, comprise the light path beam system that contracts, micro scanning device and corresponding digital image processor, microlens array, ccd detector and wave front processor; It is characterized in that before microlens array after the beam system that contracts, placing the micro scanning device.

Principle of the present invention:

The proposition of micro scanning method is its theoretical foundation with sampling theorem, and it is a kind of common method that reduces spectrum confusion.Micro scanning be exactly utilize the micro scanning device with image that optical system became at x, the y direction is carried out the displacement of 1/N (N is an integer, and it is that N is 2 that the present invention adopts 2 * 2 patterns) pixel distance respectively, obtains N * N (promptly 2 * 2) frame and owes sampled images; And use Digital Image Processor that the image reconstruction of multiframe process sub-pix displacement is become a two field picture, thereby reach the purpose that final realization improves resolution.The effect that utilizes micro scanning can improve resolution applies it in the Hartmann wave front sensor, can reach the purpose that CCD resolution is improved, and then improves the picture element accuracy of detection of Hartmann wave front sensor.

The present invention compared with prior art has following advantage: the present invention increases traditional Hartmann wave front sensor to the wavefront accuracy of detection under the prerequisite that does not change the visual field.

Description of drawings

Fig. 1 is traditional Hartmann wave front sensor principle light channel structure synoptic diagram

The Hartmann wave front sensor light channel structure synoptic diagram (also as Figure of abstract) that Fig. 2 proposes for the present invention based on micro scanning

The Hartmann wave front sensor STRUCTURE DECOMPOSITION key diagram that Fig. 3 proposes for the present invention based on micro scanning

Fig. 4 is the dull and stereotyped translation optical path analysis of monolithic figure

Fig. 5 is standard 2 * 2 micro scanning pattern diagram

Among the figure: 1, the beam system front lens that contracts, 2, the beam system rear lens that contracts, 3, the micro scanning device is the parallel flat of Piezoelectric Ceramic, 4, microlens array, 5, ccd detector, 6, computing machine.

Embodiment

As shown in Figure 1, traditional Hartmann wave front sensor mainly is made up of contract beam system, microlens array, ccd detector and wave front processor (computing machine) of light path.It utilizes sub-aperture segmentation before the signal wave of microlens array to incident, and light signal focuses on the CCD thereafter in each sub-aperture, utilizes CCD target surface energy distributions situation to carry out centroid position and calculates.

Like Fig. 2, shown in 3, the present invention comprises that mainly contract beam system, light path of the light path that is made up of 1,2 lens contracts that the micro scanning device before the microlens array 4 promptly is made up of parallel flat 3, ccd detector 5, the computing machine 6 of Piezoelectric Ceramic after the beam system.

The course of work of the present invention is following: tested wavefront is through light path beam system 1, the 2 output directional lights that contract; Project microlens array 4 through micro scanning device 3; Cut apart the corrugated by microlens array 4 and become a lot of little wavelet faces, and focus on and be positioned on the ccd detector 5 that the focal plane goes out, if micro scanning device 3 is the parallel flat by Piezoelectric Ceramic under 2 * 2 patterns; Dull and stereotyped and optical axis angle is θ; If tilt flat plate carries out position angle when rotation around optical axis, assemble the light beam focus point and will on the focal plane, form to be the center, to be the circumference (as shown in Figure 4) of radius with the Δ with former picture point.If the rotary optical flat board rests on 45 °, 135 °, 225 ° and 315 ° these 4 90 ° the positions of being separated by respectively and owes sampling imaging (as shown in Figure 5); Then on ccd detector 5, obtain 4 frames and owe the sampled images signal and carry out Digital Image Processing by computing machine, carrying out the wavefront Processing Algorithm again, to obtain real-time phase of wave poor.

As shown in Figure 4, calculate as follows about the size of parallel flat:

$\mathrm{\Δ}=d\sin \mathrm{\θ}\·(1-\frac{\cos \mathrm{\θ}}{\sqrt{n^2-{\sin }^2\mathrm{\θ}}})---\left(1\right)$

$Z=d\cos \mathrm{\&theta;}\&CenterDot;(1-\frac{\cos \mathrm{\&theta;}}{\sqrt{n^2-{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000616600600021.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{\&theta;}}})---\left(2\right)$

In the formula: n is dull and stereotyped refractive index; D is dull and stereotyped thickness; θ is inclination angle dull and stereotyped and optical axis;

When light wave passes flat board because refraction action, emergent ray can be in the plane of incidence along the dull and stereotyped direction displacement Δ that tilts, shift length Z vertically.

Neighbouring sample point in the micrometric displacement amount of detector face is:

P＝L/2 (3)

In the formula: L is a pel spacing; The micro scanning displacement is:

$\mathrm{\&Delta;}=\frac{\sqrt{2}L}{4}---\left(4\right)$

Parallel flat is referred in the Hartmann wave front sensor, and when the CCD parameter of having confirmed Hartmann wave front sensor and microlens array parameter, known L obtains Δ by formula 4, known n, and d obtains θ by formula 1 again.

Claims (3)

1. detect based on the picture element of micro scanning and use Hartmann wave front sensor, comprise the light path beam system that contracts, micro scanning device and corresponding digital image processor, microlens array, ccd detector and wave front processor; It is characterized in that before microlens array after the beam system that contracts, placing the micro scanning device.

2. micro scanning device according to claim 1 is the parallel flat by Piezoelectric Ceramic.

3. the picture element based on micro scanning according to claim 1 detects uses Hartmann wave front sensor; It is characterized in that: tested wavefront projects microlens array 4 through light path beam system 1, the 2 output directional lights that contract through micro scanning device 3, cuts apart the corrugated by microlens array 4 and becomes a lot of little wavelet faces; And focus on and be positioned on the ccd detector 5 that the focal plane goes out; If micro scanning device 3 is the parallel flat by Piezoelectric Ceramic under 2 * 2 patterns, dull and stereotyped and optical axis angle is θ, if tilt flat plate is when optical axis carries out the position angle rotation; Assembling the light beam focus point will form with former picture point on the focal plane to be the center, to be the circumference (as shown in Figure 4) of radius with the Δ.If the rotary optical flat board rests on 45 °, 135 °, 225 ° and 315 ° these 4 90 ° the positions of being separated by respectively and owes sampling imaging (as shown in Figure 5); Then on ccd detector 5, obtain 4 frames and owe the sampled images signal and carry out Digital Image Processing by computing machine, carrying out the wavefront Processing Algorithm again, to obtain real-time phase of wave poor.

Images