The Structure of High Strehl Ratio Point‐Spread Functions

Perrin, Marshall D.; Sivaramakrishnan, Anand; Makidon, Russell B.; Oppenheimer, Ben R.; Graham, James R.

doi:10.1086/377689

Cited by 162 publications

(154 citation statements)

References 21 publications

(27 reference statements)

Supporting

Mentioning

148

Contrasting

Unclassified

Order By: Relevance

“…We can estimate the tiptilt errors with an accuracy of the order of 1.3 × 10 −2 λ/D in the case of a 19 nm rms WFE (λ/40) and 2.5 × 10 −2 λ/D for 38 nm rms (λ/20). The residual tip-tilt errors are roughly proportional to the rms WFE, as expected from the analytical derivation of extreme adaptive optics PSF (Perrin et al 2003). With our method, we are able to estimate and compensate for tip-tilt errors upstream of a coronagraphic mask by directly computing the intensity differences on the final coronagraphic image.…”

Section: A126 Page 4 Of 11mentioning

confidence: 70%

“…The measured intensity difference ΔI y is never nought and for T x = 0 and T y = 0, ΔI x and ΔI y are not nought. The WFE φ induces a slight asymmetrical speckle pattern in the focal plane (Perrin et al 2003), hence in the signals of the selected quadrants. There is thus a new coupling between the x and y axes linked to the WFE-induced speckle pattern.…”

Section: Simulation With Wavefront Error (φ 0)mentioning

confidence: 99%

See 1 more Smart Citation

Tip-tilt estimation and correction using FQPM coronagraphic images

Mas

Baudoz

Rousset

et al. 2012

A&A

View full text Add to dashboard Cite

Context. Direct imaging of exoplanets located a few AU from their hosting star requires angular resolution at the diffraction limit of large telescopes and a contrast level in the image of 10 5 to 10 10 . Simultaneous use of adaptive optics and coronagraphy is mandatory to fulfil these requirements. Aims. Coronagraphs are usually very sensitive to pointing errors upstream of their focal plane mask. Approaches to measuring these errors in conventional adaptive optics systems consist in setting a wavefront sensor in an additional channel. Differential aberrations between the coronagraphic channel and the additional one induce a loss in performance. To tackle this limitation, we propose a new technique for measuring the tip-tilt errors directly from the coronagraphic image. Methods. Our method uses the relations between the intensity distribution in the coronagraphic image and upstream tip-tilt errors. We also propose a method of estimating the tip-tilt errors downstream of the focal plane mask. We validate at visible wavelength our upstream and downstream tip-tilt estimation and compensation techniques with numerical simulation images and on laboratory images. Results. Numerical simulations predict that our techniques correct for the tip-tilt errors to a 1.3 × 10 −2 λ/D level when considering a λ/40 wavefront error upstream of the coronagraph. In laboratory, where the coronagraph is mostly limited by wavefront errors, we correct for the tip-tilt errors with an accuracy better than 6.5 × 10 −2 λ/D. Conclusions. We demonstrate in numerical simulations and in laboratory that our technique can efficiently estimate the tip-tilt errors directly from the coronagraphic image with no additional channel. It is robust and can be used with small wavefront errors. It should be applicable to planet imager systems currently in preparation, such as SPHERE and MIRI/JWST.

show abstract

Section: A126 Page 4 Of 11mentioning

confidence: 70%

Section: Simulation With Wavefront Error (φ 0)mentioning

confidence: 99%

Tip-tilt estimation and correction using FQPM coronagraphic images

Mas

Baudoz

Rousset

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…Implementation of this concept in SPHERE as an upgrade path appears as an efficient and realistic means of obtaining subnanometric precision for NCPA compensation in the H-band, representing an improvement in terms of wavefront error by a factor of 3 to 10. According to Perrin et al (2003), the residual speckles in a highly corrected coronagraphic image are proportional to the power spectral density of the wavefront, hence proportional to the square of the rms wfe. We can therefore expect a reduction of the residual speckles in SPHERE images by a factor ranging from 10 to 100.…”

Section: Application To a Real System Error Budgetmentioning

confidence: 99%

Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor

N’Diaye

Dohlen

Fusco

et al. 2013

A&A

111

View full text Add to dashboard Cite

Context. Several exoplanet direct-imaging instruments (VLT-SPHERE, Gemini Planet Imager, etc.) will soon be in operation, providing original data for comparative exoplanetary science to the community. To this end, exoplanet imagers use an extreme adaptive optics (XAO) system to correct the atmospheric turbulence and provide a highly corrected beam to a near-infrared (NIR) coronagraph for suppressing diffracted stellar light. The performance of the coronagraph is, however, limited by the non-common path aberrations (NCPA) due to the differential wavefront errors existing between the visible XAO sensing path and the NIR science path and leading to residual speckles that hide the faintest exoplanets in the coronagraphic image. Aims. Accurate calibration of the NCPA in exoplanet imagers is mandatory to correct the residual, quasi-static speckles remaining in the coronagraphic images after XAO correction in order to allow the observation of exoplanets that are at least 10 6 fainter than their host star. Several approaches have been developed during these past few years to reach this goal. We propose an approach based on the Zernike phase-contrast method operating in the same wavelength as the coronagraph for the measurements of the NCPA between the optical path seen by the visible XAO wavefront sensor and that seen by the NIR coronagraph. Methods. This approach uses a focal plane phase mask of size ∼λ/D, where λ and D denote the wavelength and the telescope aperture diameter, respectively, to measure the quasi-static aberrations in the upstream pupil plane by encoding them into intensity variations in the downstream pupil image. The principle of this approach as described in several classical optical textbooks is simplified by the omission of the spatial variability of the amplitude diffracted by the phase mask. We develop a more rigorous formalism, leading to highly accurate measurement of the NCPA, in a quasi-linear way during the observation. Results. With prospects of achieving subnanometric measurement accuracy with this approach for a static phase map of standard deviation 44 nm rms at λ = 1.625 μm (0.026 λ), we estimate a possible reduction of the NCPA due to chromatic differential optics by a factor ranging from 3 to 10 in the presence of adaptive optics (AO) residuals compared with the expected performance of a typical current-generation system. This would allow a reduction of the level of quasi-static speckles in the detected images by a factor 10 to 100, thus correspondingly improving the capacity to observe exoplanets.

show abstract

“…For small optical aberrations (much less than 1 rad), i.e., at high Strehl ratio, the phase can be expressed as a convergent Taylor series e iÈ ¼ 1 þ iÈ À È 2 /2 À iÈ 3 /6 þ È 4 /24 þ : : :. A full expansion of the speckles for the aberrated PSF was discussed by Perrin et al (2003). Here we rederive it according to our application in different format up to the fourth-order speckle.…”

Section: Speckle Modelingmentioning

confidence: 99%

“…Furthermore, the size of the speckle is very similar to that of the companion's image and is a potential source of false signal. To overcome these difficulties, many pioneer researches have been conducted in recent years (Bloemhof 2003(Bloemhof , 2004a(Bloemhof , 2004bBloemhof & Oppenheimer 2001;Aime & Soummer 2004;Perrin et al 2003;Boccatletti et al 2002;Sivaramakrishnan et al 2001Sivaramakrishnan et al , 2002Sparks & Ford 2002;Marois et al 2000;Racine et al 1999), which greatly improved the understanding of speckle properties.…”

Section: Introductionmentioning

confidence: 99%

Spectral Subtraction: A New Approach to Remove Low‐ and High‐Order Speckle Noise

Ren

Wang

2006

ApJ

View full text Add to dashboard Cite

We present a novel ''spectral subtraction algorithm'' (SSA) technique to remove speckle noise. It consists of a loworder and a high-order SSA and is based on a three-dimensional image spectroscopy in which the three-dimensional data cube is available and thus the speckle noise introduced by the wave-front error can be efficiently subtracted. For the low-order SSA, speckles up to the second or third order can be totally subtracted, leaving the residual speckles dominated only by the third or fourth order, respectively, and imaging contrast is increased consequently; for the high-order SSA, speckles up to the fourth or fifth order can be subtracted, leaving the residual speckles dominated only by the fifth or sixth order, respectively, and the performance is further improved. This is the first demonstration that such high-order speckles could be subtracted. Since the SSAs are conducted over a wide spectral band, a whitelight image can be re-assembled from the three-dimensional data cube. The white-light image would increase the single-to-noise ratio and reduce the exposure time, which are crucial for the search of faint companion objects. Combined with a coronagraph, the SSA can provide an extra contrast gain for the coronagraph imaging, relax the requirement for the wave-front quality (no adaptive optics correction is required for a space-borne imaging system), and significantly increase the performance of exoplanet imaging and biomarker spectroscopy.

show abstract

The Structure of High Strehl Ratio Point‐Spread Functions

Cited by 162 publications

References 21 publications

Tip-tilt estimation and correction using FQPM coronagraphic images

Tip-tilt estimation and correction using FQPM coronagraphic images

Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor

Spectral Subtraction: A New Approach to Remove Low‐ and High‐Order Speckle Noise

Contact Info

Product

Resources

About