All Figures

$\begin{figure} {% \includegraphics[width=8.5cm]{4158fig1.eps} } \end{figure}$ Figure 1: Rejection $\tau$ of a monochromatic component as a function of the spectral resolution R. The continuous line is for the analytical formula whereas the diamonds show coronagraphic numerical simulation results.
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In the text

$\begin{figure} { \includegraphics[width=13.5cm]{4158fig2.eps} } \end{figure}$ Figure 2: Principle of a FQPM using halfwave plates. Each individual quadrant consists of a two material stack (Quartz, MgF₂). Two quadrants along one diagonal are rotated by $90^\circ$ around their normals with respect to the two others. The subscript a and b stand for the Quartz and MgF₂ plates whereas the o and e ones, for the ordinary and extraordinary indices, respectively. The bottom right picture shows the final component assembled on a silicate substrate. Fixation points (optical glue) are clearly visible at the waveplate external edges. The 8 mm-diameter circular working area is at the center of the component.
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In the text

$\begin{figure} {\includegraphics[width=7.8cm]{4158fig3.ps} } \end{figure}$ Figure 3: Numerical simulation result for achromatic halfwave plates. The curve shows the phase residuals around $\pi$ in radian versus wavelength (microns). The diamonds indicate the points where the birefringences have been precisely measured by the manufacturer. The phase error standard deviation over the full wavelength range is 0.118 rad rms.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm]{4158fig4.ps}\end{figure}$ Figure 4: This figure presents the spectral filter response as measured on our coronagraphic bench. The spectral sampling is 0.55 nm/pixel. The two peaks below, convolved with the PSF, correspond to calibration lines obtained with a YAG:Nd and a $\rm He-Ne$ laser, respectively. The maximum transmission of the filter is $96 \pm 3 \%$ .
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In the text

$\begin{figure} { \includegraphics[width=7.8cm]{4158fig5.ps} } \end{figure}$ Figure 5: Experimental and theoretical coronagraphic profiles: the grey solid curve is the experimental PSF for the 500-900 nm bandpass. The total exposure time for the PSF is 60 s. The continuous black line shows the coronagrapic profile obtained with our achromatic waveplate mask. The coronagraphic image was obtained adding forty exposures of 30 s each. The dashed line presents the coronagraphic simulation results taking into account the waveplate phase residuals, the defocus error, the spectral response of the halogen lamp and the camera. For comparison, the dotted line presents the simulation results for a monochromatic mask used in the same conditions. All curves are azimuthally averaged (for this reason, the on-axis attenuation seems to be greater than the measured peak attenuation value of 755).
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In the text

$\begin{figure} { \includegraphics[width=8.5cm]{4158fig6.ps} }\end{figure}$ Figure 6: Polychromatic coronagraphic residual image (logarithmic scale) for 500-900 nm bandpass. We use a 77% Lyot stop for spatial filtering. The angular resolution is given for $\lambda_0=700~$ nm and for the entrance pupil (full pupil without diaphragm). The classical FQPM four-spot pattern is easily recognizable though somewhat blurred.
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In the text

$\begin{figure} { \includegraphics[width=8cm]{4158fig7.ps} } \end{figure}$ Figure 7: Experimental and theoretical coronagraphic profiles: the grey solid curve is the experimental PSF for the 700-1000 nm bandpass. The total exposure time for the PSF is 60 s. The continuous black line shows the coronagrapic profile obtained with our achromatic waveplate mask. The coronagraphic image was obtained adding forty exposures of 30 s each. The dashed line presents the coronagraphic simulation results taking into account the waveplate phase residuals, the defocus error, the spectral response of both the halogen lamp and the camera. For comparison, the dotted line presents the simulation results for a monochromatic mask used in the same conditions. All curves are azimuthally averaged (for this reason, the on-axis attenuation seems to be greater than the measured peak attenuation value of 561).
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In the text

$\begin{figure} {% \includegraphics[width=8.5cm]{4158fig1.eps} } \end{figure}$	Figure 1: Rejection $\tau$ of a monochromatic component as a function of the spectral resolution R. The continuous line is for the analytical formula whereas the diamonds show coronagraphic numerical simulation results.
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$\begin{figure} {\includegraphics[width=7.8cm]{4158fig3.ps} } \end{figure}$	Figure 3: Numerical simulation result for achromatic halfwave plates. The curve shows the phase residuals around $\pi$ in radian versus wavelength (microns). The diamonds indicate the points where the birefringences have been precisely measured by the manufacturer. The phase error standard deviation over the full wavelength range is 0.118 rad rms.
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$\begin{figure} \par\includegraphics[width=7.6cm]{4158fig4.ps}\end{figure}$	Figure 4: This figure presents the spectral filter response as measured on our coronagraphic bench. The spectral sampling is 0.55 nm/pixel. The two peaks below, convolved with the PSF, correspond to calibration lines obtained with a YAG:Nd and a $\rm He-Ne$ laser, respectively. The maximum transmission of the filter is $96 \pm 3 \%$ .
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$\begin{figure} { \includegraphics[width=8.5cm]{4158fig6.ps} }\end{figure}$	Figure 6: Polychromatic coronagraphic residual image (logarithmic scale) for 500-900 nm bandpass. We use a 77% Lyot stop for spatial filtering. The angular resolution is given for $\lambda_0=700~$ nm and for the entrance pupil (full pupil without diaphragm). The classical FQPM four-spot pattern is easily recognizable though somewhat blurred.
Open with DEXTER