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Schroeder D.J. Astronomical optics(AP, 1987)(400dpi)(T)(364s)_EO_.djvu |
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camera example for a Ritchey-Chretien telescope, we omit the details of
specific designs...
Getting an external focus requires a
folded Schmidt camera with a tilted plane mirror between the corrector and
sphere, as shown in Fig...
It is convenient to represent the
intensity in this Form to facilitate comparison oF intensity profiles for
apertures with different central obscurations...
For other values of e in Table
10.1, the factor 1.22 is replaced by the appropriate numerical factor...
Assuming a passband of 1000 centered at
A = 550 nm and a star of apparent magnitude 25, we find I(0)=0.0182
II...
The coordinate systems used to locate points on the
wavefront and near the image are given in Eq...
The rms wavefront error is a useful parameter for characterizing a high-
quality optical system because its value can be calculated once the type
and magnitude of aberrations are known...
Note
that LSA is 2x the shift from the paraxial focus to the diffraction focus for
spherical aberration given in Table 10.4 for e = 0...
Comparisons of different
optical systems, or the same system at different wavelengths, are most often
made in normalized units...
Another source of image degradation
is motion of an image due to effects from outside the optical system...
For discussion of other
forms of c(u) and comparison with measured results, the reader should
consult the reference by Wetherell...
,
the effect of this error is to depress the disk and inner ring and raise the
outer rings...
This is a result of both pointing error and nonfigure contributors to the
degradation function...
Many of the results that follow apply to either
type of instrument, but if there is a difference the distinction is noted...
This is not the case in the direction
along the dispersion, where it is necessary to take 3/'= r7 to account for
possible magnification effects due to the disperser...
Consider a small, uniformly radiating
surface element of area dS and photometric brightness B, as shown in Fig...
For an excellent discussion of the
principles of image slicers and their practical realization, the reader should
consult the reference by Hunten...
Cross section of slit of width b
with path difference A = (b/2) sin 0 between
center and marginal ray...
If the grating is to accept all of the light from the collimator,
it follows that W = ddcos a is required, where W is the width of the grating...
An additional complication at these large
angles is that the diffracted beamwidth d2 is significantly greater than d...
(13.5.3) by about a factor of two, when
the angular diameter of the exit aperture is set according to Eq...
The
object and image points are at Q and Q', respectively, and an arbitrary ray
from Q intersects the grating surface at B(x, y, z)...
(14.1.4)
Terms in higher powers lead to aberrations and their forms are given in a
subsequent section...
The factors left
out of the aberration coefficients with this choice are of order 2 and ,2
smaller than those that remain...
Grating Aberrations; Concave Grating Spectrometers
where the total length of the tangential image is 21TASI...
Note that these lengths depend only on the grating size and are indepen-
dent of the output beam focal ratio...
Assume a camera of focal length f that is aberration-free and a concave
grating for which the collimator focal ratio is F...
Because R2 and R2 have the same sign, the astigmatisms of the two
mirrors add to give the system astigmatism...
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