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Date: 08 Dec 2006 22:37:40
From: Robert Clark
Subject: Multiple pinhole cameras for extrasolar planet detection.
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I was looking up references to pinhole cameras when I came upon this
page that gives the size of the image compared to the size of the
source:
Finding the Size of the Sun and Moon.
http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_03.html
The page explains that the ratio of the size of the source to the
distance of the source to the pinhole is the same as the ratio of the
size of the image to the distance between the pinhole and the imaging
screen.
Then couldn't this be used to resolve two far away point sources of
light that are at a very small angular distance from each other?
If an extrasolar planet was at a distance of 10 million km from its
parent star (such as a "hot Jupiter") and the system was 10 light-years
away, about 100 trillion km, that's a ratio of 1 to 10 million. Then
the ratio of the distance between the two imaged points to the size of
the camera (distance from pinhole to screen) will also be 1 to 10
million. So if the camera was 10 meters long, the distance between the
two imaged points would be 1 micron.
Moving the imaging screen further away will allow the separate light
sources to be more easily resolved however this reduces the intensity
of the light reaching the screen. For the dim planet, you don't want to
reduce the intensity too greatly. It would also require longer exposure
time for the camera film or, more likely, CCD:
Pinhole camera.
"Pinhole cameras are often constructed with a sliding film holder or
back so that the distance between the film and the pinhole can be
adjusted. This allows the angle of view of the camera to be changed and
also the effective f-stop ratio of the camera. Moving the film closer
to the pinhole will result in a wide angle field of view and a shorter
exposure time. Moving the film farther away from the pinhole will
result in a telephoto or narrow angle view and a longer exposure time."
http://en.wikipedia.org/wiki/Pinhole_camera
The optimal size of the pinhole is given also on this page to minimize
diffraction effects as d = 1.9*sqrt(f*lamda), d the diameter, f the
camera size (length) and lambda the wavelength of the light. A smaller
pinhole provides a sharper image, but increases diffraction effects,
thus there is an optimal diameter.
A single pinhole would not be able to detect definitively the weak
light coming from the planet. So the idea would be to use many millions
of pinholes producing images on the same screen. The screen would
consist of a single very large CCD or very many separate sensitive
CCD's. Then positive signals at the expected positions for several of
the CCD's would be taken as a positive detection at the statistically
significant level.
It may also be possible to form a single image from the many separate
pinholes. There has been developed a pinhole mirror camera, called a
"pinhead mirror" by the developer:
Pinhead mirror.
http://en.wikipedia.org/wiki/Pinhead_mirror
The tiny mirrors used are comparable in size to the pinholes. This
method allows the image to be projected to a desired location. Then the
very many images could be directed to all overlap to a single image.
Despite the separation of the imaged point sources it still might be
that the light from the star would wash out the light from the planet
on the detectors. Then in that case we could use an occulting disk
inside each of the pinholes, or a mask on the pinhole mirrors. For a
star of about 1 million km across, i.e., of solar size, that's 1/10th
the distance of a planet orbiting at 10 million km. Then we could make
the occulting disk 1/10th the size of the pinhole. However, since we
won't know precisely the size of the star and might only have an
approximate idea of the size of the orbit, some method would have to
be used that allows a variation of the position of the mask within the
pinhole.
To eliminate stray light also coming in from nearby stars we might
also want to allow only light from the system under study to enter each
pinhole. One way to do this would be to have the pinhole cut in a flat
sheet having some thickness. Usually you want it to be as thin as
possible so that light coming in at less than 90 degrees does not hit
the sides of the sheet. However, this may also allow a means to reduce
stray light from other stars.
NASA is funding a study of space-based systems using the principal of
pinhole cameras to search for extrasolar planets:
Alien Planets to Pose for Giant Pinhole Camera in Space.
03.10.05
By Ronald Toland
NASA Goddard
http://www.nasa.gov/vision/universe/newworlds/new_worlds_imager.html
This though would be a large single, pinhole meters across based in
space.
Bob Clark
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Date: 09 Dec 2006 07:10:55
From:
Subject: Re: Multiple pinhole cameras for extrasolar planet detection.
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In article <1165646259.979773.220750@16g2000cwy.googlegroups.com >, "Robert Clark" <rgregoryclark@yahoo.com> writes:
> I was looking up references to pinhole cameras when I came upon this
>page that gives the size of the image compared to the size of the
>source:
>
>Finding the Size of the Sun and Moon.
>http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_03.html
>
> The page explains that the ratio of the size of the source to the
>distance of the source to the pinhole is the same as the ratio of the
>size of the image to the distance between the pinhole and the imaging
>screen.
> Then couldn't this be used to resolve two far away point sources of
>light that are at a very small angular distance from each other?
Diffraction limits.
Mati Meron
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Date: 09 Dec 2006 10:42:11
From: George Dishman
Subject: Re: Multiple pinhole cameras for extrasolar planet detection.
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<mmeron@cars3.uchicago.edu > wrote in message
news:3kteh.46$45.375@news.uchicago.edu...
> In article <1165646259.979773.220750@16g2000cwy.googlegroups.com>, "Robert
> Clark" <rgregoryclark@yahoo.com> writes:
>> I was looking up references to pinhole cameras when I came upon this
>>page that gives the size of the image compared to the size of the
>>source:
>>
>>Finding the Size of the Sun and Moon.
>>http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_03.html
>>
>> The page explains that the ratio of the size of the source to the
>>distance of the source to the pinhole is the same as the ratio of the
>>size of the image to the distance between the pinhole and the imaging
>>screen.
>> Then couldn't this be used to resolve two far away point sources of
>>light that are at a very small angular distance from each other?
>
> Diffraction limits.
http://en.wikipedia.org/wiki/New_Worlds_Imager
Cash's proposal was presented at the October
meeting this year:
http://www.niac.usra.edu/library/meetings/annual/oct06.html
The presentation:
http://www.niac.usra.edu/files/library/meetings/annual/oct06/1200Cash.pdf
George
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Date: 09 Dec 2006 22:24:38
From:
Subject: Re: Multiple pinhole cameras for extrasolar planet detection.
|
In article <ele3tk$deh$1@news.freedom2surf.net >, "George Dishman" <george@briar.demon.co.uk> writes:
>
><mmeron@cars3.uchicago.edu> wrote in message
>news:3kteh.46$45.375@news.uchicago.edu...
>> In article <1165646259.979773.220750@16g2000cwy.googlegroups.com>, "Robert
>> Clark" <rgregoryclark@yahoo.com> writes:
>>> I was looking up references to pinhole cameras when I came upon this
>>>page that gives the size of the image compared to the size of the
>>>source:
>>>
>>>Finding the Size of the Sun and Moon.
>>>http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_03.html
>>>
>>> The page explains that the ratio of the size of the source to the
>>>distance of the source to the pinhole is the same as the ratio of the
>>>size of the image to the distance between the pinhole and the imaging
>>>screen.
>>> Then couldn't this be used to resolve two far away point sources of
>>>light that are at a very small angular distance from each other?
>>
>> Diffraction limits.
>
> http://en.wikipedia.org/wiki/New_Worlds_Imager
>
>Cash's proposal was presented at the October
>meeting this year:
>
> http://www.niac.usra.edu/library/meetings/annual/oct06.html
>
>The presentation:
>
> http://www.niac.usra.edu/files/library/meetings/annual/oct06/1200Cash.pdf
>
>George
>
That's true but having little to do with the original question, i.e.
resolving two points using a pinhole, where you get finite resolution
due to diffraction in the pinhole. As an aside, for the purpose of
the business at hand there is no deifference between a telescope and a
pinhole.
Mati Meron
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Date: 10 Dec 2006 11:20:09
From: George Dishman
Subject: Re: Multiple pinhole cameras for extrasolar planet detection.
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<mmeron@cars3.uchicago.edu > wrote in message
news:GIGeh.48$45.336@news.uchicago.edu...
> In article <ele3tk$deh$1@news.freedom2surf.net>, "George Dishman"
> <george@briar.demon.co.uk> writes:
>>
>><mmeron@cars3.uchicago.edu> wrote in message
>>news:3kteh.46$45.375@news.uchicago.edu...
>>> In article <1165646259.979773.220750@16g2000cwy.googlegroups.com>,
>>> "Robert
>>> Clark" <rgregoryclark@yahoo.com> writes:
>>>> I was looking up references to pinhole cameras when I came upon this
>>>>page that gives the size of the image compared to the size of the
>>>>source:
>>>>
>>>>Finding the Size of the Sun and Moon.
>>>>http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_03.html
>>>>
>>>> The page explains that the ratio of the size of the source to the
>>>>distance of the source to the pinhole is the same as the ratio of the
>>>>size of the image to the distance between the pinhole and the imaging
>>>>screen.
>>>> Then couldn't this be used to resolve two far away point sources of
>>>>light that are at a very small angular distance from each other?
>>>
>>> Diffraction limits.
>>
>> http://en.wikipedia.org/wiki/New_Worlds_Imager
>>
>>Cash's proposal was presented at the October
>>meeting this year:
>>
>> http://www.niac.usra.edu/library/meetings/annual/oct06.html
>>
>>The presentation:
>>
>> http://www.niac.usra.edu/files/library/meetings/annual/oct06/1200Cash.pdf
>>
>>George
>>
> That's true but having little to do with the original question, i.e.
> resolving two points using a pinhole, where you get finite resolution
> due to diffraction in the pinhole.
Blast, I should have explained, sorry. I have
been aware of this idea for some years and it
didn't cross my mind that the references to it
being a pinhole design had been removed.
The New Worlds Imager proposal started life as a
pinhole camera. They proposed a large sheet with
a hole in the centre with the interesting spikes
pointing inwards to control diffraction effects.
Subsequently they realised that the performance
would be the same if the inverted the logic and
turned it into a starshade.
> As an aside, for the purpose of
> the business at hand there is no deifference between a telescope and a
> pinhole.
Exactly.
George
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Date: 10 Dec 2006 19:08:50
From:
Subject: Re: Multiple pinhole cameras for extrasolar planet detection.
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In article <elgqgq$4vd$1@news.freedom2surf.net >, "George Dishman" <george@briar.demon.co.uk> writes:
>
><mmeron@cars3.uchicago.edu> wrote in message
>news:GIGeh.48$45.336@news.uchicago.edu...
>> In article <ele3tk$deh$1@news.freedom2surf.net>, "George Dishman"
>> <george@briar.demon.co.uk> writes:
>>>
>>><mmeron@cars3.uchicago.edu> wrote in message
>>>news:3kteh.46$45.375@news.uchicago.edu...
>>>> In article <1165646259.979773.220750@16g2000cwy.googlegroups.com>,
>>>> "Robert
>>>> Clark" <rgregoryclark@yahoo.com> writes:
>>>>> I was looking up references to pinhole cameras when I came upon this
>>>>>page that gives the size of the image compared to the size of the
>>>>>source:
>>>>>
>>>>>Finding the Size of the Sun and Moon.
>>>>>http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_03.html
>>>>>
>>>>> The page explains that the ratio of the size of the source to the
>>>>>distance of the source to the pinhole is the same as the ratio of the
>>>>>size of the image to the distance between the pinhole and the imaging
>>>>>screen.
>>>>> Then couldn't this be used to resolve two far away point sources of
>>>>>light that are at a very small angular distance from each other?
>>>>
>>>> Diffraction limits.
>>>
>>> http://en.wikipedia.org/wiki/New_Worlds_Imager
>>>
>>>Cash's proposal was presented at the October
>>>meeting this year:
>>>
>>> http://www.niac.usra.edu/library/meetings/annual/oct06.html
>>>
>>>The presentation:
>>>
>>> http://www.niac.usra.edu/files/library/meetings/annual/oct06/1200Cash.pdf
>>>
>>>George
>>>
>> That's true but having little to do with the original question, i.e.
>> resolving two points using a pinhole, where you get finite resolution
>> due to diffraction in the pinhole.
>
>Blast, I should have explained, sorry. I have
>been aware of this idea for some years and it
>didn't cross my mind that the references to it
>being a pinhole design had been removed.
>
>The New Worlds Imager proposal started life as a
>pinhole camera. They proposed a large sheet with
>a hole in the centre with the interesting spikes
>pointing inwards to control diffraction effects.
>Subsequently they realised that the performance
>would be the same if the inverted the logic and
>turned it into a starshade.
>
Babinet's principle in action. Good thinking.
>> As an aside, for the purpose of
>> the business at hand there is no deifference between a telescope and a
>> pinhole.
>
>Exactly.
>
>George
>
>
Mati Meron
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Date: 11 Dec 2006 02:00:04
From: Jim Black
Subject: Re: Multiple pinhole cameras for extrasolar planet detection.
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Robert Clark wrote:
> A single pinhole would not be able to detect definitively the weak
> light coming from the planet. So the idea would be to use many millions
> of pinholes producing images on the same screen. The screen would
> consist of a single very large CCD or very many separate sensitive
> CCD's. Then positive signals at the expected positions for several of
> the CCD's would be taken as a positive detection at the statistically
> significant level.
> It may also be possible to form a single image from the many separate
> pinholes. There has been developed a pinhole mirror camera, called a
> "pinhead mirror" by the developer:
>
> Pinhead mirror.
> http://en.wikipedia.org/wiki/Pinhead_mirror
>
> The tiny mirrors used are comparable in size to the pinholes. This
> method allows the image to be projected to a desired location. Then the
> very many images could be directed to all overlap to a single image.
Now imagine an array of these mirrors, each one tilted slightly
differently from its neighbors. Do you suppose they could be joined
together to form a single smooth surface?
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Date: 11 Dec 12:57:15
From:
Subject: Re: Multiple pinhole cameras for extrasolar planet detection.
|
In article <1165831204.088067.254490@j44g2000cwa.googlegroups.com >,
"Jim Black" <tramspap@yahoo.com > wrote:
>Robert Clark wrote:
>> A single pinhole would not be able to detect definitively the weak
>> light coming from the planet. So the idea would be to use many millions
>> of pinholes producing images on the same screen. The screen would
>> consist of a single very large CCD or very many separate sensitive
>> CCD's. Then positive signals at the expected positions for several of
>> the CCD's would be taken as a positive detection at the statistically
>> significant level.
>> It may also be possible to form a single image from the many separate
>> pinholes. There has been developed a pinhole mirror camera, called a
>> "pinhead mirror" by the developer:
>>
>> Pinhead mirror.
>> http://en.wikipedia.org/wiki/Pinhead_mirror
>>
>> The tiny mirrors used are comparable in size to the pinholes. This
>> method allows the image to be projected to a desired location. Then the
>> very many images could be directed to all overlap to a single image.
>
>Now imagine an array of these mirrors, each one tilted slightly
>differently from its neighbors. Do you suppose they could be joined
>together to form a single smooth surface?
>
Could the OP build one with items found in the kitchen or toy
box? Then the OP could "see" how stuff works.
/BAH
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