Efficiency of cheap macro lenses at near infrared?

Discussion in 'Digital Photography' started by mianileng, Nov 21, 2011.

  1. mianileng

    mianileng Guest

    This does not directly involve photography but I thought the
    people here would be knowledgeable enough about the subject to
    help.

    I'm working on an electronics project for which I'd like to have
    an inexpensive way of focusing incoming infrared rays onto a
    sensor. The radiation is from a distant emitter, a bunch of
    infrared LEDs sending coded pulses of IR energy from about 400m
    (1300 ft) away. The project is for non-photographic work and
    optical quality is not important. What *is* important is an
    efficient concentration of the IR energy and I thought of using a
    cheap macro lens of about +10 dioptre.

    The LEDs operate at 940nm. Transmission curves at the following
    link for soda lime, borosilicate and UV glasses indicate quite
    good transmissivity (for my purpose) at that wavelength.
    http://www.sinclairmfg.com/datasheets/optical3.html
    So far I haven't found comparable data for the glass used to make
    the cheap lenses I mentioned. Can anyone please provide some
    information about that?
    mianileng, Nov 21, 2011
    #1
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  2. mianileng

    Me Guest

    On 22/11/2011 8:34 a.m., mianileng wrote:
    > This does not directly involve photography but I thought the
    > people here would be knowledgeable enough about the subject to
    > help.
    >
    > I'm working on an electronics project for which I'd like to have
    > an inexpensive way of focusing incoming infrared rays onto a
    > sensor. The radiation is from a distant emitter, a bunch of
    > infrared LEDs sending coded pulses of IR energy from about 400m
    > (1300 ft) away. The project is for non-photographic work and
    > optical quality is not important. What *is* important is an
    > efficient concentration of the IR energy and I thought of using a
    > cheap macro lens of about +10 dioptre.
    >
    > The LEDs operate at 940nm. Transmission curves at the following
    > link for soda lime, borosilicate and UV glasses indicate quite
    > good transmissivity (for my purpose) at that wavelength.
    > http://www.sinclairmfg.com/datasheets/optical3.html
    > So far I haven't found comparable data for the glass used to make
    > the cheap lenses I mentioned. Can anyone please provide some
    > information about that?
    >
    >

    Perhaps this helps:
    http://dpanswers.com/content/irphoto_lenses.php
    Macro may not be the way to go, on this list Nikon and Canon 50mm f1.8
    lenses are cheaper and larger aperture than typical macro lenses (f2.8).
    If longer focal length is needed, then a cheap mirror telephoto lens
    might be perfect. Slower aperture, but you can get 500mm focal length
    very cheaply, also you can focus visible light from the source to the IR
    sensor, and not have to offset this for IR.
    Me, Nov 21, 2011
    #2
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  3. mianileng

    Martin Brown Guest

    On 21/11/2011 19:34, mianileng wrote:
    > This does not directly involve photography but I thought the
    > people here would be knowledgeable enough about the subject to
    > help.
    >
    > I'm working on an electronics project for which I'd like to have
    > an inexpensive way of focusing incoming infrared rays onto a
    > sensor. The radiation is from a distant emitter, a bunch of
    > infrared LEDs sending coded pulses of IR energy from about 400m
    > (1300 ft) away. The project is for non-photographic work and
    > optical quality is not important. What *is* important is an
    > efficient concentration of the IR energy and I thought of using a
    > cheap macro lens of about +10 dioptre.
    >
    > The LEDs operate at 940nm. Transmission curves at the following
    > link for soda lime, borosilicate and UV glasses indicate quite
    > good transmissivity (for my purpose) at that wavelength.
    > http://www.sinclairmfg.com/datasheets/optical3.html
    > So far I haven't found comparable data for the glass used to make
    > the cheap lenses I mentioned. Can anyone please provide some
    > information about that?


    If you only need a couple why not get a simple planoconvex lens from any
    of the generic suppliers or surplus shed (for about $5).

    http://www.surplusshed.com/lens.cfm

    You don't need a fancy achromat for this sort of thing your source is
    close to monochromatic +/- 30nm - though you might need a slightly
    clever baffled optical design and an IR pass filter if the thing has to
    work well in daylight. You might even get away with a Fresnel reading
    lens or bits taken from an old redundant OHP.

    --
    Regards,
    Martin Brown
    Martin Brown, Nov 21, 2011
    #3
  4. mianileng

    PeterN Guest

    On 11/21/2011 2:34 PM, mianileng wrote:
    > This does not directly involve photography but I thought the
    > people here would be knowledgeable enough about the subject to
    > help.
    >
    > I'm working on an electronics project for which I'd like to have
    > an inexpensive way of focusing incoming infrared rays onto a
    > sensor. The radiation is from a distant emitter, a bunch of
    > infrared LEDs sending coded pulses of IR energy from about 400m
    > (1300 ft) away. The project is for non-photographic work and
    > optical quality is not important. What *is* important is an
    > efficient concentration of the IR energy and I thought of using a
    > cheap macro lens of about +10 dioptre.
    >
    > The LEDs operate at 940nm. Transmission curves at the following
    > link for soda lime, borosilicate and UV glasses indicate quite
    > good transmissivity (for my purpose) at that wavelength.
    > http://www.sinclairmfg.com/datasheets/optical3.html
    > So far I haven't found comparable data for the glass used to make
    > the cheap lenses I mentioned. Can anyone please provide some
    > information about that?
    >
    >


    This has the aroma of a homework project.

    --
    Peter
    PeterN, Nov 22, 2011
    #4
  5. mianileng

    Peter Irwin Guest

    mianileng <> wrote:
    >
    > The LEDs operate at 940nm. Transmission curves at the following
    > link for soda lime, borosilicate and UV glasses indicate quite
    > good transmissivity (for my purpose) at that wavelength.
    > http://www.sinclairmfg.com/datasheets/optical3.html
    > So far I haven't found comparable data for the glass used to make
    > the cheap lenses I mentioned. Can anyone please provide some
    > information about that?
    >

    I second the recommendation for www.surplusshed.com.
    Practically any glass should be fine at that wavelength,
    and the ones that aren't would be fairly exotic. A simple
    plano-convex or positive meniscus lens should be fine since
    you only have one wavelength to focus.

    The very cheap "educational optics" tend to be soda-lime
    glass. Most of the rest are probably borosilicate glass,
    but it shouldn't matter for your purposes.

    Peter.
    --
    Peter Irwin, Nov 22, 2011
    #5
  6. mianileng

    mianileng Guest

    Me wrote:
    > On 22/11/2011 8:34 a.m., mianileng wrote:
    >> This does not directly involve photography but I thought the
    >> people here would be knowledgeable enough about the subject to
    >> help.
    >>
    >> I'm working on an electronics project for which I'd like to
    >> have
    >> an inexpensive way of focusing incoming infrared rays onto a
    >> sensor. The radiation is from a distant emitter, a bunch of
    >> infrared LEDs sending coded pulses of IR energy from about
    >> 400m
    >> (1300 ft) away. The project is for non-photographic work and
    >> optical quality is not important. What *is* important is an
    >> efficient concentration of the IR energy and I thought of
    >> using a
    >> cheap macro lens of about +10 dioptre.
    >>
    >> The LEDs operate at 940nm. Transmission curves at the
    >> following
    >> link for soda lime, borosilicate and UV glasses indicate quite
    >> good transmissivity (for my purpose) at that wavelength.
    >> http://www.sinclairmfg.com/datasheets/optical3.html
    >> So far I haven't found comparable data for the glass used to
    >> make
    >> the cheap lenses I mentioned. Can anyone please provide some
    >> information about that?
    >>
    >>

    > Perhaps this helps:
    > http://dpanswers.com/content/irphoto_lenses.php
    > Macro may not be the way to go, on this list Nikon and Canon
    > 50mm f1.8
    > lenses are cheaper and larger aperture than typical macro
    > lenses
    > (f2.8). If longer focal length is needed, then a cheap mirror
    > telephoto lens might be perfect. Slower aperture, but you can
    > get
    > 500mm focal length very cheaply, also you can focus visible
    > light
    > from the source to the IR sensor, and not have to offset this
    > for IR.


    Thanks for your interest. Your reply made me realise that I left
    out something, namely that the macro lenses I'm considering are
    not SLR compound lenses, but one of the simple $3 add-on
    attachments. A $1 magnifying glass would also do - provided that
    it passes IR well enough, except that it will be easier to secure
    a lens with a standard thread to the front of the receiver box
    and to attach an IR filter once the focusing's done with visible
    light.

    Yes, I'd intended to do just what you suggest about focusing with
    visible light and then adding an IR-pass filter. The offset in
    focal plane wouldn't matter even for a shorter focal length
    because I'd planned to leave it somewhat out of focus anyway.
    This is because
    1) the sensor area is about 0.2in in diameter and spreading the
    IR image will reduce the possibility of overheating a spot when
    it's tested at closer range,
    2) it will compensate for slight misalignment, albeit with some
    loss in efficiency. It's a trade-off between the two.

    My calculations allow for some loss of efficiency from spreading
    the image to an area somewhat larger than the sensor, from
    absorbtion by the intervening 400m of air and by the glass. The
    question is how much loss the last one will contribute.
    mianileng, Nov 22, 2011
    #6
  7. mianileng

    mianileng Guest

    Martin Brown wrote:
    > On 21/11/2011 19:34, mianileng wrote:
    >> This does not directly involve photography but I thought the
    >> people here would be knowledgeable enough about the subject to
    >> help.
    >>
    >> I'm working on an electronics project for which I'd like to
    >> have
    >> an inexpensive way of focusing incoming infrared rays onto a
    >> sensor. The radiation is from a distant emitter, a bunch of
    >> infrared LEDs sending coded pulses of IR energy from about
    >> 400m
    >> (1300 ft) away. The project is for non-photographic work and
    >> optical quality is not important. What *is* important is an
    >> efficient concentration of the IR energy and I thought of
    >> using a
    >> cheap macro lens of about +10 dioptre.
    >>
    >> The LEDs operate at 940nm. Transmission curves at the
    >> following
    >> link for soda lime, borosilicate and UV glasses indicate quite
    >> good transmissivity (for my purpose) at that wavelength.
    >> http://www.sinclairmfg.com/datasheets/optical3.html
    >> So far I haven't found comparable data for the glass used to
    >> make
    >> the cheap lenses I mentioned. Can anyone please provide some
    >> information about that?

    >
    > If you only need a couple why not get a simple planoconvex lens
    > from
    > any of the generic suppliers or surplus shed (for about $5).
    >
    > http://www.surplusshed.com/lens.cfm
    >
    > You don't need a fancy achromat for this sort of thing your
    > source is
    > close to monochromatic +/- 30nm - though you might need a
    > slightly
    > clever baffled optical design and an IR pass filter if the
    > thing has
    > to work well in daylight. You might even get away with a
    > Fresnel
    > reading lens or bits taken from an old redundant OHP.


    You're quite right about not needing a fancy lens. In fact, I'd
    intended to use one of those simple $3 add-on lenses _and_ an
    IR-pass filter. Please see my reply to "Me" for details.
    mianileng, Nov 22, 2011
    #7
  8. mianileng

    mianileng Guest

    PeterN wrote:
    > On 11/21/2011 2:34 PM, mianileng wrote:
    >> This does not directly involve photography but I thought the
    >> people here would be knowledgeable enough about the subject to
    >> help.
    >>
    >> I'm working on an electronics project for which I'd like to
    >> have
    >> an inexpensive way of focusing incoming infrared rays onto a
    >> sensor. The radiation is from a distant emitter, a bunch of
    >> infrared LEDs sending coded pulses of IR energy from about
    >> 400m
    >> (1300 ft) away. The project is for non-photographic work and
    >> optical quality is not important. What *is* important is an
    >> efficient concentration of the IR energy and I thought of
    >> using a
    >> cheap macro lens of about +10 dioptre.
    >>
    >> The LEDs operate at 940nm. Transmission curves at the
    >> following
    >> link for soda lime, borosilicate and UV glasses indicate quite
    >> good transmissivity (for my purpose) at that wavelength.
    >> http://www.sinclairmfg.com/datasheets/optical3.html
    >> So far I haven't found comparable data for the glass used to
    >> make
    >> the cheap lenses I mentioned. Can anyone please provide some
    >> information about that?
    >>
    >>

    >
    > This has the aroma of a homework project.


    Not at all. This is for a very professional job. It's an
    expansion of custom-designed equipment that I built two years ago
    and has been in use since then. I like to use standard, cheap and
    readily available material wherever possible and pass on the cost
    savings to my customers.
    mianileng, Nov 22, 2011
    #8
  9. mianileng

    mianileng Guest

    Peter Irwin wrote:
    > mianileng <> wrote:
    >>
    >> The LEDs operate at 940nm. Transmission curves at the
    >> following
    >> link for soda lime, borosilicate and UV glasses indicate quite
    >> good transmissivity (for my purpose) at that wavelength.
    >> http://www.sinclairmfg.com/datasheets/optical3.html
    >> So far I haven't found comparable data for the glass used to
    >> make
    >> the cheap lenses I mentioned. Can anyone please provide some
    >> information about that?
    >>

    > I second the recommendation for www.surplusshed.com.
    > Practically any glass should be fine at that wavelength,
    > and the ones that aren't would be fairly exotic. A simple
    > plano-convex or positive meniscus lens should be fine since
    > you only have one wavelength to focus.
    >
    > The very cheap "educational optics" tend to be soda-lime
    > glass. Most of the rest are probably borosilicate glass,
    > but it shouldn't matter for your purposes.
    >

    Thanks for your interest. As I said in reply to "Me", I forgot to
    mention that I did intend to use a cheap add-on lens rather than
    some SLR glass.
    mianileng, Nov 22, 2011
    #9
  10. mianileng

    PeterN Guest

    On 11/21/2011 10:35 PM, Rich wrote:
    > PeterN<> wrote in news:4ecaf9cc$0$13254
    > $-secrets.com:
    >
    >> On 11/21/2011 2:34 PM, mianileng wrote:
    >>> This does not directly involve photography but I thought the
    >>> people here would be knowledgeable enough about the subject to
    >>> help.
    >>>
    >>> I'm working on an electronics project for which I'd like to have
    >>> an inexpensive way of focusing incoming infrared rays onto a
    >>> sensor. The radiation is from a distant emitter, a bunch of
    >>> infrared LEDs sending coded pulses of IR energy from about 400m
    >>> (1300 ft) away. The project is for non-photographic work and
    >>> optical quality is not important. What *is* important is an
    >>> efficient concentration of the IR energy and I thought of using a
    >>> cheap macro lens of about +10 dioptre.
    >>>
    >>> The LEDs operate at 940nm. Transmission curves at the following
    >>> link for soda lime, borosilicate and UV glasses indicate quite
    >>> good transmissivity (for my purpose) at that wavelength.
    >>> http://www.sinclairmfg.com/datasheets/optical3.html
    >>> So far I haven't found comparable data for the glass used to make
    >>> the cheap lenses I mentioned. Can anyone please provide some
    >>> information about that?
    >>>
    >>>

    >>
    >> This has the aroma of a homework project.
    >>

    >
    > So what if it is? So the guy might be asking for information he hasn't
    > been able to find elsewhere? Would helping him out KILL you, sourpuss?


    Have you ever heard of intellectual integrity? If I had a deep knowledge
    of the area I might steer him. But, I would not supply the answer.

    BTW your informed answer is striking by its absence.


    --
    Peter
    PeterN, Nov 22, 2011
    #10
  11. mianileng

    RichA Guest

    On Nov 22, 5:59 am, PeterN <> wrote:
    > On 11/21/2011 10:35 PM, Rich wrote:
    >
    >
    >
    >
    >
    >
    >
    >
    >
    > > PeterN<>  wrote in news:4ecaf9cc$0$13254
    > > $-secrets.com:

    >
    > >> On 11/21/2011 2:34 PM, mianileng wrote:
    > >>> This does not directly involve photography but I thought the
    > >>> people here would be knowledgeable enough about the subject to
    > >>> help.

    >
    > >>> I'm working on an electronics project for which I'd like to have
    > >>> an inexpensive way of focusing incoming infrared rays onto a
    > >>> sensor.  The radiation is from a distant emitter, a bunch of
    > >>> infrared LEDs sending coded pulses of IR energy from about 400m
    > >>> (1300 ft) away. The project is for non-photographic work and
    > >>> optical quality is not important. What *is* important is an
    > >>> efficient concentration of the IR energy and I thought of using a
    > >>> cheap macro lens of about +10 dioptre.

    >
    > >>> The LEDs operate at 940nm. Transmission curves at the following
    > >>> link for soda lime, borosilicate and UV glasses indicate quite
    > >>> good transmissivity (for my purpose) at that wavelength.
    > >>>http://www.sinclairmfg.com/datasheets/optical3.html
    > >>> So far I haven't found comparable data for the glass used to make
    > >>> the cheap lenses I mentioned. Can anyone please provide some
    > >>> information about that?

    >
    > >> This has the aroma of a homework project.

    >
    > > So what if it is?  So the guy might be asking for information he hasn't
    > > been able to find elsewhere?  Would helping him out KILL you, sourpuss?

    >
    > Have you ever heard of intellectual integrity? If I had a deep knowledge
    > of the area I might steer him. But, I would not supply the answer.
    >
    > BTW your informed answer is striking by its absence.
    >
    > --
    > Peter


    I never claimed to have an answer, you dour old man.
    RichA, Nov 22, 2011
    #11
  12. mianileng

    RichA Guest

    On Nov 21, 11:52 pm, "mianileng" <> wrote:
    > Peter Irwin wrote:
    > > mianileng <> wrote:

    >
    > >> The LEDs operate at 940nm. Transmission curves at the
    > >> following
    > >> link for soda lime, borosilicate and UV glasses indicate quite
    > >> good transmissivity (for my purpose) at that wavelength.
    > >>http://www.sinclairmfg.com/datasheets/optical3.html
    > >> So far I haven't found comparable data for the glass used to
    > >> make
    > >> the cheap lenses I mentioned. Can anyone please provide some
    > >> information about that?

    >
    > > I second the recommendation forwww.surplusshed.com.
    > > Practically any glass should be fine at that wavelength,
    > > and the ones that aren't would be fairly exotic. A simple
    > > plano-convex or positive meniscus lens should be fine since
    > > you only have one wavelength to focus.

    >
    > > The very cheap "educational optics" tend to be soda-lime
    > > glass. Most of the rest are probably borosilicate glass,
    > > but it shouldn't matter for your purposes.

    >
    > Thanks for your interest. As I said in reply to "Me", I forgot to
    > mention that I did intend to use a cheap add-on lens rather than
    > some SLR glass.


    If you don't care about edge definition, just the centre, and you can
    find one of the right focal length, a quartz lens element will work as
    it will pass IR. One with a focal length no faster than about f4.0 is
    a good idea as anything faster will have other aberrations. Older,
    single coated (magnesium fluorite as opposed to more modern
    multicoating) SLR lenses will work as well. Look for older Nikon E-
    series lenses from the 1970's, Pentax Takumar lenses from the 1960's,
    with M42 screw mounts or other similar lenses from that era. If you
    locate a quartz lens, you have to use infrared filters because it will
    not bring colours to a common focus. Focusing will have to be done by
    experimentation.
    RichA, Nov 22, 2011
    #12
  13. mianileng

    Peter Irwin Guest

    RichA <> wrote:
    >
    > If you don't care about edge definition, just the centre, and you can
    > find one of the right focal length, a quartz lens element will work as
    > it will pass IR.


    For what he wants, a toy magnifying lens will do just fine.
    Just about any glass is transparent at 940nm infrared. Finding
    a glass that wasn't would require something exotic.

    He doesn't need colours brought to a common focus because
    he is using monochromatic infrared. He needs to be able to adjust
    focus to give him the best output from his device, but a single
    element lens will be fine.

    Quartz lenses are mostly used for ultraviolet. Ordinary
    glass will pass near-UV tolerably well, though many camera
    lenses made in recent decades filter even that. Quartz
    passes a very wide UV spectrum. Ordinary glass passes
    quite a lot of infra-red.

    Peter.
    --
    Peter Irwin, Nov 22, 2011
    #13
  14. mianileng

    PeterN Guest

    On 11/22/2011 8:41 AM, RichA wrote:
    > On Nov 22, 5:59 am, PeterN<> wrote:
    >> On 11/21/2011 10:35 PM, Rich wrote:
    >>
    >>
    >>
    >>
    >>
    >>
    >>
    >>
    >>
    >>> PeterN<> wrote in news:4ecaf9cc$0$13254
    >>> $-secrets.com:

    >>
    >>>> On 11/21/2011 2:34 PM, mianileng wrote:
    >>>>> This does not directly involve photography but I thought the
    >>>>> people here would be knowledgeable enough about the subject to
    >>>>> help.

    >>
    >>>>> I'm working on an electronics project for which I'd like to have
    >>>>> an inexpensive way of focusing incoming infrared rays onto a
    >>>>> sensor. The radiation is from a distant emitter, a bunch of
    >>>>> infrared LEDs sending coded pulses of IR energy from about 400m
    >>>>> (1300 ft) away. The project is for non-photographic work and
    >>>>> optical quality is not important. What *is* important is an
    >>>>> efficient concentration of the IR energy and I thought of using a
    >>>>> cheap macro lens of about +10 dioptre.

    >>
    >>>>> The LEDs operate at 940nm. Transmission curves at the following
    >>>>> link for soda lime, borosilicate and UV glasses indicate quite
    >>>>> good transmissivity (for my purpose) at that wavelength.
    >>>>> http://www.sinclairmfg.com/datasheets/optical3.html
    >>>>> So far I haven't found comparable data for the glass used to make
    >>>>> the cheap lenses I mentioned. Can anyone please provide some
    >>>>> information about that?

    >>
    >>>> This has the aroma of a homework project.

    >>
    >>> So what if it is? So the guy might be asking for information he hasn't
    >>> been able to find elsewhere? Would helping him out KILL you, sourpuss?

    >>
    >> Have you ever heard of intellectual integrity? If I had a deep knowledge
    >> of the area I might steer him. But, I would not supply the answer.
    >>
    >> BTW your informed answer is striking by its absence.
    >>
    >> --
    >> Peter

    >
    > I never claimed to have an answer, you dour old man.


    Oh! That is clever.

    --
    Peter
    PeterN, Nov 22, 2011
    #14
  15. mianileng

    gregz Guest

    "mianileng" <> wrote:
    > This does not directly involve photography but I thought the
    > people here would be knowledgeable enough about the subject to
    > help.
    >
    > I'm working on an electronics project for which I'd like to have
    > an inexpensive way of focusing incoming infrared rays onto a
    > sensor. The radiation is from a distant emitter, a bunch of
    > infrared LEDs sending coded pulses of IR energy from about 400m
    > (1300 ft) away. The project is for non-photographic work and
    > optical quality is not important. What *is* important is an
    > efficient concentration of the IR energy and I thought of using a
    > cheap macro lens of about +10 dioptre.
    >
    > The LEDs operate at 940nm. Transmission curves at the following
    > link for soda lime, borosilicate and UV glasses indicate quite
    > good transmissivity (for my purpose) at that wavelength.
    > http://www.sinclairmfg.com/datasheets/optical3.html
    > So far I haven't found comparable data for the glass used to make
    > the cheap lenses I mentioned. Can anyone please provide some
    > information about that?


    I saw a similar project many years ago. I thought they used a tube to
    reject outside interference.
    It would seem dependent on sensor. Is it one inch wide or one mm wide, or
    microns ?

    Greg
    gregz, Nov 22, 2011
    #15
  16. mianileng

    mianileng Guest

    gregz wrote:
    > "mianileng" <> wrote:
    >> This does not directly involve photography but I thought the
    >> people here would be knowledgeable enough about the subject to
    >> help.
    >>
    >> I'm working on an electronics project for which I'd like to
    >> have
    >> an inexpensive way of focusing incoming infrared rays onto a
    >> sensor. The radiation is from a distant emitter, a bunch of
    >> infrared LEDs sending coded pulses of IR energy from about
    >> 400m
    >> (1300 ft) away. The project is for non-photographic work and
    >> optical quality is not important. What *is* important is an
    >> efficient concentration of the IR energy and I thought of
    >> using a
    >> cheap macro lens of about +10 dioptre.
    >>
    >> The LEDs operate at 940nm. Transmission curves at the
    >> following
    >> link for soda lime, borosilicate and UV glasses indicate quite
    >> good transmissivity (for my purpose) at that wavelength.
    >> http://www.sinclairmfg.com/datasheets/optical3.html
    >> So far I haven't found comparable data for the glass used to
    >> make
    >> the cheap lenses I mentioned. Can anyone please provide some
    >> information about that?

    >
    > I saw a similar project many years ago. I thought they used a
    > tube to
    > reject outside interference.
    > It would seem dependent on sensor. Is it one inch wide or one
    > mm
    > wide, or microns ?
    >

    The sensor is a commercial module of the type used in consumer
    remote control receivers. The sensitive area is about 0.2" in
    diameter. For other applications where the distance between
    transmitter and receiver are much less (up to about 70 ft), I use
    a single IR LED transmitter and a tube at the receiving end to
    minimize the effects of ambient light. This one will operate at
    nearly 20 times the distance and hence 400 times weaker
    intensity. Even after boosting the transmitter output by using
    multiple LEDs, there will still be a need to concentrate the
    received radiation. That's where the lens comes in.
    mianileng, Nov 22, 2011
    #16
  17. mianileng

    RichA Guest

    On Nov 22, 9:36 am, PeterN <> wrote:
    > On 11/22/2011 8:41 AM, RichA wrote:
    >
    >
    >
    >
    >
    >
    >
    >
    >
    > > On Nov 22, 5:59 am, PeterN<>  wrote:
    > >> On 11/21/2011 10:35 PM, Rich wrote:

    >
    > >>> PeterN<>    wrote in news:4ecaf9cc$0$13254
    > >>> $-secrets.com:

    >
    > >>>> On 11/21/2011 2:34 PM, mianileng wrote:
    > >>>>> This does not directly involve photography but I thought the
    > >>>>> people here would be knowledgeable enough about the subject to
    > >>>>> help.

    >
    > >>>>> I'm working on an electronics project for which I'd like to have
    > >>>>> an inexpensive way of focusing incoming infrared rays onto a
    > >>>>> sensor.  The radiation is from a distant emitter, a bunch of
    > >>>>> infrared LEDs sending coded pulses of IR energy from about 400m
    > >>>>> (1300 ft) away. The project is for non-photographic work and
    > >>>>> optical quality is not important. What *is* important is an
    > >>>>> efficient concentration of the IR energy and I thought of using a
    > >>>>> cheap macro lens of about +10 dioptre.

    >
    > >>>>> The LEDs operate at 940nm. Transmission curves at the following
    > >>>>> link for soda lime, borosilicate and UV glasses indicate quite
    > >>>>> good transmissivity (for my purpose) at that wavelength.
    > >>>>>http://www.sinclairmfg.com/datasheets/optical3.html
    > >>>>> So far I haven't found comparable data for the glass used to make
    > >>>>> the cheap lenses I mentioned. Can anyone please provide some
    > >>>>> information about that?

    >
    > >>>> This has the aroma of a homework project.

    >
    > >>> So what if it is?  So the guy might be asking for information he hasn't
    > >>> been able to find elsewhere?  Would helping him out KILL you, sourpuss?

    >
    > >> Have you ever heard of intellectual integrity? If I had a deep knowledge
    > >> of the area I might steer him. But, I would not supply the answer.

    >
    > >> BTW your informed answer is striking by its absence.

    >
    > >> --
    > >> Peter

    >
    > > I never claimed to have an answer, you dour old man.

    >
    > Oh! That is clever.
    >
    > --
    > Peter


    Glad you enjoyed it, now why are you still reading what I post? Lead
    by example.
    RichA, Nov 22, 2011
    #17
  18. mianileng

    Bruce Guest

    RichA <> wrote:
    >
    >Glad you enjoyed it, now why are you still reading what I post? Lead
    >by example.



    Why are you even replying to the malicious old troll?

    Lead by example.
    Bruce, Nov 22, 2011
    #18
  19. mianileng

    PeterN Guest

    On 11/22/2011 12:41 PM, RichA wrote:
    \> Glad you enjoyed it, now why are you still reading what I post? Lead
    > by example.


    You are a sad example of an individual who desperately needs help.

    But unlike Brucie, I don't claim to bury my head in the sand.
    In fact, Brucie has claimed to plonk so many people, that his comments
    have become irrelevant.


    --
    Peter
    PeterN, Nov 22, 2011
    #19
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