New silicon 100-500x more light sensitive

Discussion in 'Digital SLR' started by RichA, Oct 13, 2008.

  1. RichA

    RichA Guest

    SiOnyx Brings “Black Silicon” into the Light; Material Could Upend
    Solar, Imaging Industries
    Wade Roush 10/12/08

    http://www.xconomy.com/boston/2008/...erial-could-upend-solar-imaging-industries/2/

    Silicon is a wonderfully cooperative element. It takes relatively
    little energy to promote the electrons in a silicon crystal from their
    usual, docile orbits around the atomic nuclei into wild, free
    circulation. That’s what makes silicon a semiconductor—valuable for
    electronic switching devices such as transistors, sensing devices such
    as the CCDs in cameras and X-ray machines, and energy-generating
    devices such as photovoltaic cells.

    But silicon would be more wondrous if it were even more responsive—if
    an incoming photon needed less energy to knock loose an electron, for
    example, or if a single photon could kick loose many electrons. In
    pursuit of this vision, chemists, physicists, and engineers have spent
    decades trying out various ways of modifying silicon crystals—for
    example, by doping them with atoms of arsenic or other elements that
    put more free electrons into the mix.

    Almost ten years ago, graduate students in the laboratory of physics
    professor Eric Mazur at Harvard University stumbled across a new way
    of making silicon more responsive: they found that if they blasted the
    surface of a silicon wafer with an incredibly brief pulse of laser
    energy in the presence of gaseous sulfur and other dopants, the
    resulting material—which they called “black silicon”—was much better
    at absorbing photons and releasing electrons. And this week, after
    nearly three years in hyper-stealth mode, a spinoff company with an
    exclusive license from Harvard to commercialize the process has begun
    talking with reporters.

    Executives for the company, called SiOnyx, believe that its technology
    will help semiconductor manufacturers build far more sensitive
    detectors and far more efficient photovoltaic cells, using essentially
    the same silicon-based processes they currently depend on—thereby
    revolutionizing areas such as medical imaging, digital photography,
    and solar energy generation.

    The venture-funded startup has emerged with a bang, securing exclusive
    coverage by New York Times technology writer John Markoff in today’s
    edition. But SiOnyx CEO Stephen Saylor and principal scientist James
    Carey, a PhD graduate of Mazur’s lab, also showed me around their
    Beverly, MA, facility last week, on the condition that this post would
    appear after Markoff’s story.

    SiOnyx principal scientist James Carey (L) and CEO Stephen Saylor (R)
    “You’ve never been able to detect light the way this stuff detects
    light,” says Saylor, referring to black silicon’s remarkable
    sensitivity to incoming photons, especially photons at infrared
    energies, which pass through normal silicon as if it were transparent.
    That property could make it an ideal, and inexpensive, replacement for
    less-sensitive detectors in devices as varied as X-ray and CRT
    machines, surveillance satellites, night-vision goggles, and consumer
    digital cameras. “It means that you solve a clear and obvious pain
    point for a very large number of customers,” Saylor says.

    And because black silicon is just silicon that’s been roughed up a bit
    by femtosecond laser pulses and chemical treatment, SiOnyx’s
    technology could theoretically be integrated into existing
    semiconductor fabrication lines without much disruption. “You can do
    everything we’re talking about without extraordinary, Herculean
    effort, and you can do it in a way that fits with high-volume
    manufacturing flows,” says Carey.

    SiOnyx was incorporated in 2005, secured the Harvard license in early
    2006, and obtained $11 million in venture financing from Harris &
    Harris, Polaris Venture Partners, and RedShift Ventures in 2007. The
    company is going public with its story because “we have enough
    momentum now both with strategic partners and with the technology that
    it makes sense at this point to share a little more about what we are
    up to,” say Saylor.

    Harvard, for its part, is holding up SiOnyx as one early result of the
    ongoing overhaul of the university’s technology licensing efforts. The
    school gained a reputation early in this decade as being unresponsive,
    even hostile, toward faculty and students who wished to commercialize
    discoveries made in the university’s labs, especially in areas outside
    of biotechnology and drug development. For years after the discovery
    of black silicon in Mazur’s lab, the school’s technology transfer
    office “wasn’t very excited” about the work, according to Carey.

    But in 2005 the university brought in university licensing veteran
    Isaac Kohlberg to rebuild its technology transfer operation from
    scratch. Saylor and Carey say it was Kohlberg and his staff who
    finally understood black silicon’s potential and ironed out the
    licensing deal that made SiOnyx possible.

    “The exciting steps being taken to develop [black silicon] for
    commercial application serve as even more evidence of the
    entrepreneurial energy that continues to gel and accelerate at
    Harvard,” Kohlberg says in a press release set to be issued tomorrow
    by SiOnyx and Harvard’s Office of Technology Development.

    Bob Metcalfe, a general partner at Polaris Ventures who sits on
    SiOnyx’s board, thinks Kohlberg is right: “Harvard seems to be getting
    its act together in patent licensing,” he says.

    Exactly what makes black silicon such an effective absorber of photons
    is a question that even Mazur and Carey couldn’t answer at first. The
    material is one of many offshoots of work going on in Mazur’s lab in
    the late 1990s using femtosecond lasers—devices that can emit an
    intense pulse of light lasting only a millionth of a billionth of a
    second. Mazur lab researchers found that zapping a silicon wafer with
    such pulses in the presence of sulfur hexafluoride gas—an experiment
    initially carried out on a whim—left the wafer festooned with tiny
    cones. Silicon roughened in this way soaks up almost all of the light
    that strikes it in visible wavelengths, appearing black—hence the
    name.

    “It took several years for us to begin thinking properly about what we
    had,” says Carey. “The original thought was that the surface
    roughening process was what created the advantage.” The researchers
    hypothesized that photons were bouncing from cone to cone—and that the
    more times they bounced, the higher the likelihood that they’d be
    absorbed, thus dislodging electrons. But then Carey and his coworkers
    realized that black silicon was also absorbing infrared light, “which
    you can’t explain just by roughening it.” It takes photons of a
    certain energy to bump electrons in silicon’s outermost layer of
    electrons, called the “valence band,” into the so-called “conduction
    band,” where they’re free to circulate between atoms—and infrared
    photons just don’t have enough. So by all rights, these photons should
    have been passing right through without interacting with the material,
    just as if it were frosted glass.

    “That was the real discovery point,” says Carey. The genesis of
    SiOnyx, he explains, came when the Mazur lab dug into the changes
    caused by the femtosecond laser pulses at the atomic level. And as it
    turned out, he says, “the cones weren’t really paramount at all”—
    although they certainly look cool (electron micrographs of the cone
    forests, like the one below, still appear alongside almost any
    discussion of black silicon).

    What’s really going on—though this is where Carey and Saylor start to
    get cagey, since it gets at the proprietary heart of SiOnys’x
    technology—is that the laser pulses force unusually large numbers of
    dopant atoms into a thin layer of silicon on the surface of the cones.
    “The laser allows you to put in a million times more sulfur than you
    would normally get in if you just combined and heated them,” says
    Carey. “In that millionth of a billionth of a second you get
    structural arrangements frozen at the atomic level.”

    Black siliconWith its new structure, the “band gap” in this thin
    silicon layer—the difference in energy between the valence band and
    the conduction band—is smaller. That means less energy is required to
    knock electrons into the conduction band, which explains why infrared
    photons can do the job. Another fringe benefit: applying a small
    voltage to black silicon (engineers call this “bias”) creates
    conditions in which a single incoming photon can knock loose dozens of
    electrons. So, not only is the material responsive to wavelengths that
    silicon-based devices simply couldn’t detect in the past—it also
    produces a much stronger signal in response to a weak stimulus. Black
    silicon is between 100 and 500 times more sensitive to light than
    untreated silicon, the company says.

    These properties mean that SiOnyx is in a position to pioneer new
    types of solar cells that could capture the sun’s energy across a
    broader spectrum, achieving greater efficiency than today’s
    photovoltaic cells.
    “Harnessing nuclear fusion energy arriving from Sol—solar energy at
    1366 Watts per square meter—is the most promising technology for
    meeting accelerating world needs for cheap and clean energy,” says
    Polaris’s Metcalfe. Black siliicon “promises to dramatically increase
    the photo-response (Amps per Watt) of silicon, and not just in the
    visible spectrum, but also in the infrared, where silicon currently
    misses half of Sol’s energy. Delivering on that promise is very
    exciting.”

    But that’s the “long shot” applicaiton for the material, Metcalfe
    acknowledges. Closer in is the possibility of major sensitivity
    improvements in imaging applications such as night vision,
    surveillance, digital cameras, and medical imaging. Saylor says that
    the company has negotiated strategic partnerships with two “industry
    leaders,” and though he won’t name names, he says one of them is
    active in the medical imaging area.

    The attraction of black silicon in medical imaging is obvious: If you
    could build a more sensitive detector for a CT or mammography machine,
    you could expose patients to a lower dose of X-rays. (Black silicon,
    of course, can’t detect X-rays directly; modern digital X-ray machines
    include a component called a scintillator that emits visible light
    when struck by X-rays, and that light is what’s recorded by a sensor.)
    “If we can do something that allows women to get risk-free mammograms
    twice a year or reduce the number of chest-X-ray equivalents that you
    get from a CT scan, or address other pain points, we will have an
    immediate path to market,” says Saylor.

    While SiOnyx is telling some of its story, it’s keeping big pieces of
    it under wraps. Asked how many employees the company has, Saylor says
    it’s more than 10 and fewer than 50. (Significantly fewer, from what I
    could see around SiOnxy’s offices—a space in the former United Shoe
    Machinery factory in Beverly, far outside of Boston, that the company
    picked because the previous tenant had installed a clean room.) The
    company won’t build semiconductors or even semiconductor fabrication
    equipment, but will instead work with as-yet-unnamed partners to
    develop specifications for machines that can treat isolated areas of
    silicon wafers to create black silicon.

    SiOnyx engineers were using an automated testing device to examine
    sections of such a wafer when I visited. “We are a process engineering
    company, not a product engineering company,” says Saylor. “Our job is
    to make a transferable process that conforms to [our partners']
    manufacturing flow. We are doing a tremendous amount of development
    around what are the optimal conditions for making this black silicon—
    how do you do it uniformly, how do you make it massively scalable, and
    how do you transfer it to a foundry.”

    Metcalfe says the biggest challenges before SiOnyx right now are “to
    move the black silicon process from labs to fabs, from experimental
    facilities/processes at Harvard to production facilities/processes at
    SiOnyx” and “to navigate through black silicon’s many opportunities to
    the right go-to-market products.”

    Saylor says he hopes the company won’t have to raise any more venture
    capital to do that. “The first strategic relationships are going to be
    with very well-aligned industry leaders, so those will lead to
    development relationships and eventually product-revenue
    relationships,” he says. The company will be “careful with cash” until
    it can grow to the point that it “becomes interesting to someone
    outside the venture investing community,” he says.

    There’s an interesting irony to SiOnyx’s business: a large chunk of
    the semiconductor industry’s effort over the past 50 years has gone
    toward making silicon as pure as possible. But now SiOnyx and other
    companies are showing how useful—and perhaps profitable—it can be to
    craft silicon devices with impurities, defects, and unconventional
    structures.

    “We are messing up perfectly good silicon,” Carey admits. “But in the
    end, the properties speak for themselves.
     
    RichA, Oct 13, 2008
    #1
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  2. RichA

    Pete D Guest

    SiOnyx Brings “Black Silicon” into the Light; Material Could Upend
    Solar, Imaging Industries
    Wade Roush 10/12/08

    http://www.xconomy.com/boston/2008/...erial-could-upend-solar-imaging-industries/2/

    Silicon is a wonderfully cooperative element. It takes relatively
    little energy to promote the electrons in a silicon crystal from their
    usual, docile orbits around the atomic nuclei into wild, free
    circulation. That’s what makes silicon a semiconductor—valuable for
    electronic switching devices such as transistors, sensing devices such
    as the CCDs in cameras and X-ray machines, and energy-generating
    devices such as photovoltaic cells.

    But silicon would be more wondrous if it were even more responsive—if
    an incoming photon needed less energy to knock loose an electron, for
    example, or if a single photon could kick loose many electrons. In
    pursuit of this vision, chemists, physicists, and engineers have spent
    decades trying out various ways of modifying silicon crystals—for
    example, by doping them with atoms of arsenic or other elements that
    put more free electrons into the mix.

    Almost ten years ago, graduate students in the laboratory of physics
    professor Eric Mazur at Harvard University stumbled across a new way
    of making silicon more responsive: they found that if they blasted the
    surface of a silicon wafer with an incredibly brief pulse of laser
    energy in the presence of gaseous sulfur and other dopants, the
    resulting material—which they called “black silicon”—was much better
    at absorbing photons and releasing electrons. And this week, after
    nearly three years in hyper-stealth mode, a spinoff company with an
    exclusive license from Harvard to commercialize the process has begun
    talking with reporters.

    Executives for the company, called SiOnyx, believe that its technology
    will help semiconductor manufacturers build far more sensitive
    detectors and far more efficient photovoltaic cells, using essentially
    the same silicon-based processes they currently depend on—thereby
    revolutionizing areas such as medical imaging, digital photography,
    and solar energy generation.

    The venture-funded startup has emerged with a bang, securing exclusive
    coverage by New York Times technology writer John Markoff in today’s
    edition. But SiOnyx CEO Stephen Saylor and principal scientist James
    Carey, a PhD graduate of Mazur’s lab, also showed me around their
    Beverly, MA, facility last week, on the condition that this post would
    appear after Markoff’s story.

    SiOnyx principal scientist James Carey (L) and CEO Stephen Saylor (R)
    “You’ve never been able to detect light the way this stuff detects
    light,” says Saylor, referring to black silicon’s remarkable
    sensitivity to incoming photons, especially photons at infrared
    energies, which pass through normal silicon as if it were transparent.
    That property could make it an ideal, and inexpensive, replacement for
    less-sensitive detectors in devices as varied as X-ray and CRT
    machines, surveillance satellites, night-vision goggles, and consumer
    digital cameras. “It means that you solve a clear and obvious pain
    point for a very large number of customers,” Saylor says.

    And because black silicon is just silicon that’s been roughed up a bit
    by femtosecond laser pulses and chemical treatment, SiOnyx’s
    technology could theoretically be integrated into existing
    semiconductor fabrication lines without much disruption. “You can do
    everything we’re talking about without extraordinary, Herculean
    effort, and you can do it in a way that fits with high-volume
    manufacturing flows,” says Carey.

    SiOnyx was incorporated in 2005, secured the Harvard license in early
    2006, and obtained $11 million in venture financing from Harris &
    Harris, Polaris Venture Partners, and RedShift Ventures in 2007. The
    company is going public with its story because “we have enough
    momentum now both with strategic partners and with the technology that
    it makes sense at this point to share a little more about what we are
    up to,” say Saylor.

    Harvard, for its part, is holding up SiOnyx as one early result of the
    ongoing overhaul of the university’s technology licensing efforts. The
    school gained a reputation early in this decade as being unresponsive,
    even hostile, toward faculty and students who wished to commercialize
    discoveries made in the university’s labs, especially in areas outside
    of biotechnology and drug development. For years after the discovery
    of black silicon in Mazur’s lab, the school’s technology transfer
    office “wasn’t very excited” about the work, according to Carey.

    But in 2005 the university brought in university licensing veteran
    Isaac Kohlberg to rebuild its technology transfer operation from
    scratch. Saylor and Carey say it was Kohlberg and his staff who
    finally understood black silicon’s potential and ironed out the
    licensing deal that made SiOnyx possible.

    “The exciting steps being taken to develop [black silicon] for
    commercial application serve as even more evidence of the
    entrepreneurial energy that continues to gel and accelerate at
    Harvard,” Kohlberg says in a press release set to be issued tomorrow
    by SiOnyx and Harvard’s Office of Technology Development.

    Bob Metcalfe, a general partner at Polaris Ventures who sits on
    SiOnyx’s board, thinks Kohlberg is right: “Harvard seems to be getting
    its act together in patent licensing,” he says.

    Exactly what makes black silicon such an effective absorber of photons
    is a question that even Mazur and Carey couldn’t answer at first. The
    material is one of many offshoots of work going on in Mazur’s lab in
    the late 1990s using femtosecond lasers—devices that can emit an
    intense pulse of light lasting only a millionth of a billionth of a
    second. Mazur lab researchers found that zapping a silicon wafer with
    such pulses in the presence of sulfur hexafluoride gas—an experiment
    initially carried out on a whim—left the wafer festooned with tiny
    cones. Silicon roughened in this way soaks up almost all of the light
    that strikes it in visible wavelengths, appearing black—hence the
    name.

    “It took several years for us to begin thinking properly about what we
    had,” says Carey. “The original thought was that the surface
    roughening process was what created the advantage.” The researchers
    hypothesized that photons were bouncing from cone to cone—and that the
    more times they bounced, the higher the likelihood that they’d be
    absorbed, thus dislodging electrons. But then Carey and his coworkers
    realized that black silicon was also absorbing infrared light, “which
    you can’t explain just by roughening it.” It takes photons of a
    certain energy to bump electrons in silicon’s outermost layer of
    electrons, called the “valence band,” into the so-called “conduction
    band,” where they’re free to circulate between atoms—and infrared
    photons just don’t have enough. So by all rights, these photons should
    have been passing right through without interacting with the material,
    just as if it were frosted glass.

    “That was the real discovery point,” says Carey. The genesis of
    SiOnyx, he explains, came when the Mazur lab dug into the changes
    caused by the femtosecond laser pulses at the atomic level. And as it
    turned out, he says, “the cones weren’t really paramount at all”—
    although they certainly look cool (electron micrographs of the cone
    forests, like the one below, still appear alongside almost any
    discussion of black silicon).

    What’s really going on—though this is where Carey and Saylor start to
    get cagey, since it gets at the proprietary heart of SiOnys’x
    technology—is that the laser pulses force unusually large numbers of
    dopant atoms into a thin layer of silicon on the surface of the cones.
    “The laser allows you to put in a million times more sulfur than you
    would normally get in if you just combined and heated them,” says
    Carey. “In that millionth of a billionth of a second you get
    structural arrangements frozen at the atomic level.”

    Black siliconWith its new structure, the “band gap” in this thin
    silicon layer—the difference in energy between the valence band and
    the conduction band—is smaller. That means less energy is required to
    knock electrons into the conduction band, which explains why infrared
    photons can do the job. Another fringe benefit: applying a small
    voltage to black silicon (engineers call this “bias”) creates
    conditions in which a single incoming photon can knock loose dozens of
    electrons. So, not only is the material responsive to wavelengths that
    silicon-based devices simply couldn’t detect in the past—it also
    produces a much stronger signal in response to a weak stimulus. Black
    silicon is between 100 and 500 times more sensitive to light than
    untreated silicon, the company says.

    These properties mean that SiOnyx is in a position to pioneer new
    types of solar cells that could capture the sun’s energy across a
    broader spectrum, achieving greater efficiency than today’s
    photovoltaic cells.
    “Harnessing nuclear fusion energy arriving from Sol—solar energy at
    1366 Watts per square meter—is the most promising technology for
    meeting accelerating world needs for cheap and clean energy,” says
    Polaris’s Metcalfe. Black siliicon “promises to dramatically increase
    the photo-response (Amps per Watt) of silicon, and not just in the
    visible spectrum, but also in the infrared, where silicon currently
    misses half of Sol’s energy. Delivering on that promise is very
    exciting.”

    But that’s the “long shot” applicaiton for the material, Metcalfe
    acknowledges. Closer in is the possibility of major sensitivity
    improvements in imaging applications such as night vision,
    surveillance, digital cameras, and medical imaging. Saylor says that
    the company has negotiated strategic partnerships with two “industry
    leaders,” and though he won’t name names, he says one of them is
    active in the medical imaging area.

    The attraction of black silicon in medical imaging is obvious: If you
    could build a more sensitive detector for a CT or mammography machine,
    you could expose patients to a lower dose of X-rays. (Black silicon,
    of course, can’t detect X-rays directly; modern digital X-ray machines
    include a component called a scintillator that emits visible light
    when struck by X-rays, and that light is what’s recorded by a sensor.)
    “If we can do something that allows women to get risk-free mammograms
    twice a year or reduce the number of chest-X-ray equivalents that you
    get from a CT scan, or address other pain points, we will have an
    immediate path to market,” says Saylor.

    While SiOnyx is telling some of its story, it’s keeping big pieces of
    it under wraps. Asked how many employees the company has, Saylor says
    it’s more than 10 and fewer than 50. (Significantly fewer, from what I
    could see around SiOnxy’s offices—a space in the former United Shoe
    Machinery factory in Beverly, far outside of Boston, that the company
    picked because the previous tenant had installed a clean room.) The
    company won’t build semiconductors or even semiconductor fabrication
    equipment, but will instead work with as-yet-unnamed partners to
    develop specifications for machines that can treat isolated areas of
    silicon wafers to create black silicon.

    SiOnyx engineers were using an automated testing device to examine
    sections of such a wafer when I visited. “We are a process engineering
    company, not a product engineering company,” says Saylor. “Our job is
    to make a transferable process that conforms to [our partners']
    manufacturing flow. We are doing a tremendous amount of development
    around what are the optimal conditions for making this black silicon—
    how do you do it uniformly, how do you make it massively scalable, and
    how do you transfer it to a foundry.”

    Metcalfe says the biggest challenges before SiOnyx right now are “to
    move the black silicon process from labs to fabs, from experimental
    facilities/processes at Harvard to production facilities/processes at
    SiOnyx” and “to navigate through black silicon’s many opportunities to
    the right go-to-market products.”

    Saylor says he hopes the company won’t have to raise any more venture
    capital to do that. “The first strategic relationships are going to be
    with very well-aligned industry leaders, so those will lead to
    development relationships and eventually product-revenue
    relationships,” he says. The company will be “careful with cash” until
    it can grow to the point that it “becomes interesting to someone
    outside the venture investing community,” he says.

    There’s an interesting irony to SiOnyx’s business: a large chunk of
    the semiconductor industry’s effort over the past 50 years has gone
    toward making silicon as pure as possible. But now SiOnyx and other
    companies are showing how useful—and perhaps profitable—it can be to
    craft silicon devices with impurities, defects, and unconventional
    structures.

    “We are messing up perfectly good silicon,” Carey admits. “But in the
    end, the properties speak for themselves.

    Could be a while, but in the end there are still only so many photons to
    collect, this may not help normal photography all that much.

    Pete
     
    Pete D, Oct 13, 2008
    #2
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  3. RichA

    RichA Guest

    I think they mean photons used to knock electrons out of their
    orbits.
    I was under the impression that consumer camera sensors were about 40%
    efficient, with some thinned, back illuminated sensors used in
    scientific fields up to 90% efficient.
     
    RichA, Oct 14, 2008
    #3
  4. RichA

    Me Guest

    So 100-500x more efficient, as in the subject line you posted means that
    each photon can shift 40 - 200 electrons? (100-500x).
    So, even if current sensor were 40%, and 100% could be achieved, then
    that's one (...and a bit) photographic stop return for a miracle? And
    this is a big deal?
     
    Me, Oct 14, 2008
    #4
  5. [Blubb]

    I smell a rat the size of an elephant.
    http://clarkvision.com/imagedetail/digital.photons.and.qe/index.html

    With a 1.4x converter and 500mm f/4 lens:
    Total QE of a 10D (green band) is 9.5%
    Total QE of a 1D MkIII (green band) is 15%.

    And yes, Total QE includes all the light lost in the lens, in the
    bayer filters, between the pixels (less than 100% fill factor)
    --- everything!

    Without inventing photons and with a *completely* *lossless*
    lens, blur filter, green filter, and 100% fill factor you can
    not get better than ~6.7 times -- or more than 2.7 stops.

    Even against the old 10D, you cannot get betzter than 10.5
    times or a tiny bit over 3 stops. Again, with "unobtainium"
    lenses.


    100 (6 2/3 stops) to 500 times (9 stops)? No way, unless you
    use a photomultiplier. Which, since we are already counting
    single electrons, doesn't give us anything, except "louder" and
    "more noise".

    But RichA won't understand that if it bit his behind.

    -Wolfgang
     
    Wolfgang Weisselberg, Oct 14, 2008
    #5
  6. RichA

    RichA Guest

    Thanks, I've used PM tubes and image intensification gear.
     
    RichA, Oct 14, 2008
    #6
  7. RichA

    John Sheehy Guest

    Not exactly. 100x as much charge for each photon does not multiply the
    read noise, so read noise, relative to absolute exposure, is extremely low.
    Of course, unless some way of reducing electron gain is available, low ISOs
    will not be available without ND filters.
     
    John Sheehy, Oct 24, 2008
    #7
  8. You are still photon noise bound --- and it's not like a
    photomultiplier was without noise.
    Reducing the voltage to the photomultiplier should do that easily.

    -Wolfgang
     
    Wolfgang Weisselberg, Oct 24, 2008
    #8
  9. RichA

    John Sheehy Guest

    That's like saying "but you are still closer to paradise".

    There's nothing much more I can ask for a camera than to give me the
    photons. The read noise is what turns images to crap.

    There is no patterning in photon noise; no blanketing of shadows in a noise
    floor. Black is BLACK.
     
    John Sheehy, Oct 25, 2008
    #9
  10. RichA

    Guest Guest

    | So 100-500x more efficient, as in the subject line you posted means that
    | each photon can shift 40 - 200 electrons? (100-500x).
    | So, even if current sensor were 40%, and 100% could be achieved, then
    | that's one (...and a bit) photographic stop return for a miracle? And
    | this is a big deal?

    Next thing they will be telling us is they can get 100 to 500 times the heat
    out of a 1000 watt electric heater.
     
    Guest, Oct 25, 2008
    #10
  11. RichA

    John Sheehy Guest

    That isn't a very good analogy.

    Whatever the actual photon capture is, it has to compete against noises
    added in reading the sensor. Getting multiple electron charges from a
    single photo capture means that read noise, relative to signal, is
    drastically reduced.

    Even reducng read noise to 50% of what it is at high ISOs in the best DSLRs
    would be semi-revolutionary. Reducing it to 1% would be astounding, if
    dark current noise doesn't become the main issue.
     
    John Sheehy, Oct 25, 2008
    #11
  12. RichA

    John Sheehy Guest

    Right now, for a short exposure, in the shadows, at high ISO, read noise is
    by far, the overwhelming source of noise. Losing most of the read noise,
    and still having thermal noise, and shot noise, would be relative nirvana.
     
    John Sheehy, Oct 26, 2008
    #12
  13. RichA

    rjn Guest

    I presume they are calling this "black" silicon because
    that's what it looks like. Light hits it, and doesn't come back.
    Normal Si cells are somewhat reflective (photo sensors more
    so, due to the AA filter).

    Back at the press release:
    "Black silicon “promises to dramatically increase the photo-response
    (Amps per Watt) of silicon, and not just in the visible spectrum, but
    also in the infrared, where silicon currently misses half of Sol’s
    energy.
    Delivering on that promise is very exciting.”"

    IR is heat. Use these things for PV and they are going to
    get hot, very hot, is my guess. The promoters seem to sense that...

    "But that’s the “long shot” application for the material,
    Metcalfe acknowledges."

    The article does not explain why.

    "Black" could also refer to the hole in which the VC money
    will disappear, or not. We'll see.
     
    rjn, Oct 26, 2008
    #13
  14. A point which many low noise enthusiasts often forget it that if you
    have more pixels than you need for a particular image, you can
    sacrifice some of them to reduce noise. I'm not sure how much noise
    you lose in practice by downsizing by 50%, but you certainly reduce it
    a lot. In other words a high pixel count isn't necessarily to concede
    ground in the noise wars, because you can use those extra pixels for
    improved resolution or cropping freedom in good light, and for noise
    reduction in poor light.
     
    Chris Malcolm, Oct 27, 2008
    #14
  15. Chris Malcolm wrote:
    []
    Usually, the signal adds linearly, and the noise in an RMS way. So if you
    mean 50% linear scaling (24MP => 6MP), each output pixel would have four
    times the signal and twice the noise, and hence a 2:1 improvement in SNR.

    David
     
    David J Taylor, Oct 27, 2008
    #15
  16. Nope. Do you really believe that photomultipliers are less noisy?
    They can pump up the signal level making detection easier, they
    can even be used in a logarithmically response curve.
    Please do check for yourself how little influence read noise has.
    There Is No Black.

    -Wolfgang
     
    Wolfgang Weisselberg, Oct 27, 2008
    #16
  17. I see. Can you quantify that?

    According to clarkvision.com, some read noises are:
    D200 7.4 e- at ISO 800 and ISO1600
    D50 7.47 e- at ISO 800
    D300 4.6 e- at ISO1600
    1D MkIII 4.0 e- at ISO3200
    1D MkII 3.90 e- at ISO1600
    5D (not II) 3.7 e- at ISO1600 and ISO3200
    350D 3.7 e- at ISO1600
    20D 3.6 e- at ISO1600
    -Wolfgang
     
    Wolfgang Weisselberg, Oct 27, 2008
    #17
  18. A 4:1 pixel reduction (50% height, 50% width), if done correctly,
    will reduce the noise by SQRT(4) == 2. However, at the same
    output size that will change nothing. You need to reduce the
    output size (or view both versions at 100%, versus viewing the
    original at 50%), which'll change the DOF as seen by the viewer.
    And because viewing or printing at a size smaller than "100%"
    *is* a size reduction, you get the noise reduction for free.
    The only way to beat that game is to use pixel binning, where
    the charge from a group of pixels is pushed through the reader
    as one, in which case you incur read noise only once, instead of
    once for each pixel.

    -Wolfgang
     
    Wolfgang Weisselberg, Oct 27, 2008
    #18
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