Some of Our Current and Recent Work
EOI works with customers of all sizes, from garage startups and
university research groups to the largest companies in the
electronics, defense, and semiconductor equipment industries. We do
research, technology selection, product design, and expert
witness work in both patent and trade secret cases. We're always
ready to help with debugging and firefighting—we learned some
of this stuff the hard way too.
Last significant update February 14, 2015: At trial in TAOS v.
Intersil; working on doubling the spatial resolution of silicon
microscopes; and doing calculations on the use of coherent lidar for
vehicle and marine navigation.
Doubling the Resolution of Solid Immersion
Microscopes This is a very exciting development, in cooperation with a
semiconductor equipment manufacturer. Back in 1989, my
colleagues and I started working on a contact-lens
into the interior of silicon chips through the back surface.
In 1992 I took a picture at a numerical aperture of 2.5, with
resolution equivalent to NA 3.5 due to a confocal design.
The combination of this with my thesis work on doubling
conventional microscope resolution via heterodyne interferometry
and digital filtering was going to allow us to take images at an
equivalent numerical aperture of 6.4. I never got to build the
full scale system.
Now, over 20 years later, I finally get to do it for
real. I'm designing and prototyping a microscope to work at NA
6.4, which will have resolution on the order of 15 nm (10%-90%
rise). That's pretty cool stuff for a visible-light
microscope, and if it works, it should give me bragging rights
for a long, long time.
Shot-Noise Limited Sub-Nanoamp Photoreceiver for
Spectroscopy This is a smaller job for a sensor manufacturer, interesting
mostly for the size, weight, and power (SWaP) requirements. It
has to be shot noise limited above 500 pA with a 1600 pF
photodiode. (This is possible only because the bandwidth is
Plate Reader for Water Quality Assay This is a research project with a small division of a very
large manufacturer. It's a complete optical/electronic design
to measure optical absorbance in a rapidly moving assay plate.
In-Chamber Hypersonic Debris Detection and Mapping for
EUV Lithography Sources Latest: Work began in early October; progress to
date has been encouraging but (due to resource
constraints) not quite as fast as we'd like.
on my In Situ Coherent Lidar
(ISICL) particle detection technology, this new and more
advanced ISICL will be capable of detecting individual
0.18 μm metal particles moving at up to 3 km/s
(Mach 9) anywhere in the vacuum chamber and mapping them in 8
dimensions [position (x, y, z), velocity
(vx, vy, vz), time, and
particle size]. The Doppler frequencies are as high as
7 GHz, which is pretty different from the original ISICL's
2 MHz, but somewhat surprisingly the basic design is the
same; the only major changes are a somewhat more powerful laser,
a longer working distance, and a much higher bandwidth back end.
Blood Detector for Egg Grading A bit of a departure from our usual fare: a low cost, high
speed sensor for detecting blood spots in eggs using spectral
differencing. I'm going to be doing the firmware as well as the
optics and electronics, and this will be the first actual client
work for our newly qualified PCB designer, Magdalen.
Competing devices use xenon flashtubes and very
expensive photodiodes, but still need a lot of calibration and
tweaking. That makes it a good candidate for our signature
technique: A really careful photon budget followed by a design
that actually reaches the theoretical optimum performance.
Egg grading is a good example of a measurement dominated
by nuisance data: normal variations between samples that
have to be distinguished from the thing you're looking for. Big
eggs, small eggs, white eggs, brown eggs, thick and thin shells,
double yolks, mottling, you name it.
High speed egg-grading machines can inspect and pack as
many as 250,000 eggs per hour; running two shifts a day, that's
enough to keep up with about 4 million hens!
Update: Design and prototyping completed, 12/2014;
productizing underway at a contract engineering firm in the
SWIR Grating Spectrometer Proof of Concept
Optical and optomechanical design, detection and control
electronics and software, prototype construction: first spectra
were taken 5/16/2013, and technology transfer to a contract
engineering firm was essentially completed 6/14/2013.
Most notable was the schedule requirement: from a
standing start, in less than 6 weeks' work, I did a complete
photon budget, designed and built all of the optics and
electronics, wrote all the software, integrated and shipped the
Because of the schedule, the prototype was built mostly
out of stuff I had in my drawer. That meant that all the
coatings were mistuned, which cost a lot of light, but it
nevertheless works very well. There are a few amusing
For instance, the grating is mounted on a
servomotor intended for radio-controlled airplanes. While
rather unorthodox, this is actually a pretty sweet solution for
a lowish-resolution spectrometer—you get a rare-earth
magnet motor, titanium gear train, magnetic position encoder,
and servo control electronics in a 2-cubic-inch device that
costs $139 in quantity one. It has to be designed out of the
actual product, because it isn't quite good enough at making
very small moves repeatably, and besides, it wouldn't do to show
the Food & Drug Administration a device built with toy parts!
If you want to try this, I suggest putting an optical
position sensor on the grating, e.g. by putting a
barefoot diode laser next to the slit and detecting the specular
reflection with a lateral-effect photodiode or a webcam sensor.
That way, minor nonrepeatability of the tuning doesn't turn the
slopes into absorption error. Human tissue has a huge
absorption slope in the SWIR—about 2 AU in
100 nanometres—so this is a real issue.
Nanoamp Laser Noise Canceller
This one is in cooperation with the Kuno biochemistry group at Notre
Dame—A front end for picosecond spectroscopy with a filtered
supercontinuum source. The interesting part about this one is that it has
to have good cancellation performance down to about 10 nA, about 1000 times
less than the original noise canceller or the New Focus Nirvana (which is
closely modelled on my original design, except that mine is 40
Bootstrap Charge Sensitive Front End This is for for a scanning surface potential measurement tool, used in
contamination detection in
semiconductors: 40 attocoulomb sensitivity in a 4 MHz bandwidth
Biochips Based on Photonic Waveguides Using POEMS to design waveguides, coupling
structures, and optical/chemical interaction regions; consulting on
Instrumentation: Wideband Laser Noise Canceller > 60 dB of
RIN cancellation out to > 10 MHz, about 100 times faster than
current commercial devices
Current Amplifier for Nanopore
Biochips for DNA Sequencing This one came from a
a major industrial research laboratory: near shot noise limited
detection of 1 nA currents in 100 MHz bandwidth.
This was one that I wasn't at all sure would work: it's
pretty sporty trying to detect a few dozen electrons at
100 MHz in a built-up circuit. (A 100-MHz lowpass has a
time-domain response about 5 ns wide, and 1 nA in 5 ns is 31
electrons.) Obviously to get the highest available signal
voltage, the input-node capacitance has to be absolutely the
minimum possible: less than 1 pF.
Doing this required another novel transimpedance design, and
the use of microwave transistors: 20 GHz GaAs pHEMTs and
40 GHz SiGe:C bipolars. Because performance verification of such a device is
very difficult, I also designed an on-board calibrator that used
the same sorts of devices to produce a 50-kHz triangular wave that
was really really triangular: the corner showed less than 1 ns of
curvature. When differentiated by a very small coupling
capacitance, this produces a square wave current of about
10 nA at the input, which is a convenient calibration
Compressive-Scan Camera: 1-Channel IR Detector Analog
Front End In cooperation with InView Technology. Compressive scanning
is a scheme for doing image sensing with a single-element
detector, without suffering the N2 speed
penalty of raster scanning. It's a sort of
combination of scanning and image compression—you use a
digital micromirror device (DMD) to multiply the image by a series
of 1-bit digital basis functions, measure the resulting
photocurrent, and then invert the transform to produce a
compressed image. That's not too useful in the visible, where
image sensors are cheap commodity items, but in the UV and
especially the shortwave IR (SWIR), image arrays are extremely
expensive, so there's a need for compressive scan cameras.
This front end had to reach the shot noise limit with
high-capacitance SWIR photodiodes at very low photocurrents, which
is a difficult combination.
32-Channel IR Detector for Compressive
Scanning Camera (first images taken, June 2012)
A follow-on to the single channel version. This one had to
work at very much lower power, which required a new
amplifier topology based on local feedback around a very low noise
JFET. This was a very fruitful development, which has been
used in a number of follow-on designs.
Nonproliferation: 100-MHz Noise Cancelling Front End
This was in cooperation with Mesa Photonics of Santa Fe NM. It's
part of a DOE program, an advanced deployable solar
occultation spectrometer for detecting volatile plumes from clandestine uranium
Their scheme uses a really cool technique
that's still under NDA, so that I can't talk about it except to
say that it's a good illustration of the importance of a photon
Interferometry: Cavity-Stabilized 1550-nm Laser This was in collaboration with a start-up in New Mexico called
Symphony Acoustics. Downhole measurements are notoriously
difficult, and this one was no exception: building a laser that
could achieve an Allan variance of 10-10 at 10,000
seconds, and do it 5000 feet down a 2-inch cased drillhole. Due
to the casing thickness, the maximum outer diameter of the
instrument package was 38 mm, including its own casing and
two concentric zones of thermal control.
The stabilization strategy was one I patented in about 1992: Send
the beam through a fixed etalon; detect both the reflected and
transmitted beams; form a linear combination
C = T-αR for some convenient value
0 < α < 1; and servo the laser tuning to
null out C, which can be done very accurately, without
needing a high finesse cavity. The key observation is that by
choosing α correctly, you can completely eliminate the
coupling between AM and FM laser noise, so that besides excellent
laser stability, you can also get outstandingly stable amplitude
measurements by forming the combination
A = T+αR. If you choose the right value of
α = -(dT/dν) / (dR/dν), then
so none of the FM noise of the laser gets turned into AM noise.
(I'm not entirely certain that I was the first one to do this, but
that was pretty early days for diode laser based instruments.)
When combined with laser noise cancellation to get rid of the
actual AM noise of the laser, this scheme lets you do shot-noise
limited measurements inside a passive resonant cavity, which is a
very useful trick.
A modern telecom DFB laser doesn't current-tune very
far. It's easy to say, but a lot of design effort has gone into
making this happen. DWDM channels are very closely spaced; when
you current-modulate one laser to send some data, you don't want
it to scribble all over the adjacent channels. That's
excellent for telecoms, but inconvenient for laser
stabilization, because the tuning range is too narrow.
Thus this design needed a combination temperature- and
current-tuning loop. Only current-tuning could achieve the
required feedback loop bandwidth, and only temperature tuning
could cover the required wavelength range. The breadboard
prototype worked very well, in fact well enough to advance the
state of the measurement art, but funding ran out before the
actual downhole version could be completed. There were a few very
interesting temperature-control concepts that came out of this
work as well. I'd very much like to revisit it if I have the
Instrumentation: Nanowatt Photodetector The standard problem with conventional nanowatt photoreceivers
is that in order to get near the shot noise, you have to use
feedback resistors so gigantic that you can't maintain decent
This one has what I think is a completely novel photo-feedback
architecture, i.e. rather than using a feedback resistor in
the TIA, it uses two secondary photocurrents to cancel the input
current. Putting the two secondary photodiodes in series makes
the cancellation current 3 dB quieter than the shot noise, and a
feedback system prevents them from fighting, as series-connected
current sources normally would.
This results in a noise floor asymptotically only
10 log(1.5) ≈ 1.76 dB above the shot noise of
the signal photocurrent, instead of 3 dB for straight
Ad Hoc Optical Battlefield Network:
Optical Data Receiver This was a collaboration with Chris Wieland of Della
Enterprises on an Army Research contract.
Carrier Flight Deck Optical Communications Link Photon Budget and
Optical Data Receiver
This one was a somewhat similar application for the Navy.
Long-range IR transceiver For a large Far
Eastern consumer electronics manufacturer to use in virtual
reality games. A greatly improved transimpedance amplifier got them a
factor of 10 in range (30 m vs. 3 m) for about
the same amount of power.
Nano-Antennas for Thermal Infrared Pixels This was a seedling design study for a DARPA program that
never got funded. It leveraged POEMS and my antenna-coupled
tunnel junction devices, adding a couple of novel wrinkles:
metal-insulator-metal varactors and parametric readout using a 10
GHz pump frequency. Hopefully there will be a chance to revisit
this, because it was potentially a pretty sweet solution.
Touch Panel Displays: Low-Cost Optical Front End In cooperation with Flatfrog Laboratories AB, Lund, Sweden.
This one was interesting mostly due to the requirement for
high and stable performance at an absolute rock-bottom cost.
Polymer Dosimeter For a start-up: HV power supply and
readout electronics for a low-cost radiation dosimeter.
Photon Budgets and Performance Calculations How well can it
One of our specialties is calculating the expected performance of
electro-optical systems: you can't know if it's any good unless
you know how good it could be.
Shot-noise limited detectors
Laser measurement systems of all sorts
Ultrasensitive front ends
Noise cancelling detectors
Ultralow drift optics and electronics
Laser heterodyne receivers
3-D Electromagnetic simulation and device synthesis
Laser safety limits for free space optical communications
Beam propagation in the atmosphere
Noise and interference sources
Design Support Consulting Smaller jobs helping folks with design, debug, and
RF Design for Ion Trap Mass Spectrometer RGA Producing an integrated model of circuit conditions and ion
motion, allowing optimization of circuit and excitation
parameters, plus sanity checking
EUV Lithography: Tin Droplet Detection System When you're hitting a droplet with enough pulsed CO2
light to generate X-rays efficiently,
you have to know exactly when it's going to cross the focus.
TIA front ends for compressive-scan cameras A shootout between the two major classes of transimpedance
amplifier (TIA) designs for one difficult corner of the design
Downlink for Antisubmarine Warfare (ASW) sonobuoys Another Della project for the Navy: I did a photon budget that
showed that this could be done optically within the power and
weight constraints, and would work in bright sun as well as at
night. (Optical communications are much harder to intercept or to
jam than radio.)
head-mounted projection displays I chaired a series of formal design reviews for a start-up
company making immersive displays with resolution better than the
touchscreens This was for a midsize start-up making very large,
high resolution touchscreen displays—they needed an outside
pair of eyes to do some sanity checking of a couple of their
detectors based on optical coherence
tomography This was a photon budget for an OCT system—interesting
primarily for the effect of path delay in turning FM noise in
the superluminescent diode (SLD) into AM noise in the measurement.
Resonance Spectrometer Use of my laser noise canceller to achieve shot-noise limited
performance in SPR spectroscopy (in cooperation with Xi Wang and
Andre Knoesen of UC Davis, and a bunch of my friends at IBM Almaden
Refrigeration Thermoacoustic fridges are magic: you heat one end, and the
other end gets cold. (Of course you have to sink all that
heat from the middle.) They can easily be made long and skinny, and
so are a natural for use down drillholes. They're also made
entirely of metal, and have no moving parts, so they will
survive bouncing around in the back of a truck.
This was a design study for a general purpose fridge for 2-inch
cased holes (38 mm maximum OD) that would solve many of the
temperature problems of downhole operation for a wide variety of
Drift and 1/f Noise at 70-90 °C
Sometimes you have to find out things that aren't in the
datasheet, and even the manufacturer may not know.
Expert Witness Cases Testifying expert in patent and trade secret
cases There's also my detailed case
Texas Advanced Optoelectronic Solutions, Inc. v.
Testifying defense expert in an action for patent
infringement and trade
secret misappropriation after unsuccessful negotiations for an
acquisition. After a wait of almost exactly three years,
we received a claim construction ruling in June 2013.
February 15, 2015: At trial.
v. Banyan Energy A patent interference case concerning solar
concentrators, this one settled quickly.
v. Lockheed Martin Testifying expert representing Lockheed Martin in an action
for alleged patent infringement in optical particle counting.
December 23, 2013: Based in large
part on my expert reports and reverse engineering of
accused products, Judge O'Connell granted Lockheed Martin's
Request for Summary Judgment.
Nintendo of America, et al. Testifying expert representing ThinkOptics in an action for
patent infringement concerning video games, specifically the human
interface of the Nintendo Wii.
February 15, 2015: Settled after an
Technology Research Institute
LG Corporation, et al. Testifying expert representing ITRI in an action for patent
infringement concerning optical discs.
Voxpath RS, LLC
Desay A&V Science and Technology Co. Ltd, et al. Testifying defense expert representing Samsung in an action
for patent infringement concerning optical storage, holographic
optical elements, tracking servos, and signal integrity.
DCG Systems, Inc.
v. Checkpoint Technologies, LLC:
Testifying defense expert in an action for patent infringement
concerning solid-immersion microscopy and laser voltage
measurement in semiconductors.
April 2012: Wrote claim construction declaration;
May 1, 2012: Gave deposition in support of
claim construction declaration;
May 23, 2012: Assisted in tutorial
December 2012: Case settled
v. Oplink Communications, Inc.
Testifying defense expert in an action for patent infringement in
GBIC optical transceivers. Advised and performed some reverse
(settled quickly in 2011)
NTech Industries, Inc. v. Holland Scientific, Inc.
Testifying defense expert in an action for patent infringement in optical
sensors for precision agriculture. Prepared expert reports on
noninfringement and invalidity. The case settled very favourably
in 2009, shortly before my scheduled deposition.
hobbs @ electrooptical.net
Send me an email and let's talk about your application. Comments,
corrections, suggestions, or questions are also welcome.
Innovations LLC, 160 North State Road, Suite 203,
Briarcliff Manor, NY 10510 (914) 236-3005