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USB2000
Data Sheet
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User Manual
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OCEAN OPTICS USB2000+ Data Sheet

USB2000+ Data Sheet

Description

The Ocean Optics USB2000+ Spectrometer includes the linear CCD-array optical bench, plus all the circuits necessary for spectrometer operation. The result is a compact, flexible system, with no moving parts, that's easily integrated as an OEM component.
The detector used in the USB2000+ spectrometer is a high-sensitivity 2048-element CCD array from Sony, product number ILX511. (For complete details on this detector, visit Sony’s web site at www.sony.com. Ocean Optics applies a coating to all ILX511 detectors, so the optical sensitivity could vary from that specified in the Sony datasheet).
The USB2000+ operates off of a single +5VDC supply and either a USB or RS-232 interface. The USB2000+ is a microcontroller-controlled spectrometer, thus all operating parameters are implemented through software interfacing to the unit.
A special 500 lines/mm groove density grating option used in the USB2000+XR spectrometer provides broader spectral coverage with no sac ri fice in performance. This extended-range spectrometer is preconfigured with this new grating for general-purpose UV-NIR applications.
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USB2000+ Data Sheet

Features

• ILX511 Detector
• High sensitivity detector
• Readout Rate: 2.4MHz
• Optics
• An optical resolution of ~0.3nm (FWHM)
• A wide variety of optics available
• 14 gratings, plus Grating #31for the XR version
• 6 slit widths
• 3 detector coatings
• 6 optical filters
• Electrical Performance
• 16 bit, 3MHz A/D Converter
• Integration times from 1ms to 65s
• 5 triggering modes
• Embedded microcontroller allows programmatic control of all operating parameters &
Standalone operation
• USB 2.0 480Mbps (High Speed) & 12Mbps (Full speed)
• RS232 115Kbaud
• Multiple Communication Standards for digital accessories (SPI, I
• Onboard Pulse Generator
• 2 programmable strobe signals for triggering other devices
• Software control of nearly all pulse parameters
• Onboard GPIO
• 8 user programmable digital I/O
• EEPROM storage for
• Wavelength Calibration Coefficients
• Linearity Correction Coefficients
• Absolute Irradiance Calibration (optional)
• Plug-n-Play Interface for PC applications
• 22-pin connector for interfacing to external products
• CE Certification
2
C)
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USB2000+ Data Sheet

Specifications

Specifications Criteria
Absolute Maximum Ratings: V
CC
Voltage on any pin Physical Specifications:
Physical Dimensions Weight
Power: Power requirement (master) Supply voltage Power-up time
Spectrometer: Design Focal length (input) Focal length (output) Input Fiber Connector Gratings Entrance Slit
Detector Filters
Spectroscopic: Integration Time Dynamic Range Signal-to-Noise Readout Noise (single dark spectrum) Resolution (FWHM)
Stray Light Spectrometer Channels
Environmental Conditions: Temperature Humidity
Interfaces: USB RS-232
+ 5.5 VDC Vcc
89.1 mm x 63.3 mm x 34.4 mm 190 g
250 mA at +5 VDC
4.5 – 5.5 V ~2s depending on code size
Asymmetric crossed Czerny-Turner 42mm 68mm (75, 83, and 90mm focal lengths are also available) SMA 905 14 different gratings, plus Grating #31 for the XR version
5, 10, 25, 50, 100, or 200 μm slits. (Slits are optional. In the
absence of a slit, the fiber acts as the entrance slit.) Sony ILX511B CCD
nd
2
and 3rd order rejection, long pass (optional)
1 ms – 65 sec
8
2 x 10
(system), 1300:1 (single acquisition) 250:1 single acquisition 50 counts RMS, 300 counts peak-to-peak
0.03 – 10.0 nm varies by configuration (see
www.Oceanoptics.com for configuration options)
<0.05% at 600 nm; <0.10% at 435 nm One
-30° to +70° C Storage & -10° to +50° C Operation 0% - 90% noncondensing
USB 2.0, 480 Mbps 2-wire RS-232
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USB2000+ Data Sheet

Mechanical Diagrams

Figure 1: USB2000+ Outer Dimensions
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USB2000+ Data Sheet
Pin#
Description
Alt Function
A1
A2
1 VUSB
2
Tx
3
Rx
4
LampEnable
5
ContStrobe
6
GND
7
ExtTrigIn
8 Single Strobe
9 SCL
10
SDA
11
MOSI
12
MISO
13
GPIO-1 (1P)*
14
GPIO-0 (2P)
15
GPIO-3 (1N)
Integration Clock
16
GPIO-2 (2N)
Reserved
17
GPIO-5 (3P)
Acquire Spectra (Read Enable)
18
GPIO-4 (4P)
Reserved
19
GPIO-7 (3N)
SH CCD pin
20
GPIO-6 (4N)
ICG CCD pin
Pin orientation
20 18 16 14 12 10 8 6 4 2 A2

Electrical Pinout

Listed below is the pin description for the USB2000+ Accessory Connector located on the front vertical wall of the unit. The connector is a Samtec part # IPT1-111-01-S-D-RA connector. The vertical mate to this is part #IPS1-111-01-S-D-VS and the right angle PCB mount is part #IPS1-111­01-S-D-RA.
SPI_CLK SPICS_OUT
19 17 15 13 11 9 7 5 3 1 A1
Looking at Front of USB2000+
Master Clock Base Clock
Notes:
• GPIO nP & nN notation is for future LVDS capability
• 5V Aux pin on the GPIO header is output only
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USB2000+ Data Sheet
Function Input/Output Description
VCC , V
RS232 Tx Output RS232 Transmit signal – for communication with PC connect to
RS232 Rx Input RS232 Receive signal – for communication with PC connect to
Lamp Enable Output A TTL signal that is driven Active HIGH when the Lamp Enable
Continuous Strobe
Ground Input/Output Ground Single Strobe Output TTL output pulse used as a strobe signal, which has a
ExtTrigIn Input
or 5Vin Input or Output This is the input power pin to the USB2000+. Additionally when
USB
Output TTL output signal used to pulse a strobe that is divided down from
operating via a Universal Serial Bus (USB) this is the USB power connection (+5V) which can be used to power other peripherals (Care must be taken to insure that the peripheral complies with USB Specifications). NOTE: Do not connect both USB power and Auxiliary power (as an input) at the same time.
DB9 pin 2
DB9 pin 3.
command is sent to the USB2000+
the Master Clock signal
programmable delay relative to the beginning of the spectrometer integration period.
The TTL input trigger signal. In External Hardware Trigger mode this is a rising edge trigger input. In Software Trigger Mode this is an Active HIGH Level signal. In External Synchronization Mode (or External hardware Level Trigger Mode) this is a clock input, which defines the integration period of the spectrometer.
SCL Input/Output
SDA Input/Output
Input/Output 8 2.5V General Purpose Software Programmable Digital
GPIO(0-7)
Output The SPI Master Out Slave In (MOSI) signal for communications to
MOSI
Input The SPI Master In Slave Out (MISO) signal for communications to
MISO SPI CLK
SPICS_OUT
Output Output The SPI Chip/Device Select signal for communications to other
The I2C Clock signal for communications to other I2C peripherals
The I2C Data signal for communications to other I2C peripherals
Inputs/Outputs
other SPI peripherals
other SPI peripherals The SPI Clock signal for communications to other SPI peripherals
SPI peripherals
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USB2000+ Data Sheet

CCD Overview

CCD Detector

The detector used for the USB2000+ is a charge transfer device (CCD) that has a fixed well depth (capacitor) associated with each photodetector (pixel).
Charge transfer, reset and readout initiation begin with the integration time clock going HIGH. At this point, the remaining charge in the detector wells is transferred to a shift register for serial transfer. This process is how the array is read.
The reset function recharges the photodetector wells to their full potential and allows for nearly continuous integration of the light energy during the integration time, while the data is read out through serial shift registers. At the end of an integration period, the process is repeated.
When a well is fully depleted by leakage through the back-biased photodetector, the detector is considered saturated and provides the maximum output level. The CCD is a depletion device and thus the output signal is inversely proportional to the input photons. The electronics in the USB2000+ invert and amplify this electrical signal.

CCD Well Depth

We strive for a large signal-to-noise (S:N) in optical measurements so that small signal variations can be observed and a large dynamic range is available. The S:N in photon noise-limited systems is defined and measured as the square root of the number of photons it takes to fill a well to saturation. In the USB2000+, the well depth of the CCD pixels is about 160,000 photons, providing a S:N of 400:1 (S:N can also be measured as the saturation voltage divided by near-saturation RMS noise). There is also a fixed readout noise component to all samples. The result is a system with a S:N of ~275:1.
There are two ways to achieve a large S:N (e.g., 6000:1) in CCD detectors where photon noise is predominant.
1. Use a large-well device that integrates to saturation over a long period of time until the photon
noise is averaged out by the root of n multiples of a defined short ∆t.
2. Use a small-well device that integrates to saturation at one short ∆t and then signal average
mathematically n times.
Theoretically, both approaches achieve the same results, though there are large differences in actual operation. Traditional spectroscopic instruments use large-well devices and 16-bit ADCs to achieve the defined S:N. The USB2000+ uses a small-well device and utilizes signal averaging to achieve the same S:N. A brief comparison of large and small-well devices is shown in the table below.
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USB2000+ Data Sheet
Well Depth Comparison
Large-well CCDs Small-well CCDs
Low photon noise Medium photon noise that can be averaged out Low optical sensitivity High optical sensitivity High power consumption Low power consumption >10 MHz operating speeds Moderate operating speeds (~2 MHz)

Signal Averaging

Signal averaging is an important tool in the measurement of spectral structures. It increases the S:N and the amplitude resolution of a set of samples. The types of signal averaging available in our software are time-based and spatial-based.
When using the time-base type of signal averaging, the S:N increases by the square root of the number of samples. Signal averaging by summing is used when spectra are fairly stable over the sample period. Thus, a S:N of 2500:1 is readily achieved by averaging 100 spectra.
Spatial averaging or pixel boxcar averaging can be used to improve S:N when observed spectral structures are broad. The traditional boxcar algorithm averages n pixel values on each side of a given pixel.
Time-based and spatial-based algorithms are not correlated, so therefore the improvement in S:N is the product of the two processes.
In review, large-well devices are far less sensitive than small-well devices and thus, require a longer integration time for the same output. Large-well devices achieve a good S:N because they integrate out photon noise. Small-well devices must use mathematical signal averaging to achieve the same results as large-well devices, but small-well devices can achieve the results in the same period of time. This kind of signal averaging was not possible in the past because analog-to-digital converters and computers were too slow.
Large-well devices consume large amoun ts of pow er, resul ting in the need to bui ld therm oelec tric cool ers to control temperature and redu ce el ect roni c nois e. Then , eve n mor e powe r is requ ire d for th e tem per ature stabilization hardware. But small-well devices on ly nee d to use s igna l ave ragi ng to ac hiev e the sam e results as large-well devices, and hav e the adv an tage s of remaining cool and less noisy.

Internal Operation

Pixel Definition

A series of pixels in the beginning of the scan have been covered with an opaque material to compensate for thermal induced drift of the baseline signal. As the USB2000+ warms up, the baseline signal will shift slowly downward a few counts depending on the external environment. The baseline signal is set at the time of manufacture. If the baseline signal is manually adjusted, it should be left high enough to allow for system drift. The following is a description of all of the pixels, both as they exist on the hardware device and as they are actually read from the device via USB:
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USB2000+ Data Sheet
Pixels on the Device
Pixel Description
0–11 Not usable 12–29 Optical black pixels 30–31 Not usable 32–2079 Optical active pixels 2080–2085 Not usable
Pixels Read from the Device via USB
Pixel Description
0–17 Optical black pixels 18–19 Not usable 20-2047 Optical active pixels
It is important to note that the USB2000+ only digitizes the first 2048 pixels.

CCD Detector Reset Operation

At the start of each integration period, the detector transfers the signal from each pixel to the readout registers and resets the pixels. The total amount of time required to perform this operation is ~8 − 9µs. The user needs to account for this time delay when the pixels are optically inactive, especially in the external triggering modes.

Timing Signals

Strobe Signals

Single Strobe

The Single Strobe signal is a programmable TTL pulse that occurs at a user-determined time during each integration period. This pulse has a user-defined High Transition Delay and Low Transition Delay. The pulse width of the Single Strobe is the difference between these delays. It is only active if the Lamp Enable command is active.
Synchronization of external devices to the spectrometer's integration period is accomplished with this pulse. The Strobe Delay is specified by the Single Strobe High Transition Delay (SSHTD) and the Pulse Width is specified by the Single Strobe Low Transition Delay (SSLTD) minus the Single Strobe High Transition Delay ( PW = SSLTD – SSHTD). Both values are programmable in 500ns increments for the range of 0 to 65,535 (32.7675ms).
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USB2000+ Data Sheet
External Trigger Input
φROG
Single Strobe
t_SOID+TD t_SSHTD
SOI
t_SOID Start Of Integration Delay (8.2 - 8.5us)
t_TD Trigger Delay
t_SSHTD Single Strobe High Transition Del ay
t_SSLTD Single Strobe Low Transition Delay
t_SSLTD
The timing of the Single Strobe is based on the Start of Integration (SOI). SOI occurs on the rising edge of φROG which is used to reset the Sony ILX511 detector. In all trigger modes using an External Trigger, there is a fixed relationship between the trigger and the SOI. In the Normal mode and Software Trigg er m ode, the SOI still marks the beginning of the Single Strobe, but due to the nondeterministic timing of the software and computer operating system, this timing will change over time and is not periodic. That is, at a constant integration time, the Single Strobe will not be periodic, but it will indicate the start of the integration. The timing diagram for the Single Strobe in External Hardware Trigger mode is shown below:
Single Strobe (External Hardware Trigger/External Synchronous Trigger Mode)
The Trigger Delay (TD) is another user programmable delay which specifies the time in 500ns increments that the SOI will be delayed beyond the normal Start of Integration Delay (SOID).
An example calculation of the Single Strobe timing follows: If the TD = 1ms, SSHTD = 50ms, and SSLTD = 70ms then, the rising edge of the Single Strobe will
occur approximately 51.82ms (1ms + 50ms + 8.2us) after the External Trigger Input goes high and the Pulse Width will be 20ms (70ms – 50ms).

Continuous Strobe

The Continuous Strobe signal is a programmable frequency pulse-train with a 50% duty cycle. It is programmed by specifying the desired period whose range is 2us to 60s. This signal is continuous once enabled, but is not synchronized to the Start of Integration or External Trigger Input. The Continuous Strobe is only active if the Lamp Enable command is active.

Synchronizin g St r obe Events

If the application requires more than one pulse per integration period, the user needs to insure the continuous strobe and integration period are synchronized. The integration time must be set so that an equal number of strobe events occurs during any given integration period.
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USB2000+ Data Sheet

Triggering Modes

The USB2000+ supports four triggering modes, (plus Normal mode), which are set with the Trigger Mode command. Detailed information of each triggering mode follows. Also refer to the External Triggering Options document for Firmware versions 3.0 and above located on our website at
http://www.oceanoptics.com/technical/External-Triggering2.pdf
describe these modes. For firmware version below 3.0, see
http://www.oceanoptics.com/technical/External-Triggering.pdf.

Normal

In the Normal (Free-run) mode, the spectrometer will acquire a spectrum based on the integration period specified through the software interface. This data is made available for reading as soon as all the data is stored. The spectrometer will then immed iately try to acquire two additional spectra even if none have been requested. If a new spectrum request has come from the user, during either the second or third integration cycle then the appropriate spectrum will be availab le to the use r. If a second spectrum has not been requested then the Spectrometer will not save the second or third spectrum and will go into an idle mode waiting for a new spectrum request from the user. In this scenario, a new acquisition begins when a new spectrum is requested. No further spectra are acquired until the original spectrum is read by the user.

Software Trigger Mode

. The following paragraphs
In this level-triggered mode, the spectrometer is “free running,” just as it is in the Normal mode. The spectrometer is continually scanning and collecting data. With each trigger, the data collected up to the trigger event is transferred to the software. If you continuously apply triggers (for example, by holding down the button on via an external switch), this mode is equivalent to operating in the Normal mode.
In the Software Trigger mode, you set the integration time (as well as all other acquisition parameters) in the software. The source for the integration clock comes from the A/D converter.

External Synchronous Trigger Mode

In the External Synchronous Trigger mode, two external triggers are required to complete a data acquisition. The first rising edge starts the integration period and the second rising edge stops the integration and starts the next. Thus the integration time is the period between the two external trigger pulses. After the integration period, the spectrum is retrieved and available to the user. As in normal mode, no further spectra are acquired until the original spectrum is read by the user.

External Hardware Level Trigger Mode

In the External Hardware Level Trigger mode, a rising edge detected by the spectrometer from the External Trigger input starts the integra tion per iod spe cified th rough the software interface. After the integration period, the spectrum is retrieved and is ready to be read by the user. As long as the trigger level remains active in a logic one state, back-to-back acquisitions can occur, as in the Normal mode, until the trigger transitions to an inactive level. As in normal mode, no further spectra are acquired until the original spectrum is read by the user.
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USB2000+ Data Sheet

External Hardware Edge Trigger Mode

In the External Hardware Edge Trigger mode, a rising edge detected by the spectrometer from the External Trigger input starts the integ ra tion period spe cified th roug h the softwar e interf ace. After the integration period, the spectrum is retrieved and is ready to be read by the user. If another trigger is sent a new integration cycle will begin. If a spectrum request is not received before the integration cycle has ended then that data will be deleted and a new trigger and spectrum request is required. Only one acquisition will be performed for each External Trigger pulse, no matter what the pulse’s duration is. No further spectra are acquired unti l the original spectrum is read by the user.

Digital Inputs & Outputs

General Purpose Inputs/Outputs (GPIO)

The USB2000+ has 8 user programmable 2.5V TTL digital Input/Output pins, which can be accessed at the 22-pin accessory connector. Through software, the state of these I/O pins can be defined and used for multi-purpose applications such as communications buses, sending digital values to an LCD/LED display, or even implementing complex feedback systems.
GPIO Recommended Operating Levels: VIL(max) = 0.7V VIH(min) = 1.7V
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