Flame Spectrometer’s Flexible  Design

Our new Flame Spectrometer employs the classic Ocean Optics model of modular design and build to order options that let you optimize the system to best meet your needs!  Better manufacturing techniques, faster, quieter electronics and even greater modularity are incorporated. The legacy of this approach goes back to the original S1000 spectrometer invented in 1992. With the options now available, the number of primary model variations is 4,680!  If we include the option of starting wavelength, the number of variations grows even bigger. We set out to build spectrometers that could meet ANY need, and we come very close to meeting that goal.

Flame Spectrometer De-constructed!

Flame Spectrometer Deconstructed - Spectrecology

 

Flame Spectrometer – Function and Options

The 10 parts to the Flame optical bench and detector are labeled in the image to the right.

Click on the item below to expand and view all the details

Spectrecology - Flame optical bench design

Light from a fiber enters the optical bench through the SMA 905 Connector. The SMA 905 bulkhead provides a precise location for the end of the optical fiber, slit, absorbing filter and fiber clad mode aperture. While we supply SMA connectors as standard, FC connectors are also available. We also offer a screw on lens to convert the optical fiber port into a free-beam port.
Light passes through the installed slit, which acts as the entrance aperture. Slits come in various widths from 5 µm to 200 µm. The slit is fixed in the SMA 905 bulkhead to sit against the end of a fiber. Smaller slit sizes achieve the best optical resolution while larger slits have higher light throughput. Slit size is labeled as shown.

Cheangeable slits for Ocean Optics spectrometers - Spectrecology

Slit Description Pixel Resolution
INTSMA-5 5-µm wide x 1-mm high ~3.0 pixels
INTSMA-10 10-µm wide x 1-mm high ~3.2 pixels
INTSMA-25 25-µm wide x 1-mm high ~4.2 pixels
INTSMA-50 50-µm wide x 1-mm high ~6.5 pixels
INTSMA-100 100-µm wide x 1-mm high ~12 pixels
INTSMA-200 200-µm wide x 1-mm high ~24 pixels
INTSMA-000 Interchangeable bulkhead with no slit NA
INTSMA-KIT Interchangeable SMA Kit  connectors; 5µm; 10µm; 25µm; 50µm; 100µm and 200µm NA

Ocean Optics also offers a range of FC connector slits in the same slit widths, with the product code INTFC-XXX. An INTFC-KIT is also available. Note that these items are made to order and have a longer lead time.

If selected, an absorbing filter is installed between the slit and the aperture in the SMA 905 bulkhead. The filter is used to limit bandwidth of light entering spectrometer or to balance color. Filters are installed permanently. A filter is for a specific slit. If you anticipate needing the filter with multiple slit sizes, then you must specify this at the time you order. You will know which filter is installed in each slit because of the color-coded dots on the outside as shown in the figure and described in the table below.

Spectrecology long pass filter in slit assembly color code

Item Code Description Dot 1 Dot 2
OF1-BG28 Bandpass filter, transmits >325 and <500 nm blue red
OF1-WG305 Longpass filter; transmits light >305 nm black white
OF1-U325C Bandpass filter, transmits >245 and <390 nm white green
OF1-GG375 Longpass filter; transmits light >375 nm red black
OF1-GG395 Longpass filter; transmits light >395 nm white red
OF1-CGA420 Longpass filter; transmits light >420 nm orange white
OF1-GG475 Longpass filter; transmits light >475 nm green green
OF1-OG515 Longpass filter; transmits light >515 nm pink yellow
OF1-OG550 Longpass filter; transmits light >550 nm orange orange
OF1-OG590 Longpass filter; transmits light >590 nm red pink
OF1-RG695 Longpass filter; transmits light >695 nm white blue
OF1-RG830 Longpass filter; transmits light >830 nm black blue
OF1-CGA1000 Nonfluorescing longpass filter, transmits >1000 nm red green
OF1-CGA760 Nonfluorescing longpass filter, transmits >760 nm blue black
OF1-CGA780 Nonfluorescing longpass filter, transmits >780 nm white yellow
OF1-CGA830 Nonfluorescing longpass filter, transmits >830 nm green orange
OF1-CGA475 Nonfluorescing longpass filter, transmits >475 nm yellow pink

The collimating mirror is matched to the 0.22 numerical aperture of our standard optical fibers. Light reflects from this mirror, as a collimated beam, toward the grating. You can opt to install a standard Al mirror or a NIR-enhancing but UV absorbing special coated Ag (SAG+) mirror.

SAG+ mirrors are often specified for fluorescence. These mirrors absorb nearly all UV light, which reduces the effects of excitation scattering in fluorescence measurements. Unlike typical silver-coated mirrors, the SAG+ mirrors won’t oxidize. They have excellent reflectivity — more than 95% across the VIS-NIR.

Mirror Options for Ocean Optics spectrometers - Spectrecology

We install the grating on a platform that we then rotate to select the starting wavelength you have specified. Then we permanently fix the grating in place to eliminate mechanical shifts or drift.

Spectrecology grating spectrometers

Flame and USB Series Custom Configured Gratings and Wavelength Range

Gratings for Ocean Optics spectrometers are permanently fixed in place at the time of manufacture to ensure long-term performance and stability. Choose from among multiple gratings for your custom configured spectrometer. When selecting your grating, consider groove density (resolution), spectral range (wavelength range) and blaze wavelength (determines the most efficient range). We offer ruled and holographic diffraction gratings. Holographic gratings produce less stray light while ruled gratings are more reflective, resulting in higher sensitivity.

Tip: Use our interactive Range & Resolution Calculator to determine your spectrometer’s anticipated optical resolution over a specific wavelength range.

Grating
Number

Intended Use

Groove Density

Allowable
Start
Wavelength

Typical
Spectral
Range*
(nm)

Blaze
Wavelength

Best
Efficiency (>30%)
(nm)

1

UV

600

150-400 nm

700-670

300 nm

200-575

2

UV-VIS

600

150-400 nm

700-670

400 nm

250-800

3

VIS-Color

600

300-500 nm

680-660

500 nm

350-850

4

NIR

600

400-700 nm

670-630

750 nm

530-1100

5

UV-VIS

1200

150-250 nm

325

Holographic UV

200-400

6

NIR

1200

425-880 nm

320-250

750 nm

500-1100

7

UV-VIS

2400

150-350 nm

170-140

Holographic UV

200-500

9

VIS-NIR

1200

330-600 nm

325-300

Holographic VIS

400-800

10

UV-VIS

1800

150-510 nm

235-175

Holographic UV

200-635

11

UV-VIS

1800

320-800 nm

210-110

Holographic VIS

320-720

12

UV-VIS

2400

150-640 nm

170-70

Holographic VIS

260-780**

14

NIR

600

450-725 nm

670-630

1000 nm

650-1100

31

UV-NIR

500

150-250 nm

925

250 nm

200-450

* Spectral range will be smaller when starting wavelength is longer. Spectral range also depends on exact spectrometer model. Please use our Range & Resolution Calculator tool for best approximation of spectral range.

** For applications >720 nm, please consult an Application Sales Engineer.

Groove Density:

The Groove Density (mm-1) of a grating determines its dispersion, while the angle of the groove determines the most efficient region of the spectrum. The greater the groove density, the better the optical resolution possible, but the more truncated the spectral range.

Spectral Range:

The dispersion of the grating across the linear array; also expressed as the “size” of the spectra on the array. The spectral range (bandwidth) is a function of the groove density and does not change. When you choose a starting wavelength for a spectrometer, you add its spectral range to the starting wavelength to determine the wavelength range. For several gratings, the Spectral Range of a grating varies according to the starting wavelength range. The rule of thumb is: the higher the starting wavelength, the more truncated the spectral range.

Blaze Wavelength:

For ruled gratings, the Blaze Wavelength is the peak wavelength in an efficiency curve. For holographic gratings, it is the most efficient wavelength region.

Best Efficiency (>30%):

All ruled or holographically etched gratings optimize first-order spectra at certain wavelength regions; the “best” or “most efficient” region is the range where efficiency is >30%. In some cases, gratings have a greater spectral range than is efficiently diffracted. For example, Grating 1 has about a 650 nm spectral range, but is most efficient from 200-575 nm. In this case, wavelengths >575 nm will have lower intensity due to the grating’s reduced efficiency.

This mirror focuses first-order spectra on the detector plane. Both the collimating and focusing mirrors are made in-house to guarantee the highest reflectance and the lowest stray light possible. You can opt to install a standard Al or special coated Ag (SAG+) mirror. As with the collimating mirror, the mirror type needs to be specified when ordering.

Mirror Options for Ocean Optics spectrometers - Spectrecology

This optional cylindrical lens is fixed to the detector to focus the light from the tall slit onto the shorter detector elements. It increases light-collection efficiency and reduces stray light. The slit height in our spectrometers is 1mm. However the illuminated portion of the slit is equal to the diameter of the fiber that is connected to the spectrometer.  When using large fibers, the lens focusses more of the light onto the 200um tall sensor pixels. For small fibers, such as 50um core, the lens doesn’t appreciably affect signal strength.

L2 and L4 detector lenses - Spectrecology

There are two choices of detector available for the Flame. We offer a 2048-element FLAME-S (Sony ILX511B) or a 3648 element FLAME-T (Toshiba TCD1304AP) linear CCD array. These both have an effective range of 190-1100 nm. The optics split the light into its component wavelengths which fall across the different pixels. Each pixel responds to the wavelength of light that strikes it. The detector outputs an analog signal from each pixel that is converted via the ADC into a digital signal. The driver electronics process this signal and send the spectrum via the USB connection to the software. The best choice of detector will depend on the application.

Detector Specification

Specification S Type (FLAME-S) T Type (FLAME-T)
Detector: Sony ILX511B linear silicon CCD array Toshiba TCD1304AP linear silicon CCD array
Strengths:
  • Strong response < 350nm, good for UV measurements.
  • Fast data output rate.
  • Larger pixel size improves sensitivity
  • Slightly higher SNR due to well depth
  • Larger number of pixels can offer better resolution with small slits.
  • Electronic shutter
Watch for: N/A – Offers strong all-around performance
  • Signal lag at low integration times
  • Signal may bleed to neighboring pixels at high intensities (blooming)
  • Higher minimum integration time

 

Detector specifications sheets:

Toshiba-TCD1304AP-CCD-array

SONY-ILX511B

Our proprietary filters precisely block second- and third-order light from reaching specific detector elements. Light reflected off the grating can propagate 2nd and 3rd order effects at whole multiples of the incident light wavelength. So, for example, 250nm light hits the first order position at 250nm, and the second order position at 500nm.  While 2nd order is generally weaker than first order signals, they are troublesome when looking at broad band spectra.. Order sorting filters reject this stray light only allowing the desired 1st order wavelength through to the detector.

Order sorting filters are installed on detectors and are listed in the detector selection pane below. They are only available at set wavelength ranges, as the filters have to be fabricated to align all the proper blocking bands to specific ranges on the detectors. These must be specified at the time of ordering.

The standard BK7 glass window on the detector absorbs light < 340nm. For applications in the UV, < 360nm, we recommend the UV quartz detector window upgrade. This replaces the BK-7 glass with Quartz. Typically these are used in conjunction with an OFLV order sorting filter to block the impact of 2nd and 3rd order effects at higher wavelengths.

Detector Description Spectrometer
DET2B-200-535 Sony ILX511B detector, installed, with Custom OFLV Coated Window Assembly for Grating#5 and Grating#5U, S-bench FLAME-S
DET2B-200-850 Sony ILX511 detector, installed, with 200 – 850 nm variable longpass filter and UV2 quartz window;
Best for UV-VIS systems configured with Grating #1 or #2
FLAME-S
DET2B-200-1100 Sony ILX511 detector, installed, with 200 – 850 nm variable longpass filter and UV2 quartz window;
Best for UV-VIS systems configured with XR-1 grating
FLAME-S
DET2B-350-1000 Sony ILX511 detector, installed, with 350 – 1000 nm variable longpass filter;
Best for VIS systems configured with Grating #2 or #3
FLAME-S
DET2B-UV Sony ILX511 detector, installed, with UV2 quartz window;
Best for systems configured for <360nm
FLAME-S
DET2B-VIS Sony ILX511 detector, installed, with VIS BK7 window;
Best for systems configured for >400nm
FLAME-S
DET4-200-535 Toshiba TCD1304AP detector, installed, with Custom OFLV Coated Window Assembly for Grating#5 and Grating#5U, S-bench FLAME-T
DET4-200-850 Toshiba TCD1304AP detector, installed, with 200 – 850 nm variable longpass filter and UV2 quartz window;
Best for systems configured with Grating #1 or #2
FLAME-T
DET4-200-1100 Toshiba TCD1304AP detector, installed, with 200 – 850 nm variable longpass filter and UV4 quartz window;
Best for systems configured with XR-1 grating
FLAME-T
DET4-350-1000 Toshiba TCD1304AP detector, installed, with 350 – 1000 nm variable longpass filter;
Best for VIS systems configured with Grating #2 or #3
FLAME-T
DET4-UV Toshiba TCD1304AP detector, installed, with UV4 quartz window;
Best for systems configured for <360 nm
FLAME-T
DET4-VIS Toshiba TCD1304AP detector, installed, with VIS BK7 quartz window;
Best for systems configured for >400 nm