Flat Field Fiber System (Wide Flat)
- Steve Gibson
Table of Contents:
Introduction
The flat field fiber system (also known as the “wide flat” system) is used to project broadband light onto the main spectrometer CCDs. The projected light consists of a series of bands (one per echelle diffraction order), with each band being wider in cross-dispersion than the five orderlets from the Science, Sky and Simultaneous Cal fibers. This allows one to flat field and calibrate the response of pixels both within the orderlets, and also between and outside of the orderlets (which are normally not illuminated).
The system consists of a broadband source, a shutter, and a filter wheel (or in this case an aperture wheel). The aperture wheel is populated with various apertures, which are used to change the f/# of the beam leaving the output fiber (as shown below). This in turn changes the width of the bands in cross-dispersion on the main spectrometer CCDs and allows one to adjust the band overlap.
Note that a shutter is included to set the wide flat image exposure times.
Within the aperture wheel there is also a blank port, which allows no light to pass. This should be in-beam whenever the wide flat system is not in use, to prevent accidental stray light entering the main spectrometer vacuum chamber.
Relevant Devices
Descriptions | Qty | Source | Part Number | Notes |
|---|---|---|---|---|
Filter Wheel | 2 | Thorlabs | FW102C | RS-232 connectivity
|
RS-232 to Ethernet Adapter | 1 | Lantronix | UDS2100 | This is the version with two serial ports (and standard 9-pin RS-232 connectors) |
Smaller Footprint Power Supply for Lantronix | 1 | Tri-Mag, LLC | Tri-Mag PN: L6R12H-120 DigiKey PN: 364-1264-ND | The stock Lantronix power supplies do not work well with the PDUs (as they block two extra outlets). KPF uses these replacement supplies since they only take up one PDU outlet. |
Broadband Source | 1 | Thorlabs | SLS201L | |
Shutter Controller | 1 | Uniblitz | VED24 |
|
Shutter | 1 | Uniblitz | DSS25B1T0 | 25mm Optical Shutter Bi-stable (only requires power for transitions) Ordering options:  |
Relevant Functional Block Diagrams & Cable Details
Cable | Qty | Details | Notes |
|---|---|---|---|
Ethernet | 1 | Cat6 Copper Ethernet Cable M-M, 6 feet long | Entirely within Cal Rack. |
Flat Field Fiber Filter Wheel RS-232 | 1 | See Calibration Rack External Cables | Calibration Rack to Calibration Unit Interconnects | |
Flat Field Fiber Filter Wheel Power | 1 | See Calibration Rack External Cables | Calibration Rack to Calibration Unit Interconnects | |
DB9 Right-angle M-F Adapter | 1 | Premium DB9 right angle male to female Adapter alt orientation | Allows for a strain-relief loop on the serial cable within the Flat Field Fiber enclosure. |
Cable | Qty | Details | Notes |
|---|---|---|---|
Flat Field Fiber Shutter | 1 |
| |
Uniblitz-Supplied 510F Cable | 1 | Ships with Uniblitz VED24 Shutter Controller |
|
Uniblitz-Supplied 5M203D Cable | 1 | Ships with Uniblitz VED24 Shutter Controller |
|
Cable | Qty | Details | Notes |
|---|---|---|---|
Input Fiber | 1 | Thorlabs Custom Patch Cable | These were ordered using the Thorlabs custom fiber builder online: Custom Fiber Optic Patch Cables |
Output Fiber | 1 | Thorlabs Custom Patch Cable | |
SMA-SMA Adapter | 2 | Thorlabs ADASMAV - Vacuum-Compatible SMA to SMA Mating Sleeve | One needed on external (air) side of flange, one needed on internal (vacuum) side |
Vacuum Fiber | 1 |  A 5m-long custom version of the standard 1m Thorlabs MV64L1. | This internal (vacuum) fiber is not shown on the diagram but included here for reference. This fiber carries light between the feedthrough above and the flat field fiber lens above the reformatter. |
Pictures of Devices
Look-up Table for Filter Wheel Aperture Positions
Position | Short Name | Part Number | Description |
|---|---|---|---|
1 | Blank Port | Thorlabs SM1PL | Externally SM1-Threaded Plug |
2 | 6 mm aperture (f/5) | KPF-FFF-MEC-205 | 6 mm diameter aperture feeds fiber at f/5 |
3 | 7.5 mm aperture (f/4) | KPF-FFF-MEC-204 | 7.5 mm diameter aperture feeds fiber at f/4 |
4 | 10 mm aperture (f/3) | KPF-FFF-MEC-203 | 10 mm diameter aperture feeds fiber at f/3 |
5 | 13.2 mm aperture (0.22 NA) | KPF-FFF-MEC-202 | 13.2 mm diameter aperture feeding fiber at f/2.3 (sized to match NA of flat field fiber within vacuum chamber) |
6 | Open Port (f/1.4) | - | No aperture disk (aperture set by 22.9 mm diameter of open filter wheel port) |
Relevant Datasheets & Manuals
Description | File | Source | |
|---|---|---|---|
| 1 | Device Manual | 
| |
| 2 | Software Manual |  | |
| 3 | SDK |  | |
| 4 | Lantronix UDS 2100 Quick Start Guide |  | https://www.lantronix.com/products/uds2100/#tab-docs-downloads
|
| 5 | Lantronix UDS 2100 User Guide |  | |
| 6 | Smaller Footprint Power Supply Datasheet |  | https://www.tri-mag.com/wp-content/uploads/2021/05/L6R12H_Series_2021-01.pdf (Linked off the DigiKey product page) |
| 7 | Uniblitz VED24 Controller Datasheet |  | |
| 8 | Uniblitz VED24 Controller Manual
|  | |
| 9 | Uniblitz DSS25B Shutter Datasheet |  | |
| 10 | Uniblitz DSS25B Shutter Solid Model
|  |