KPF Cameras
Winlight Inspection Reports
Entire Camera - Green
Description | Date | File |
|---|---|---|
Final Inspection - Green | Sept. 28, 2021 |
Camera Coatings - Green
Description | Date | File |
|---|---|---|
Coating Inspection | May 25, 2021 |
Individual Lenses - Green
Description | Date | File |
|---|---|---|
Green L1 (Asphere) | Sept. 28, 2021 | |
Green L2 | Sept. 28, 2021 | |
Green L3 | Sept. 28, 2021 | |
Green L4 | Sept. 28, 2021 | |
Green Field Lens (Cylinder) | Sept. 28, 2021 |
Entire Camera - Red
Description | Date | File |
|---|---|---|
Final Inspection - Red | Jan. 3, 2022 |
Camera Coatings - Red
Description | Date | File |
|---|---|---|
Coating Inspection | Nov 23, 2021 | |
Camera Throughput Calculation | Received |
Individual Lenses - Red
Description | Date | File |
|---|---|---|
Red L1 (Asphere) | Feb 19, 2021 | |
Red L2 | Jan 25, 2021 | |
Red L3 | Dec. 3, 2020 | |
Red L4 | Dec. 3, 2020 | |
Red Field Lens (Cylinder) | Sept. 28, 2021 |
Green Camera Pre-Ship Compliance
KPF Requirement Topic | KPF Requirement Text | Verification Method | Compliant? | |
|---|---|---|---|---|
| 1 | Pass band | Green: 445 nm to 599 nm | Inspection, Analysis | Yes, described in Justificative Report. Wavelengths verified in Zemax file. |
| 2 | Throughput | The end-to-end throughput requirements for each of  | Test | Yes, described in coating inspection report WS-PVR1155-A. |
| 3 | Image quality and stability | The imaging specifications are shown in Table 3. Imaging requirements include the design residual, alignment, fabrication and environmental tolerances and may be met with compensation. Because each channel’s VPHG disperses nearly parallel-beam incident light at an approximate pupil to the camera, the imaging performance requirements are chromatic, that is the camera design will only achieve geometric blur requirements when tested at the actual wavelength associated with a given location on the detector. These performance requirements apply to all of the output objects as defined by the KPF Reformatter unit. The Reformatter’s output fields are also given in the full spectrograph system Zemax optical model. A Zemax model is also provided with point source fields at its output in place of the Reformatter fields. These performance requirements apply to the Camera at its operating environment, with the CCD sensor at its cryogenic temperature (-110C +/- 0.1 C TBC) and held within an isothermal radiative environment at 20C +/- 0.1 C. These performance requirements are defined separately for:
The 1FSR range is defined in Table 3a for each of the nine orders defined in the Zemax design. Wavelengths in a particular order are considered to fall inside or outside of 1FSR if they are between the cut-on and cut-off wavelengths defined in that order. The same requirements will be met for both the green and red cameras. | Test | Yes, described in final inspection report WS-PVC3963-A. |
| 4 | 'Nice to have' goals | Imaging Performance Goals for KPF Science KPF radial velocity science performance may benefit by considering these imaging optimization goals that mitigate unwanted perturbations to the PSF centroid location. Goals for PSF symmetry Goal: The shape of the PSFs across a single order should be symmetric about the center of the order Cause: Pupil variations may cause the centroid to shift differently for each wavelengths PSF. If there is PSF symmetry about an orders’s center, then the average shift of all spots across an order will be minimized because spots will shift in opposite directions across the centerline Goal for PSF similarity Goal: The shape of the PSF within a single order should be similar. Cause: Observed spectra will shift within an order at different observing epochs. If PSF similarity exists within an order, then a PSF’s centroid will appear consistent at different epochs. | Analysis | Yes Within Justificative Report they claim they meet these goals because they're using the prescription that KPF provided which was based on these goals, and that any asymmetries are generated in the spectrometer and not within the camera (seems reasonable) |
| 5 | Focal Length | The effective focal length in the x-direction (EFLX in Zemax) at the center of the field shall be 495 mm ± 0.25% (TBC), for both green and red cameras. The effective focal length in the y-direction (EFLY in Zemax) at the center of the field shall be within 5mm of the EFLX value. These values may be different from previous optical prescriptions of the cameras, when focal length may not have been well specified. | Inspection, Analysis | Yes, described in final inspection report WS-PVC3963-A. |
| 6 | Camera unit Definition | The Camera Unit consists of three separate subassemblies, the lens barrel assembly (LBA), the field lens assembly (FLA) and the Grism Mount Assembly (GMA). The FLA will connect after delivery to the CCD cryostat to form a vacuum sealed unit. The cryostat is attached to the camera assembly to form a functional Camera. The Grism Mount Assembly attaches to the LBA. | Inspection | Yes, met by design. Described in Green Camera Mechanical report (WS3088-001-RAP002-A) |
| 7 | Camera unit ICD | The Camera Mechanical ICD shows interface details for joining the Camera to the optical bench mount and to the detector cryostat. The camera unit shall include an alignment cube to allow for metrology during camera integration and performance testing as well as for spectrograph alignment & integration. The camera unit shall include features to facilitate lifting and lowering the camera barrel and assembly. | Inspection | Yes, ICD pages are shown in camera final inspection report WS-PVC3963-A with majority of dimensions verified for as-built part. Final WL mechanical model verified within KPF optical bench model. |
| 8 | Camera unit vacuum compatibility | All elements and regions of the Camera Unit shall be constructed for compatibility with repeated evacuation from atmospheric pressure to high-vacuum conditions, i.e. all internal cavities shall be vented (the purge port can be considered a way to vent the camera main internal volume). All elements and regions shall use clean, high-vacuum compatible materials, including any bearings. | Inspection | Yes, met by design. Winlight also vacuum-tested camera mechanical assembly before installation of optics (Justificative Report said they would do this at 90C) |
| 9 | Camera unit mass | The estimated total mass of the Camera Unit, including the mounted GMA and the FLA, shall not exceed 90 kg ±10% without the notification and approval of KPF. | Inspection | Yes, described in final inspection report WS-PVC3963-A. |
| 10 | Camera unit – natural frequency | The mounted Camera Unit assembly, including the grism assembly, shall have a natural harmonic frequency exceeding 100 Hz. | Analysis | Yes, described in Green Camera Mechanical report (WS3088-001-RAP002-A). |
| 11 | Camera unit – Grism setting | The Grism Specification Drawings describe the Grism elements and their positioning requirements, form and mass properties. The final mounting angle in the Grism dispersion plane with respect to the Camera axes will not be known to better than +/-1 degree before the Grism is produced and examined. The Grism mount must accommodate the ability to set the dispersion mounting angle to a precision of 0.1 degree using fixed adjustment (such as shims) and not using a mechanism. | Inspection | Yes, met by design. |
| 12 | Lens Barrel and Field Lens Assemblies Materials | The Camera Unit shall be designed using materials to provide thermal compensation so that optical performance over the specified thermal operation range will be satisfied. Lenses must use densified coatings or equivalent to ensure satisfaction of operational vacuum and humidity requirement. Magnesium Fluoride coatings may not be used on the Field Lens due to the potential of damage by condensation. | Analysis | Yes. Athermalization met by design. Justificative report mentions use of densified coatings and avoidance of MgF2. Emails about coatings describe densified coatings. |
| 13 | Focus Method & Access | The Camera Unit Design shall allow for adjustment of the optical focus on the CCD sensor to compensate for as-built compensation within the Camera optics, as-built defocus errors in the spectrograph optics, and for variations in atmospheric operating and test conditions (sea-level, mountain-top, high vacuum). The method of focal adjustment is to vary the axial positioning of the FLA-cryostat assembly with respect to the LBA. The focus adjustment shall use fixed spacers and not an adjusting mechanism and not require removing the cryostat from the Camera or exposing the camera internals to the outside environment. | Inspection | Yes, met by design. |
| 14 | GMA Integration and Alignment | The GMA shall be integrated with the LBA. They shall be relatively aligned to the nominal separations defined in the green and red camera optical prescriptions. The nominal separations may be updated slightly if the camera optical prescription changes, or if the KPF spectrometer prescription changes. The alignment tolerances shall be within 0.2mm in x,y,z, and 0.05 degrees in pitch, yaw, and clocking. Verification of the final separation may be done using mechanical measurements. Note that the provided grism contains a grating, and the grating substrate edges may not be parallel to the grating grooves, by up to 1 degree error. The prism grooves will be well aligned to the prism, therefore when the grism is aligned to its nominal clocking position (based on the grooves), the grating substrate may be clocked by up to 1 degree. The GMA mount must have sufficient clearance to accept this possible 1 degree error of the grating substrate. KPF will have knowledge of this angle error several months before the grism is delivered to Winlight. | Inspection | Description given in Winlight final report is "with respect to camera optical axis" which must be a typo as that is mechanically impossible. Will ask Winlight. If numbers given within final report are "with respect to nominal" (as I suspect) then they easily meet our alignment tolerances. |
| 15 | GMA Alignment Adjustment | The Camera Unit Design shall allow for adjustment by the customer of the GMA with respect to the LBA, in pitch, yaw, and clocking directions. The resolution of the adjustments shall be less than 0.03 degrees in pitch, yaw, and clocking. The range of the adjustments shall be at least ±0.4 degrees, in pitch, yaw, and clocking, with the ranges centered on the nominal angular position of the GMA as defined in the prescriptions. | Inspection | Yes, met by design. |
| 16 | Optical Scattering, Baffling & Cleaning - Stray light | The camera design shall minimize stray light propagation and scattering and exclude outside light. The outer edges of lenses, and any lens barrel and lens clamp surfaces that are visible to the focal surface shall be coated with low reflectivity and low scatter material having < 5% TIS that is compatible with adjacent materials and operating at clean high vacuum (Total Mass Loss (TML) < 1% and Collected Volatile Condensable Material (CVCM) < 0.1%). Surface treatments shall not be hygroscopic, including any coatings to reduce stray light. An inorganic black anodization treatment is acceptable. Also, an appropriate high-temperature vacuum bake of anodized parts may be done before camera part assembly to remove sulfuric acid outgassing. A low outgassing paint is also acceptable, such as Aeroglaze Z306 with vacuum baking. Baffle apertures should be considered (TBD) in the lens assembly to prevent direct scatter paths from barrel edges to the focal plane. Barrels and extended surfaces may also be grooved to prevent grazing surfaces for incident light. | Inspection | Justificative report said they would do these things and also put mechanics through thermal-vac cycle. |
| 17 | Optical Scattering, Baffling & Cleaning - Roughness | Optical elements shall be polished to a low scatter surface roughness (< 10Å RMS isotropic). | Inspection | Yes, all lens report show < 1nm RMS (< 10 A RMS) |
| 18 | Optical Scattering, Baffling & Cleaning – FLW planar extrusion | The field lens shall include a planar extension of at least 10 mm in radius beyond the working clear aperture. The extension and lens edges shall be coated with low reflectivity and low scatter material having < 5% TIS materials and operating at clean high vacuum. | Inspection | Yes, met by design. We agreed with WL's assessment in the Justificative Report to not apply the coating to the lens edges. |
| 19 | Optical Scattering, Baffling & Cleaning – Cleanliness | Particulate cleanliness Level 300 shall be maintained within the lens barrel assembly. The focus scheme shall not allow for the direct contamination of the lens barrel interior with particulate matter. Particulate cleanliness Level 500 shall be maintained on external optical surfaces. | Inspection | Likely OK, but we don't have any documentation from WL saying they did these things |
| 20 | Ghost reflections | Ghost reflections within the working image field shall not exceed an irradiance of 10-5 relative to the incident object irradiance, over more than 1% of the entire CCD sensor area (~60 x 60 mm). | Analysis | Met by analysis in Justificative Report. |
| 21 | Cleaning procedure | Cleaning procedures for supplied components shall be compatible with materials, cleanliness levels, and vacuum exposure, where required. Cleaning procedures shall be specified prior to production. | Inspection | Nothing from Winlight on these (yet?). |
| 22 | Sealing Gaps in Camera Unit | The gaps between the GMA and LBA, and also the LBA and FLA, should be sealed to keep out most light and contamination. The seal does not need to be vacuum-tight. The seal could be made with a simple labyrinth design, or a flexible bellows, or some other definitive mechanical method. | Inspection | Met by design, justificative Report describes chicanes. |
| 23 | Clear Aperture | Optics and mounts within the lens shall be oversized so that no vignetting occurs if the chief ray at the entrance pupil, compared to its ideal location, is shifted laterally by +/- 0.5 mm and in angle by +/- 5 arcminutes. | Analysis | Met by design, analysis described within Justificative Report. |
| 24 | Shipping | The camera (GMA, LBA, FLA) will be delivered as a complete unit, rather than in separate pieces. The camera shall be provided with protective covers for both input and output apertures. | Inspection | Yes, described in final inspection report WS-PVC3963-A. |
| 25 | LBA Optical & Mechanical Interface | The Camera Mechanical ICD shows the Lens Barrel assembly mounting interface requirements including the optical axis location, and the structural mounting scheme, a six-point kinematic interfaces to Zerodur shim stacks. The Grism location and interface specifications are shown in the Mechanical ICD. The LBA shall be provided with protective covers for both input and output apertures. | Inspection | Yes, ICD pages shown in WS-PVC3963-A report with majority of dimensions verified for as-built part. Final WL mechanical model also verified within KPF optical bench model. Justificative Report shows shipping cover designs. |
| 26 | FLA Optical & Mechanical Interface | The Camera Mechanical ICD shows a Field Lens Assembly interface requirements including the structural mounting, positioning, alignment, metrology and focusing features. The FLA shall be removable, and replaceable such that all performance requirements are still met. KPF would like the cryostat to be installed on the camera without needing to dismount the camera from the spectrograph, and will give information about the cryostat installation procedure and tooling (TBD). | Inspection | Yes, ICD pages shown in WS-PVC3963-A final report with majority of dimensions verified for as-built part. Final WL mechanical model also verified within KPF optical bench model. Cryostat installation procedure not expected to require additional information from Winlight. |
| 27 | FLA - Radioisotope Content | The FLA lens shall limit the use radioactive coatings or materials. Coatings shall have U ≤ 80 ppm, Th ≤ 250 ppm, and K ≤ 3.0 % (by weight), assuming a total coatings thickness of 100 μm. This will likely rule out using ThF4 and ThOF2. Glass materials shall not include elements with significant natural radioactive isotope content, such as K,U and Th. | Inspection | WL said they would pass this info on to the coating vendors. No documentation provided on what materials actually used (but this is not typically provided). Likely OK. |
| 28 | FLA - Cryo-Vacuum operation | The camera optical performance requirements shall be met when the FLA is subject to vacuum and the CCD is operating at cryogenic temperatures. The field lens is used during laboratory testing under a pressure difference from external atmospheric pressure on the lens barrel side to high vacuum (10-6 mbar) on the sensor cryostat side. The field lens may also be subject to internal pressurization during cryostat venting operations, not exceeding 1.33 atmospheres. Consequently, the field lens assembly shall include high-vacuum sealing features to the cryostat and to the field lens and shall accommodate the possibility of internal overpressure. The FLA vacuum total vacuum seal leak rate shall not exceed 10-8 mbar liter sec-1 under 1 atm external pressure. The field lens assembly shall be made with best practice for safe cryogenic vacuum or pressure operations and shall be verified by analysis or test to survive the pressure conditions. The lens shall not have any internally radiused steps unless approved by KPF, and all surfaces shall be polished or acid-etched. The vacuum side of the field lens will be located at approximately 5 mm from the cryogenic CCD active face that operates at -110°C. Consequently, the field lens will operate substantially below ambient temperature. The mounting surface to which the field lens assembly is attached will operate at a temperature shown in the environmental specifications. The operational temperature or pressure-gradient environments shall not degrade the Camera Unit’s operational optical performance requirements. | Test, Analysis | Yes. Vacuum leak rate tested, described in camera final report (WS-PVC3963-A). Temperature gradient across field lens analyzed within the Justificative Report. |
| 29 | FLA – Stress limit | Stress within the field flattener lens shall be less than 4.44 MPa for long term loads (5 years). For analysis, assume load is 1 atmosphere of external pressure. Stress within the field flattener lens shall be less than 5.55 MPa for short term loads (12 hours). For analysis, assume load is 1.3 atmospheres of internal pressure. Evaluate maximum tensile stress. | Analysis | Yes. Winlight checked this in their mechanical Justificative Report. Chris Smith also did analysis on KPF side. |
| 30 | Environmental specification | All specifications (throughput, imaging, etc.) must be met over the operational environmental range. The cameras must still be able to perform to specifications when returned to operational ranges after being exposed to the survival environmental range. The throughput must meet specifications after being exposed to the operational environments for 10 years. The camera unit as packed for shipment may be subject to shock, thermal and pressure conditions. The camera units shall be handled & shipped in such a way as to not exceed the specified survival environment. The survival range may be modified to reflect expected shipping conditions. Bonded lenses shall be subject to an analysis and test program for like materials, configuration and environmental conditions as expected for the Camera lens elements. Bonded lens assemblies shall be verified as environmentally sound by test using three temperature cycles through the survival temperature range at a slew rate of 10 C/hour, with each cycle including thermal soaks at the extreme temperature limits of no less than 12 hours. | Analysis | Yes. Justificative Report says these conditions taken into account throughout the various analysis. They did not quote on a bonding test program, and did not undertake one, so last paragraph no longer applies. |
Winlight PDR (December 20, 2019)
WL answers to several questions in table below: KPF camera - questions answers - 14-04-2020.docx
For reference, latest camera models (in SolidWorks format) are also in the vault:
Latest Winlight Data Pack - Green:
Description | File | Email Date for File | Comments |
|---|---|---|---|
Green camera justificative report | January 3, 2020 | Latest version | |
Green camera optical tolerancing | December 19, 2019 | Latest version | |
Green camera mechanical report | January 3, 2020 | Latest version | |
Green STEP file of camera assembly | June 26, 2020 | Latest version | |
Green camera overview drawing |