Requirement Document_Interferometer v2-8-13-26.docx

NIST Requirements Document For

Camera-based Fizeau interferometer Prepared By: Dimensional Metrology Group (DMG), Date: 6/22/2026

1. Background The National Institute of Standards and Technology (NIST) Dimensional Metrology Group (DMG), located in Gaithersburg, MD, delivers world class dimensional calibration services to support United States manufacturing and other industries. Of particular importance is the calibration of spheres, which serve as reference objects to universal length measuring machines and coordinate measurement machines used internally at NIST and by customers. The NIST DMG is seeking a camera-based Fizeau interferometer to replace ageing equipment responsible for the calibration of the diameter of spheres. A description of the existing equipment and its operation can be found here: https://www.nist.gov/publications/sphere-diameter-interferometry-nanometer-uncertainty.

2. Scope The NIST DMG is seeking one camera-based Fizeau interferometer for use in our measurement services. The interferometer will be used to provide low-uncertainty measurements of sphere diameter under SKU 11033C: Sphere Diameter by Interferometry.

3. Minimum Requirements The system shall meet or exceed the minimum requirements identified below. All items must be new. Used or remanufactured equipment will not be considered for award. Experimental, prototype, or custom items will not be considered. The use of “gray market” components not authorized for sale in the U.S. by the Contractor is not acceptable. All line items shall be shipped in the original manufacturer’s packaging and include all original documentation and software, when applicable.

The Contractor shall provide the following one camera-based Fizeau interferometer that meets the following minimum specifications:

Physical Specifications

1. The interferometer shall be a Fizeau interferometer.

2. The interferometer shall be capable of taking measurements in both horizontal and downward-facing vertical orientations. (Stronger consideration will be given to manufacturers who also sell a vertical-mount stand capable of holding interferometer at least 305 mm above surface of table.)

3. The interferometer shall have a maximum weight of 25 kg (excluding stands and accessories).

4. The interferometer shall have handles located on the case to assist with lifting and mounting.

5. The interferometer shall be capable of operating in environmental temperatures between 15 °C and 30 °C and relative humidities between 5% and 95% (non-condensing) without damage to the instrument. The interferometer only needs to meet performance specifications listed elsewhere in this document at temperatures between 19.1 °C and 20.1 °C and relative humidities between 25% and 60% (non-condensing).

6. The interferometer shall be powered by a cable compatible with standard United States AC electrical supply (type A or B socket).

Optical System Specifications

7. The interferometer shall have a sealed optical path which prevents dust intrusion.

8. The interferometer shall be designed such that a transmission flat may be directly mounted to the instrument in the beam path and the transmission flat is angle-adjustable by hand and removeable.

9. The interferometer shall be capable of imaging interference fringes formed from reflections between the transmission flat and a fused silica optical flat nearly parallel to the transmission flat.

10. The interferometer shall have a nominally collimated outlet beam when the transmission flat is removed.

11. The interferometer shall be designed to operate at a wavelength of approximately 633 nm. (Stronger consideration will be given to interferometers that can also perform sufficiently well at 514 nm, 543 nm, and/or 771 nm to image interference fringes and employ the method of excess fractions to determine fringe order. See https://doi.org/10.1364/AO.50.005484 for details on the method of excess fractions.)

12. The interferometer shall come with a frequency-stabilized laser with a nominal wavelength of 633 nm and stability <0.0001 nm. The laser shall be ANSI Z136.1-2022 laser class 3R or lower or FDA class IIIa or lower.

13. The interferometer’s laser shall be removeable from the instrument without extensive disassembly. Either a power supply for the laser or specifications necessary for a variable power supply unit to run the laser shall be included. (Stronger consideration will be given to interferometers with a fiber optic port for coupling light into the instrument from an external laser source.)

14. The interferometer shall be capable of measuring surfaces with reflectance between 1% and 40%.

15. The interferometer shall be capable of isolating reflections from surfaces of interest and while excluding reflections from other surfaces.

16. The interferometer shall contain a camera with at least 1200 by 1200 pixels for imaging interference fringes.

17. The interferometer shall be capable of at least 5X optical zoom.

18. The interferometer shall have a minimum outlet beam diameter of 100 mm and a ± 3° field of view.

19. The interferometer’s outlet beam diameter (), maximum optical zoom (), and number of camera pixels in each direction ( and ) shall satisfy relation , where is the lesser of and .

20. The interferometer shall perform with an RMS simple repeatability of 0.06 nm or better.

Software Specifications

21. The interferometer’s manufacturer shall provide all software with installation media and a perpetual license that can be transferred between computers.

22. The interferometer’s manufacturer-provided software shall be capable of:

a. Remotely controlling the instrument,

b. Measurement and analysis of full-area surface form error, and

c. Exporting measurement data and results to a plain-text file format.

23. The interferometer shall be remotely controlled over a wired connection of at least 25 ft.

24. The interferometer’s manufacturer shall provide means for a Python script to interface with the instrument without using the manufacturer’s software. The Python interface shall be established using a widely used Python library, for example PySerial, PyVISA, PyModbus, Python.NET, ctypes, etc. The Python connection shall be capable of setting and getting camera settings, initiating and retrieving camera images, and any motorized alignment of optics necessary to take a clear image of interference fringes. While documentation is sufficient to satisfy this requirement, stronger consideration will be given to manufacturers that supply a working script.

Required System Information

25. The manufacturer shall provide engineering drawings showing the exterior dimensions of the interferometer, mounting point locations, the center of gravity of the interferometer, and any other information necessary to construct mounting fixtures for the instrument. Stronger consideration will be given to interferometers that come with a CAD file showing exterior features of the interferometer.

26. If the included laser is normally housed inside the interferometer, the manufacturer shall provide engineering drawings of the laser and any mounting hardware that fixes the laser in place. The engineering drawing shall also contain the location of the emission axis of the laser. Additionally, the manufacturer shall provide a documented procedure to remove, reinstall and realign the laser.

27. Stronger consideration will be given to manufacturers who provide an optical system design file of the interferometer for Ansys Zemax OpticStudio or a similar commercial ray tracing software. A Zemax black box file (or similar) which enables simulations while protecting intellectual property satisfies this requirement. In the case of a black box file, the obscured portion of the optical system shall not include the laser input, reference flat, or observation plane of all cameras. Additionally, obscured optical elements shall have sufficiently defined spectral data (coating reflectance/transmittance and refractive index) to run simulations with wavelengths between 450 nm and 1100 nm.

DELIVERABLE SCHEDULE

4. Delivery Terms Delivery shall be FOB Destination (or equivalent terms, such as INCOTERMS Delivered Duties Paid) are required and shall occur not later than (NLT) 30 weeks ARO.

FOB Destination means: The contractor shall pack and mark the shipment in conformance with carrier requirements, deliver the shipment in good order and condition to the point of delivery specified in the purchase order, be responsible for any loss of and/or damage to the goods occurring before receipt and acceptance of the shipment by the consignee at the delivery point specified in the purchase order; and pay all charges to the specified point of delivery. The contractor shall deliver all Line Items to:

The National Institute of Standards and Technology 100 Bureau Drive, Building 219, Room F036 Gaithersburg, MD 20899

5. Inspection and Acceptance In addition to the inspection and acceptance terms articulated in 52.212-4, the Government reserves the right to perform such performance tests and evaluations as defined below to verify specified system performance. Such tests and evaluations, if performed, shall be conducted within the environment that the system is to be operated. The Contractor has the right to be present during the tests and evaluations, if performed, at the Contractor’s expense.

Performance Tests:

1. Python script will be used to pull camera images of interference fringes directly from instrument

The Government will test, inspect, and accept the equipment onsite within 7 business days of the receipt of the Fizeau interferometer. A visual inspection of the Fizeau interferometer will be performed by the NIST TPOC to identify surface defects or any form of indication that the Fizeau interferometer was damaged during transport to NIST. The Government shall have sole discretion to require repair or replacement of damaged and/or nonconforming supplies at no cost to the Government. The Government at any time prior to acceptance shall reject the Fizeau interferometer due to defects and/or nonconformance.

6. Warranty The contractor shall warrant the entire system for a period of a minimum of 1 year and the included laser for 3 years after receipt of the equipment and shall be in accordance with terms in FAR 52.212-4.

7. Payment Schedule The Contractor shall be paid, in accordance with Net 30-day payment terms, upon receipt and acceptance of a proper invoice, in accordance with the following schedule:

1. 100% after installation and acceptance by the TPOC of fully installed system.

2. The Government anticipates inspection will occur upon:

a. After the testing procedures set forth in this document have been completed.