Case Study 4: AZURE ELS-85 mm Machine-Vision Surrogate

This page documents the surrogate layout Machine Vision 85 mm Azure (Datasheet 0.5X-2.0X). It is based on the local datasheet:

attachment/Lens/ELS-85 4.5V16K_specification.pdf

The AZURE Photonics ELS-85/4.5V16K is a large-format 16K/12K line-scan machine-vision lens. It is built the same way as the PYRITE 85 mm surrogate (see Case Study 3: PYRITE 85 mm Machine-Vision Surrogate); the two are near twins (both 85 mm, F/4.5, 0.5x-2.0x), so they can be used interchangeably for layout work.

What The Surrogate Is

The vendor datasheet does not provide the internal prescription, so the KrakenOS layout is a first-order blackbox model, not a decoded prescription. It uses two ideal thin-lens groups and one aperture stop inside the published optical vertex span. The goal is to make the UI behave like the 85 mm line-scan lens at the level needed for layout work, field sampling, camera-distance studies, and Open 3D placement. Because the model is ideal it carries no real aberration – a traced spot is defocus only; attach a Zemax wavefront / spot-radius export (as for the 150 mm 15056 lens) to augment it with the vendor’s measured OPD.

The model uses these public datasheet values:

Quantity	Datasheet value	Surrogate use
Product	ELS-85/4.5V16K (material code 3.A01.018545V16K-A)	Menu title and documentation identity
Effective focal length	85 mm	Paraxial effective focal length
Magnification range	0.5x to 2.0x, nominal 1x	Default layout is the 1x conjugate
F-number	F/4.5, manual iris	Default aperture is F/4.5
Image format	57.3 mm (16K) / 62 mm (12K), max image circle 68 mm	Image and object row diameter (68 mm); the sampled field uses the shared camera workflow
Resolution	3.5 µm (16K) / 5 µm (12K)	Pixel scale the lens is designed to resolve
Maximum chief-ray angle	9.54 degrees	Field / telecentricity sanity check
Working-distance range	225 / 142 / 99 mm at 0.5x / 1.0x / 2.0x (optimum 142 mm)	Checked against the 0.5x to 2.0x model conjugates
Back focus	141.85 mm	Rear glass vertex to image at 1x
Optical total length (TTL)	196.8 mm	Front glass vertex to image at 1x; TTL - back focus pins the glass span
Distortion / relative illumination	< 0.0025 % / 93.7 %	Near-distortion-free, near-flat illumination (not modelled by the ideal groups)

The datasheet does not publish the Gaussian cardinals. They are inferred below from the symmetric 1x geometry, giving SF = -56.85 mm, S'F' = +56.85 mm, H1 = 28.15 mm behind the front vertex and H2 = 28.15 mm ahead of the rear vertex (HH' = -1.30 mm).

Vendor STEP Overlay

The preset records the local vendor STEP file:

attachment/Lens/ELS-85-4.5V16K.STEP

The STEP is used as a mechanical overlay, while the KrakenOS table remains the paraxial blackbox optical surrogate. OpenCascade extraction finds the two usable glass vertex surfaces as:

STEP face	Role in this surrogate	STEP local axis coordinate
F062	First glass surface / front optical vertex	+13.283194712 mm
F064	Last glass surface / rear optical vertex	-41.716909857 mm

Those two surfaces are separated by 55.000104570 mm. The datasheet gives no explicit Σd, but TTL - back focus = 196.8 - 141.85 = 54.95 mm matches the STEP glass span to within the 0.1 mm rounding of the published TTL – which also confirms that “back focus” is referenced to the rear glass vertex. The surrogate uses the exact STEP glass span for its front-to-rear vertex distance. It stores a lens STEP placement offset of -3.848950487 mm so the STEP’s first and last glass vertices overlay the surrogate’s front and rear optical vertex datums. The mechanical front shoulder of the STEP is intentionally not used as the optical datum.

Default UI Settings

The preset follows the same working defaults as Machine Vision 150Mm Measured so the layouts can be used the same way in Open 3D. It inherits the same ray display, source, detector, non-sequential, tolerance, atmosphere, optimization, and CAD overlay defaults, including the Allied Vision hr25MCX camera model and attachment/Cameras/3D_CAD_HR25xCXP.STEP camera overlay. The image format is camera- and FOV-driven at runtime; the 68 mm image-circle row diameter only sets the maximum the lens can cover.

Only lens-specific defaults differ from the 150 mm measured layout:

• The aperture default is F/4.5 from the ELS-85 datasheet.

• The real-image field default is 11.52 mm so the initial field sampling matches the shared camera workflow rather than the full 68 mm image-circle capability.

• The lens STEP overlay uses attachment/Lens/ELS-85-4.5V16K.STEP and the glass-vertex alignment offset described above.

• The auxiliary Open 3D optical STEP overlay is left empty.

How The Blackbox Is Built

At 1x the lens is symmetric (front working distance = back focus = 141.85 mm), so each principal plane sits one focal length short of the 2f’ conjugate:

H1 = 2 f' - back focus = 170 - 141.85 = 28.15 mm  (behind the front vertex)
H2 = 28.15 mm                                       (ahead of the rear vertex)

That makes SF = H1 - f' = -56.85 mm and S'F' = f' - 28.15 = +56.85 mm. Two equal thin-lens groups (f = 159.48852477 mm) placed symmetrically about a centred stop reproduce EFL = 85, SF, S'F', H1 and H2 exactly in the 55.0001 mm glass span.

The surrogate rows are:

Row	Role	Distance / power
Object	1x finite object plane	141.85 mm before the first optical vertex datum
Front Optical Vertex Datum	First optical vertex reference	17.63852477 mm to group 1
Blackbox Group 1	Ideal thin-lens group	f = 159.48852477 mm
Aperture Stop F/4.5	Stop / F-number control	9.86152751 mm after group 1 (centred stop)
Blackbox Group 2	Ideal thin-lens group	f = 159.48852477 mm
Rear Optical Vertex Datum	Last optical vertex reference	141.85 mm to image at 1x
Image / Sensor	1x sensor plane	68 mm image circle

The same cardinals imply these finite-conjugate working points when measured from the optical vertex datums:

Magnification	Object to front optical vertex	Rear optical vertex to image
0.5x	226.85 mm	99.35 mm
1.0x	141.85 mm	141.85 mm
2.0x	99.35 mm	226.85 mm

The published working-distance range (225 / 142 / 99 mm) is measured to the first mechanical element, so the optical-vertex distances bracket the datasheet range with the expected small mechanical offset.

Rendered Layout

Load Machine Vision 85 mm Azure (Datasheet 0.5X-2.0X) from the Machine Vision menu and open it in Open 3D. The layout shows optical vertex datums, two blackbox thin-lens groups, an F/4.5 stop, the 1x image plane, and the vendor barrel STEP as a mechanical overlay. The STEP is a multi-body assembly, so it is loaded with lens_step_largest_component_only = False to render the whole ~52 mm barrel (the largest single connected solid is only an ~18 mm ring). Its optical axis is the STEP’s local -X; the front-face = "max" alignment plus the -3.849 mm glass-vertex offset seat the front glass surface on the front optical-vertex datum (141.85) and the rear glass on the rear datum (196.85), enclosing the two thin-lens groups – so no 180-degree flip is used (unlike the +Z-authored PYRITE 85 STEP).

Known Limits

• Internal curvatures, glasses, aspheres, coatings, tolerances, and MTF are not reconstructed from the datasheet.

• The two thin-lens groups reproduce first-order cardinal data; they do not reproduce the vendor’s real aberration correction (the traced spot is defocus only until a wavefront export is attached).

• The 1x symmetric assumption is taken from the near-equal front working distance and back focus; a vendor prescription would pin any residual asymmetry.

• The mechanical V-mount, iris, filter thread, and barrel outline are represented by the STEP overlay rather than by the sequential surrogate rows.

Validation

The validation script checks that the layout is discoverable in the Machine Vision menu, that the two-thin-group paraxial matrix reproduces the inferred effective focal length, front/back focal distances, and principal planes, and that the vendor STEP’s F062 and F064 remain the matched first and last glass surfaces spanning the surrogate’s optical vertex distance:

python -m KrakenOS.UI.validate_machine_vision_azure_85_surrogate