Alternatives to the FA Lens on a Hikrobot Industrial Camera: 6 Checks

Within the POMEAS global company intelligence set of 2,602 companies, 32 have public material indicating Hikrobot industrial cameras in use. Stations built around that class share a history: the lens was chosen to get the station running, the focal length went on the drawing, and the rest of the specification was never recorded. When the lens is replaced, the engineer inherits a mount and a focal length.

That is possible, but not from two numbers. The gap sits in three places: whether the substitute covers the sensor, whether it focuses across the range the fixture allows, and whether its geometry is close enough for the existing calibration to survive — image circle, closest imaging distance and distortion, the three most likely to be missing from an entry-level datasheet.

The six parameters to verify before substituting

The first three eliminate lenses that cannot form an image; the last three eliminate lenses that fail in service. Where POMEAS publishes no value, the table says so.

1. Sensor format and the image circle it demands

Start from the camera, because that number is fixed. Read the format and active area from the camera datasheet, then require the lens's published image circle to meet or exceed the diagonal of that area.

POMEAS publishes coverage as format, active area and circle — 2/3-inch as 8.8 × 6.6 mm with an 11 mm circle, 1-inch as 12.8 × 9.6 mm with a 16 mm circle, 4/3-inch with a 22 mm circle — or as a single diameter. Two POMEAS series sold as 4/3-inch quote 22 mm and 23 mm, which is why the millimetre figure and not the format name is compared. A larger circle is safe; a smaller one vignettes.

2. Focal length and the angle of view published for your format

FA lenses carry no magnification figure, so the thin-lens estimate applies:

FOV ≈ sensor size × working distance / focal length

Use it to shortlist focal lengths and check a supplier's arithmetic; it ignores principal-plane separation and focus extension. Confirm the shortlist against measured angles for your format: PMS-LFEH-0816M(A) at 8 mm gives 66.8° × 55.8° × 43.3° on 2/3-inch.

3. Distortion, with its format and image height attached

Distortion is published per format at a stated image height, because a smaller sensor samples a smaller part of the lens's own field. PMS-LFHHH-5020M is −0.14% @ y=11.0 mm on 4/3-inch, −0.05% @ y=8.0 mm on 1-inch and −0.02% @ y=5.5 mm on 2/3-inch: one optic, three correct figures.

The reverse case matters as much. PMS-LFEH-0816M(A), PMS-LFEHH-0824M(D), PMS-LFEH-5018(A) and PMS-LFPHM-1228M(C) publish nothing. That does not make them unsuitable — it makes them unqualified for a station whose output is a dimension until the figure is obtained at your format.

4. Aperture range and closest imaging distance

Aperture range sets the exposure and depth-of-field envelope; closest imaging distance decides whether the lens focuses on your fixture. The apertures run F1.6–F22 to F2.8–F16, and the distances 0.1 m, 0.25 m and 0.4 m — not evenly distributed across focal length, and not inferable from it.

The 8 mm PMS-LFEH-0816M(A) reaches 0.1 m while the 8.0 mm PMS-LFEHH-0824M(D) starts at 0.25 m; the 50 mm PMS-LFEH-5018(A) starts at 0.4 m. Where a model publishes nothing, as with PMS-LFHHH-5020M, treat it as unknown.

5. Back focal length in air

Back focal length (后焦距) is the distance from the lens mounting face to the image plane, measured in air. It governs whether the rear of the lens clears the camera's front plate and any filter glass, and where the focus range lands once seated.

Because the C-mount flange distance is fixed by the standard, a substitute whose back focal length differs shifts the usable focus range. Published values run from 14.45 mm in air (mechanical 10.63 mm) on PMS-LFPHM-1228M(C), through 18 mm on PMS-LFHHG-3512M(B), to 20.29 mm on PMS-LFHHH-5020M. Three models here publish none; compare it with the flange distance from the camera datasheet.

6. Mechanical envelope, filter thread and operating temperature

Three items decide whether the lens fits and survives. Barrel: PMS-LFEHH-0824M(D) is Φ40 mm diameter and 68.48 mm long; PMS-LFPHM-1228M(C) is Ø46.5 ± 0.05 mm at 130 ± 5 g. Filter thread varies and is not published for every model: M40.5×0.5 on PMS-LFHHH-5020M, not published on PMS-LFHHG-3512M(B) and PMS-LFPHM-1228M(C). Temperature is −10 °C to +50 °C on most of the line, −20 °C to +60 °C on the 12 MP series, −30 °C to +70 °C on the 20 MP series.

Writing a replacement specification when the original lens is discontinued

Specify the function, not the part number: sensor format and active area, field of view at the available working distance, the focal length that follows, largest acceptable distortion with its image height, closest imaging distance, mount and rear clearance, barrel envelope, filter thread, temperature band, and whether vibration makes locking mandatory.

Mark each line must-hold or preferable — coverage, focus range, back focal length and envelope are must-hold, aperture range usually preferable. Add the line easiest to forget: where the original datasheet had no distortion figure, require the supplier to confirm one at your format.

Where POMEAS optics land on those six

The three 2/3-inch models show the entry-level trade-off. PMS-LFEH-0816M(A) is the widest and closest-focusing at 8 mm and 0.1 m, at 170.5 g. PMS-LFEHH-0824M(D) is the 10 MP version at 8.0 mm, but starts at 0.25 m and declares a Φ40 mm by 68.48 mm envelope — the figure to check against a housing built for a shorter barrel. PMS-LFEH-5018(A) is the opposite end: 50 mm, 12.5° × 10.1° × 7.6° on 2/3-inch, from 0.4 m. None of the three publishes distortion or back focal length.

The two 4/3-inch models are where geometry is documented. PMS-LFHHH-5020M publishes three distortion figures and three sets of angles with a 20.29 mm back focal length. PMS-LFHHG-3512M(B) is rated 12 MP on a 23 mm format and covers approximately 121.0 × 96.7 × 72.4 mm of object at its 0.2 m close limit. PMS-LFPHM-1228M(C) is the wide-angle 20 MP option at 12 mm on 1.1-inch, covering approximately 230 × 184 × 137 mm at the 0.1 m limit, with no distortion published: specified for coverage and focus, unqualified for gauging. Figures in different rows are measured on different formats and image heights and are not to be read as if obtained under one set of conditions.

What those numbers mean on the line

Scenario 1 — Wide-angle 2/3-inch station built for coverage, not geometry

PMS-LFEH-0816M(A) at 8 mm and 0.1 m with 66.8° diagonal coverage on 2/3-inch is the direct answer, and its F1.6 aperture helps on a poorly lit line. A missing distortion figure is acceptable because the station does not measure; if it later has to, wide-angle geometry will be the limiting term.

Scenario 2 — Same field, higher pixel count

When the camera is upgraded but the housing is not, the field has to be reproduced and the barrel has to fit. PMS-LFEHH-0824M(D) gives a comparable field at 68.4° × 56.6° × 44° on 2/3-inch at 10 MP, but its 0.25 m closest imaging distance and 68.48 mm length differ from the 5 MP part.

Scenario 3 — A station that measures, on a sensor larger than 2/3-inch

Distortion is the first filter, not the last. PMS-LFHHG-3512M(B) publishes −0.52% @ y=11.5 mm on 4/3-inch, −0.42% @ y=8.0 mm on 1-inch and −0.12% @ y=4.0 mm on 1/2-inch, so it can be evaluated at whichever sensor the station uses; from 0.2 m it covers approximately 121.0 × 96.7 mm on 4/3-inch.

Scenario 4 — Long working distance with geometry that survives calibration

PMS-LFHHH-5020M at 50 mm on 4/3-inch publishes the lowest distortion figures here and angles for three formats, which makes it the candidate when the camera stands back and still holds a dimension. The items to confirm are the two it does not publish: closest imaging distance, and any band beyond the −10 °C to +50 °C it declares.

What this comparison does not tell you

This is a parameter reference, not a compatibility statement. No claim is made that any POMEAS FA lens is a drop-in replacement for the lens fitted to a Hikrobot camera, and none should be inferred. Whether a substitute works depends on the camera's flange distance and front recess, filter glass in the path, the housing's clearance, the illumination and the algorithm's tolerance.

Hikrobot appears here only as recorded in customer-supplied intelligence: within the POMEAS global company intelligence set of 2,602 companies, 32 have public material indicating Hikrobot industrial cameras in use. No Hikrobot specification is quoted, because none was independently verified.

Optical resolution is not measurement accuracy. Resolution is set by the lens, the wavelength and the sensor pitch; accuracy additionally depends on contrast, edge definition, illumination stability, calibration and the algorithm. A 12 MP or 20 MP rating is a design target for a sensor class, not a promise about the smallest dimension a station holds.

The existing POMEAS article on C-mount lens selection covers the generic method: choosing a lens from scratch, the focal length formula and the full FA series matrix.

FAQ

Can I choose a replacement from the focal length alone?

No. Focal length gives the field of view only with the sensor size and working distance, and says nothing about image circle, closest imaging distance or distortion.

What does it mean when a lens publishes no distortion figure?

That the value was not published — not that it is zero, and not that it is poor. PMS-LFEH-0816M(A), PMS-LFEHH-0824M(D), PMS-LFEH-5018(A) and PMS-LFPHM-1228M(C) are all in that group. If the station measures, ask for it at your format.

Why do two 4/3-inch lenses quote different format diameters?

Because the format name is a class, not a dimension. PMS-LFHHH-5020M is 17.6 × 13.2 mm with a 22 mm circle; PMS-LFHHG-3512M(B) is 23 mm. Compare the millimetre figure with your sensor's diagonal.

How do I check that the lens will physically fit?

Three dimensions: back focal length in air against the flange distance, barrel diameter and length against the housing, filter thread against the filter already fitted. PMS-LFEHH-0824M(D) publishes Φ40 mm by 68.48 mm.

Is a 20 MP lens worth it on a station that only checks presence?

Usually not. The resolution class has to match the camera's pixel count; a 20 MP lens on a 5 MP sensor buys nothing.

What should a replacement specification contain?

Sensor format and active area, field of view at the available working distance, focal length, maximum distortion with its image height, closest imaging distance, mount and filter thread.

Next Step

If you are specifying a replacement and need measured values for your own conditions — your sensor size, your working distance, your feature size — send us those four numbers and we will run them against the current catalogue and tell you what actually fits, including when nothing does.