Screw thread length and diameters in one image: a telecentric worked example
A worked example, not a customer project: an M10 × 1.5 screw on a 42 mm collimated backlight, imaged by a 0.271x bi-telecentric lens, shows about 31 mm of thread at once for length, diameter and pitch checks. Every number is calculated from the parts' printed rows.
Choose magnification by the thread length that must fit, then confirm sampling against the tightest tolerance.
- Field of view (derived)About 31.2 × 26.1 mm
- Sampling (derived)About 12.7 µm per pixel
- Working distance (lens spec)118 ± 3 mm
- Depth of field (lens spec)± 6.0 mm @ F11
Explore it in 3D
Camera CAD is the published model. Lens and light envelopes use printed dimensions. The linked station uses its published base size and column height; carriage, brackets, fittings, the part and spacing are illustrative. Confirm load, travel, fasteners and clearances before ordering. Light paths explain the arrangement and do not simulate optical performance. The part is a generic example, not a real customer part.
The challenge
Thread length, major and minor diameter and pitch are all read from the profile. A 0.438x lens samples finer but its field is only about 19 mm, so a longer thread needs two images and a join.
Flanks and crests reflect front light unevenly, and a screw lying on a tray can roll slightly and change its distance from the lens.
How it was solved
The LS-TCL-2682 prints 0.271x, 118 ± 3 mm working distance and ± 6.0 mm depth of field at F11. With the MV-CS050-10GM(NPOE) sensor of about 8.45 × 7.07 mm the field is about 31.2 × 26.1 mm, so about 31 mm of thread (about 20 pitches of 1.5 mm) fits along its long side.
The LS-CLM-0068 is the lens's printed matching light: a 42 mm collimated beam, which covers the field diagonal of about 40.6 mm, and a 40-80 mm light working distance. The screw lies across the beam on the glass tray of the LS-MNT-0097 station.
Why it works
- 1
Sampling is about 3.45 µm / 0.271 = 12.7 µm per pixel: a 1.5 mm pitch spans about 118 pixels and the 10 mm major diameter about 786. Measurement uncertainty still has to come from a study on real screws.
- 2
Against the 0.438x lens, the 0.271x lens trades about 1.6 times coarser sampling for about 1.6 times more field. Choose by the longest thread that must be seen in one image and the tightest tolerance.
- 3
The printed ± 6.0 mm depth of field is at F11. The lens's printed best aperture is F4.9; a wider aperture resolves finer detail but gives less depth of field, so set it with the screw's height variation in mind.
Worked application example (calculated, no test image)
Evidence you can inspect
No camera image is shown. This is a worked example built from catalog rows, not a test of a real part.
Nothing is reported as measured. Field, sampling and light coverage are calculated from the lens's printed magnification, working distance and depth of field, the camera's printed pixel count and pixel size, and the light's printed beam diameter.
The numbers describe what the optics sample, not a measurement uncertainty or a detection limit. Run a trial and a measurement study with real parts before relying on any tolerance.
From image contrast to a production decision
What to validate on your part
- 01
Calibrate the scale
Use a traceable artefact or thread gauge at the height of the screw axis.
- 02
Check rolling and seating
Rotate the screw in steps, reload it and compare the readings.
- 03
Run a measurement study
Compare with thread gauges or an optical comparator and assess repeatability at the limits.
From the demo to your test bench
Parts in this setup
Bi-telecentric lensOur pick
LS-TCL-2682
Bi-telecentric lens for 2/3" cameras, 0.271x, WD 118 mm, C-mount (LS-TCL-2682)
0.271x, 118 ± 3 mm working distance, ± 6.0 mm @ F11 depth of field and an 11.4 mm maximum sensor size, as printed.
$1,769.00
In proposed setup
Collimated lightOur pick
LS-CLM-0068
Collimated (telecentric) illumination, beam dia. 42 mm, length 130.4 mm (LS-CLM-0068)
Printed 42 mm beam (covers the field diagonal of about 40.6 mm) and 40-80 mm light working distance. Green shown; red, blue and white versions are listed.
$629.00
In proposed setup
CameraOur pick
MV-CS050-10GM(NPOE)
Hikrobot MV-CS050-10GM(NPOE) 5 MP GigE area scan camera, IMX264, Gen 2 basic version, Mono, Without PoE
Monochrome C-mount camera, 2448 × 2048 px of 3.45 µm (printed); its sensor diagonal of about 11.0 mm is within the lens's 11.4 mm limit.Not available in the United States. Available for delivery to other countries.
$819.00
In proposed setup
Camera test stationOur pick
LS-MNT-0097
Camera stand with XZ adjustment and glass tray, height 600 mm, 600 x 450 mm base (LS-MNT-0097)
600 mm column, 600 × 450 mm breadboard, XZ adjustment, glass tray and two lighting holders as listed. Proposed bench fixture; confirm loads, travel and camera/lens clamps.
$1,309.00
In proposed setup
"Tested" marks the part the manufacturer used in its application test. "Our pick" is our proposed alternative or supporting part, not tested by the manufacturer in this set-up. Confirm colour, optics, controllers, power supplies, cables and mounting before ordering.
The set-up
| Lens | LS-TCL-2682 · bi-telecentric · 0.271x · C-mount |
|---|---|
| Light | LS-CLM-0068 · collimated · 42 mm beam |
| Camera | MV-CS050-10GM(NPOE) · 2448 × 2048 px · 3.45 µm |
| Working distance | 118 ± 3 mm (lens spec) |
| Field of view (derived) | About 31.2 × 26.1 mm: 2448 × 2048 px × 3.45 µm / 0.271x |
| Mounting (proposed) | LS-MNT-0097 · camera test station with glass tray and two lighting holders |
Mount the optics with intent
The station is an optical test bench, with its two lighting holders included in the catalog listing. The 3D column and base follow the published height and footprint. Carriages, clamps and part supports are schematic: confirm camera screw pattern, lens support, light fasteners, permissible load and actual travel before ordering.
Complete the electrical system
This collimated light prints DC 3 V with 350 mA operating current at 1 W and 750 mA at 3 W (1000 mA maximum): it needs a constant-current driver set to those values. Confirm current, colour, connector and power before selecting a controller; a general 24 V voltage controller is not a substitute. Camera cables and PC are separate selections.
Build this system
Start from this setup, adapt it to your part.
The configurator opens with this study's camera, lens, light and station picked. Swap any part, check fit and price, then buy or ask for a quote.
Camera CAD is the published model. Lens and light envelopes use printed dimensions. The linked station uses its published base size and column height; carriage, brackets, fittings, the part and spacing are illustrative. Confirm load, travel, fasteners and clearances before ordering. Light paths explain the arrangement and do not simulate optical performance. The part is a generic example, not a real customer part.
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Make the next trial specific.
Tell us the part size, smallest defect or tolerance, available working distance, material and line speed. Include what a good part and a reject look like.
Worked application example (calculated, no test image): No camera image is shown. This is a worked example built from catalog rows, not a test of a real part. The numbers describe what the optics sample, not a measurement uncertainty or a detection limit. Run a trial and a measurement study with real parts before relying on any tolerance.