Machine Vision Zoom Lens Configuration Guide

Four ways into the same machine vision zoom lens configuration — this page sends you down the one that matches the number you already have.

Start Here: Which of These Four Situations Are You In?

Zoom lens enquiries arrive with one number attached: a clearance figure from the fixture drawing, a part width from the quality plan, or a camera bought last quarter and already bolted to a bracket. The number people volunteer is rarely the number that should decide the configuration.

Start with whichever number is hardest to move, because the other two can usually be adjusted. A caution before the tables: a calculated magnification is not a measured result, and a published resolution is an optical limit, not a promise about your lighting.

How Zoom Lens Configuration Locks Magnification, FOV and Working Distance

Three numbers describe a zoom setup, and only two of them are free. That is why configuration feels harder than it looks.

On the standard POMEAS route — zoom body, auxiliary objective, TV tube, the combination POMEAS documents as the A-class chain — the relationship is multiplicative:

effective magnification = base zoom × objective factor × TV factor

Field of view then falls out of the sensor: HFOV = sensor width ÷ effective magnification, and VFOV uses the sensor height. A 2/3-inch sensor is 8.8 × 6.6 mm; a 1-inch sensor is 12.8 × 9.6 mm.

The APO route adds a relay factor: effective magnification = TV factor × zoom × APO magnification × 0.55. The 0.55 is the relay factor confirmed with customers for this combination. That is why a 5X APO objective behind a 1X TV tube does not behave like a plain 5X, and why working distance on that route belongs entirely to the objective. Derivations are on the APO matrix page.

Path 1 — You Know Your Working Distance

The 12.5X body has seven objective positions, each landing on a specific clearance figure.

• Step 1. Find the row that clears your fixture without overshooting it.
• Step 2. Read the magnification band it leaves with a 1X TV tube fitted.
• Step 3. If two rows clear the fixture, choose on resolution and depth of field.

The table is calculated from the 12.5X published zoom range of 0.58X–7.5X with a 1X TV tube on a 2/3-inch sensor (8.8 × 6.6 mm). Working distance is a published objective figure.

Two rows carry most of the weight. The 155 mm row is the balanced choice for most cells: room for a ring light, a usable band, a field scaling from 30 mm to 2.3 mm. The 297 mm row exists where something is in the way — heat, a moving axis, a large holder. Read the 155 mm working distance setup and the ~300 mm working distance route for the trade-offs at each tier.

Path 2 — You Know Your FOV

Working backwards from a field takes three lines: required effective magnification = sensor width ÷ target HFOV; find the objective and TV product that reaches it; confirm the combination sits inside your sensor's image circle.

The second line is where projects stall. No bare zoom body reaches a 30 mm field on 2/3-inch: the 6.5X starts at 0.7X, which works out to 12.6 mm, and the 12.5X starts at 0.58X, which works out to 15.2 mm (calculated). Both are already narrower than the part, so the field has to be bought with front-end optics.

Three routes then cover the 30 mm target: a 0.5X auxiliary objective at 155 mm, a 0.5X TV tube at 77.4 mm, or a 4K body on a 1-inch sensor reaching 37.6 → 5.1 mm with a 0.5X TV tube (calculated). They differ in clearance and in room left for growth.

The comparison — including what happens when next quarter's part is 60 mm — is on the 30 mm FOV reverse selection page. For the arithmetic, the magnification and FOV calculator walkthrough shows every step and the FOV calculator tool handles the usual sensor sizes.

Path 3 — You Need High Magnification for Micro Features

When the requirement is a small feature rather than a large part, the question changes from how much field to how much detail the optics stack can deliver. That is a published number, worth reading before any multiplier gets applied.

The break point is easy to state. A zoom body is the right tool while the detail stays coarser than its best published figure — 3.05 µm for the 12.5X from 4.5X upward, 2.80 µm for the 14X. Below that, front optics cannot create information the objective does not carry.

Two rules keep the numbers honest. Resolution figures are optical limits, so visibility also depends on sampling, contrast and lighting — a 50X objective is not a guarantee that a 0.5 µm feature will be detected. And depth of field collapses as you climb, from 91 µm at 2X to 0.9 µm at 50X.

Route the class change through the APO configuration matrix, and read why magnification is not resolution before assuming more magnification is the answer.

Path 4 — You Already Have a Camera

A 2/3-inch sensor is the design point for the 6.5X, 12.5X and 14X bodies, all specified against 2/3-inch. A 1-inch sensor belongs behind the 4K 7.5X body, specified against 1-inch. A 1-inch sensor behind a 2/3-inch body gets you a wider field on paper and dark corners in practice.

The second check is the field ceiling: sensor width divided by the minimum effective magnification, not the working distance. A longer standoff widens the space, not the field — the 0.25X objective at 297 mm with a 1X TV tube, and the 0.5X objective at 155 mm with a 0.5X TV tube, both land on 0.145X–1.875X and 60.7 → 4.7 mm (calculated).

Work through sensor and image circle matching before the bracket design is committed, and check the 300 mm page where a longer standoff is unavoidable.

Zoom Body Cheat Sheet: 6.5X vs 12.5X vs 14X vs 4K

Four bodies cover nearly every A-class request. All figures below are published specifications, not calculations.

Two readings go wrong often. The 12.5X resolution is 13 µm at 0.58X improving to 3.05 µm from 4.5X — not 11.18 µm, which belongs to the 6.5X. And "14X" is the zoom ratio, not a 14× magnification. The 12.5X also holds TV distortion — image-side distortion at the sensor — down to 0.001%, which matters when you measure rather than find.

For a body-level comparison worked through in depth, read the 6.5X vs 12.5X selection guide.

Body pages: 12.5X LZL-12101, 6.5X LZ-650104, 14X continuous zoom, 4K PMS-LZH-7505W.

Auxiliary Objective or TV Tube: Two Different Knobs

Both multiply magnification, which is why they get confused. Only one moves the lens away from the part.

If clearance is the constraint, you need the objective. If the field is wrong and the standoff already works, the TV tube moves magnification without redesigning the bracket. Both take a 12.5X body to roughly 0.29X–3.75X, but only one of them takes the lens to 155 mm.

One caution on mixing families. The WD table for the 12.5X family and the generic chart for the 6.5X and K families are not interchangeable: 0.25X is 297 mm against 240 mm, and 0.5X is 155 mm against 135 mm. Quote the table for your body. Background is in what an auxiliary lens is.

The Continuous Configuration Map: 121 mm FOV Down to Sub-Millimetre

The A-class rows below are calculated; the APO rows use the 0.55 relay factor. All are 2/3-inch unless stated.

Two limits on reading the map. Depth of field is not published for these combinations and does not transfer from the base lens, so a body's 1.9–0.1 mm figure cannot be carried into a stacked configuration. And APO working distance is fixed by the objective: a 50X objective keeps you 13 mm from the part at any TV factor.

What Every Step Costs: DOF, Brightness and Resolution

Every move here buys something and charges for it, and the charges are why two configurations with identical fields behave differently on a line.

Brightness is the cost people underestimate. Higher effective magnification spreads the same object light over a larger image, so it is dimmer per unit area. At low magnification the reverse shows up as corner falloff before the centre dims.

Depth of field has a clean answer and a muddy one. Clean: published DOF belongs to a body or objective on its own. Muddy: nobody publishes DOF for every stacked combination, so a configuration that matters should be confirmed. Read how working distance and depth of field trade off.

Manual, Motorized or Rail: When the Choice Matters

The optics decision is not finished until the drive is chosen, because the drive decides whether a magnification setting can be repeated.

The drive also settles detented against continuous: a detented body gives repeatable click positions when operators change magnification by hand, a continuous body lets a controller land anywhere in the band. Note too that the manual 6.5X body sits at 87 ± 2 mm and the motorized at 82 ± 2 mm — 5 mm that matters once a fixed camera plate is in the design. Depth is in choosing between manual and motorized zoom and the motorized zoom complete guide.

Four Worked Examples, One per Path

Path 1 — working distance first. A fixture leaves roughly 150 mm of clearance and the part is 40 mm across. One tier row clears it without wasting standoff: the 0.5X objective at 155 mm, which keeps room for a ring light and a short bracket. With a 1X TV tube the effective magnification works out to 0.29X–3.75X (calculated) and the horizontal field runs 30.3 mm down to 2.3 mm — which does not hold a 40 mm part at the wide end. Moving to a 0.5X TV tube gives 0.145X–1.875X and 60.7 → 4.7 mm (calculated). Same 155 mm, field problem solved, object-side sampling halved, and nothing else in the fixture moves.

Path 2 — field of view first. The part is 30 mm wide and the cell is tight, so clearance cannot buy the field. Three lines of arithmetic: 8.8 ÷ 30 ≈ 0.29X. No bare body reaches it, since the 12.5X stops at 0.58X and a 15.2 mm field, and the 6.5X stops at 12.6 mm. Two routes land on 0.29X–3.75X and 30.3 → 2.3 mm (calculated): the 0.5X objective at 155 mm, or the 0.5X TV tube at 77.4 mm with no front optic at all. Both hold the part. They differ in clearance, in object-side sampling, and in how much zoom travel is kept for the next change.

Path 3 — magnification first. The requirement is detail finer than the 3.05 µm best case of the 12.5X body, so front optics will not fix it and the class has to change. A 6.5X body with a 5X APO objective and a 1X TV tube gives 1.925X–12.375X (calculated), a 35 mm working distance and a 4.6 → 0.7 mm horizontal field. Depth of field for the stack itself is not published, so budget it from the objective and verify before sign-off. A 50X APO behind a 2X TV tube reaches 38.5X–247.5X (calculated) at 13 mm, with a 0.23 → 0.04 mm field, and the objective's own depth of field becomes the limit on the working envelope.

Path 4 — camera first. A 2/3-inch camera is already on the bracket, so the 12.5X body is specified against exactly that sensor and the field follows from whichever front optic Path 1 or Path 2 selected. A 1-inch camera is already on the bracket, so it belongs behind the 4K 7.5X body: with a 0.5X TV tube that setup gives 0.34X–2.5X and 37.6 → 5.1 mm horizontal (calculated). Putting that same 1-inch camera behind a 2/3-inch body is the one combination to avoid, because the corners go dark before the field becomes useful — and no amount of zoom travel recovers them. Sensor choice, not lens choice, sets that ceiling.

FAQ: Configuration Questions Engineers Actually Ask

I only know my working distance. Where do I start?

Use the tier table for the 12.5X body and pick the objective whose published working distance clears your fixture without wasting standoff: 0.25X gives 297 mm, 0.5X gives 155 mm, 0.75X gives 93 mm, 1X gives 77.4 mm. Then read the magnification band that row leaves with a 1X TV tube. Those figures are calculated, not measured.

I only know the field of view I need. Which path fits?

Path 2. Divide sensor width by the target field: on 2/3-inch, 8.8 mm divided by a 30 mm field is approximately 0.29X. Then find the objective and TV product that reaches it. No bare zoom body reaches 30 mm on 2/3-inch, because the 12.5X stops at a 15.2 mm field and the 6.5X at 12.6 mm.

What is the highest magnification this configuration route reaches?

On the A-class route, a 12.5X body with a 2X objective and a 2X TV tube reaches 2.32X–30X, calculated, with a horizontal field down to 0.3 mm. The APO route goes much higher: a 50X APO objective behind a 2X TV tube works out to 38.5X–247.5X, calculated, with a 0.04 mm field at 13 mm.

How do I match a zoom lens to a camera I already own?

Match the image circle first. The 6.5X, 12.5X and 14X bodies are specified against a 2/3-inch sensor, while the 4K 7.5X body is specified against 1-inch. A 1-inch sensor behind a 2/3-inch body will vignette the corners. Then check the field ceiling: sensor width divided by minimum effective magnification, not working distance.

Auxiliary objective or TV tube — which one changes what?

Both multiply magnification and shrink the field. Only the auxiliary objective changes working distance, and it also alters object-side NA and the depth-of-field budget. The TV tube sits on the camera side, so the standoff stays where the objective put it. If clearance is the constraint you need the objective.

Which body should I start from: 6.5X, 12.5X, 14X or 4K?

Start with the sensor and the field. A 2/3-inch camera needing range points at the 12.5X body, which spans 0.58X–7.5X and resolves down to 3.05 µm from 4.5X. A 1-inch camera points at the 4K 7.5X body. The 14X is a 0.55X–7.6X zoom ratio, not a 14x magnification, and the 6.5X suits wider fields.