Machine Vision Optics Technical Guides

POMEAS optical applications team · Reviewed by Tiger Xie · Published 2026-10-16

These guides explain how the optics behave and how to control them. They are the reference layer behind the selection guides: once a lens class is chosen, the questions become how magnification, brightness and depth of field interact, how the lens is driven from the machine controller, and how the setup is verified and held over time.

The groups below follow that order, from principle through control to verification.

1. The guides in this index

A. Principles and definitions

• What Is a Motorized Zoom Lens? Definition, Axes & Selection — A motorized zoom lens moves magnification and focus with motors instead of by hand.
• What Is a Telecentric Lens? Working Principle, Types, and When to Use One — Learn how a telecentric lens keeps magnification constant to eliminate perspective error in machine vision measurement - working principle, the three types, and when to...
• Zoom vs Magnification: What Is the Difference? — Zoom and magnification are not the same thing.
• Magnification Is Not Resolution: What Actually Determines the Smallest Visible Feature? — Engineers often start a vision project with a magnification number: “I need 20X,” “I want 400X,” or “The defect is 5 µm, so give me 1000X.” Magnification is easy to say...
• Telecentric Lens for Dimensional Measurement and Inspection — How to build a telecentric-lens measurement station: turning tolerances into magnification, FOV and depth of field, choosing illumination, and preventing the failure modes...

B. Optical behaviour that affects the image

• Why Image Brightness Changes with Zoom Magnification — Image brightness falls as zoom magnification rises - geometry plus f-number.
• Zoom Lens with APO Objectives: Magnification, Vignetting and Industrial Applications — How a zoom lens works with 2X-50X APO objectives: total magnification and FOV calculations, why vignetting appears at the low-magnification end, and how to choose a...
• Motion Blur in Machine Vision: Exposure Time and Conveyor Speed — How to calculate and control motion blur in machine vision: the blur formula, object-side pixel size, acceptable blur in pixels, shutter type and strobe lighting.

C. Control and integration

• Motorized Zoom Lens Guide: Selection, Control and Integration — A motorized zoom lens changes magnification under software control.
• PMSOpticDll SDK V4.4.7: Motorized Lens Control API — PMSOpticDll SDK V4.4.7 exposes 44 functions for motorized zoom lens control over serial or TCP, with dual-motor and encrypted control-card families documented.
• How to Integrate a Motorized Zoom Lens into AI Vision Equipment — Step-by-step motorized zoom lens integration into AI vision equipment: camera and sensor size, FOV, working distance, mechanical length, mount and centering, PLC/PC...
• How RS232 Magnification Feedback Enables Repeatable Automated Inspection — RS232 magnification position feedback makes zoom lens setups repeatable and auditable.
• Programmable Optics for Machine Vision: Capabilities — What programmable optics means for machine vision: magnification and focus are programmable, aperture is not, plus the checklist that separates implemented from integrable.
• Programmable Optics for AI Vision: Adaptive FOV, Motorized Zoom & Autofocus — What programmable optics means for AI vision and AOI equipment: adaptive FOV, adaptive magnification, adaptive focus, optical recipes and why a motorized zoom lens is the...
• Active Optical Perception: How AI Can Control Zoom and Focus — Traditional machine vision fixes the optics, captures one image, and then runs an algorithm.
• How to Build a Motorized Digital Microscope with Zoom Lens, APO Objective and Autofocus — A motorized digital microscope combines a continuous zoom body, a high-NA apochromatic (APO) objective, an industrial camera, and a motorized focus axis so that...

D. Setup, testing and stability

• Zoom Lens Parfocality and Centering: Adjustment SOP — Step-by-step parfocality and centering procedure for continuous zoom lenses: 5 steps each, a 0.01 mm pass criterion, and why parfocality must be adjusted first.
• Zoom Lens Parfocality and Repeatability FAQ — Why the image softens or shifts after zooming, how to measure parfocality and zoom repeatability with the machine s own camera, and when a fixed-focal lens is the better...
• Motorized Zoom Lens Repeatability: 10-Cycle Test Method — Verify motorized zoom lens repeatability and magnification consistency with a bench setup, N≥10 round-trip cycles, R/sigma statistics and pass-fail thresholds.
• Calibration and Measurement Stability FAQ — How contamination, temperature, vibration and LED ageing move a measurement, how often to verify calibration on a running line, and how to detect drift before bad parts...

2. How to use this index

Read the principles group first if the optics are new to you, and skip to control and integration if the optics are already chosen. The setup and stability group is the one to return to after installation, because that is where drift appears first.

3. Frequently asked questions

What is the practical difference between zoom and magnification?

Magnification is the ratio of image size to object size at a given setting. Zoom is the ability to change that ratio continuously without changing the lens. A zoom lens therefore has a magnification range, not a magnification value, and every other parameter that depends on magnification moves with it.

Why does the image get darker when I increase magnification?

Because the same optical power is spread over a larger image of the object. Raising magnification narrows the field of view and increases the angle over which light is collected, so illumination to the sensor falls. The practical response is to increase exposure, add illumination, or accept a lower frame rate, and the trade-off is worked through in the brightness guide below.

How is a motorised zoom lens controlled from a machine controller?

Typically over a serial link such as RS-232, using a small command set for position and status, with the magnification position expressed as a pulse count that maps to a magnification value. The protocol and the pulse-to-magnification mapping are documented in the reference pages in the calculators index, and the SDK guide covers the software route.

What does parfocality mean and why does it matter?

A parfocal zoom lens keeps focus while magnification changes, so a part stays sharp as the system zooms. Without it every magnification change needs a refocus, which costs cycle time and introduces variation. Parfocality and centring are set during installation and drift is a common cause of gradual quality loss.

How much repeatability does a motorised zoom lens need?

Enough that returning to the same command produces the same magnification within a fraction of the object-side pixel size. If the process tolerance is expressed in micrometres, magnification repeatability has to be small enough not to consume a meaningful share of that budget, which is why the repeatability guides below use a multi-cycle test rather than a single check.

Can optics be changed programmatically during a run?

Yes, and this is what programmable optics means in practice: magnification, focus and sometimes aperture are driven by the machine rather than fixed at build time. The limit is time. Every optical change consumes part of the cycle, so the technique pays off when the alternative is a station change or a manual reset.

How do I verify an optical setup after installation?

With a calibration artefact of known dimensions and a repeatability test: measure the same feature repeatedly across the working range, across magnification settings if the lens zooms, and over a temperature cycle if the environment varies. Record the residuals rather than a pass or fail, so drift becomes visible before it becomes a defect.

4. Related POMEAS resources

• Machine Vision Optics Selection Guides: Complete Index
• Machine Vision Inspection Application Cases: Complete Index
• Machine Vision Optics Calculators and Formulas: Complete Index
• Machine Vision Optics Comparisons: Complete Index
• Machine Vision Optics Troubleshooting: Symptom Index
• All POMEAS machine vision knowledge articles
• POMEAS zoom lenses
• POMEAS telecentric lenses
• POMEAS FA lenses
• POMEAS machine vision lighting
• POMEAS Technical Reference Series — full-length notes on optical imaging performance testing and measurement method
• POMEAS TR-001 — 16 test methods for machine vision optical imaging systems

Talk to a POMEAS Engineer About Optics Integration

If the optics are chosen and the open questions are control and stability, send the lens and controller you intend to use, the interface available on your machine, and the magnification positions the process needs. We can work from the control and repeatability requirements.

Email: [email protected] | WhatsApp: +86 185 9810 2007

Reviewed by Tiger Xie.