Oct 21, 2026
CLI and MLI Explained: How Changeable and Multiple Laser Images Protect ID Cards
Tilt a modern national ID card or driving licence and a small area changes: the photo becomes the date of birth, or a number turns into a second, smaller portrait. That effect is a changeable laser image (CLI) or a multiple laser image (MLI). It is one of the most effective level 1 security features available today, because anyone can check it in a second and almost no one can fake it.
This guide explains how CLI and MLI work, why they are hard to counterfeit, how to inspect them and what an issuer needs to produce them.
What CLI and MLI Are
Both are laser-engraved images that change depending on the viewing angle. They sit in a small, usually rectangular area of the card, often next to the main portrait.
A changeable laser image typically shows two different pieces of information. Seen from one angle, the area shows, for example, the holder’s portrait. From another angle, it shows the date of birth or the document number.
A multiple laser image works on the same principle and can show more than two images, or images with different content and effects as the card moves.
The terminology is not perfectly consistent across suppliers. Some use CLI and MLI almost interchangeably. What matters for the issuer is the effect: personalised content that changes with the viewing angle, written by laser through a lens structure in the card.
How They Are Made
Step 1: the lens structure
The card body manufacturer prepares a window in the card. During lamination, a fine pattern of tiny cylindrical lenses is embossed into the transparent top layer over that area. These lenticular lenses are like the ones used in 3D postcards, but much smaller and integrated into the polycarbonate.
This step happens at the card factory, before personalisation. Without the lens structure, a personalisation system cannot produce CLI or MLI.
Step 2: laser engraving through the lenses
During personalisation, the laser engraves through the lenses at two or more precise angles. Each lens focuses the beam onto a narrow strip of the laser-sensitive layer beneath. The first angle writes thin strips of image A. The second angle writes thin strips of image B, interleaved with the first.
When someone looks at the card, each lens shows the strip that matches the viewing angle. Tilt the card, and the eye moves from the strips of one image to the strips of the other. The image appears to switch.
Matica describes the process in simple terms: the card body is prepared with a CLI or MLI window, then the laser prints the text or image through it at two different angles.
Step 3: precise registration
The laser must hit the lenses at exactly the right position and angle. A small misalignment blurs the images or mixes them. Personalisation systems use vision cameras to locate the lens area on each card and adjust the laser before engraving.
Why CLI and MLI Are Hard to Fake
They need the genuine card body. The lens structure is created during card manufacture. A counterfeiter would need to reproduce the lenses with the right pitch and depth, inside a laminated polycarbonate card.
They need laser personalisation. The images are engraved inside the card through the lenses. Printing on the surface cannot reproduce the effect.
They carry personal data. Because the content is the holder’s own portrait or data, a counterfeiter cannot use a generic pre-made feature. Each card is unique.
They link to the rest of the card. The inspector can compare the portrait or the date of birth in the CLI with the main data. Any mismatch is immediately visible.
They resist alteration. Changing the main portrait or date of birth on a genuine card would leave the CLI showing the original data.
How to Inspect a CLI or MLI
Inspection takes a few seconds and needs no equipment.
Hold the card at reading distance and tilt it slowly forward and backward, or from side to side, depending on the design.
Check that the image changes cleanly. Each view should be sharp, with no mixing of the two images at normal viewing angles.
Compare the content with the main data. The portrait should match the main photo. The date of birth or document number should match the printed data.
Feel the surface. The lens area often has a slightly different texture from the rest of the card.
Look for signs of tampering. Scratches, glue or lifted edges around the window suggest an attempt to modify the card.
Training matters. A CLI only protects the card if police officers, border guards and bank staff know where it is and what it should show.
CLI, MLI and Other Laser Features
CLI and MLI work best alongside other laser-engraved features. Together they create layers that a counterfeiter would have to reproduce all at once.
- Laser-engraved portrait. What it does: Writes the main photo inside the card. What the inspector checks: Sharp grey-scale image, no surface print.
- Ghost image. What it does: A smaller second portrait, often in a different area. What the inspector checks: Matches the main portrait.
- Tactile engraving. What it does: Raised data that can be felt. What the inspector checks: Relief on name, number or date.
- Transparent window. What it does: Clear area with engraved data or image. What the inspector checks: Visible from both sides.
- Floating image. What it does: Data that appears to float inside the card. What the inspector checks: Depth effect when tilted.
- Edge engraving. What it does: Data engraved along the card edge. What the inspector checks: Matches the document number.
- CLI or MLI. What it does: Images that change with the viewing angle. What the inspector checks: Clean switch, data matches.
Thales, for example, offers a laser-engraved floating image that makes the holder’s personalised data appear to float within the credential. Different suppliers have their own variants. When designing a document, choose features that your inspectors can check quickly and that your personalisation equipment can reproduce reliably.
What an Issuer Needs
A card body with the lens structure
The card supplier must integrate the lens area during manufacture. Agree early on its position, size and lens specification, because the personalisation system needs to match them.
A personalisation system that supports CLI and MLI
Not every laser system can engrave through lenses at controlled angles. Some desktop systems offer MLI as standard and CLI as an option. Check which effects are supported, on which card bodies, and at what speed.
Registration and verification
The system must find the lens area precisely on every card and confirm the result. Automated inspection should check that both images are present and readable, not only the main portrait. LIZAR’s DRACO system combines laser personalisation with AI-based quality inspection after engraving.
Qualification on your own cards
Lens structures differ between card manufacturers. Before rollout, personalise a batch on your own card body, check the images at several angles and adjust the settings if needed.
Common Problems and How to Avoid Them
Blurred or mixed images. Usually a registration error or a mismatch between laser settings and lens specification. Solve with vision-based registration and qualification on the actual card body.
Faint images. The laser power or the sensitivity of the layer may not match. Test on cards from each production batch.
Images too small to read. A CLI that holds too much data becomes unreadable. Keep content simple: a portrait and one short data element.
Features nobody checks. Without training and clear public reference material, even a perfect CLI adds little protection.
Frequently Asked Questions
What is a CLI on an ID card?
A changeable laser image is a laser-engraved area that shows different personal information, such as the portrait and the date of birth, depending on the angle at which you look at the card.
What is the difference between CLI and MLI?
Both use a lens structure and laser engraving at different angles. A CLI typically shows two images. An MLI can show more images or different effects. Suppliers do not always use the terms in the same way.
How are CLI and MLI images made?
The card manufacturer embosses tiny lenses into the card’s transparent layer. During personalisation, a laser engraves through the lenses at precise angles, writing interleaved strips of each image.
Why are CLI and MLI hard to counterfeit?
They require the genuine card body with its lens structure, laser personalisation inside the card and personal data unique to each holder.
How do I check a CLI on an ID card?
Tilt the card slowly. The image should switch cleanly between views, each view should be sharp and the content should match the main portrait and data.
Can any laser system produce CLI and MLI?
No. The system must locate the lens area precisely and engrave through it at controlled angles. Always check support for your specific card body.
Do CLI and MLI work on PVC cards?
They are designed for polycarbonate cards with an integrated lens structure. Polycarbonate is the standard material for documents that use these features.
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