Multiple Laser Image (MLI)
A multiple laser image is two or more pictures engraved into one area of a polycarbonate document beneath a lenticular lens structure, revealed in sequence as the document is tilted top to bottom. It is the vertical-axis counterpart to a changeable laser image.
| Abbreviation | MLI |
| Mechanism | Interleaved images laser-engraved under a lenticular lens array |
| Tilt direction | Top to bottom, using horizontal lens elements |
| Typical content | Portrait, document number, date of birth, national emblem |
| Image count | Two or more, revealed in sequence |
| Requires | Polycarbonate or another laser-engravable layered substrate |
| Close relative | CLI — changeable laser image |
The same technique on a different axis
The production method is identical to a CLI. Fine cylindrical lenses are formed into the card surface, the images are cut into interleaved strips and carbonized inside the polycarbonate by laser, and each lens presents only the strip beneath it at the current viewing angle.
What differs is orientation. An MLI uses horizontal lens elements, so the images change as the document rotates about its horizontal axis — tilting the top edge toward and away from you. A CLI uses vertical elements and changes as you rotate side to side.
Because the effect runs along a different axis, MLI is often used for sequences of more than two images, cycling through a portrait, a number, and an emblem as the tilt continues. In practice many issuers use both features on the same document, on perpendicular axes, so the card reveals different content depending on which way it is rotated.
Why MLI matters for identity verification
The verification value is the same as a CLI and worth restating because it is easy to miss: the feature physically co-locates data that would otherwise sit in separate places on the card.
A printed portrait and a printed document number can be altered independently. A portrait and a number interleaved beneath a shared lens array cannot — changing either means cutting into a structure that produces both, and the lens geometry does not survive the intervention.
Operationally, the practical consequence for capture is specific: MLI and CLI respond to tilts on perpendicular axes. A capture flow that prompts a user to tilt in only one direction will reveal one and miss the other entirely. That is a real design detail for anyone building guided capture into identity document verification, and a reason a single scripted movement is not enough on documents carrying both.
What tilting reveals
| Feature | Tilt axis | What changes |
|---|---|---|
| MLI | Top to bottom | The engraved image switches |
| CLI | Side to side | The engraved image switches |
| Hologram / DOVID | Any | Image shifts, moves, or changes color |
| Optically variable ink | Any | Color shifts between two states |
| Latent image | Shallow angle | A hidden image appears |
What an MLI can’t do
The wrong tilt axis reveals nothing. Rotating side to side on a document with an MLI shows a static image, which can read as a missing feature when it is simply the wrong movement.
A single frame cannot capture it. The feature is defined by change, and one photograph has one angle.
It needs polycarbonate. Laminated paper and PVC cards cannot carry the engraving or the lens structure.
It confirms personalization, not identity. The card was made properly and its data was written together. Whether the holder is the rightful owner requires liveness detection and biometric matching.
Frequently asked questions
Is an MLI the same as a CLI?
They use the same technology and differ in axis. A multiple laser image changes as the document tilts top to bottom using horizontal lens elements; a changeable laser image changes side to side using vertical ones. Many documents carry both.
How many images can an MLI hold?
Two at minimum, often three or more revealed in sequence as the tilt continues. Adding images reduces the resolution available to each, so issuers balance count against legibility.
Why does my ID look normal when I tilt it?
Possibly the wrong axis. An MLI responds to top-to-bottom rotation and a CLI to side-to-side. Trying only one direction is the commonest reason someone concludes a document has no tilt feature.
Can an MLI be photocopied?
No. The effect comes from a lens structure formed into the surface and images engraved inside the material. A copy reproduces whichever single image the copier saw, flat and unchanging.
