In Optics for Anti-Counterfeit: Part 1, we covered some of the integral optical systems for anti-counterfeit technology, such as holography and barcodes. Part 2 of the series focuses on ink-based technologies and encryption, which require optics systems for authentication.
Anti-Counterfeiting Technologies with Optical Components
Ink-Based Technologies
Ink-based technologies are often used for product authentication, but they could be used for identification and tracking in combination with a unique product identification code. Typically, ink-based technologies are used for documents and paper products.
Several types of ink can be used to market products, which may be distinguished by:
- A reaction to chemicals
- A reading tool
- A reading procedure
- Characteristics
Anti-counterfeiting inks may be visible or invisible. The latter is used to avoid altering the appearance of a product, limit interference with product processing, and prevent detection by counterfeiters.[1]
The types of ink-based technologies include:
UV-Sensitive Inks
UV-sensitive inks are photosensitive and change colors or disappear when exposed to ultraviolet light. This is due to fluorescent pigments, which are one shade in natural light and another under UV light. Only certain devices can detect UV-sensitive inks, such as a Wood’s lamp that emits electromagnetic radiation.
These inks may be used for:
- Authentication
- Anti-tampering
- Anti-alteration
- Physical products and packaging
- Very small, small, medium, and large products
UV-sensitive inks are both visible and invisible and require a reading device, though they don’t require a connection to a server.
IR-Sensitive Inks
IR-sensitive inks are invisible to the naked eye and can only be detected with an infrared reader. They can be used on a variety of materials to prevent unauthorized photocopying. Typically, IR-sensitive inks are used to hide barcodes and prevent unauthorized reproduction.
They may be used for:
- Authentication
- Anti-tampering
- Anti-alteration
- Physical products and packaging
- Very small, small, medium, and large products
IR-sensitive inks are invisible to the naked eye and require a special infrared reading device. They don’t require any connection to a server.
Magnetic Inks
Magnetic inks contain metallic pigments that respond to magnets with special reading devices. They’re usually used with serialization and numbering on currency and checks, but they may be used to encode and authenticate documents.
Magnetic inks are suitable for:
- Physical products and packaging
- Authentication
- Anti-tampering
- Anti-alteration
- Very small to very large products
They are invisible to the naked eye and require no connection to a server, but they do require a reading device.
Optical Variable Inks
Optical variable inks (OVI) and iridescent inks use pigments that look like two different colors at different angles – much like color-shifting paint. They may be red-green, green-blue, or gold-silver. This technology is one of the best for preventing document forgery because it’s challenging to reproduce (if not impossible) with copiers and scanners.
These inks are suitable for:
- Authentication
- Anti-tampering
- Anti-alteration
- Very small to very large products
- Physical products and packaging
OVI inks are visible and require no connection to a server or special reading device.
Thermochromic Inks
Thermochromic inks change color when exposed to different temperatures, even as slightly as rubbing the material with a fingertip.[2] In some cases, thermochromic ink will return to its original color when the temperature stabilizes, but some inks are irreversible once the color change occurs. In addition, some thermochromic inks become clear under heat, which shows the background color.
These inks are suitable for:
- Authentication
- Anti-tampering
- Anti-alteration
- Very small to large products
- Physical products and packaging
Thermochromic inks are visible (except with inks that turn clear) and require no server connection or reading device.
Reactive Inks
Reactive inks have a reaction to different chemicals or solutions. The properties differ between inks, with some undergoing a color transformation, some disappearing, and some running or smudging – all of which indicate tampering or alteration.[3]
These inks may be used for:
- Authentication
- Anti-tampering
- Anti-alteration
- Physical products and packaging
- Very small to large products
Reactive inks are visible and require no server connection or reading device.
Encrypted Images
Encrypted images obscure information on photographs or documents using encryption. The encrypted information is printed in its encoded format, which isn’t detectable by the naked eye. It’s only visible when viewed through a special viewer (decoding lens) or lab equipment like a scanner or video camera with specialized image processing software.
This technology is suitable for:
- Authentication
- Physical products and packaging
- Very small to large products
Encrypted images are invisible and require both a special reading device and a connection to a server.
Optics for Anti-Counterfeiting at Apollo Optical Systems
Apollo Optical Systems offers optical and mechanical design and engineering for custom optical projects, including anti-counterfeiting technology. Contact us today to learn more about our services.
Sources:
[1] https://spie.org/news/nerac-0308?SSO=1 [2] https://www.sciencedirect.com/topics/engineering/thermochromic-material [3] https://core.ac.uk/download/pdf/200249565.pdf