1) Lens 2) Microscope 3) Telescope 1) Scientific instrument 
A magnifier is a device used for magnification. Magnifier can also refer to: ...[Windows] Magnifier, formerly Microsoft Magnifier, is a screen magnifier program intended for the visually impaired to use Microsoft Windows. When it is run, it creates a bar at the top of the screen that greatly magnifies where the mouse is. Magnifier was first included as a sample in the Active Accessibility SDK/RDK for Windows 95 and lat...
• (n.) One who, or that which, magnifies.
Mag'ni·fi`er noun One who, or that which, magnifies. 
[n] - a scientific instrument that magnifies an image
magnifier 1. A person who or a thing that magnifies. 2. A lens or fixed combination of lenses used to increase the apparent size of an object when viewed directly; a magnifying glass; also, an eyepiece.
noun a scientific instrument that magnifies an image