Range: Typically +5D to +40D. Example values: +5D, +10D, +20D.
Definition: Lens Power (P) refers to the optical power of the magnifying lens, measured in diopters (D). A higher diopter value indicates a stronger lens that can magnify objects more effectively.
Range: 0.05 meters (5 cm) to 0.5 meters (50 cm). Example values: 0.1m, 0.2m, 0.3m.
Definition: Image Distance (v) is the distance from the magnifying lens to the image formed by the lens, measured in meters. A shorter distance generally means higher magnification.
Range: 0.1 meters (10 cm) to 0.4 meters (40 cm). Example values: 0.1m, 0.2m, 0.3m.
Definition: Working Distance (z) is the distance between the magnifying lens and the observer's eye. A longer working distance allows the user to view the magnified object comfortably.
Lens Power (P): Lens power is the optical strength of the magnifier, measured in diopters (D). Higher diopter values mean stronger magnification. For example, a lens with +10D power will magnify more than a lens with +5D power.
Image Distance (v): The image distance refers to how far away the image is formed behind the magnifying lens. This is affected by the lens power and the distance of the object. By measuring the image distance, we can calculate how the light bends and forms the magnified image.
Working Distance (z): The working distance is the distance between the magnifier and the observer’s eye. A longer working distance allows for comfortable viewing of the magnified image, making it essential for proper ergonomic use of stand magnifiers.
Vergence (U and V): Vergence refers to the convergence or divergence of light rays as they pass through the magnifying lens. The object vergence (U) and image vergence (V) tell us how the lens bends light to create a focused image. Image vergence (V) is calculated by the formula V = 1/v, where "v" is the image distance. Object vergence (U) is derived from the formula U = V - P.
Enlargement Ratio (ER): The enlargement ratio is the amount of magnification provided by the lens, calculated as the ratio of the object vergence to image vergence (ER = U/V). This value tells us how much larger the object appears compared to its original size.
Equivalent Viewing Distance (EVD): The equivalent viewing distance gives an estimate of how far away the magnified image appears to be, allowing the observer to determine the relative ease of viewing the object. It is calculated using the formula EVD = (z + v) / ER, where z is the working distance and v is the image distance.