Two-lens interactive explorer

Open this page through a web server with JavaScript enabled to explore. The static reference below shows the baseline used by the interactive explorer.

Lenses of 100 and 150 mm focal length, separated by 250 mm, image an object 100 mm before the first lens onto a plane 150 mm after the second, with magnification minus 1.5.

Explore: departures from the 4-f baseline

Move the object or change the lens separation. Compare the best-focus plane with a sensor held one focal length after the second lens.

Object-distance change, d₁ − f₁ Lens-separation change, s − (f₁ + f₂) Sensor mode

The focal lengths are f₁ = 100 mm and f₂ = 150 mm. Lens 1 stays at z = 0. Increasing d₁ moves the object left; increasing s moves lens 2 right. In fixed mode, the sensor stays 150 mm after lens 2 and moves with it.

Fixed schematic axes: z = −180 to +550 mm; x = −14 to +14 mm. Axial and transverse scales differ. Solid, dashed, and dotted rays start at x = 3 mm with angles −0.04, 0, and +0.04 rad.

Curves vary the object distance at the selected lens separation. Dashed gray curves show the baseline separation s = 250 mm; circles mark the current setting. Magnification describes the refocused image, even when the sensor is held away from focus.