MVLscope LESSON 07 / About 28 min
Find where the image really is.
Lenses & Image Formation
Build a signed ray picture, pair object and image planes, and discover why microscope objectives depend on the rest of the optical system.
Before you begin
Light & Matter · Numerical Aperture
Try a setting, save an observation, then change one thing. The explanation checks are optional.
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MAKE SENSE OF WHAT YOU SEE
A QUESTION TO THINK ABOUT
See the assembly in 3D Optional · all controls also work above
Optional 3D view. The calculated diagram above is the measurement reference.
YOUR EVIDENCE
Keep the comparison.
Saved images and readouts stay as they were when you captured them. Save a second setting to compare side by side.
Your notebook is empty. Use “Save this observation” beside an experiment.
Lesson outline
Where does the image exist?
A lens changes a ray’s direction. An image is where rays from one object point meet—or appear to have come from. Move the object through the focal plane and watch that distinction change.
Real versus virtual describes ray geometry. “Virtual” does not mean invisible.
Match the screen to its conjugate
Object and image planes come as a pair. The lens equation chooses the partner plane; the camera does not choose it by being placed there.
Changing aperture changes the out-of-plane footprint, not the paraxial conjugate distance.
Two lenses make an infinity microscope
An infinity objective sends each in-focus object point into its own parallel bundle. A tube lens turns bundle angle into image position.
The objective encodes position as angle; the tube lens converts angle back into position.
Respect the objective’s design
A finite objective and an infinity objective aim their outgoing rays differently. Compare two ideal designs, each with its own correctly placed specimen.
Identify the intended conjugates and the matched optical system before swapping parts.
A field stop is not a pupil stop
Two openings can have the same diameter yet control different information. One selects specimen positions; the other selects directions of light from each position.
Ask which plane contains the stop: specimen positions or ray directions?
Model, limits & sources
All calculations are paraxial geometric optics, with ideal thin lenses and a homogeneous surrounding medium. This is not a lens prescription or a compatibility calculator.
Negative image distance denotes a virtual image on the object side; signed transverse magnification is negative for an inverted real image.
The infinity relay assumes an in-focus specimen, unlimited clear apertures, no aberrations, and a detector one tube-lens focal length behind that lens.
The stop illustration models geometric cropping and uniform-pupil light throughput. It does not calculate diffraction or an actual specimen image.
Read further
PUT THE IDEA TO WORK
Trace a selected specimen point through a complete microscope and explore focus in depth.