Below is my take on optical calculator that helps with adapting a microscope objective to your camera for macro-photography. I originally wrote it as a quick helper tool for assembling my current optical inspection setup. It worked pretty well, so I decided to share it here. And before anyone asks – yes! It works not only for phono styluses but for bugs and bees too!
Optical System Calculator
Outputs
Theoretical introduction
Practical application
Input Field Explanations
Light
- Wavelength: Slider to adjust wavelength of light illuminating object.
- Wavelength (μm): Wavelength converted into micrometers.
- Color: The perceived color corresponding to the selected wavelength.
Sensor
- Type: Monochrome is set by default. This means only light intensity is sampled and sensor resolution is the same for all wavelengths. Color – assumes worst case Bayer filter influence on color sensor resolution when using monochromatic light.
- Format: Select the type or size standard of the camera sensor to update sensor width and height.
- Resolution: Select standard sensor resolutions to update sensor width in pixels.
- Sensor width (mm): The physical width of the sensor in millimeters.
- Sensor height (mm): The physical height of the sensor in millimeters.
- Sensor width (pixels): The horizontal resolution of the sensor in pixels.
- Pixels per Rayleigh distance: Number of pixels covering the diffraction-limited spot size (Rayleigh criterion).
- Pixels per Circle of Confusion: Number of pixels spanning the diameter of the Circle of Confusion, relating to perceived sharpness.
Objective
- Type: Finite is assumed by default.
- Magnification: The optical enlargement provided by the objective lens.
- Aperture (NA): Numerical Aperture; defines the light-gathering and resolving power of the lens.
- Field Number: Diameter of the observable field in the intermediate image plane, in millimeters.
- FOV object side (mm): Field of view on the sobject side, in millimeters.
- Nominal Tube length (mm): Standard distance between the objective and eyepiece for focus and nominal magnification.
- Used Tube length (mm): The actual distance used in the setup. For infinity-corrected objective this is tube lens focal length.
Output Field Explanations
Sensor
- Sensor diagonal (mm): The diagonal size of the sensor in millimeters.
- Pixel size (μm): The size of each pixel on the sensor, in micrometers.
Optics and Resolution
- FOV image side (mm): Field of view diameter in the intermediate image plane.
- Tube magnification: Magnification introduced by the mismatch of nominal and used tubes.
- Crop magnification: Effect of the sensor size compared to a full-frame reference.
- Real magnification: Combined magnification considering objective and sensor.
Aperture and Resolution
- Effective aperture: The effective aperture at sensor, adjusted for the tube magnification and Numerical Aperture.
- Optical resolution (μm): Smallest resolvable feature on the sensor, based on the wavelength and numerical aperture.
- Sensor resolution (μm): Smallest resolvable feature based on pixel size and number of pixels per Rayleigh sampling distance.
Focus and Depth
- Circle of Confusion (μm): Maximum blur diameter still perceived as sharp.
- DOField (classical) (μm): Depth of field using geometrical optics.
- DOField (wave) (μm): Depth of field considering wave optics and diffraction.
- DOFocus (mm): Depth of focus at image plane where the image remains sufficiently sharp, when moving only sensor.
- ΔTube Tolerance: Tolerance to variation of Tube Length, where we can refocus image and not loose any sharpness. Doesn’t apply to infinity-corrected objective.