F-Theta Field Error
Compare measured scan position with the ideal f-theta field position.
Description
An f-theta scan lens ideally maps angle to focal length times angle.
An f-theta scan lens ideally maps angle to focal length times angle. Measured-minus-ideal error is normalized to the signed ideal coordinate.1
Compare measured scan position with the ideal f-theta field position.
When to use F-Theta Field Error
Use this tool to compare measured scan position with the ideal f-theta field position.
Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
How to use F-Theta Field Error and understand its results
- Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
- Enter focalLengthMillimeters, scanAngleRadians, measuredPositionMillimeters using the field table and calculation rules, then run the tool.
- Read idealPositionMillimeters, fieldErrorMillimeters, relativeFieldErrorPercent. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| focalLengthMillimeters | F-theta focal length (mm) | number; minimum: 0 | Required |
| scanAngleRadians | Scan angle (rad) | number | Required |
| measuredPositionMillimeters | Measured field position (mm) | number | Required |
Enter nonnegative focal length and finite signed angle/position, requiring nonzero ideal coordinate. Return ideal, error and signed percentage.
ideal=f×angle; error=measured−ideal; relative%=100error/ideal Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| idealPositionMillimeters | Ideal f-theta position (mm) | number |
| fieldErrorMillimeters | Field-position error (mm) | number |
| relativeFieldErrorPercent | Relative field error (%) | number |
{
"input": {
"focalLengthMillimeters": 100,
"scanAngleRadians": 0.1,
"measuredPositionMillimeters": 11
},
"output": {
"idealPositionMillimeters": 10,
"fieldErrorMillimeters": 1,
"relativeFieldErrorPercent": 10
}
}Limitations and assumptions
The center position is rejected because relative normalization is undefined. No calibration surface or distortion compensation is generated.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Galvo Grid Error: Summarize radial positioning error from a galvo calibration grid. For a complementary task, use Optical Phased-Array Steering: Calculate phased-array beam steering from wavelength, element spacing, and adjacent phase shift.
References
-
F-Theta Field Error — tool.io
Similar or alternative tools
- Galvo Grid Error
Summarize radial positioning error from a galvo calibration grid.
- Optical Phased-Array Steering
Calculate phased-array beam steering from wavelength, element spacing, and adjacent phase shift.