SAL/IR Seeker Spreader Homogenizes Laser Energy
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Solution Overview
Problem
Co-boresighted dual-mode SAL/IR seekers for projectiles experience boresight shift and slope non-linearities due to obscurations and vignetting, requiring labor-intensive calibration to meet system requirements.
Innovation Solution
A two-mirror telescope optical system with a secondary lens positioned on the forward side of the secondary mirror and a spreader between the secondary mirror and SAL detector to spatially homogenize laser energy, forming a small spot on the SAL detector and increasing its size to meet slope requirements, thereby reducing boresight shift and slope non-linearities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a co-boresighted dual-mode SAL/IR seeker uses a two-mirror telescope optical system with a common aperture, then both IR and laser energy can be collected and focused onto a secondary mirror/lens, but obscurations and vignetting cause boresight shift and slope non-linearities in the SAL detector's system transfer function
Solution Approach 1:
A spreader element is introduced as an intermediary component in the SAL optical path between the secondary mirror/lens and the SAL detector. This spreader spatially homogenizes the laser energy, creating a more uniform spot distribution that compensates for the non-linearities caused by obscurations and vignetting in the common aperture optical system.
Solution Approach 2:
The optical configuration is modified by positioning the secondary lens on the forward side of the secondary mirror/lens and adjusting the SAL detector position to form a small spot of focused laser energy. The spreader then modifies this spot size and distribution to meet slope requirements, changing the spatial parameters of laser energy distribution to reduce boresight shift and improve linearity.
2Manufacturing precision
If the secondary lens is positioned on the forward side of the secondary mirror and the SAL detector is positioned to form a small spot, then the optical system can meet slope requirements, but the spot size is too small causing excessive sensitivity to position variations
Solution Approach 1:
The spreader element changes the spatial parameters of the laser energy spot by spatially homogenizing it. This increases the spot size from a small focused point to a larger, more uniform distribution, reducing the system's sensitivity to position variations while maintaining compliance with slope requirements through proper optical configuration.
3Manufacturing precision
If calibration is performed to meet slope requirements, then the system transfer function can be adjusted, but the calibration process is labor-intensive and time-consuming
Solution Approach 1:
The spreader element is positioned and configured during system assembly to pre-establish the optimal spot size and distribution characteristics. This preliminary configuration of the optical parameters reduces or eliminates the need for labor-intensive post-assembly calibration, as the system is pre-adjusted to meet slope requirements through the spatial homogenization effect of the spreader.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration simplifies the calibration process, reduces boresight shift and slope non-linearities, and improves the system transfer function, allowing the guidance system to operate effectively with minimal calibration.
Implementation Method 1
a two-mirror telescope optical system provides a common aperture at the primary mirror for collecting and focusing both IR and laser energy onto a secondary mirror/lens that reflects the IR energy
Implementation Method 2
collecting and focusing both IR and laser energy onto a secondary mirror/lens
Implementation Method 3
positioning the SAL detector to form a small spot of focused laser energy on the SAL detector
Implementation Method 4
The spreader is configured to spatially homogenize the laser energy to increase the size of the spot of focused laser energy on the SAL detector
Data Source
AI summary
In a co-boresighted SAL/IR seeker, the optical system and particularly the secondary lens and position of the SAL detector are configured to produce a well-corrected spot of laser energy at the SAL detector. A spreader is positioned between the secondary mirror/lens and the SAL detector, possibly on the secondary mirror, away from the aperture stop and not in the optical path to the IR detector. The spreader is configured to spatially homogenize the laser energy to increase the size of the spot of focused laser energy at the SAL detector to set the system transfer function to meet slope requirements. Spatial homogenization serves to reduce both boresight shift and slope non-linearities. This approach greatly simplifies the time and labor intensive calibration of the SAL detector's system transfer function.