Thermo Optical Analysis Consulting

 

OSCI Inc. has already established a reputation for consulting and training in the field of optical system design, optical instrument design and development, and general optical engineering.  OSCI Inc. has now teamed with Kleinfeld Technical Services, Inc. (KTS) to offer combined optical and thermo-optical analysis consulting.  KTS has extensive experience in thermal analysis, finite element analysis (FEA), computational fluid dynamics (CFD), and infrared (IR) thermography for thermal process diagnosis, trouble shooting, analysis, and improvement projects.  KTS has established a world-wide reputation and has published widely in the areas of infrared thermography, heat transfer and thermal analysis, and has presented  webinars for worldwide audiences.

The field of thermo-optical analysis incorporates several different disciplines for the main purpose of understanding how temperature will affect the optical performance of an optical instrument or optical system.  OSCI Inc. and KTS perform thermo-optical analysis on optical systems that are in design , development, or are in the field and experiencing thermally induced performance problems.  We perform the thermo-optical analysis on imaging and non-imaging (illumination) optical systems and instruments using OSCI Inc.'s state-of-the art optical modeling tools and optical engineering experience of over 20 years combined with KTS's analysis and measurement capabilities based on over 30 years of engineering experience.

Some of the common analysis areas for our consulting services are:

• Thermally induced aberrations—thermal surface deformations of lenses, mirrors, and prisms
• Thermally induced optical alignment problems
• Thermal modeling of refractive and reflective optical systems including optical element mounts, metering structures between
  elements, and flexures.
• Passive athermalization of optical systems (stay in focus over temperature by design)
• Active athermalization of optical systems
• Thermal Airflow analysis of optical systems and optical instruments
• High Power LED illumination systems and cooling analysis
• Thermal process analysis such as: UV adhesive curing, laser welding, laser cutting, etc.
• Thermally induced mirror mounting stress analysis and optical system wavefront analysis
• Light weight mirror bi-metallic thermal deformation—Ni shell on Be substrate for example
• Thermal analysis of various optical mounting methods—elastomeric lens mount (RTV), mirror clips, retaining rings, structural epoxy,
  RTV pads, etc.

An example of the results available from a thermo-optical analysis of a simple optical system component

This optical instrument subsystem has been simplified to present only the combining prism.  The impact of other components, air flow, and mounting methods has not been shown—but if that is what YOUR system needs, then this is the place to get it. 

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To inquire about how we can help you solve your thermal design, analysis, or improvement project on your optical system please give us a call at 541-255-2165 or email info (at) oscintl . com with your basic requirements.

Thermal Analysis Results

These FEA results show the temperature and thermally induced stresses in the combiner prism above.  Note that the prism has been rotated to show the combined light exit face on the lower left, since it is the most aberrant location -- it has the highest temperature and the greatest stress concentration.  The stresses shown are based solely on the combiner prism's behavior.  They will be affected by the prism mount, which was not incorporated in this calculation.  Additional results that are available, even from this simple analysis, include the distortion of the faces of the prism and the effect on the optical performance of the prism. 

Von Mises Stress:  Thermally induced stress	Temperature profile on prism surfaces

Thermal profile in cross section of beam combiner prism.  The shadowed areas in the cross section show the illuminated paths in the prism.  Note that the highest temperatures occur inside the prism where the blue + green and the red light paths overlap. 

A simplified example of a beam combiner thermal analysis in an optical instrument at operational temperature.

Beam Combiner Prism Ray Trace, with the Blue + Green inlet at the lower left and the Red inlet at the upper left.  The combined light exits to the upper right prism face. (Not shown.)   Note that the upper prism gets 3X as much irradiance as the bottom prism.  This affects the temperature profile of the prisms in operation, as shown below in the thermal analysis results.

The graph below is actual data from an optical instrument.  Note that there is a significant temperature rise experienced by the prism inside the instrument.  Its temperature rise is approximately 45° to 50°F ( 25° to 27°C).

Actual optical element measurement of temperature rise
in operating instrument for thermal soak analysis