Frequently Asked Questions: Rigid Endoscope Service - Page 4
Service Turn-Around Time and Equipment Protection
Disassembly and Repair Process
Final Inspection and Test
Image Resolution
Do you use the 1956 U.S. Air Force resolution targets? If so, describe method for determining resolution.
Visual control is determined using the U.S. Air Force resolution targets or customized IMS targets. Both are available as part of our optical bench.
Acceptable resolution is determined by inspecting the clarity of identified test markings on either of these targets. These test lines must be clear on the endoscope image in order for resolution to be deemed acceptable.
Is resolution measured in on-axis and off-axis (near edge of visible field)? Describe this process.
Yes. The scope is placed in a holding bracket and resolution targets are placed in the center of view and evaluated. The targets are then moved to the edge of the visible field to check resolution.
Image distortion
Describe the method for measuring optical (field) distortion.
If distortion is present, it is checked by visual observation, picture analysis, and resolution measurements.
What standard is used for determining fitness for use?
The U.S. Air Force resolution targets or customized IMS targets are used to observe distortions.
Ocular fine focus
Describe methods used to set fine focus. How is working distance for center of depth of field determined?
Working distance for center of depth of field is a working parameter set by the manufacturer for a particular endoscope optical design and should remain constant.
Using a Diopter telescope, IMS technicians verify that the marker plate and image are concurrently in focus (at the correct distance) to ensure adherence to this manufacturer parameter.
What is the criteria for determining the focus envelope? Is focus boundary a function of degradation of MTF, resolution, blur circle? Describe method in detail.
- The endoscope is secured in the Endobench™ device
- Targets are placed in the center of the visual field (as set by the manufacturer) to verify resolution at the center of the focus envelope.
- Targets are moved to the outer limits of the visual field (the focus boundary) and resolution is verified.
Fiber illumination pattern
How do you determine if individual fiber strands are broken?
A light source is attached to the scope and light degradation is mathematically determined.
What percentage of broken fibers is permissible?
This depends on customer preference, but no more than 30% breakage before the scope becomes nonfunctional.
How is the percentage of broken fibers determined?
The surface area is visually inspected and the amount that is black represents the percentage of broken fibers.
How is the overall light pattern shape and spread determined?
The light is projected on a flat surface and a target at the optical bench.
How is the illumination intensity (shading or uniformity) determined?
Illumination intensity is measured with a light meter.
If shading is unacceptable, what steps can be taken to generate a more Gaussian profile?
If shading is determined to be unacceptable, the scope must be refibered.
Fiber illumination to field of view alignment
What is your criteria for field of view to illumination pattern alignment?
The illumination (circle) has to align (overlap) the field of view. This is tested on the optical bench using a tolerance sheet.
Is overlap set at center of depth of field (optimum focus)?
Yes.
Describe how this is confirmed.
The field of view, angle of view, and illumination overlap are evaluated.
What is the specification for this criteria?
The value of the field of view, the value of the angle of view, and illumination overlap compared with the field of view.
Image centration within field of view
How do you ensure that the optical image is centered in the field of view?
Optical image centering is achieved by using proper optical components, a straight shaft, and ensuring that the optical axis and the mechanical axis are centered.
What standard is used to confirm centration?
Testing is performed at the optical bench and the camera system is used for final validation.
Shaft form and factor acceptability
What standard defines the maximum size of surface scratches, dents, kinks or other anomalies?
- Surface scratches, dents, kinks, or other anomalies are removed and smoothed for stainless steel parts when:
- Those imperfections render the scope unable to perform to its original performance standards.
or
- They present the opportunity for bioburden to collect on endoscope surfaces.
- If scratches, dents, etc. create one of these conditions, they must be removed or the part must be replaced.
What standards are employed to ensure that shaft length is maintained to specified lengths for critical length devices?
IMS has a comprehensive list of all endoscope lengths / working lengths with the tube diameter, etc.
What methods are taken to ensure the distal tip end conforms to OEM specified geometries?
Measurements are controlled with a calibrated digital caliper. Conformance to OEM specified geometries are verified against redesigned drawings of all specific distal ends within our Quality Manual and work instructions.
Light pipe performance
How is transmission efficiency measured? Describe process and instrumentation used to determine fiber throughput.
A light meter / Ulbricht sphere is used to measure light transmission.
Does your refurbishment process involve the polishing of the fiber bundle at the optical connector?
Yes. Our polishing process includes polishing the optical connector and then it is rebuilt to OEM performance standards.
If repolishing is performed, describe the steps that can be taken to ensure the bundle / collector's face remains durable and resistant to sterilization.
Our repairs are rigorously tested using all common methods of sterilization to include Steris®, Sterrad®, steam, and gluteraldehyde and are compatible using all four methods. IMS uses a laser welder during its repair process for autoclavable scopes to increase durability of its repairs and ensure resistance during the sterilization process.
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