| Anchor | ||||
|---|---|---|---|---|
|
Section Half Imaging Logger Light Array Installation and Calibration: Advanced User Guide
Manual Information
Author(s): | B. Crawford |
Reviewer(s): | J. Beck, T. Fulton |
Supervisor Approval (Name, Title, Date): |
Audience: | Imaging and Laboratory Specialists |
Current Version | Draft 11/14/08 |
Revised: | Draft 1/7/14 (IODP-II) |
Domain: | Physics |
Analysis: | Section Half Imaging |
Introduction
This manual presents techncial staff with information about installing and calibrating the light array.
...
Initial Lighting Installation
Level all mounting plates by measuring using the gantry base plates as a datum marker. |
Mount light pair B1-A and B2-A 100 mm from the core surface ("zero") using the second set of countersunk holes from the bottom of the plate. |
Mount light pair B1-B and B2-B 100 mm from 15 mm below the surface of the core (–15) using the third set of countersunk holes. |
Mount light pair B1-C and B2-C 100 mm from 25 mm below the surface of the core (–25) using the fourth set of countersunk holes. |
Lighting Adjustment
Lighting adjustment occurs in 2 major steps, initial adjustment and fine adjustment.
Making Initial Adjustments to Lighting
...
Place the calibration target sample in the core sample rail support. |
Using the grab function and free gantry travel, center target on screen (ensure camera is set to grab mode). |
Align the target precisely to the single line of pixels. |
Turn on the lowest bank of lights (pair A) and slightly loosen the countersunk adjustment screws. |
Point each light on either side of the target and split each beam at the surface (level zero) of the target. |
Slightly snug the countersunk screws. |
Slightly loosen the countersunk screws on light pair B and turn on the lights. |
Adjust the lights to span the level 15 mm below the target surface (–15) to touch the beam of light pair A. |
Slightly snug the countersunk screws. |
Slightly loosen the countersunk screws of light pair C and turn on the lights. |
Adjust the lights to place the beam between the level 25 mm below the target surface (–25) and touching the beam from light pair B. |
Slightly snug the countersunk screws. |
Fine Adjustment
| Wiki Markup |
|---|
Up to this point, the vertical target line has been used to align the lights. The 45° slope line will be used in the fine adjustment to achieve feathering or overlap of the beam. During fine adjustment, the line represents the line of pixels that camera images. On the line it is apparent that target areas are not covered smoothly, as the beam edges may not touch. Disregard the intensity or apparent brightness of the beams and concentrate on "painting" the line from top to bottom with light. Density adjustments will be made during a later step.Note that 3 pairs of lights at 5 mm beam width each will not quite cover the full 35 mm of core depth. If needed, bias the light coverage starting at the top of the core, as this is the most frequently imaged. Sacrificing the deepest 5 mm (level 30-35 mm below the core surface \[-30 to -35\]) in light coverage and focus is acceptable. |
...
Making Fine Adjustments to Lighting
...
Carefully overlap the beams until they barely touch, maintaining even light coverage along the target line. |
Tighten all countersunk screws to set the beam adjustments. |
Proceed to final adjustment and calibration of the camera color and exposure (see "Camera Calibration"), after which the density adjustment for the sample at different levels will be achieved by adjusting the power settings. |
Power Intensity Adjustment
...
Adjusting Light Power Intensity
...
After the camera is calibrated and adjusted, image the multilevel core calibration standard. |
Read density targets in PhotoShop. Disregard normal density gray card settings (e.g., 128) because the dynamic range of the camera is not linear. Expect gray card densities in the range 70–128. |
Look at trends and ratios to the topmost density target on the core standard and then match the lower targets using power settings for light pairs B and C. |
Author: I have callouts and captions but no photos for the following figures:
- Light source with distances A, B, and C in relation to the split core sample.
- Light source with baffles or multiple beams.
- Arrangement of six lights.
- LED bulbs and LED lens focus lengths.
- Naming of light banks and levels.
- Overlapping light beams.Provide screenshots, drawings, photos, or applicable.