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--- song_spectrograph_assembly [2025/05/02 14:24] – holtz
+++ song_spectrograph_assembly [2025/05/30 17:55] (current) – 172.59.0.80
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+====== Spectrograph assembly guide ======
 ===== Room requirements/setup =====
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     - input fiber unit
     - input LED source
-    - 100mm lens assembly
+    - 100mm lens assembly [[https://www.thorlabs.com/thorproduct.cfm?partnumber=ACA254-100-A| Thorlabs ACA254-100-A]]
     - (removable) beam splitter
     - laser input
     - (removable) beam splitter
-    - slit viewing camera
+    - slit viewing camera with 150mm reimaging optics
-    - right angle unit and 100mm (?) reimaging optics
+    - right angle unit and 100mm reimaging optics (same as above)
     - slit
   - collimating telescope mount, rail with two diagonal mirrors
@@ Line 67: / Line 68: @@
       - rotate far diagonal to direct towards diagonal under collimator for all positions of far diagonal
       - adjust diagonal under collimator to get beam in collimator.
-{{ :spec:collimator.jpg?direct=300 }}
+{{ :spec:collimator.jpg?direct=400 }}
   * With aligned collimator install flat (grating flat, FM2, and FM3 on table in desired location. Also install prism mount for convenience before adding upper table. For each of the three flats:
@@ Line 73: / Line 74: @@
     * Focus autocollimator to get retroreflection reticle
     * adjust tip-tilt of flat to get alignment
-{{ :spec:flats.jpg?direct&300 }}
+{{ :spec:flats.jpg?direct&400 }}
   *  set up upper table on main optical bench in correct location. Install:
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     - collimating assembly with 1-inch 100mm lens in tube. Clear area is ~22mm, giving f/4.5 beam (or slower if input beam is slower)
     - laser input via removable beam splitter,
-    - camera output via removable beam splitter,
+    - camera output via removable beam splitter with 150 mm focusing lens
-    - output focusing lens, also 100mm??
+    - output focusing lens, also 100mm
   * Alignment of laser: laser must be in location of chief ray to use it to align spectrograph optics!
-      * use laser and white light source, adjust laser and two input diagonal mirrors so that laser is in center of white light beam, but also in the center of a diffuser attached to beam splitter.
+      * use laser and white light source, adjust laser and two input diagonal mirrors so that laser is in center of white light beam, but also in the center of a diffuser attached to beam splitter: use first diagonal to put laser in hole of diffuser, second mirror to put laser in center of white beam (at large a distance as possible!)
+      * laser should be in center of white beam on table; if not, something is not right!
+      * put flat mirror on table at beam, look for reflected laser at laser source, adjust diagonal down-pointing mirror until laser reflection returns exactly to laser.
+{{ :spec:upper.jpg?direct=400 }}
   * Install slit to ensure focal plane is at desired height above optical table
-  * Install FM1 at desired height (175mm): this sets the plane of the spectrograph. Rotate FM1 to get desired deflection angle
+    * measure distance from bottom of slit holder to slit (10mm)
-  * Install grating mirror and align with collimating telescope
+    * using imaging camera, adjust slit to lens distance to get sharp image
-  * Install FM2 and align with collimating telescope (do now to ensure consistency with grating mirror)
+    * position slit-lens assembly to put slit at 235mm above the table
-  * Install FM3 and align with collimating telescope (do now to ensure consistency with grating mirror)
+  * Install FM1
-  * Install OAP1. Adjust initial height and tilt using autocollimator off mirror on back of mount. Adjust lateral so laser falls at appropriate location on the OAP (52mm from edge?).
+    * at desired height (175mm): this sets the plane of the spectrograph.
+    * correct tilt to ensure laser stays at same height at range of distances
+    * Rotate FM1 to get desired deflection angle per table marking
+    * lateral position so that full white beam barely fits on left edge of FM1
+  * Check grating mirror alignment
+  * Install OAP1. Adjust initial pitch and yaw using autocollimator off mirror on back of mount. Adjust lateral so laser falls at appropriate location on the OAP (62mm from edge).
   * Align OAP1 using 10micron fiber input to minimize aberration
+    * inspect images through focus
+    * move images with lateral and inspect images through focus
+    * adjust lateral to get best images
+    * same with height
   * Rotate spectrograph mirror to get 15mm separation between input and output laser. Adjust further to ensure that reflected beam misses FM1.
-  * Install OAP2. Adjust initial height and tilt using autocollimator off mirror on back of mount. Adjust lateral so laser falls at appropriate location on the OAP.
+  * Install OAP2. Adjust initial pitch and yaw using autocollimator off mirror on back of mount. Adjust lateral so laser falls at appropriate location on the OAP.
-  * Rotate FM3 so that return beam goes back into camera.
+    * Rotate FM3 so that return beam goes back into camera.
-  * Align OAP2 using 10 micron fiber input to minimize aberration
+    * Align OAP2 using 10 micron fiber input to minimize aberration
-  * Install prism. Rotate FM3 to ensure correct beam location
+  * If desired, install camera at non-final location to do imaging through full system. Imaging of 10um fiber is good for assessing single-pass image quality.
+  * Install prism. Rotate FM3 to ensure correct beam location.
   * Install camera. Adjust to ensure correct beam location: no light falling outside any optic
-  * Image cross-disperser fiber. Ensure expected width. Adjust detector to make vertical spectrum. Rough prism adjustment to get laser at correct location on detector.
+  * Image cross-disperser fiber. Ensure expected width. Adjust detector to make vertical spectrum. Adjust FM3 further to ensure good wavelength coverage on chip (laser is at 632nm, should be near red end, LED peak is at 450nm, should be near blue end)
   * Install grating.
   * Adjust grating tilt and prism to ensure good spectral coverage: grating so that peak of blaze function near center of detector, and prism to ensure good wavelength coverage.
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 {{:spec:DSC_0013.JPG?direct&300}}
 {{:spec:DSC_0014.JPG?direct&300}}
+Photos of the fully assembled spectrograph at APO on May 7, 2025.
+{{:spec:spectrograph_may07_above.jpg?300|}}
+{{:spec:spectrograph_may07_low.jpg?300|}}