H-BCAM


The H-BCAM is a double-ended metrology camera equipped with four laser diode light sources and two white LED illuminators for retro-reflecting targets. Its field of view is 100 mrad × 75 mrad. Its absolute accuracy with respect to its kinematic mounting balls is 50 μrad rms. Its tracking accuracy is 5 μrad rms across the entire field of view for ranges 80 cm and greater. Its laser positions are known to better than 10 μm rms. The photograph below shows the blue version, which we also refer to as the right-handed H-BCAM. For a photograph of the black left-handed version, see here. The H-BCAM is one of a family of metrology cameras called BCAMs. We designed the H-BCAM for use in the alignment system of a particle accelerator called HIE-ISOLDE, as we describe in HIE-ISOLDE, General Presentation of MATHILDE.


Figure: A Blue H-BCAM. We are looking at the front end of the BCAM. We see the front camera lens. On either side are the two laser diodes, and above and below are the four white LEDs. The LWDAQ cable that controls and reads out the H-BCAM plugs into the opposite side wall, like this.

The example in the photograph above has 5-mW laser diodes, and so requires a Class II laser warning label. The location of the lens holder, being flush with the front face of the chassis, implies a focal range of the front camera is 1.5 m. The serial number Q0232 is on the lid, and allows us to look up its calibration constants in the BCAM parameter database.

The H-BCAM's powerful lasers are intended for use with retroreflecting sphere targets. A sphere made of glass with refractive index 2.0, such as part number 48-895 from Edmund Optics, acts as a retroreflector, as we describe here. We can measure the position of the sphere by looking at the reflection of an H-BCAM laser using the H-BCAM's camera. The sphere requires no electronics. It can endure cryogenic temperatures. The HIE-ISOLDE alignment of cryogenic modules used such spheres within the modules, seen through sapphire windows by H-BCAMs mounted outside the modules on metal plates.


Figure: A HIE-ISOLDE Cryogenic Module Under Construction. The H-BCAM was designed for use in the HIE-ISOLDE alignment system.

The original H-BCAM, manufactured before 2016, uses two forks to hold the two image sensors, and its chassis is machined out of one piece of aluminum. The two forks are held in place by two screws through the bottom of the chassis. The H-BCAMs manufactured after 2016 have frames screwed to the side walls to hold the CCDs, and the chassis consists of three pieces: a base and two identical flanges for the end walls. Each flange is held in place with four screws.

Blue H-BCAM (with Flanges)
Base: Drawing of base
Flange: Drawing of end wall
Frame: Drawing of CCD frame
Collection: Set of BCAMs with Drivers
Black H-BCAM (with Flanges)
Base: Drawing of base
Flange: Drawing of end wall
Frame: Drawing of CCD frame
Black H-BCAM (with Forks)
Assembled: 3D view
Chassis: Drawing of chassis
Front: Drawing of front face
Rear: Drawing of rear face
Fork: Drawing of fork
Bottom: Drawing of kinematic base
Cover: Drawing of cover
Blue H-BCAM (with Forks)
Assembled: 3D view (JPG)
Chassis: Drawing of chassis
Front: Drawing of front face
Rear: Drawing of rear face
Fork: Drawing of sensor mounting fork
Bottom: Drawing of kinematic base
Cover: Drawing of lid
Electronics and Documentation
BCAM Head (A3025): Main board.
BCAM Side Head (A3026): Side board.
ICX424 Minimal Head (A2076): Sensor board.
BCAM Home Page: BCAM Documentation.