| Schematic | PCBs | Assembly |
The Azimuthal BCAM Side Head (A2049) is dual laser driver circuit with two lasers mounted on the printed circuit board. The lasers can be the LDP65001E, DL3147, or any elecrically and mechanically equivalent device. The two lasers we name emit ruby-red light in a rectangular cone. The base of the cone is a tiny light-emitting surface roughly 10 μm by 50 μm. A BCAM is an optical surveying instrument (Brandeis CCD Angle Monitor) consisting of digital cameras and laser diodes acting as optical point sources.
The following versions of the A2049 exist.
| Version | Description |
|---|---|
| F | CSC Rear Laser Pair |
| G | CSC Front Laser Head |
| L | Black Azimuthal BCAM Side Head (mirror image of A2049R) |
| R | Blue Azimuthal BCAM Side Head (mirror image of A2049L) |
| M | Black Azimuthal BCAM Side Head with ZIF Connector (mirror image of A2049N) |
| N | Blue Azimuthal BCAM Side Head with ZIF Connector (mirror image of A2049M) |
All varieties of the A2049 will work with the Azimuthal BCAM Head (A2048), the Azimuthal Source Head (A2051S), and the CSC Source Head (A2050G).
The A2049F and A2049G are designed to work with the CSC Source Head (A2050G). The ZIF connectors on the boards are oriented so that the A2049F will work only when connected to A2050G-J2, and the A2049G will work only when connected to A2050G-J1.
For A2049F and A2049G board dimensions and hole locations, see this drawing. To see how the A2049F and A2049G connect to the CSC Laser Head (A2050), look at this drawing. The A2049F connects to J3 on the A2050G, and provides source elements 1 (LD1) and 2 (LD2). The A2049G connects to J2 on the A2050G, and provides source elements 3 (LD1) and 4 (LD2).
The A2049 provides two laser drivers. Each driver takes a common positive voltage and a negative turn-on voltage. The metal can of the laser is connected to the common positive voltage. The metal can of the laser must be isolated from any metal chassis holding the driver circuit, or else the LWDAQ grounding rules will be broken.
With R5 and R11 set to 10 kΩ, the nominal power output from either a LDP65001E or DL3147 is 1 mW. Across two thousand DL3147 lasers, we found the output power varied from 0.5 mW to 2 mW. Our first one thousand LDP65001E lasers produced the same range of power, but our second thousand suddenly jumped to between 2 mW and 8 mW, which indicates that the monitor current at 5 mW is close to the lower extreme specified in the laser's data sheet. To reduce the power below 4 mW, we changed R5 and R11 to 33 kΩ.
The A2049 connects the packages of its two lasers together, and so will operate when the lasers are connected together by a metal mounting plate with two holes in it. In BCAMs, we anodize the aluminum surface of the holes into which the lasers mount, so that the lasers are not in electrical contact with the munting surface. The A2049 connects both laser packages together, and provides connection to them on the two V+ pins of its flex connector. To turn on laser A, you bring the voltage of input LDA down to between six and twenty volts below V+.
Given a step input on the LDA of -10V with respect to V+, the A2049 will turn its laser on to full power within 5 μs. When LDA returns to V+ again, the laser turns off.
Note: All our schematics and Gerber files are distributed under the GNU General Public License.
