Laser Display System

Christopher Nigro

David Merillat

Description / Overview (1)

• Produce a simple binary graphical display using a set of diode lasers.– Support text displays (stationary and scrolling)

with the possibility of images and simple video.– Minimize lasers required for display.

• Should help minimize cost.

– Provide enough accuracy and synchronization to ensure resulting image appears consistent with minimal jitter and flicker.

Description / Overview (2)

Rotating mirror

Slotted disc

~45

~10

~20

~90

Wall

Laser array

Optical Shield

RotatingMirror

Laser beam

Display Specifications

Specification Value

Refresh Rate 60 Hz ± 5 Hz

Vertical Resolution 16 pixels

Vertical Height 12.5 cm ± 0.5 cm

Vertical Jitter < ½ pixel

Horizontal Resolution 100 pixels

Horizontal Field of View 90° ± 1°

Horizontal Jitter < ½ pixel

Optimal Projection Distance 70 cm

Target Display Modes• Target Deliverables

– Basic Text Display• Display basic 8-point text.

– Scrolling Text Display• Display scrolling 8-point text at a configurable speed.

– Pause Display• Pause displays between commands.

• Goal Deliverables– Binary Image Display

• Display ASCII-encoded binary images.

– Binary Video Display• Display animation, or correlated sets of ASCII-encoded binary

images.

Analysis and Feasibility (1)

• Specification: 60Hz Display– Requires a 4-face mirror spinning at 900 RPM.– Thus, required laser operating frequency must

be approximately 50 kHz.

• Specification: 16 x 100 Pixel Resolution– Frame Size: 200 Bytes– Required Bandwidth: 12 kB/s

• Expected Brightness Approximately 350 cd.

Analysis and Feasibility (2)

• Horizontal Accuracy– Requires electrical timing accuracy of

approximately 40 us.– Mirror mounting accuracy (horizontal) is not

important and can be compensated for in software.

• Vertical Accuracy– Requires vertical mirror mounting accuracy of

approximately 0.5 degrees.

Other Technical Difficulties• Mirror Mounting

– Mirror faces not mounted on motor shaft’s axis of rotation.

– Causes nonlinearities in laser reflection angles.

• Frame Construction– Many of the components in this system require accurate

or precise mounting.

• Motor Speed Control– If a decent synchronous motor is not found, a speed

control system must be implemented to keep mirror rotation speed consistent.

Project Status

• Current Activities– Acquiring Components

• System Microprocessor Acquired and Functional– Motorola MC68332 20 MHz Microprocessor

• Lasers, motor, and materials required for accurate construction and mounting of system components.

– Subsystem Design• Motor Control

• Output FIFO Control

• Output Driver Channel

Conclusion

• Questions?

• Comments?

• Suggestions?