Laser Scanning Disc Camera (LSDC)


Multiply Scattered Imaging Mode

The LS­DC can finely ad­just the off­set of its con­focal aper­ture with re­spect to the il­lu­min­a­tion light on the ret­ina elec­tron­ic­ally in real-time. With a con­focal aper­ture off­set, the LS­DC re­cords im­ages com­posed of mul­tiply scattered light from the deep­er lay­ers of the ret­ina, while re­ject­ing the much stronger dir­ect backs­cat­ter from su­per­fi­cial lay­ers. The res­ult is in­creased sens­it­iv­ity to scat­ter­ing de­fects such as drusen and to the pres­ence of ed­ema.

Refraction Using Structured Illumination Mode

The LS­DC’s il­lu­min­a­tion source is more com­monly used in tele­com­mu­nic­a­tion ap­plic­a­tions that re­quire in­tens­ity mod­u­la­tion. In struc­tured il­lu­min­a­tion mode, the source is mod­u­lated while ima­ging, pro­du­cing a se­quence of stripes across the im­age. The con­trast or amp­litude of the stripes meas­ured through-fo­cus provides a loc­al­ized point-spread func­tion. When meas­ured near the fo­vea, this mode provides auto-fo­cus; when com­bined with peri­pher­al point-spread func­tion meas­ure­ments, the to­po­graphy of the fo­cused light on the ret­ina can be re­con­struc­ted. Com­mon uses for to­po­graphy in­clude mod­el­ing peri­pher­al re­frac­tion and de­tect­ing ret­in­al thick­en­ing com­monly as­so­ci­ated with eye dis­ease.

Photos of the LSDC

Images taken with the DLM (below):

Human Retina

Image of the Retina taken in green illumination only60 year old Caucasi­an fe­male sub­ject with dry age-re­lated mac­u­lar de­gen­er­a­tion and wide­spread hard drusen. A 20-frame av­er­aged stand­ard LS­DC im­age is shown on the left, and a 20-frame av­er­aged mul­tiply scattered mode on the right. Stand­ard and mul­tiply scattered im­age frames were al­tern­ately ac­quired.
Image of the Retina taken in green illumination only60 year old Caucasi­an fe­male sub­ject with dry age-re­lated mac­u­lar de­gen­er­a­tion and wide­spread hard drusen. A 20-frame av­er­aged stand­ard LS­DC im­age is shown on the left, and a 20-frame av­er­aged mul­tiply scattered mode on the right. Stand­ard and mul­tiply scattered im­age frames were al­tern­ately ac­quired.
Image of the Retina taken in green illumination onlyLSDC image of a 23 year old Caucasian male with structured illumination. Tip: Try looking at the image up close and farther away. At farther distances, your eye will better average out the stripes, providing a clearer view of the retina.”

 

Specifications
Pupil Diameter 2.8 mm
Illumination Wavelengths 850 nm
Time Averaged Power at the Cornea 2 mW
Field of View of the Retina ~ 36°
Default Imaging Frame Rate 15.2 Hz
Default Target Fixation and Stimulus Resolution on the Retina <0.1°