portable slit lamp design manual

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Portable slit lamp design manual Prepared for portable slit lamp project from Kellogg Eye Center Any further questions please contact Jingxi Lu, [email protected]

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Portable slit lamp design manual

Prepared for portable slit lamp project from Kellogg Eye Center

Any further questions please contact Jingxi Lu, [email protected]

No. Part numberQuantit

yPrice Total price

1 base-bot 1 3DP2 [NUT]M4X2.2MM_90695A035 3 $0.02 $0.06 3 topscrew-96016A117 1 $0.54 $0.54 4 eyebrow rest 1 3DP5 4Xlens-8539T65 1 $14.56 $14.56 6 prismtower 1 3DP7 object_cylinder 1 3DP8 guideway 1 3DP9 M3x90353A152 3 $0.06 $0.17

10 aperture-middle-width 1 3DP11 aperture-bot-filter 1 3DP12 flash light 1 $8.84 $8.84 13 M3.5X20CM_91800A193 2 $0.18 $0.37 14 aperture-top-length 1 3DP15 slit_selector_cover-bot-1 1 3DP16 slit_selector_cover-top 1 3DP17 slit_selector_cover-bot-2 1 3DP18 2-way-mirror 1 NA19 M4X18MM_90116A215 4 $0.19 $0.78 20 battery 1 $25.99 $25.99 21 phoneclamp-left 1 3DP22 clampphone-top 1 3DP23 spring-94135K8 1 $1.19 $1.19 24 M5X100MM_92010A370 2 $1.31 $2.62 25 clampphone-bot 1 3DP26 base-top 1 3DP27 phoneclamp-right 1 3DP28 M4X55CM_92005A242 1 $0.19 $0.19 29 Wingnut_M4_94300A310 1 $0.17 $0.17 30 M4X40CM_92005A236 1 $0.08 $0.08 31 7Xlens-8539T34 1 $14.56 $14.56

BOM for all parts

Smart device (iPhone, iTouch, Samsung etc.)

Adjustable clamp

Removable chinrest (optional)

Battery

Portable slit lamp for smart devices

Optical system

Base

Adjustable clamp

• Suggested clamp width: 5-8 cm• The adjustable clamp adjusts both the vertical and horizontal axes of the

smart device so its camera center axis can be aligned with the magnifier lens axis.

• When using, clamp the smart device (phone) first and align its horizontal position, then untighten the wingnut a little bit to align its vertical position. At the end tighten the wingnut again to make sure the phone doesn’t drop.

• When assembling the spring, fix one end first with M4 screw, then use a thin wire to pull the other end of spring to a point where another M4 screw can be inserted.

Long bolts prevent clamp tilting (they are more robust than 3D printed plastic rods).

Insert this cylinder into slit lamp base.

Extension spring for clamping smart devices

Adjustable clamp: assembling procedures

When assembling the spring, fix one end first with M4 screw, then use a thin wire to pull the other end of spring to a point where another M4 screw can be inserted.

Pull with thin wireSmall opening below

Acrylic mirror

Prism tower

7X magnifier lens (inside)

Object cylinder

Slit selector

Flash light (inside)

Two M3 slot screw, 20 mm

Optical system: overall picture

Two M4 cross screw, 18 mm

Cut the acrylic mirror to desired size (9 x 14 mm) and sand polish the edges. Make sure it can be pressed into the prism tower tightly.

Optical system: assembling procedures

1* 2 3 4 5 6 7 8

9 10 11 12 13 14• At 1st step use tape to fix these two parts temporary. Keep adjusting the height the of optical system to make sure the center of light beam is in the center view.

• The guideway (purple part) is only shown in the 1st step. However it must be assembled first

Optical system: overall picture

• Measured object distance: 64 mm, Image distance 80 mm.

• Distance between camera and focus point: 89.5 mm

• Focal length of 4X magnifier lens: 58.5 mm

• > 8X total magnification ratio (4x from camera)

Removable handle

Slit selector, discrete (current version)

Length selectorWidth selector

Filter selector

The size of light beam is larger than that of slit itself. The ratio is about 1.25 (image distance/object distance = 80/64 = 1.25 ) . Based on this ratio the size of slit can be determined.

Clean the thinnest slit with thin paper only!

Make sure the gap between two pairs of slit selector are as close as possible (0.5~1mm is acceptable). Otherwise the light beam image may not have sharp edges.

Slit selector, continuous (optional version)

Part name Description Quantity PriceTotal price

flash lightUltrafire® Cree 7W 300LM Mini LED One

Mode Flashlight1 $8.84 $8.84

middleplate 2 3DP

RACK

Molded Nylon 14-1/2 Degree Angle Spur Gear, Rack, 48 Pitch, 1/8"

Face Width, 1/8" Overall Height, 1' Long

4 $4.78 <$1

rackbase 2 3DP

cover-bot 1 3DP

cover-top 1 3DP

Left GEAR

Molded Nylon 14-1/2 Degree Angle Spur Gear, 48 Pitch, 20 Teeth, 0.417" Pitch Diameter, 1/8" Bore, 3/8” O’all

length, 1/8” face width

2 $4.09 $8.18

Right GEAR Same as “Left GEAR” 2 $4.09 $8.18

90353A152

Metric Pan Head Slotted Machine Screw. Zinc-

Plated Steel, M3 Size, 35mm Length, .5mm Pitch

4 $0.06 $0.23

90695A033Class 04 Steel Thin Hex Nut - DIN 439BZinc Plated, M3x0.5 Thread Size, 5.5mm

Wide, 1.8mm High

4 $0.03 $0.12

All parts can be found in gearbox-subassembly.rar

Optical system: slit selector, continuous

• Two pairs of gears & rack are used. Each pair of them is in charge of the adjustment of width or length.

• Use M3 bolts as axes for gears can prevent axes break, which is a common failure mode when the axes were 3D printed.

• Leave 0.25mm gap between frictional parts (such as gate and base) can prevent excessive friction force.

Flash light

Make sure the gap between two pairs of gates are as close as possible (1mm is acceptable). Otherwise the light beam image may not have sharp edges.

The drawback of this design is the slit edges might not be parallel.

Base design• The handle should be removable so that the whole device is

more portable• Make sure there is enough space between handle and slit box

(about 100mm long, 15mm wide will be acceptable)• Add supporting ridge to make the handle stiffer• Openings for electric wires are necessary• Openings for adjustable chinrest subassembly

Electric components• The output voltage of batter is 5V, which is too high for the flash

light. Potential failure modes due to high input voltage include: 1. at first the light intensity is very strong and flashlight becomes overheat 2. light becomes dim after a while 3. flashlight turns off automatically in 10 sec. The working voltage and current for the flashlight are about 1.5V and 200mA• Current solution for reducing the input voltage is to use 15 Ω

resistor. However the disadvantages are: the input voltage on flashlight drops to 0.8 V, and the considerable amount of heat generated by resistors reduces the energy efficiency of the device quite significantly.

• Another severe failure mode is the poor electric connection. Since the optical system moves all the time when using, if the wire pins hit any obstacles, the circuit breaks very easily. Need to solve this problem in the future.

Some real pictures