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OPT3101: Capsule Endoscape use OPT3101

shuang Cao
Intellectual 385 points
Part Number: OPT3101

Our customer want to use OPT3101 in Capsule Endoscape for close range measure. Want to confirm the feasibility.

demand as below:

Chip size. Maximum dimension (diagonal) <10mm

Thickness <2mm

LED, photodiode and chip can be separated (optional).

LED and photodiodes can use small devices (0603 package).

Range range: 0~100mm (or 0~50mm, water)

Error <10% @100mm

The environment is full of digestive juice (such as water).

No environmental light, or use under LED white light

There is a transparent optical front shell between the infrared transmitting and receiving window and the target being measured. The thickness is less than 1mm, and the arc is shaped.

The target is digestive tract mucosa or villus (yellow to red).

Environmental temperature 37~42 C

Measurement frequency is less than 20Hz, adjustable

Circuit requirements. Working voltage is less than 3.0V

The working current is less than 30mA (non rigid requirements, as small as possible).

Other requirements: multipoint measurement

  • 0
    TI__Mastermind 25895 points
    Hi Shuang,

    OPT3101 requires a 3.3V supply. The diagonal dimensions are just for the IC and not the IC+ LED+PD correct? If this is the case than the OPT3101 looks to fit. Please refer to the datasheet for some of the other specs like these.

    For the application, can you give some more info on the target object? Is it solid? Do we need to differentiate between other type of materials that may be present as well?

    For the medium and cover, we have done some preliminary testing using OPT3101 behind a transparent sheet and you have to be careful in the design to prevent reflections off the glass from making it into the photodiode (PD), but if this is done it can work. The arc shaped cover may be an issue if it does not prevent reflections into the PD. We have not tested for looking through a liquid. This may work but will require some testing and design to minimize reflections into the photodiode.

    When you say 0~100mm (or 0~50mm, water), why two different distances?

    Best,

    Alex
  • 0 in reply to Alex Bhandari-Young
    Intellectual 385 points

     Hi Alex,Thanks for the quick reply! 

    Regard to the main questions :

    1. The diagonal dimensions are just for the IC.

        I was wondering if there are smaller LED, PD that could be used instead (such as 0603 package size).

     

    2. The target objects are the membrane of the gastrointestinal tract. We don't need to differentiate between other type of materials right now.

     

    3. For the medium and cover, we have done some tests using other type of ToF chips before. Fortunately, it worked well according to the preliminary studies. Of course, we need to dig into it in the future.

     

    4. For the distance (measurement range of the chip in water), both 0~100 mm or 0~50 mm would be ok, while 0~100 mm is better.

  • 0 in reply to shuang Cao
    TI__Mastermind 25895 points

    Hi Shuang,

    Thanks for clarifying.

    First I just want to make clear that the OPT3101 is only an AFE (analog front end), which means that LED and PD are separate from the IC and you are free to choose any LED and PD that works with the IC requirements and meets your needs. We have a system design doc that has additional info on selecting LED and PD components www.ti.com/.../sbau305.pdf

    I have not tested any 0603 LED and PD components. The smallest I have used are SFH2701 and SFH4059. You should check in the system doc I linked to for more info on selection. If you can find smaller components that meet the requirements you should be able to use them. An important factor will be the power you can get out of the LED to meet your range requirement. Also are you considering using an external lens on the LED and PD? The range will depend on many factors like capture speed, optics used (or not used), target reflectivity, etc. Using SFH2701 and SFH4059 without lenses we get up to around 300mm range in air looking at a white target. We have not tested how good the accuracy was at this distance, however and for darker targets this range will decrease.

    Also I want to note that to minimize crosstalk between LED and PD the layout will need to be such that the LED and PD are placed very close to the IC to minimize the loop area of the traces.

    Best,

    Alex