Light modulation photo IC

What is a light modulation photo IC?

A light modulation photo IC is a photo IC with an LED driver and a function to detect signal light while synchronized with its own light emission period. This synchronous operation easily eliminates low-frequency background light, making it relatively easy to detect objects with few detection errors even under background light.

 

Light modulation photo ICs are available in two sensitivity types. What criteria are needed for selecting the desired type?

If the background light is not very strong and the detection distance is long, then we advise using the high-sensitivity type. But if the background light is strong, then we recommend the type with high allowable background light level.

 

What LED types are best when using in combination with a light modulation photo IC?

Visible light cutoff type is sensitive to light at a wavelength from 700 to 1100 nm (peak sensitivity wavelength: 850 nm), so an LED that emits light at 800 to 950 nm is recommended. Transparent plastic package type has sensitivity in the 400 to 1100 nm range (peak sensitivity wavelength: 800 nm), so an LED in the visible to infrared range would be suitable.

 

How can I increase the LED drive current in order to extend the detection distance?

This requires installing an external amplifier circuit using transistors, etc. The drive current has a duty ratio of 1:16, so the current should be set so as not to exceed the LED rating.

 

I want to use light modulation photo ICs arrayed in parallel, but I'm worried about mutual interference. What should I do?

Measures are needed such as alternately arranging an LED and light modulation photo IC, and/or installing an aperture right in front of the photo IC so that only signal light in the optical axis direction is received.

 

Increasing the LED drive current sometimes clamps the output. What is the reason for this?

A large instantaneous current flowing along the wiring can cause voltage fluctuations while driving the LED. This sometimes makes the IC unstable, causing faulty operation. Take countermeasures such as placing a bypass capacitor (about 0.1 uF) near the light modulation photo IC, and inserting a capacitor (electrolytic capacitor, etc.) in the LED power supply line to stabilize the power.

 

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