CMOS sensor design ?

[el hou]

Hi all,

I try to design a CMOS sensor (without lense ) to capture an object of size 2 cm² and I didn't find the necessary equation to calculate the size of this sensor. In this case, is the sensor has the same size as the object?
If the lens is necessary, what are the reasons to use and what are the consequences of non-use it

Thank's

 

[BradtheRad]

I guess your sensor is a grid of photodetectors?

Without a lens...
You need to create a lit background around the object, so the light rays project onto the sensor. The light rays form a silhouette in the shape of the object. The sensor needs to be as large or larger than the object.

With a lens...
It focusses light rays from the object, to create an image on the sensor. The sensor can be tiny. This is how a digital camera works.

If the object is close, the lens must have a short focal length.

If the object is distant, the lens can have a long or short focal length. A long focal length creates a larger and dimmer image, which requires a larger and more sensitive sensor.

 

[el hou]

Yes it's a grid of photodetectors

But without lens, does the image appears clearly ?

 

[BradtheRad]

If you do not use a lens, you need to position the sensor close to the object, so that it casts a shadow or silhouette onto the sensor.

Or you could use a pinhole camera effect (theoretically). This can produce an image which is smaller than the object. The object must be brightly illuminated, however.