Image sensors with anti-eclipse circuitry

1. An image sensor, comprising:

a plurality of image sensor pixels;

an output line that is coupled to a portion of the plurality of image sensor pixels; and

anti-eclipse control circuitry that is coupled to the output line and that determines whether a selected pixel in the portion of the plurality of image sensor pixels is over-exposed, wherein the anti-eclipse control circuitry includes an eclipse condition judgment circuit that receives signals from the output line and that determines whether the selected pixel is over-exposed by monitoring the received signals, and wherein the eclipse condition judgment circuit obtains first and second digital pixel measurements, computes a difference of the first and second digital pixel measurements, and compares the computed difference to a predetermined threshold value to determine whether the selected pixel is over-exposed, and wherein the anti-eclipse control circuitry further includes an analog-to-digital converter interposed between the output line and the eclipse condition judgement circuit.

2. The image sensor defined in claim 1 , wherein the anti-eclipse control circuitry further includes a comparator having a first input that receives a reference voltage signal, a second input, and an output that is coupled to the eclipse condition judgment circuit.

3. The image sensor defined in claim 2 , wherein the anti-eclipse control circuitry further includes a sample and hold circuit interposed between the output line and the second input of the comparator.

4. The image sensor defined in claim 2 , wherein the eclipse condition judgment circuit determines that the selected pixel is over-exposed when the comparator outputs a deasserted value.

5. A method of operating an image sensor, comprising:

with a plurality of image sensor pixels, receiving incoming light;

with a selected pixel in the plurality of image sensor pixels, outputting a signal on a corresponding output line; and

with anti-eclipse control circuitry that is coupled to the output line, determining whether the selected pixel suffers from an eclipse condition by monitoring the output signal, wherein the anti-eclipse control circuitry includes a data converter having a comparator with a first input that receives a reference voltage signal and a second input, and wherein the anti-eclipse control circuitry includes a capacitor having a first terminal coupled to the second input of the comparator and having a second terminal that receives a control signal;

pulsing the control signal to temporarily raise the voltage level at the second input of the comparator; and

while the control signal is asserted, outputting a comparator output with the comparator.

6. The method defined in claim 5 , wherein the anti-eclipse control circuitry includes a digital eclipse condition judgment circuit, the method further comprising:

with the data converter, receiving the output signal from the output line and converting the output signal to a digital signal; and

with the digital eclipse condition judgment circuit, receiving the digital signal from the data converter and determining whether the selected pixel suffers from the eclipse condition by analyzing the digital signal.

7. The method defined in claim 6 , further comprising:

with a sample and hold circuit, sampling the output signal; and

with the second input of the comparator, receiving the sampled output signal from the sample and hold circuit.

8. The method defined in claim 5 , further comprising:

in response to determining that the comparator output is a first value, outputting a correlated double sampling (CDS) value; and

in response to determining that the comparator output is a second value that is different than the first value, outputting a maximum pixel output value instead of the CDS value.

9. A system, comprising:

a central processing unit;

memory;

a lens;

input-output circuitry; and

an imaging device, wherein the imaging device comprises:

a pixel array having a plurality of image pixels arranged in rows and columns;

a pixel column line that is coupled to a group image pixels arranged along a corresponding column in the pixel array;

image readout circuitry coupled to the column line; and

anti-eclipse control circuitry that is coupled to the pixel column line and that determines whether a selected pixel in the group of image pixels is over-illuminated, wherein the anti-eclipse control circuitry includes a comparator having a first input that receives a reference voltage and a second input that receives a signal from the pixel column line, and wherein the voltage at the second input of the comparator is temporarily raised during readout to determine whether the selected pixel is over-illuminated, and wherein the image readout circuitry and the anti-eclipse control circuitry are coupled to the column line in parallel.

10. The system defined in claim 9 , wherein the anti-eclipse control circuitry further includes a digital eclipse condition judgment circuit that monitors a pixel signal output from the selected pixel to determine whether the selected pixel is over-illuminated.

11. The system defined in claim 9 , wherein the

image readout circuitry computes a correlated double sampling (CDS) pixel output value.

12. The system defined in claim 11 , wherein the digital eclipse condition judgment circuit directs the image readout circuitry to output the CDS pixel output value when the selected pixel is not over-illuminated and directs the image readout circuitry to output a saturated pixel output value when the selected pixel is over-illuminated.