Image sensors with testing capabilities
An image sensor may include an array of imaging pixels and readout circuitry. Testing circuitry may be interposed between the imaging pixels and the readout circuitry. The testing circuitry may include first and second test rows that provide first and second respective test voltages. In a testing mode, the first test voltage may be provided to approximately half of the readout circuitry and the second the second test voltage may be provided to the remaining half of the readout circuitry. In an imaging mode, the readout circuitry may be coupled to column output lines and read out signals from the array of imaging pixels. The components that receive different test voltages may be arranged in an alternating or checkerboard pattern to ensure testing of scenarios with coupling between adjacent components.
1. An image sensor comprising:
an array of imaging pixels;
readout circuitry configured to read out signals from the array of imaging pixels;
a first test row that is configured to provide a first test voltage to the readout circuitry; and
a second test row that is configured to provide a second test voltage that is different than the first test voltage to the readout circuitry, wherein the readout circuitry comprises a first plurality of amplifiers and analog-to-digital converters and a second plurality of amplifiers and analog-to-digital converters, wherein the first plurality of amplifiers and analog-to-digital converters is configured to receive the first test voltage, and wherein the second plurality of amplifiers and analog-to-digital converters is configured to receive the second test voltage.
2. The image sensor defined in claim 1 , wherein the first test row comprises a first test voltage input line that provides the first test voltage and the second test row comprises a second test voltage input line that provides the second test voltage.
3. The image sensor defined in claim 1 , wherein the first plurality of amplifiers and analog-to-digital converters and the second plurality of amplifiers and analog-to-digital converters are arranged in an alternating pattern.
4. The image sensor defined in claim 1 , wherein the first plurality of amplifiers and analog-to-digital converters and the second plurality of amplifiers and analog-to-digital converters are arranged in a checkerboard pattern.
5. The image sensor defined in claim 1 , wherein an amplifier of the first plurality of amplifiers and analog-to-digital converters is interposed between first and second amplifiers of the second plurality of amplifiers and analog-to-digital converters.
6. The image sensor defined in claim 1 , further comprising:
a plurality of column output lines coupled to the array of imaging pixels.
7. The image sensor defined in claim 6 , wherein the first plurality of amplifiers and analog-to-digital converters is configured to receive the first test voltage in a first mode, wherein the second plurality of amplifiers and analog-to-digital converters is configured to receive the second test voltage in the first mode, wherein the first plurality of amplifiers and analog-to-digital converters is configured to receive signals from a first subset of the plurality of column output lines in a second mode, and wherein the second plurality of amplifiers and analog-to-digital converters is configured to receive signals from a second subset of the plurality of column output lines in the second mode.
8. The image sensor defined in claim 7 , wherein the first test voltage is configured to follow a first ramped profile during the first mode and wherein the second test voltage is configured to follow a second ramped profile that is different than the first ramped profile during the first mode.
9. The image sensor defined in claim 7 , wherein the first test voltage is configured to follow a rising ramped profile during the first mode and wherein the second test voltage is configured to follow a falling ramped profile during the first mode.
10. The image sensor defined in claim 1 , wherein the first and second test rows are interposed between the array of imaging pixels and the readout circuitry.
11. The image sensor defined in claim 10 , wherein the readout circuitry is formed on a first side of the array of imaging pixels and wherein the image sensor further comprises:
additional readout circuitry formed on a second, opposing side of the array of imaging pixels;
a third test row that is configured to provide a third test voltage to the additional readout circuitry; and
a fourth test row that is configured to provide a fourth test voltage that is different than the third test voltage to the additional readout circuitry, wherein the third and fourth test rows are interposed between the array of imaging pixels and the additional readout circuitry.
12. The image sensor defined in claim 11 , wherein the third test voltage is the same as the first test voltage and the fourth test voltage is the same as the second test voltage.
13. An image sensor comprising:
an array of imaging pixels;
a plurality of column output lines coupled to the array of imaging pixels;
readout circuitry having a first plurality of components and a second plurality of components;
a first test row comprising switching circuitry that provides a first test voltage to the first plurality of components in a first state and that provides signals from the plurality of column output lines to the first plurality of components in a second state; and
a second test row comprising switching circuitry that provides a second test voltage to the second plurality of components in the first state and that provides signals from the plurality of column output lines to the second plurality of components in a second state.
14. The image sensor defined in claim 13 , wherein the first plurality of components alternate with the second plurality of components.
15. The image sensor defined in claim 13 , wherein the first plurality of components and the second plurality of components are arranged in a checkerboard pattern.
16. The image sensor defined in claim 13 , wherein the first test voltage and the second test voltage have opposing ramped profiles.
17. The image sensor defined in claim 16 , wherein a first absolute value of a first slope of a first ramped profile of the first test voltage is the same as a second absolute value of a second slope of a second ramped profile of the second test voltage.
18. An image sensor comprising:
an array of imaging pixels;
readout circuitry; and
circuitry configured to provide at least first and second test voltages to the readout circuitry in a first mode and to provide signals from the array of imaging pixels to the readout circuitry in a second mode, wherein the first test voltage is configured to follow a rising ramped profile during the first mode and wherein the second test voltage is configured to follow a falling ramped profile during the first mode.
19. The image sensor defined in claim 18 , wherein the first mode is a testing mode and the second mode is an imaging mode.