An imaging device comprising: a light source configured to be operated by a light control signal; and a pixel array comprising a plurality of pixels, each of the plurality of pixels including a pixel circuit (PC1,PC2) generating an electrical signal based on an electric charge, wherein the plurality of pixels comprises a plurality of general pixels and a plurality of phase difference detection pixels for determining a phase difference error in the pixel array, wherein each of the plurality of general pixels comprises a photodiode, wherein the photodiode is configured to generate a first electric charge in response to a received optical signal output from the light source and reflected by a subject, wherein the pixel circuit of each of the plurality of general pixels is configured to generate a first electrical signal based on the first electric charge, wherein each of the plurality of phase difference detection pixels comprises a switch element connected to the pixel circuit of each of the plurality of phase difference detection pixels and an electric charge-supply source connected to the switch element and output a second electric charge, wherein the switch element is configured to be turned on and turned off by a switch control signal, and wherein the pixel circuit of each of the plurality of phase difference detection pixels is configured to generate a second electrical signal based on the second electric charge, wherein the plurality of pixels receives a first photo-control signal and a second photo-control signal from output buffers of a clock driver, wherein the imaging device is configured to detect a phase difference error (θ) by inputting the light control signal as a switch control signal to the switch element of a phase difference detection pixel and using data from one of the phase difference detection pixels, and wherein the clock driver is configured to reflect a compensation value to the first photo-control signal and the second photo-control signal signal inputted to one of the plurality of general pixels such that the phase difference error is offset. a light source configured to be operated by a light control signal; and a pixel array comprising a plurality of pixels, each of the plurality of pixels including a pixel circuit (PC1,PC2) generating an electrical signal based on an electric charge, wherein the plurality of pixels comprises a plurality of general pixels and a plurality of phase difference detection pixels for determining a phase difference error in the pixel array, wherein each of the plurality of general pixels comprises a photodiode, wherein the photodiode is configured to generate a first electric charge in response to a received optical signal output from the light source and reflected by a subject, wherein the pixel circuit of each of the plurality of general pixels is configured to generate a first electrical signal based on the first electric charge, wherein each of the plurality of phase difference detection pixels comprises a switch element connected to the pixel circuit of each of the plurality of phase difference detection pixels and an electric charge-supply source connected to the switch element and output a second electric charge, wherein the switch element is configured to be turned on and turned off by a switch control signal, and wherein the pixel circuit of each of the plurality of phase difference detection pixels is configured to generate a second electrical signal based on the second electric charge, wherein the plurality of pixels receives a first photo-control signal and a second photo-control signal from output buffers of a clock driver, wherein the imaging device is configured to detect a phase difference error (θ) by inputting the light control signal as a switch control signal to the switch element of a phase difference detection pixel and using data from one of the phase difference detection pixels, and wherein the clock driver is configured to reflect a compensation value to the first photo-control signal and the second photo-control signal signal inputted to one of the plurality of general pixels such that the phase difference error is offset.