1. Field
The present application relates to a solid state imaging device.
2. Description of the Related Art
In a video camera and an electronic still camera, a CCD type or amplification type solid state imaging device is used. In such a solid state imaging device, a plurality of pixels having photoelectric conversion parts are arranged in a matrix shape, and signal charges are generated in the photoelectric conversion parts of the respective pixels. In an amplification type solid state imaging device, a signal charge generated and accumulated in a photoelectric conversion part of a pixel is led to a charge-voltage conversion part such as a floating diffusion, the signal charge is converted into a voltage in the charge-voltage conversion part, and a signal corresponding to the voltage is output from the pixel by an amplifying part provided in the pixel.
A solid state imaging device of XY address type or the like being such an amplification type solid state imaging device is generally provided with a vertical signal line provided to correspond to each column of a plurality of pixels and to which output signals of the pixels of the corresponding column are supplied; a sampling hold part that samples and holds signals corresponding to signals of each of the vertical signal lines in accordance with sampling control signals, and supplies the held signals to horizontal signal lines in accordance with a horizontal scanning signal; a horizontal scanning part that supplies the horizontal scanning signal to the sampling hold part; and a horizontal drive controlling part that supplies a plurality of types of pulse signals which relate to a reading of the signals supplied from the sampling hold part to the horizontal signal lines. For instance, the sampling hold part includes: a light signal accumulating capacitor and a subtracting signal accumulating capacitor provided to correspond to each of the vertical signal lines, a light signal sampling switch that makes a light signal including light information on which photoelectric conversion is performed in the pixel accumulate in the light signal accumulating capacitor, a subtracting signal sampling switch that makes a subtracting signal (a so-called dark signal or the like) including a noise element to be subtracted from the light signal accumulate in the subtracting signal accumulating capacitor, a light signal horizontal transfer switch that supplies the light signal accumulated in the light signal accumulating capacitor to a light signal horizontal signal line in accordance with the horizontal scanning signal, and a subtracting signal horizontal transfer switch that supplies the subtracting signal accumulated in the subtracting signal accumulating capacitor to a subtracting signal horizontal signal line in accordance with the horizontal scanning signal. An example of such a solid state imaging device is disclosed in Japanese Unexamined Patent Application Publication No. Hei 9-284658.
As such a solid state imaging element, one that obtains, using a differential amplifier and the like provided in the solid state imaging element, a difference between a light signal of a light signal horizontal signal line and a subtracting signal of a subtracting signal horizontal signal line and outputs a differential signal between the signals to the outside, and one that outputs each of the light signal and the subtracting signal in a parallel manner to the outside of the solid state imaging element and obtains a difference between the both signals in an external circuit or the like, are known.
Further, in such a conventional solid state imaging device, the horizontal scanning part is generally formed by using a shift register and the like, and generates the horizontal scanning signal by using a driving clock signal, a start pulse signal, and the like supplied from a drive controlling part having a timing generator and the like. The driving clock signal and the like are supplied to the horizontal scanning part during not only a horizontal scanning interval but also a horizontal blanking interval.
With the use of such a conventional solid state imaging device, the difference between the light signal and the subtracting signal can be obtained, so that a noise such as so-called fixed pattern noise is removed, resulting in that an image quality of a captured image is increased.
However, it has been proved as a result of studies undertaken by the present inventors that in the conventional solid state imaging device, when the signals corresponding to the signals of the vertical signal lines are sampled by the sampling hold part, levels of the signals are varied by an influence of noise that cannot be removed by the difference, which decreases the image quality of the captured image.