Imaging device

Abstract

An imaging device includes an imaging sensor, a switching section, and a controlling section. The imaging sensor includes a light receiving surface to which light receiving elements capable of addressing reading are arranged, and having, on the light receiving surface, an imaging area capturing a subject image and an optical black area outputting a signal of a dark current component, the optical black area which the light receiving elements are covered with a light shielding member. The switching section switching a first state and a second state. The controlling section reads a signal level by each partial area at the optical black area when a dark image is captured in the second state after capturing a normal image in the first state, sequentially compares with the signal level at a corresponding position of the normal image, and controls a exposure time of the dark image according to the comparison result.

Description

CROSS REFERENCE TO THE RELATED APPLICATIONS[0001]This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2008-109936, filed on Apr. 21, 2008, the entire contents of which are incorporated herein by reference.BACKGROUND[0002]1. Field[0003]The present embodiments relate to an imaging device including a noise reduction process function removing noise generated when an exposure is performed for a long time.[0004]2. Description of the Related Art[0005]In recent years, an electronic camera having a noise reduction (NR) mode is known as the electronic camera including an imaging sensor (for example, refer to Japanese Unexamined Patent Application Publication No. 2005-79948). Generally, the electronic camera performs a dark imaging with an exposure time which is the same as an exposure time of a normal image under a state in which the imaging sensor is light shielded just after the normal image is photographed, in this noise reduction (NR) mode...

AI Technical Summary

Benefits of technology

[0011]A proposition of the present embodiment is to provide an imaging device capable of preventing image degradation caused by a black saturation, a black floating, a white point, and so on even under an environment in which an exposure time becomes long or temperature changes, in consideration of the above-stated circumstances.

Problems solved by technology

However, there are problems as stated below in the noise reduction (NR) mode.

Accordingly, an error occurs between respective dark current components if the temperature difference exists between a normal exposure time and a dark exposure time.

There is a tendency that fluctuation of temperature becomes large and a dark current difference also becomes large as the exposure time becomes long.

Generally, when the imaging sensor is used continuously from the normal exposure to the dark exposure, the temperature rise of the imaging sensor is further incurred at the dark exposure time.

As a result, a problem occurs in which the dark current is too much subtracted in the correction process to thereby incur a black saturation (excessive correction of dark level) and so on.

Besides, when a long time exposure is performed after a live view mode displaying a live video of the imaging sensor on a liquid crystal display is used for a long time, the long time exposure is started under a state in which the temperature rises up to a saturation temperature caused by the live view operation.

In this case, power consumption is small and the temperature decreases rapidly because a mode shifts to a stand-by mode during the long time exposure.

In this case, a problem occurs in which a black floating (shortage of correction of dark level) is incurred caused by a shortage of the correction amount in the correction process.

Further, it is known that the dark current noise such as a white point occurs when the exposure is performed for a long time.

In this case, a problem occurs in which the white point remains if the dark current amounts are different between the normal exposure time and the dark exposure time.

However, there is a room for further improvement in a point that the correction cannot be performed enough when the predicted temperature rise does not occur actually.