Imaging device, imaging method, and electronic apparatus for dynamically determining ratios of exposures to optimize multi-stage exposure

1. An imaging device comprising:

an imaging unit that images a subject with three or more kinds of exposures, ratios of respective pairs of exposures of which adjacent to each other in an ascending order or a descending order are equal;

a combining unit that combines, on the basis of the ratios, pixel signals corresponding to the respective three or more kinds of exposures obtained by imaging the subject with the imaging unit; and

an exposure adjusting unit that adjusts, on the basis of information concerning brightness of an imaging environment, while keeping the ratios of the respective pairs of exposures adjacent to each other equal, a control amount for an exposure of the imaging unit such that the three or more kinds of exposures are exposures suitable for the brightness of the imaging environment.

2. The imaging device according to claim 1 , wherein, when the three or more kinds of exposures are represented as L 1 , L 2 , . . . , and Ln (n is a natural number equal to or larger than 3 and L 1 <L 2 < . . . <Ln), the imaging unit images the subject in exposure times T 1 , T 2 , . . . , and Tn (T 1 <T 2 < . . . <Tn) in which ratios of respective pairs of exposures adjacent to each other “L 2 /L 1 , . . . , Ln/L(n−1)” are equal (L 2 /L 1 =. . . Ln/L(n−1)).

3. The imaging device according to claim 1 , further comprising:

a selecting unit that selects any one determination method out of plural kinds of exposure determination methods for determining the three or more kinds of exposures; and

an exposure determining unit that determines the three or more kinds of exposures on the basis of the determination method selected by the selecting unit, wherein

the imaging unit images the subject with the three or more kinds of exposures determined by the exposure determining unit.

4. The imaging device according to claim 3 , wherein the determination methods include a method of setting a maximum exposure and a minimum exposure among the three or more kinds of exposures, calculating an intermediate exposure of exposures, the ratios of the respective pairs of exposures adjacent to each of which are equal, on the basis of the set maximum exposure and minimum exposure, and determining the three or more kinds of exposures.

5. The imaging device according to claim 4 , wherein, when the imaging device images the subject with the three kinds of exposures L 1 , L 2 , and L 3 (L 1 <L 2 <L 3 ), the exposure determining unit calculates the exposure L 2 , which is the intermediate exposure, according to the following Formula (1):

L 2= L 1×( L 3/ L 1) 1/2   (1).

6. The imaging device according to claim 1 , further comprising:

an exposure setting unit that sets a maximum exposure and a minimum exposure among the three or more kinds of exposures; and

an exposure determining unit that calculates, on the basis of the maximum exposure and the minimum exposure set by the exposure setting unit, an intermediate exposure of exposures, the ratios of the respective pairs of exposures adjacent to each of which are equal, and determines the three or more kinds of exposures.

7. An imaging method comprising:

imaging a subject with three or more kinds of exposures, ratios of respective pairs of exposures of which adjacent to each other in an ascending order or a descending order are equal;

combining, on the basis of the ratios, pixel signals corresponding to the respective three or more kinds of exposures obtained by imaging the subject; and

adjusting, on the basis of information concerning brightness of an imaging environment, while keeping the ratios of the respective pairs of exposures adjacent to each other equal, a control amount for an exposure such that the three or more kinds of exposures are exposures suitable for the brightness of the imaging environment.

8. An electronic apparatus comprising the imaging device according to claim 1 .