Autofocus imaging optical system and image pickup device

An image pickup device comprising:

• a focus lens unit that moves during focusing;
• a magnification lens unit that moves during zooming;
• a splitting optical system disposed in an optical path on an image side of the focus lens unit, wherein the splitting optical system splits a light beam from a subject into a reflected light beam and a passed light beam, and wherein the passed light beam is used for imaging the subject image;
• focus detection means for detecting a focus state of the subject image by using the reflected light beam split by the splitting optical system, wherein a reflectance of the splitting optical system against the light beam from the subject has a distribution in which the reflectance is of the maximal value on an optical axis and becomes gradually lower as the light beam is away from the optical axis, and the distribution has rotational symmetry about the optical axis, wherein the focus detection unit detects the focus state of the subject image by using a portion of the reflected light beam which is reflected by the higher reflectance portion of the splitting optical portion including the optical axis;
• drive means for driving the focus lens unit to a focal position for imaging the subject image by using the passed light beam based on a detection result of the focus detection means;
• image pickup means for taking the subject image imaged by the focus lens unit wherein the passed light beam through the focus lens unit and the magnification lens unit is directed to the image pickup means;
• image pickup means control means for controlling the image pickup means;
• aperture stop means for limiting an amount of light to the image pickup means;
• and
• aperture stop value detection means for detecting an aperture stop value of the aperture stop means;
• wherein the image pickup means is able to change a gain;
• and
• wherein the image pickup means control means controls a gain of the image pickup means based on a value detected by the aperture stop value detection means.

An image pickup device comprising:

• a focus lens unit that moves during focusing;
• focus lens position detection means for detecting a position of the focus lens unit;
• a splitting optical system disposed in an optical path on an image side of the focus lens unit, wherein the splitting optical system splits a light beam from a subject into a reflected light beam and a passed light beam, wherein the passed light beam is used for imaging the subject image, and wherein a reflectance of the splitting optical system against the light beam from the subject has a distribution in which the reflectance is of the maximal value on an optical axis and becomes gradually lower as the light beam is away from the optical axis, and the distribution has rotational symmetry about the optical axis;
• focus detection means for detecting a focus state of the subject image by using a portion of the reflected light beam which is reflected by the higher reflectance portion of the splitting optical system including the optical axis;
• drive means for driving the focus lens unit to a focal position for imaging the subject image by using the passed light beam based on a detection result of the focus detection means;
• image pickup means for taking the subject image imaged by the focus lens unit;
• image pickup means control means for controlling the image pickup means;
• a magnification lens unit for magnifying the subject image;
• and
• magnification lens position detection means for detecting a position of the magnification lens,
• wherein the image pickup means control means electrically corrects change in an amount of peripheral light based on values detected by the magnification lens position detection means and the focus lens position detection means.

An image pickup device comprising:

• a focus lens unit that moves during focusing;
• a magnification lens unit that moves during zooming;
• focus lens position detection means for detecting a position of the focus lens unit;
• a splitting optical system disposed in an optical path on an image side of the focus lens unit, wherein the splitting optical system splits a light beam from a subject into a reflected light beam and a passed light beam, wherein the passed light beam is used for imaging the subject image, and wherein a reflectance of the splitting optical system against the light beam from the subject has a distribution in which the reflectance is of the maximal value on an optical axis and becomes gradually lower as the light beam is away from the optical axis, and the distribution has rotational symmetry about the optical axis;
• focus detection means for detecting a focus state of the subject image by using a portion of the reflected light beam which is reflected by the higher reflectance portion of the splitting optical system including the optical axis;
• drive means for driving the focus lens unit to a focal position for imaging the subject image by using the passed light beam based on a detection result of the focus detection means;
• image pickup means for taking the subject image imaged by the focus lens unit, wherein the passed light beam through the focus lens unit and the magnification lens unit is directed to the image pickup means;
• image pickup means control means for controlling the image pickup means;
• an image blur correction optical system for correcting the subject image blur by moving vertically relative to the optical axis;
• and
• displacement detection means for detecting a displacement of the image blur correction optical system,
• wherein the image pickup means control means electrically corrects change in an amount of asymmetrical peripheral light based on a value detected by the displacement detection means.