Zoom camera with manual focus function
A zoom camera having enhanced focusing stability during high magnification zooming under environments of high temperatures or low temperatures. When the zoom camera performs zoom-in operations in an environment of high or low temperatures, aperture control is added as the zoom magnification becomes higher and the temperature becomes higher or lower whereby the depth of field is made deeper to assure the presence of a range with good focusability.
1. A zoom camera with manual focus function for performing focus adjustment by using a trace curve, said camera comprising:
an optical system having a zoom adjustment mechanism, an aperture adjustment mechanism and a focus adjustment mechanism;
an image pickup element for electrical conversion of light which passed through said optical system;
an automatic gain control circuit for amplifying an output of said image pickup element to a predetermined value;
temperature measurement means for detecting a temperature of the element; and
control means for enlarging an aperture value of said aperture adjustment mechanism when the temperature detected by said temperature measurement means is greater than or equal to a first setup value or, alternatively, less than or equal to a second setup value which is different from the first setup value and which is lower than the first setup value and when a zoom magnification in said manual focus function is greater than or equal to a prespecified magnification, said prespecified magnification is 24× or higher.
2. The zoom camera according to claim 1 , wherein said control means has a relation of X×A×S×F −2 =constant, where F is an aperture value of said aperture adjustment mechanism, A is a gain magnification of the automatic gain control circuit, S is an electronic shutter speed and X is illuminance of a final output image signal, and wherein said control means performs control correlating with the zoom magnification in said manual focus function.
3. The zoom camera according to claim 1 , wherein said control means performs control correlating with the detected temperature of said temperature measurement means and an aperture value F of said aperture adjustment mechanism.
4. The zoom camera according to claim 2 , wherein said control means performs control correlating with the detected temperature of said temperature measurement means and the aperture value F of said aperture adjustment mechanism.