초록 ▼

A focus detecting device gathers first image data by a couple of linear arrays of photo diodes in a CCD, which are disposed oppositely with respect to an optical axis of an objective, and second image data by a couple of photo diodes arrayed disposed close to one of the photo diode arrays. A CPU cal

A focus detecting device gathers first image data by a couple of linear arrays of photo diodes in a CCD, which are disposed oppositely with respect to an optical axis of an objective, and second image data by a couple of photo diodes arrayed disposed close to one of the photo diode arrays. A CPU calculates a integer part and fractional part of a displacement of first and second images represented by the first image data, and checks if the calculation results are reliable for focus detection, by using the first and second image data. A counter contained in the CPU counts the number of decisions of unreliable. When a count of counter reaches a preset value and when the latest decision of unreliability is made for the integer part calculation result, a subsequent lens drive is prohibited, and the integration by the CCD, and the integer part calculation are repeated, while presenting a display of “Unmeasurable”. Further, an additional reliability check is made of the result of the latest integer part calculation. If the additional reliability check shows a satisfactory reliability, the CPU goes out of the repetitive operation of the integration and the integer part calculation, and removes the prohibition of the lens drive.

대표청구항 ▼

A method for detecting a focusing state of an objective by receiving light beams emitted from an object and passing through first and second portions of the objective that are disposed oppositely with respect to an optical axis of the objective, said method comprising the steps of: receiving and con

A method for detecting a focusing state of an objective by receiving light beams emitted from an object and passing through first and second portions of the objective that are disposed oppositely with respect to an optical axis of the objective, said method comprising the steps of: receiving and converting first and second images formed respectively by light beams passed through said first and second portions into first and second electrical signals; calculating an integer part of a displacement of said first and second images one from the other by using the electrical signals formed in said receiving and converting step; checking if the integer part calculation result is reliable enough for focus detection, by using the electrical signals formed in said receiving and converting step; calculating a fractional part of said displacement of said first and second images one from the other; checking if the fractional part calculation result is reliable enough for focus detection, by using the electrical signals formed in said receiving and converting step; counting the number of decisions of unreliability made by said integer part reliability checking step and said fractional part reliability checking step; checking additionally if the latest integer part calculation result is reliable enough for focus detection, by using the electrical signals formed in said receiving and converting step; and executing such a control that when a count in said counting step reaches a preset value, and when the latest decision of unreliability is made for the integer part calculation result, a subsequent lens drive is prohibited, and the receiving and converting step and integer part calculating step are repeated, while presenting a display of “Unmeasurable”, and that when a decision of reliability is made for the integer part calculation result in said additionally checking step, said control goes out of said repetition of the receiving and converting step and the integer part calculating step, and removes the prohibition of the lens drive.