Focus control system with dual scan

An optical system comprising:

• lens means for providing a primary image of an object;
• scanning means for providing first and second scans of an auxiliary image of the object;
• range sensing means for receiving the auxiliary image and providing a correlation signal having a major extremum in each scan;
• extremum sensing means for receiving the correlation signal and providing an output signal which changes from a first to a second state only once during the second scan, the change of state being indicative of the occurrence of the major extremum during the second scan;
• lens drive means for moving the lens means;
• and
• focus control means for controlling the lens drive means to move the lens means to a position determined by the position of the scanning means during the second scan when the output signal changes from the first to the second state.

Apparatus for providing a measure of the distance between the apparatus and an object, the apparatus comprising:

• first and second detector arrays for producing signals representative of the radiation received;
• first auxiliary optical means for forming a first detection image of the object on the first detector array;
• second auxiliary optical means for forming a second detection image of the object on the second detector array, the positions and radiation distributions of the first and second detection images on the corresponding arrays changing with changes in the relative positions of the first and second auxiliary optical means and the arrays, and with changes in the object distance, there being for each object distance a relative position at which there is best correspondence of the radiation distributions on the first and second detector arrays;
• scanning means for relatively moving at least a portion of at least one of the first and second auxiliary optical means and the corresponding one of the arrays progressively through a predetermined range of relative positions during a first and a second scan, the range including one position at which there is best correspondence of the radiation distributions on the first and second detector arrays for the existing object distance;
• signal processing means for comparing the signals from the first and second detector arrays and producing a correlation signal which exhibits a major extremum when the best correspondence of the radiation distributions on the first and second detector arrays is obtained during each of the first and second scans;
• comparison signal means for providing a comparison signal, the comparison signal in the second scan being a function of the major extremum in the correlation signal during the first scan;
• and
• comparing means for comparing the correlation signal with the comparison signal and producing an output signal which is a function of the comparison.

In an optical system including primary optical means, an automatic focusing system for positioning the primary optical means, the automatic focusing system comprising:

• spatial image correlation range sensing means for providing a correlation signal having a major extremum indicative of the distance to an object, the spatial image correlation range sensing means including scanning means for providing first and second scans of an image of the object;
• comparison signal means for providing a comparison signal during the second scan which is a function of the amplitude of the major extremum in the correlation signal during the first scan;
• comparing means for comparing the correlation signal with the comparison signal and producing an output signal which changes from a first to a second state only once during the second scan, and the change being indicative of the major extremum during the second scan;
• position means for positioning the primary optical means to a position determined by the position of the scanning means when the output signal changes from the first to the second state during the second scan.

An optical system comprising:

• primary optical means for providing a primary image of an object;
• auxiliary optical means for providing first and second auxiliary images of the object;
• scanning means for providing first and second scans of the second auxiliary image;
• range sensing means for producing a correlation signal having a major extremum during each scan indicative of best correspondence of the first and second auxiliary images;
• comparison signal means for providing a comparison signal during the second scan which is a function of the amplitude of the major extremum in the correlation signal during the first scan;
• comparing means for comparing the correlation signal and the comparison signal and producing an output signal which changes from a first to a second state during the second scan only when the correlation signal has a major extremum;
• positioning means for positioning the primary optical means to a position determined by the position of the scanning means during the second scan when the output signal changes from the first to the second state.