Patent Number: 
Section: claims

1. An apparatus for making a gap between first and second objects, said apparatus comprising:a light introducing unit configured to introduce light to a first entry window formed in the first object;a first detection unit configured to detect a total intensity of light from a first exit window formed in the first object with respect to each of a plurality of values of the gap, the first exit window being at such a position that light would enter through the first entry window of the first object, reflect off the second object, and then enter the first exit window if the gap has a predetermined value;a second detection unit configured to detect a total intensity of light from a second exit window formed in the first object with respect to each of a plurality of values of the gap, the second exit window being at such a position that light would enter through a second entry window of the first object, reflect off the second object, and then enter the second exit window if the gap has the predetermined value; anda positioning mechanism configured to obtain a position of the second object, with respect to a direction of the gap, where the gap has the predetermined value based on a plurality of total intensities of light detected by said first detection unit and a plurality of total intensities of light detected by said second detection unit, and to position the second object at the obtained position,wherein said positioning mechanism is configured to obtain a first position of the second object, with respect to the direction of the gap, where said first detection unit detects the maximum total intensity of light and a second position of the second object, with respect to the direction of the gap, where said second detection unit detects the maximum total intensity of light, and to position the second object at an average position of the first and second positions. 2. A method of making a gap between first and second objects have a predetermined value, said method comprising the steps of:a first introduction step of introducing light into a first entry window on the first object;a first detection step of detecting a first total intensity of light from a first exit window on the first object with respect to each of a plurality of values of the gap, the first exit window being at such a position that light would enter through the first entry window of the first object, reflect off the second object, and then enter the first exit window if the gap has the predetermined value;a second introduction step of introducing light into a second entry window on the first object;a second detection step of detecting a second total intensity of light from a second exit window on the first object with respect to each of a plurality of values of the gap, the second exit window being at such a position that light would enter through the second entry window of the first object, reflect off the second object, and then enter the second exit window if the gap has the predetermined value;an obtaining step of obtaining a position of the second object, with respect to a direction of the gap, where the gap has the predetermined value based on a plurality of total intensities of light detected in said first detection step and a plurality of total intensities in said second detection step; anda position step of positioning the second object at the position obtained in said obtaining step,wherein the obtaining step obtains a first position of the second object, with respect to the direction of the gap, where the maximum total intensity of light is detected in said first detection step and a second position of the second object, with respect to the direction of the gap, where the maximum total intensity light is detected in the second detection step, and obtains the position of the second object where the gap has the predetermined value by averaging the first and second positions. 3. A method of making a gap between first and second objects have a predetermined value, said method comprising the steps of:a first introduction step of introducing light into a first entry window on the first object;a first detection step of detecting a first total intensity of light from a first exit window on the first object with respect to each of a plurality of values of the gap, the first exit window being at such a position that light would enter through the first entry window of the first object, reflect off the second object, and then enter the first exit window if the gap has the predetermined value;a second introduction step of introducing light into a second entry window on the first object;a second detection step of detecting a second total intensity of light from a second exit window on the first object with respect to each of a plurality of values of the gap, the second exit window being at such a position that light would enter through the second entry window of the first object, reflect off the second object, and then enter the second exit window if the gap has the predetermined value;an obtaining step of obtaining a position of the second object, with respect to a direction of the gap, where the gap has the predetermined value based on a plurality of total intensities of light detected in said first detection step and a plurality of total intensities in said second detection step; anda position step of positioning the second object at the position obtained in said obtaining step,wherein said obtaining step includes the steps of:calculating a first approximate curve for a first graph of the plurality of total intensities of light detected in said first detection step;calculating a second approximate curve for a second graph of the plurality of total intensities of light detected in said second detection step; anddetermining a first position of the second object corresponding to a peak of the first approximate curve;determining a second position of the second object corresponding to a peak of the second approximate curve; andobtaining the position of the second object where the gap has the predetermined value by averaging the first and second positions.