Focus detection method utilizing surface acoustic wave

Claim 3

A method according to claim 1, wherein the improvement further comprises the step of: arranging first and second light receiving element arrays forward and backward with respect to a predetermined focal plane of the imaging optical system, the first and second light element arrays producing first and second element array output signals; processing the first and second element array output signals by first and second processing devices, respectively, to produce first and second processing device output signals each representing an image sharpness; and detecting the focus condition of said imaging optical system in response to a difference between said first and second processing device output signals.

Claim 4

A method according to claim 2, wherein said processing the first and second element array output signals comprises effecting a Fourier transform for the first and second element array output signals to obtain first and second power spectra, and deriving said first and second processing device output signals from the first and second power spectra, respectively.

Claim 5

A method according to claim 3, wherein said Fourier transform effecting step comprises, amplitude-modulating the first and second element array output signals to generate first and second modulated signals, respectively; passing the first and second modulated signals through first and second chirp filters, each including at least one surface acoustic wave device, to derive first and second Fourier transform signals, respectively; and demodulating the first and second Fourier transform signals of the first and second chirp filters, respctively to derive first and second demodulated signals.

Claim 6

A method according to claim 4, wherein said detecting step comprises deriving a difference between the first and second demodulated signals and intergrating the difference to produce a focus detection signal representing the focus condition.

Claim 7

A method according to claim 2, wherein the improvement further comprises the steps of: arranging third and fourth light receiving element arrays apart from each other forward and backward with respect to the predetermined focal plane of the imaging optical system by a distance larger than a distance by which the first and second light receiving element arrays are apart from each other, the third and fourth light element arrays producing third and fourth element array output signals; processing the first and second element array output signals to produce a fine focus detection signal; processing the third and fourth element array output signals by means of third and fourth processing devices each including at least one surface acoustic wave device to produce a coarse focus detection signal; and selecting one of said fine and coarse focus detection signals in response to the focus condition to effect a focus adjustment.

Claim 8

A method according to claim 6, wherein said selection of the fine and coarse focus detection signals is effected in accordance with an amplitude of the coarse focus detection signal.

Claim 9

A method according to claim 1, wherein the improvement further comprises the steps of arranging first and second light receiving element arrays which receive respectively light fluxes transmitted through first and second regions of an exit pupil of said imaging optical system, the first and second light receiving element arrays producing first and second element array output signals; processing the first and second element array outputs signals by means of the same processing device to produce a correlation output signal representing an amount and direction of lateral shift between said light fluxes; and detecting the focus condition of said imaging optical system in response to said correlation output signal.

Claim 10

A method according to claim 8, wherein said first and second array output signals are supplied to a convolver including a surface acoustic wave device at a given timing to produce the correlation output signal.

Claim 11

A method according to claim 9, wherein each of the first and second element array output signals is supplied to said convolver through a peak hold circuit and a low-pass filter.

Claim 12

A method according to claim 10, wherein the focus condition of the imaging optical system is detected by processing the correlation output signal of the convolver by a peak position detector.

Claim 13

A method according to claim 8, wherein said processing the first and second element array output signals comprises supplying the first and second element array output signals to first and second Fourier transform devices, respectively, each comprising chirp filters and each including at least one surface acoustic wave device; multiplying outputs of the first and second Fourier transform devices to produce a cross spectrum; and supplying the cross spectrum to a third Fourier transform device comprising chirp filters each inlcuding at least one surface acoustic wave device to derive the correlation output signal.

Claim 14

A method according to claim 12, wherein the first and second element array output signals are supplied to said first and second Fourier transform devices through first and second peak hold circuits and first and second low-pass filters, respectively.

Claim 15

A method according to claim 13, wherein the focus condition of the imaging optical system is detected by processing the correlation output signal of the third Fourier transform device by a peak position detector.

Claim 16

A method according to claim 1, wherein the improvement further comprises the steps of: arranging first, second and third light receiving element arrays which receive respectively light fluxes transmitted through first, second and third regions of an exit pupil of said imaging optical system, said first region being arranged at a center including an optical axis and said second and third regions being arranged on respective sides of the first region, the first, second and third light element arrays producing first, second and third element array output signals; supplying the first element array output signals to a first Fourier transform device comprising chirp filters each including at least one surface acoustic wave device to produce first transform output signals; supplying a sum of the second and third element array output signals to a second Fourier transform device comprising chirp filters, each including at least one surface acoustic wave device, to produce second transform output signals; supplying the first and second transform output signals to a divider to produce a divider output signal; processing the divider output signal to produce a correlation output signal representing an amount and a direction of lateral shift of the light fluxes; and detecting the focus condition of said imaging optical system in response to said correlation output signal.

Claim 17

A method according to claim 15, wherein said processing of the divider output signal comprises supplying said divider output signal to a differentiator to produce a differentiated output, and supplying said differentiated output to a sample and hold circuit to produce the correlation output signal.

Claim 18

A method according to claim 1, wherein the improvement further comprises the steps of arranging first and second light receiving element arrays forward and backward with respect to a predetermined focal plane of the imaging optical system, and third and fourth light receiving element arrays which receive respectively light fluxes transmitted through first and second regions of an exit pupil of the imaging optical system, the first, second, third and fourth light receiving element arrays producing first, second, third and fourth element array output signals; processing the first and second element array hirput signals by first and second processing devices each including at least one surface acoustic wave device to produce a first correlation output signal representing an image sharpness, and processing the third and fourth element array output signals by third and fourth processing devices each including at least one surface acoustic wave device to produce a second correlation output signal representing an amount and direction of lateral shift between said light fluxes; selecting one of the first and second correlation output signals; and detecting the focus condition of said imaging optical system in response to the selected correlation output signal.

Claim 19

A method according to claim 17, wherein said third and fourth element array output signals are supplied to a convolver including at least one surface acoustic wave device at a given timing to produce the second correlation output signal.

Claim 20

A method according to claim 17, wherein said processing of the third and fourth element array output signals comprises supplying the third and fourth element array output signals to first and second Fourier transform devices, respectively, comprising chirp filters each including at least one surface acoustic wave device; multiplying outputs of the first and second Fourier transform devices to produce a cross spectrum; and supplying the cross spectrum to a third Fourier transform device comprising chirp filters each including at least one surface acoustic wave device to derive said second correlation output signal.

Claim 21

A method according to claim 17, wherein said selection of the first and second correlation output signals is effected in accordance with an amplitude of the second correlation output signal.

Claim 22

A method according to claim 17, wherein said processing of the first and second element array output signals comprises, effecting a Fourier transform for each of the first and second element array output signals to produce first and second power spectra; and calculating a difference between said first and second power spectra to obtain said first correlation output signal representing the image sharpness.