An image processing apparatus having a reading unit that can read both sides of an original in parallel has a processing unit that processes image data obtained by the reading unit reading an original. The apparatus controls to execute processing by the processing unit on image data of a first surface of the original and reading of a second surface of the original in parallel. The apparatus determines whether or not to start processing by the processing unit on image data of the second surface of the original when processing by the processing unit on the image data of the first surface of the original completes, and in accordance with the determination result, the apparatus controls of a start of processing by the processing unit on the image data of the second surface of the original.

An image processing apparatus having a reading unit that can read both sides of an original in parallel has a processing unit that processes image data obtained by the reading unit reading an original. The apparatus controls to execute processing by the processing unit on image data of a first surface of the original and reading of a second surface of the original in parallel. The apparatus determines whether or not to start processing by the processing unit on image data of the second surface of the original when processing by the processing unit on the image data of the first surface of the original completes, and in accordance with the determination result, the apparatus controls of a start of processing by the processing unit on the image data of the second surface of the original.

A signal processing device includes a signal output circuit, a controller, and a corrector. The signal output circuit outputs a signal according to a physical quantity being input. The controller controls the signal output circuit. The corrector corrects a signal to be corrected. The signal to be corrected is output from the signal output circuit. The signal output circuit selectively performs one of first operation of outputting a characteristic signal that indicates characteristics of the signal output circuit and second operation of outputting a pseudo signal that is generated spuriously, according to control of the controller. The corrector corrects the signal to be corrected based on one of the characteristic signal and the pseudo signal output from the signal output circuit.

A signal processing device includes a signal output circuit, a controller, and a corrector. The signal output circuit outputs a signal according to a physical quantity being input. The controller controls the signal output circuit. The corrector corrects a signal to be corrected. The signal to be corrected is output from the signal output circuit. The signal output circuit selectively performs one of first operation of outputting a characteristic signal that indicates characteristics of the signal output circuit and second operation of outputting a pseudo signal that is generated spuriously, according to control of the controller. The corrector corrects the signal to be corrected based on one of the characteristic signal and the pseudo signal output from the signal output circuit.

An image scanning system for scanning an object is disclosed. The image scanning system includes a light source, an optical lens, an image capturing unit and a light barrier element. The light source irradiates an object to produce an image light, and the optical lens converges the image light. The image capturing unit is disposed at a light leaving side of the optical lens, and the image capturing unit captures the image light to form an image. The light barrier element is disposed at a light entering side of the optical lens or disposed between the optical lens and the image capturing unit, and the light barrier element selectively allows the image light within a predetermined range of an incident angle to pass through.

An image scanning system for scanning an object is disclosed. The image scanning system includes a light source, an optical lens, an image capturing unit and a light barrier element. The light source irradiates an object to produce an image light, and the optical lens converges the image light. The image capturing unit is disposed at a light leaving side of the optical lens, and the image capturing unit captures the image light to form an image. The light barrier element is disposed at a light entering side of the optical lens or disposed between the optical lens and the image capturing unit, and the light barrier element selectively allows the image light within a predetermined range of an incident angle to pass through.

A signal processing device includes a first adjuster, a second adjuster, and a digitizer. The first adjuster coarsely adjusts an output range of a signal input to the first adjuster to output a first signal. The second adjuster adjusts an output range of a signal more finely than the first adjuster adjusts to output a second signal. The digitizer digitizes the first signal or the second signal to output a digital signal. The digital signal has an output range of a signal that is finely adjusted with the second adjuster after being coarsely adjusted with the first adjuster.

A signal processing device includes a first adjuster, a second adjuster, and a digitizer. The first adjuster coarsely adjusts an output range of a signal input to the first adjuster to output a first signal. The second adjuster adjusts an output range of a signal more finely than the first adjuster adjusts to output a second signal. The digitizer digitizes the first signal or the second signal to output a digital signal. The digital signal has an output range of a signal that is finely adjusted with the second adjuster after being coarsely adjusted with the first adjuster.

An optical scanning apparatus of the present invention includes: a splitting element which splits a light flux emitted from a light source into first and second light fluxes; a deflecting unit which deflects the first and second light fluxes to scan first and second scanned surfaces in a main scanning direction; and an imaging optical system which includes a first imaging lens on which both the first and second light fluxes deflected by the deflecting unit are incident and guides the first and second light fluxes to the first and second scanned surfaces. The condition expressed by

−1.1≦α1/α2≦−0.9

is satisfied where α1 and α2 are angles within a main scanning cross section between a first axis parallel to the main scanning cross section and directions of incidence of the first and second light fluxes on the deflecting unit, respectively.

An optical scanning apparatus of the present invention includes: a splitting element which splits a light flux emitted from a light source into first and second light fluxes; a deflecting unit which deflects the first and second light fluxes to scan first and second scanned surfaces in a main scanning direction; and an imaging optical system which includes a first imaging lens on which both the first and second light fluxes deflected by the deflecting unit are incident and guides the first and second light fluxes to the first and second scanned surfaces. The condition expressed by

−1.1≦α1/α2≦−0.9

is satisfied where α1 and α2 are angles within a main scanning cross section between a first axis parallel to the main scanning cross section and directions of incidence of the first and second light fluxes on the deflecting unit, respectively.