Optical processing apparatus and light source luminance adjustment method thereof

A light source luminance adjustment method, being adapted for use in an optical processing apparatus which is adapted to detect a pressing state and a rotational displacement of a button, the optical processing apparatus comprising a light source unit, a processing unit, and an image sensing unit, the light source unit providing a beam of light to a surface of the button facing the light source unit to generate a reflected light beam reflected from the surface of the button, the processing unit defining a frame rate, the image sensing unit receiving the reflected light beam reflected from the surface of the button, wherein the light source unit and the image sensing unit are arranged to change an image quality index in an arrangement that, when the pressing state of the button is changed between press and non-press, a part of a cross-section of the reflected light beam is shifted between impinging and not impinging on the image sensing unit due to a uniform distance change between the surface of the button and the light source unit and between the surface of the button and the image sensing unit, and the light source luminance adjustment method comprising:

• defining, by the processing unit, a plurality of first time instants within a first time interval, wherein a length of the first time interval is shorter than a reciprocal of the frame rate;
• setting, by the processing unit, the beam of light provided by the light source unit to a luminance value at each of the first time instants, wherein the luminance values are different and within a first range;
• capturing, by the image sensing unit, the reflected light beam to output a first image of the surface of the button by an exposure time length at each of the first time instants, wherein the exposure time lengths are the same;
• calculating, by the processing unit, the image quality index of each of the first images;
• comparing, by the processing unit, the image quality index of one of the first images with at least one first press threshold to identify the pressing state of the button within the first time interval,
• comparing, by the processing unit, the image quality indices of each of the first images with at least one quality threshold;
• and
• selecting, by the processing unit, more than one of the first images as a plurality of first temporary images to calculate the rotational displacement of the button when the image quality indices do not meet the at least one quality threshold;
• stop outputting the calculated rotational displacement when the pressing state of the button is identified between the press and the non-press by comparing the image quality index with the at least one first press threshold.

An optical processing apparatus, adapted to detect a pressing state and a rotational displacement of a button, the optical processing apparatus comprising:

• a light source unit configured to provide a beam of light to a surface of the button facing the light source unit to generate a reflected light beam reflected from the surface of the button;
• a processing unit, electrically connected to the light source unit, and configured to
• define successive frame capturing periods,
• define a plurality of time instants within a time interval in each frame capturing period, wherein a length of the time interval is shorter than the frame capturing period, and
• set the beam of light provided by the light source unit to a luminance value at each of the plurality of time instants within each time interval;
• and
• an image sensing unit, electrically connected to the processing unit, and configured to capture the reflected light beam to output an image of the surface of the button by an exposure time length and a gain value at each of the plurality of time instants within the each time interval,
• wherein the processing unit is further configured to
• set an image capture parameter, which includes at least one of the luminance value, the exposure time length and the gain value, at each of the plurality of time instants to be different and within a predetermined range,
• calculate an image quality index of each of the images captured within the each time interval,
• compare the image quality index of a first image among the images captured within the each time interval with at least one press threshold to identify the pressing state of the button within the each time interval, wherein the first image corresponds to a minimum image capture parameter or a maximum image capture parameter among the plurality of time instants within the each time interval, and
• calculate the rotational displacement of the button using a second image among the images captured within the each time interval, wherein the second image is one of the images, among the plurality of time instants within the each time interval, whose image quality index meet at least one quality threshold,
• wherein the light source unit and the image sensing unit are arranged to change the image quality index in an arrangement that, when the pressing state of the button is changed between press and non-press, a part of a cross-section of the reflected light beam is shifted between impinging and not impinging on the image sensing unit due to a uniform distance change between the surface of the button and the light source unit and between the surface of the button and the image sensing unit, and
• the processing unit is further configured to stop outputting the calculated rotational displacement when the pressing state of the button is identified between the press and the non-press by comparing the image quality index with the at least one press threshold.