Scanning apparatus and method for obtaining the gray level of a scanned object therein

An scanning apparatus for scanning an object, at least comprising:

• an image sensor module which receives a light reflected from the scanned object and generates a digital response representing the light reflectivity of said object;
• at least three corrective elements having different light reflectivity, whose corresponding gray levels are pre-defined and pre-stored in the scanning apparatus;
• wherein during a scanning process said corrective elements will be scanned by said image sensor module and the digital response of each of said corrective elements generated by said image sensor module will be obtained;
• and
• a processing unit converting the digital response of said object into a corresponding gray level of said object according to the digital responses of said corrective elements.

A method of obtaining the gray level of a scanned object in response to a digital response generated by an image sensor module, said image module has a non-linear transfer curve to convert a received light into said digital response, said transfer curve has a first deviated node, said method comprising the steps of:

• obtaining a minimum digital response generated by said image sensor module by making said image sensor sense no light, the corresponding gray level of said minimum digital response being defined as a minimum gray level;
• providing a first corrective element whose gray level being defined as a maximum gray level, and a first digital response being generated by said image sensor module when scanning said first corrective element;
• providing a second corrective element whose gray level being corresponding to said first deviated node of said transfer curve, and a second digital response being generated by said image sensor module when scanning said second corrective element;
• scanning said object to obtain an object digital response generated by said image sensor module;
• selecting two digital responses from the minimum, first, and second digital responses, wherein the values of the two selected digital responses are closer to the object digital response;
• and
• using the object digital response, two selected digital responses, and the gray levels corresponding to the selected digital responses in conjunction with an interpolation method to determine the corresponding gray levels of said object.

A method of determining the gray level of a scanned object in response to a digital response generated by an image sensor module, said image sensor module has a non-linear transfer curve to convert a received light into said digital response, said transfer curve has a first deviated node and a second deviated node, said method comprising the steps of:

• obtaining a minimum digital response generated by said image sensor module by making said image sensor sense no light, the corresponding gray level of said minimum digital response being defined as a minimum gray level;
• providing a first corrective element whose gray level being defined as a maximum gray level, and a first digital response being generated by said image sensor module when scanning said first corrective element;
• providing a second corrective element whose gray level being corresponding to said first deviated node of said transfer curve, and a second digital response being generated by said image sensor module when scanning said second corrective element;
• providing a third corrective element whose gray level being corresponding to said second deviated node of said transfer curve, and a third digital response being generated by said image sensor module when scanning said second corrective element;
• scanning said object to obtain an object digital response generated by said image sensor module;
• selecting two digital responses from the minimum, first, second, and third digital responses, wherein the values of the two selected digital responses are closer to the object digital response;
• and
• using the object digital response, two selected digital responses, and the gray levels corresponding to the selected digital responses in conjunction with the interpolation method to determine the corresponding gray levels of said object.