Endoscope with distance measurement function and distance measurement method used in same

An endoscope, comprising:

• a main unit, an observation unit and a flexible tube coupled between said main unit and said observation unit, said observation unit comprises a base tube, a single wavelength light source, a diffraction grating, an image acquisition unit and a shading baffle, said single wavelength light source, said diffraction grating, said image acquisition unit and said shading baffle being respectively mounted within said base tube, wherein:
• said base tube defining an opening in a front side thereof;
• said single wavelength light source being mounted in said base tube and adapted for emitting a single wavelength light of a predetermined wavelength forwardly through said opening;
• said diffraction grating comprising a plurality of slots, said diffraction grating being mounted in said base tube between said single wavelength light source and said opening and adapted for diffracting the said single wavelength light and causing the diffracted said single wavelength light to be projected through the said opening onto an object to show a zero-order bright spot, a positive first-order bright spot at one lateral side relative to said zero-order bright spot and a negative first-order bright spot at an opposite lateral side relative to said zero-order bright spot, the vector angle between said zero-order bright spot and each of the said positive first-order bright spot and said negative first-order bright spot of said single wavelength light emitted by said single wavelength light source is obtained by calculating said predetermined wavelength and the slot width of said diffraction grating;
• said image acquisition unit being mounted in said base tube, said image acquisition unit comprising an image sensor and a lens set, said lens set comprising a lens magnification, said image acquisition unit being adapted for taking an image of said object via said opening, the effective imaging range of said image acquisition unit covering said zero-order bright spot, said positive first-order bright spot and said negative first-order bright spot;
• said shading baffle being mounted in said base tube to isolate said image acquisition unit from said single wavelength light source and said diffraction grating so as to prohibit the said single wavelength light emitted by said single wavelength light source from being reflected or refracted in said base tube onto said image acquisition unit;
• said main unit comprises a computing unit, said computing unit having built therein a reference number of standard bright spot pixels, said computing unit comprising a first arithmetic logic, a second arithmetic logic and a third arithmetic logic, said first arithmetic logic being adapted for obtaining a distance magnification by calculating the lens magnification and the pixel number of any one bright spot on said image and said reference number of pixels of standard bright spot, said second arithmetic logic being adapted for calculating the distance between two adjacent bright spots on said image using said distance magnification so as to obtain the actual distance between two adjacent bright spots projected on said object, said third arithmetic logic being adapted for calculating the distance between said diffraction grating and said zero-order bright spot by matching said vector angle with the actual distance between the said two adjacent bright spots.