Spectrophotometer Jan 28, 2002 Deryck Hong Suryadi Gunawan

Presentation Outline Project Objective Project Specification Design Test Plane Power Consumption System cost

Project Objective Building a measurement tool that is used to measure color composition –Measures light reflected from an object at each wavelength. –Creating a color spectrum and measuring intensity of each color. –Using the intensities to create the color of the object and displaying the color on a screen with corresponding RGB values. –The object has to be a piece of single colored paper

Project Specification CCD sensor: –2048 pixels Blue: 150 – 650 Green: 800 – 1300 Red: –Intensity from Lens –Focal length of 80 mm Distance between object and lens is 5 cm Distance between lens and the CCD sensor is 13 cm Accuracy: –Error within (10%)

Project Specification Using C programming with GRX graphic library to create GUI Communication between PC and the CCD sensor through parallel port

Color Spectrum This project uses the wavelengths from 435 nm to 740 nm.

Design SourceLensDiffraction Grating CCD Sensor Parallel Port

Design Cont The distances between parts have to be calculated: –Between Diffraction Grating and the lens –Between Diffraction Grating and the CCD sensor Distance between the lens and the Diffraction Grating can be calculated using lens equation: 1/Object distance + 1/Image distance = 1/focal length

Design Cont. After finding the angles, the distance (D) can be calculated using the following equations: and are the displacements from the central maxima to the maxima of blue and red lights. The difference of those two displacements has to be the height of the CCD sensor. The height of the CCD sensor = 2048 * 14um = 2.867cm Then D is found to be 2.867cm/ = 5 cm

Division of Work Hardware ( Deryck & Suryadi) –Mounting of parts –Casing –Placing of light Software –Parallel port communication ( Deryck &Suryadi) –GUI ( Deryck ) –Algorithm ( Suryadi)

Work Completed CCD, Lens and grating have been mounted. Light has been placed. Casing is created. Light absorption is designed. GUI is done Parallel port communication between CCD sensor and PC is done –Still have some small problems System calibration is done –Pixels that correspond to Red, Green, and Blue are found

Work to be done Algorithm is implemented but still needs to be fully tested. Overall system testing Color Compensation for monitor viewing

Test Plan Use Color samples that has known RGB values to test the system A set of color samples have been measured using the device in the color laboratory in printing department –The device measures the LAB values of the color samples –Then the LAB values are converted to RGB values This set of color samples will be used to test the system.

Power consumption CCD board……………………… 5 watts Light source…………………….50 watts Total power consumed…….55 watts

System cost CCD and lens……………………$1040 Grating……………………………$1 Casing…………………………….$ free Light source………………………$30 Misc (tape, black paper, etc)……$15 total $1086