It seems English is not your first language.
Please fill in your location so that other members, who may be able to understand your language, can interpret the non-English wording.
Sensors...What sensors do you have in mind?
LDR?
Photodiode?
Ultrasonic?
Capacitance?
etc.
Is the table expected to be used in all light conditions, e.g. a dark or brightly lit room?
How will the sensors be arranged to detect an object in a particular zone?
What should happen if an object triggers two or more sensors? Should all or none of the LED's be lit?
Should an arm placing an object trigger a sensor? Or not?
This may SEEM to you, to be a simple project, but there are so many things to consider and you need to supply more information...