a tank including an outer wall comprising a transparent material to allow inspection of an object located in a fluid inside the tank from outside the tank;

a lighting device configured to irradiate the object;

a telecentric lens located outside the tank and configured to condense light reflected from the irradiated object;

a driver configured to move the telecentric lens along an optical axis of the telecentric lens;

a controller configured to control the lighting device to sequentially irradiate the object with a red monochromatic light beam, a green monochromatic light beam, and a blue monochromatic light beam in order of respective wavelengths of the red, green and blue monochromatic light beams, based on a predetermined period relative to a predetermined time point, and control the driver to sequentially move the telecentric lens to adjust a distance between the object and the telecentric lens in response to the respective wavelengths of the red, green and blue monochromatic light beams; and

a camera configured to receive the reflected light that has passed through the telecentric lens to acquire a plurality of images of a certain size corresponding to the red, green, and blue monochromatic light beams, respectively,

wherein the controller is further configured to detect the assembly defect of the semiconductor light emitting device by synthesizing the plurality of images into a color image of three channels.