1. Field of the Invention
The present invention relates to an image pickup apparatus for picking up an image of an object.
2. Related Background Art
Various kinds of image pickup elements such as a CCD and CMOS and image pickup apparatuses using them have been proposed.
These image pickup apparatuses are designed to guide external light scattered by an object to an image pickup element through an imaging lens system. The only way to compensate for an insufficient light amount is to cause an additional light source such as an electronic flash to emit/project light onto the object. If such a light source is added to an image pickup apparatus internally or externally, the size and weight of the apparatus undesirably increase.
In addition, a conventional apparatus has only the simplest function of picking up a two-dimensional image of an object, and hence can obtain only a simple image picked up by this function. However, this apparatus cannot obtain physical information about the object from light reflected by the object.
The physical information about the object is acquired by another device designed to irradiate the object with light from a special light source such as a laser, detect light reflected by the object as object light, and measure it with a so-called light measuring device. In addition, such a light measuring device is designed to mainly perform point or line measurement. To obtain two-dimensional or three-dimensional information, therefore, a scanning means is additionally required. When, for example, three-dimensional information is to be obtained, an object on a rotating table must be rotated about a stationary shaft or the measuring device must be moved around the object to scan the entire surface of the object. This imposes severe restrictions on the object. To make information obtained in this manner conform to images obtained by a conventional image pickup apparatus, there are still many technical hurdles to surmount. Under the circumstances, few apparatuses have been put into practice.
It is an object of the present invention to provide an image pickup apparatus which can detect the amplitude and phase of light from an object with a high SNR (Signal to Noise Ratio), attain reductions in its size and power consumption, and capture the physical properties of the object by image pickup operation under weak light.
In order to achieve the above object, according to aspect of the present invention, there is provided an image pickup apparatus comprising an image pickup unit having an array of a plurality of photodetection elements, a light-emitting element unit for emitting reference light having a predetermined frequency difference with respect to a frequency of light incident on the image pickup unit, and a wave synthesizer for synthesizing the incident light and the reference light from the light-emitting element unit and guiding the synthesized light to the image pickup unit.