A wide-field microscopy technique using a linear image sensor for obtaining 3D images

Three-dimensional (3D) microscopy is a huge field that includes several microscopy techniques. Among these techniques the confocal microscopy is widely known and used due to its improved axial resolution or optical sectioning ability. However its high cost and image acquisition time as well as low signal-to-noise ratio are important drawbacks. Other techniques use wide-field structured illumination to get depth information from the sample. The detectors in commercial microscopes are normally of the point detector type (PMTs) in confocal and area sensors (CCDs) in wide-field microscopy. Examples of microscopes that take advantage of lower cost and faster readout cycles of linear image sensors are very uncommon. The purpose of this work is to develop a low-cost microscopy technique for obtaining 3D images with lower acquisition time and higher signal-to-noise ratio (SNR) than in classical confocal microcopy. It uses a linear CMOS image sensor and specific reconstruction algorithms will be able to extract 3D information from the distribution of light intensity collected. The sensor readout circuitry has been developed and tests are currently running in a laboratory prototype in reflection mode with an epi-illuminated configuration of scanning-stage type. The light source is a commercial incandescent lamp with regulated intensity. For the development, test and optimization of the reconstruction algorithms the object is mounted on a 3-axis translation stage to scan the object in three perpendicular directions. Contrast and resolution results obtained using a resolution test slide and preliminary images of integrated circuit (IC) bonding are presented.