ProgRes C5 Camera
In addition to the laser scanning confocal system, the upright Leica DM6000 microscope is equipped with a Jenoptik ProgRes C5 colour digital camera. This allows the acquisition of images via the conventional optics of the microscope rather than the confocal scan head. The camera is capable of capturing images of up to 5 megapixels and communicates with the confocal microscope PC through a high-speed Firewire connection. It is controlled by intuitive, proprietary ProgRes software. The camera can also be mounted onto the DMIRE2 inverted microscope. When mounted on the DM6000 upright it can be used to acquire images through 4 different image modes.
Bright Field - typically used for standard imaging of tissue sections treated with conventional histological stains (eg. Haematoxylin & Eosin), as well as histochemical and immunohistochemical techniques such as immunoperoxidase. This imaging mode relies on the simple transmission of white light through the specimen, with stains absorbing different colours to generate a visible and usable image. As this technique relies simply on transmitting light through the specimen, it is extremely poor at visualising unstained samples. This imaging mode is compatible with all the installed objective lenses.
Differential Interference Contrast (DIC) - this technique works by sending a split polarised light beam along two separate optical paths through the sample. These two optical paths strike the specimen at positions slightly offset relative to each other. This means that at points where there is a difference in optical density such as the interface between a cell membrane and its surrounding fluid, a corresponding difference will be generated between the two light paths. When the light from these two optical paths is subsequently recombined, the differences generate interference between the light rays producing areas of lightness or darkness. Areas of uniform optical density such as a clear area of mounting media appear as a uniform grey-white (depending on exposure time). As this technique relies on differences in optical density rather than absorption and transmission of light, it can be used to produce images from unstained samples. This makes it particularly useful to image live cells which could be otherwise destroyed by standard staining techniques.
Polarising - polarising microscopy exploits the interactions between plane-polarised light and doubly-refracting (birefringent) samples to produce an image. This property generally occurs in highly-ordered materials such as crystals and is widely studied in chemistry and material sciences to analyse crystal structures. It is also used in biology to study similar highly-organised structures such as tooth enamel. While some biological samples will naturally exhibit birefringence it can also be imparted or enhanced using stains such as picrosirius red. This combines picric acid and sirius red stains to produce birefringence in collagen fibres. The images produced require quite specialist interpretation but can provide valuable structural information.
Fluorescence - although most fluorescence imaging on the confocal setup would be carried out using the laser scan head, the ProgRes C5 camera is versatile and sensitive enough to capture fluorescence images. This makes it very useful in situations where confocal scanning is not necessary, such as acquiring a series of quick 'snapshots' from fluorescent samples. The sensor of the camera has a Peltier cooling element to reduce the image noise that could otherwise be generated during long exposures of low-intensity fluorescent signals. The software also provides a Black Balance function, to help ensure clean black backgrounds on fluorescent images.