显微镜相机安装方法及常见问题

Connecting a camera to a microscope can be somewhat of a science in itself. There are several solutions. Some of the solutions are quite low-cost, others are DIY home-made solutions, while still other commercial options can be more costly (but may also give you the least problems). Each approach has its own distinct advantages and disadvantages. Over the past years, I have tried out several approaches and would now like to give you a short overview of the possibilities.

There are several options for connecting a camera to a microscope. The camera system can either be connected via a dedicated photo tube on a trinocular head, or can be connected to one of the microscope’s eyepieces. Depending on the set-up, there can be either intermediate optics between the camera and the microscope’s objective, or not.

The image produced by the microscope objective can be directly picked up by the sensor of a camera, without an eyepiece or other intermediate optics. Here objective of a microscope produces a real image directly on the camera’s sensor. The objective produces a relatively large image, compared to the small sensor of many cameras. Unless the sensor is large, there may be quite much empty magnification and the brightness of the image is low.

The image produced by the microscope objective can also be passed through a reduction lens before reaching the camera sensor. This way the image produced by the microscope objective is reduced in size to better match the small sensor size of the digital camera. The reduction lens produces a real image on the camera sensor. Without the reduction lens the image would be magnified too much. The reduction lens also results in a brighter image. This is an improvement to the first point from above. Eyepiece cameras for microscopes use this system. The reduction lens is not a compensating photo eyepiece and therefore does not correct lens errors produced by the objectives.

The image produced by the microscope objective is first passed through a regular eyepiece. A virtual image is produced this way, which can not be used to directly make a picture. A camera (with its own objective) then picks up the virtual image and projects it on the sensor. The camera works like the eye, which converts a virtual image to a real image. This system is used in afocal photography, in which a regular compact camera (with its own objective and all) is attached in front of the eyepiece.

The image produced by the microscope objective is passed through a photo projection ocular (photo eyepiece), which then projects a real image on the sensor of an SLR camera. There are no camera objectives involved. The projection eyepiece corrects optical errors which are produced by the microscope objective. These photo projection eyepieces are compensating optical elements. This means that they are designed to correct various lens errors that the objectives produce, including field curvature and chromatic aberration. These projection oculars are therefore manufacturer dependent and must correspond to the objectives of the manufacturer. Besides image quality, another advantage is, that parfocality is maintained between the camera and the eyepieces (i.e. both images are in focus at the same, and there is no focus deviation).
Let’s now have a look at a few real life applications:

This was one of my earlier attempts of connecting a camera to a microscope. I completely dismounted a webcam and removed all of the optics. Leaving the webcam optics in place (used in afocal photography) would result in a too small image because most webcams have wide-angle optics. I then placed the electronics with the attached sensor into a separate plastic box and attached a short metal tube to the box for easy placement on the trinocular head. There were no intermediate optics involved and the image was directly projected from the microscope’s objective. Make sure that the blue filter is still in pace in front of the sensor (they are quite red sensitive), otherwise you have to use a blue “daylight” filter (for photography) on top of the halogen lamp of the microscope.

This is my favorite solution, because of its high convenience. It is possible to do microscopic observations without looking through the eyepiece, only the computer monitor. This can be more relaxing at times. These cameras are connected directly to the computer and are controlled entirely over the computer. Full manual control is possible with the camera that I have. This is absolutely essential (especially when one wants to make panoramic images). There are reduction lenses in front of the camera, so the brightness of the image and field of view are increased (compared the the DIY webcam solution from before). And for those of you who do not have a trinocular head: these cameras can be mounted instead of an eyepiece!

The camera has a reduction lens and can be mounted on the phototube.

The camera can also be attached in place of an eyepiece.

The camera can also be attached in place of an eyepiece – another view.