Incredibly Cheap Microscope
| Polish version is here |
The following article was originally published in the journal for educators Biologia w Szkole (eng. Biology in School) (4/2015):
When we think of a microscope, we instinctively associate it with high precision. Achieving clear, detailed images depends on using top-quality lenses and carefully engineered mechanical components. Unsurprisingly, this level of craftsmanship comes at a cost — quality microscopes are rarely inexpensive. For teachers, students, passionate hobbyists, and even professional scientists, the high price tag can pose a real obstacle. In fact, the lack of funding is often cited by school administrators as a reason for the limited availability of hands-on lab activities, especially in subjects like biology.
Among other reasons, I described in the previous issue of “Biology…” a simple method for visualizing microorganisms using commonly available laser pointers [1]. This method certainly works and provides surprisingly good results — taking into account, of course, the simplicity of the setup. Still, the image obtained in this manner is not perfect because it does not show the internal structural details of the observed objects, only their outlines. This experiment is especially useful for sparking an interest in nature. However, to perform a deeper analysis of the results, we must resort to solutions that produce a more detailed image.
That is why this time I would like to propose to you, dear Reader, the construction of an inexpensive digital microscope that allows observation of a wide range of specimens: from relatively large ones, such as entire insects, to genuinely small samples, including plant cells and single-celled ciliates.
Electronic microscopes with decent specifications are available on the market and are generally more affordable than traditional light microscopes. However, in many cases, their price can still be prohibitive. Building such a device yourself can be a highly rewarding experience for any experimenter. The solution I propose is also quite budget-friendly — the total cost of my setup was just under 100 PLN (less than $20). Even with its limitations, I believe it’s well worth the effort.
Construction
The core component of the microscope described here is a simple webcam. Preferably, use the cheapest webcam you can find, connected to a computer via a USB port. A low price is actually advantageous here, because cost-cutting by manufacturers usually means the mechanical design is maximally simplified. This, in turn, makes the necessary modifications much easier.
The first step is to remove the webcam housing. This is usually straightforward — it typically involves taking out a few small fasteners. Occasionally, however, some parts may be glued together. In such cases, a sharp knife is your best tool. All of these steps should be performed with care to avoid damaging the delicate internal components.
Inside the housing, you will generally find a single circuit board holding the electronic parts of the webcam, as well as a small tube with optics (Photo.1). This board is, of course, connected to power and signal wires that run through the USB connector, which provides communication with the computer. Sometimes there are extra wires, for instance for a tiny electret microphone. We will not need that component. You can simply cut the extra wires so they do not get in the way, making sure not to cause any short circuits.
Let us pause here and consider how a webcam actually works. Fig.1 shows a simplified diagram.
The operation of the device is fairly straightforward: a lens projects an image onto a image sensor, and the resulting signal is processed by the electronic circuitry and then transmitted to a computer. The reader will likely notice the analogy to the structure and function of the human eye. Webcams typically include an infrared filter, which is often placed either in front of or behind the lens. Focus is adjusted by changing the distance between the optics and the imaging element — usually by rotating the lens, which is mounted on a fine-threaded screw. Once the lens assembly is removed, the surface of the sensor becomes visible (Photo.2). In lower-cost cameras, this is usually a CMOS (Complementary Metal-Oxide Semiconductor) type.
Be sure to keep the light-sensitive element clean. Even the smallest dust specks on its surface can noticeably degrade image quality.
Now let’s consider how this simple device can be transformed into a functional educational microscope. As mentioned earlier, focus is controlled by adjusting the distance between the lens and the image sensor. The closer the two are, the farther away the object can be while still appearing sharp. However, for our purposes, what matters more is that by increasing the gap between the lens and the chip, we can bring very close objects into clear focus. This makes it possible to achieve surprisingly high magnification — at least by the standards of such a basic setup.
The need to bring the lens very close to the observed specimen creates a need for a small modification of the lens assembly. The lens itself is located near the bottom part, so the lens tube is simply too long (Photo.3A). This could interfere with placing the observed object sufficiently close to the lens.
The lens housing should be shortened in the front section, which does not contain any optics. Since it is made of plastic, the modification is not difficult. The best approach is to cut it using a coping saw, taking care not to damage the lens or the remaining threads. Smooth the edge with fine-grit sandpaper, then clean away any residue on the lens. In the camera used for this experiment, the original lens assembly measured about 17 mm (0.67 in), and after modification it was about 9 mm (0.35 in) long (Photo.3B).
Place the modified lens assembly back onto the mount. By adjusting both the distance between the sensor and the lens, as well as the distance between the lens and the specimen, you can achieve sharp images at various magnifications.
We still need to enable adjustment of the distance between the camera lens and the observed specimen. The precision of this adjustment determines how sharp the images will be. Fig.2 shows the solution I propose.
The main load-bearing element of the microscope is a rigid bar A, which can be made from an aluminum. A threaded screw B passes through a tapped hole in this element, and it bears against the center of a flexible bar C — in this case, a standard plastic ruler. Both bars are similar in length, about 20 cm (7.87 in) in this design. They are joined at their ends by wrapping them multiple times with electrical tape. The camera D is attached to beam C with its lens pointing downward toward the specimen E. The entire assembly rests on supports F, which may be small laboratory stands, stacks of books, or anything else that provides a stable base.
By turning screw B, you control how much bar C flexes, which in turn allows for precise adjustment of the distance between the camera lens and the specimen — effectively controlling the focus. The range of movement is sufficient for fine focusing; however, take care not to bend the plastic bar too far, as it may break. Photo.4 shows the completed setup, while Photo.5 provides a close-up view of the focusing mechanism. As shown, I used steel bases from small laboratory stands, placed sideways, as structural supports.
The advantage of this solution is that it uses only readily available materials. With sufficient care in assembling the parts, the results are entirely satisfactory. I also tested another approach, using the body of a standard microscope with a macro- and micrometer screw mechanism. That approach allows for finer adjustments and is worth trying if you have access to such equipment.
The objects you examine can be transparent or opaque. A regular desk lamp works well for lighting, but you can really use almost any light source. It’s also easy to build a simple backlight illuminator. The color of the background and the light should be chosen to achieve the highest possible image contrast.
The resolution of the resulting image depends on the used camera. In inexpensive webcams, this is usually 640×480 or 800×600 pixels. This is not particularly high, but it is sufficient for numerous observations. As proof of the practical value of this design, see Photo.6. It shows the image of a micrometer slide scale obtained using this exact device.
Observations
To back up my claims, I would like to share a few results obtained with this simple microscope. These are, of course, just examples — I encourage you, dear Reader, to conduct your own experiments!
The device is excellent for examining the external anatomy of small creatures, such as insects.
The head of the median wasp Dolichovespula media, a member of the order Hymenoptera, already makes quite an impression (Photo.7). Notice the massive mandibles, segmented antennae, and large compound eyes.
The eyes in vespids Vespidae have a kidney-like shape, clearly visible in the photo. As we know, insects Insecta, which belong to the phylum Arthropoda, typically have mosaic compound eyes. This is easy to notice in Photo.8A, which shows the eye under greater magnification.
Each compound eye consists of many individual ommatidia, which is why this type of eye is also referred to as a faceted eye. Moreover, insects often have additional simple eyes known as ocelli. In this wasp, there are three ocelli located between the compound eyes (Photo.7B and Photo.8B). They do not provide a clear image, but they do give the insect information about light [2].
More subtle observations require slightly higher magnifications. Take Photo.9 of a housefly’s leg, for example: it immediately illustrates why arthropods are so named. They were once called “joint-legged animals” [3]. Among the structures visible on the leg, the two small claws on the last tarsomere are especially interesting. Together with accompanying pulvilli (not shown here), these allow the insect to climb rough and smooth surfaces.
Observing water fleas, also known as daphnids, is a memorable experience. These small crustaceans Crustacea from the order Cladocera inhabit freshwater environments, including those that dry out periodically. They are notable in that their thin chitinous shell, called a carapace, is transparent. Consequently, we can easily analyze not only external but also internal structures, for instance in the common water flea Daphnia pulex (Photo.10). Their main locomotive organ is the greatly enlarged, branched second pair of antennae. The first pair of antennae is reduced and serves sensory functions. Like other cladocerans, daphnids have a single compound eye. Under higher magnification, one can also see a vestigial nauplius eye. The five pairs of thoracic limbs are flattened and located under the carapace — they filter organic matter from the water for food. The crustacean’s heart, beating at a high rate, is truly impressive.
Interestingly, daphnids can reproduce via parthenogenesis. Under favorable conditions, they produce eggs that develop without fertilization — these are known as summer eggs. They grow within a brood chamber under the carapace and hatch into subsequent parthenogenetic generations of females. Much smaller males appear only sporadically, especially before winter. They fertilize the so-called winter eggs, which can withstand harsh conditions so that new generations of females can develop in spring. This phenomenon is called heterogony [4].
Exploring the detailed body structure of small animals does not exhaust the possibilities of this microscope. It can also be used to observe both plant and animal cells.
Preparing a sample from onion epidermis is particularly simple. The natural (unstained) tissue is almost transparent, so typically only the structure of the epidermal cells is visible (Photo.11A). To improve contrast, appropriate stains can be used — such as eosin, safranin, crystal violet, or other compounds that bind to specific cellular components. As a result, the image in Photo.11B is much more defined, and the dark-stained nuclei are clearly visible. Nearly the entire volume of each cell is occupied by a single vacuole, while the pink cytoplasm is confined to the cell’s periphery. One can even attempt to observe plasmolysis by placing the cells in a hypertonic solution [5].
Even at relatively low magnifications, one can make interesting observations of algal cells, such as those of Spirogyra (Photo.12). Inside the filamentous cells, you can readily see the green, helical structures, which are, of course, chloroplasts.
Ciliates Ciliata are also excellent subjects for us. They are considered among the most highly organized organisms within the kingdom Protista Protista. Their name refers to the large number of cilia, which serve as organelles for locomotion or for acquiring food. The cilia are arranged in characteristic rows and can move in a coordinated fashion. The pellicle covering the ciliate’s cell has a very complex structure, so contractile vacuoles form or empty only in regions without cilia. Food is taken in through the cytostome, and undigested remnants are eliminated through the cytopyge. There are swimming, creeping, and sessile forms among the ciliates.
Paramecia Paramecium are among the most familiar ciliates. They are heterotrophic, meaning they cannot photosynthesize and must acquire organic nutrients. However, the cells of the paramecia shown in Photo.13 appear green. How can this be explained?
It turns out that Paramecium bursaria lives in endosymbiosis with the alga Chlorella paramecii. The alga living inside the host cell is called a zoochlorella. Because it is autotrophic, it provides carbohydrates (mainly maltose and glucose) and oxygen generated via photosynthesis to the ciliate. This arrangement allows the paramecium to thrive under conditions unfavorable to other ciliate species lacking zoochlorella. Meanwhile, the alga receives minerals and metabolites from its host, plus protection from the environment and the ability to move [6][7].
As you can see, even with such a simple and inexpensive device, we can make a great many fascinating discoveries. A lack of major financial resources should not be used as an excuse! All it takes is some curiosity about the world, and you will always find a way.
References:
- [1] Ples M., Laserowy mikroskop - Zrób to sam (eng. Laser Microscope: A DIY Project), Biologia w Szkole (eng. Biology in School), 3 (2015), Forum Media Polska Sp. z o.o., pp. 60-62 back
- [2] Razowski J., Słownik entomologiczny, Państwowe Wydawnictwo Naukowe, Warszawa, 1987 back
- [3] Simm K., Zoologia dla przyrodników i rolników. T. 2 - Członkonogi (dokończenie), szkarłupnie, mięczaki, strunowce, Poznań, 1949 back
- [4] Jura Cz., Bezkręgowce, Wydawnictwo Naukowe PWN, Warszawa, 1997 back
- [5] Szweykowska A., Szweykowski J., Botanika. Tom 1 – Morfologia, Wydawnictwo Naukowe PWN, Warszawa, 2007 back
- [6] Kawecka B., Eloranta P. V., Zarys ekologii glonów wód słodkich i środowisk lądowych, Wydawnictwo Naukowe PWN, Warszawa, 1994 back
- [7] Kvitko K.V., Migunova A.V., Karelov D.V., Prokosheva M.J., Molecular taxonomy of virus-sensitive Chlorella sp. – symbionts of Paramecium bursaria, Protistolog, 2 (2), 2001 back
All photographs and illustrations were created by the author.
Addendum
As a complement to the article above, I would like to share a short video that offers a concise summary.
Marek Ples