Indian Journal of Pathology and Microbiology

: 2020  |  Volume : 63  |  Issue : 2  |  Page : 258--261

Development and applicability of a smartphone torch based emergency light source for microscopy

Himel Mondal1, Shaikat Mondal2, Debasish Das1,  
1 Department of Physiology, Fakir Mohan Medical College and Hospital, Balasore, Odisha, India
2 Department of Physiology, Kalna SD Hospital, Kalna, Purba Bardhaman, West Bengal, India

Correspondence Address:
Himel Mondal
Department of Physiology, Fakir Mohan Medical College and Hospital, Balasore - 756 019, Odisha


Background: Modern microscopes are equipped with built-in illuminator. However, during a power outage, microscopy is not possible with extra mirror system if an alternative light source is not available. Smartphone torch can serve as a light source. Holding it under the microscope is difficult when both hands are engaged in microscopy. Aim: The aim of the study was to develop a stand for smartphone torch and to check the applicability of smartphone torch-based light source in microscopy. Materials and Methods: A stand was made with cardboard for keeping the smartphone on it. An optical diffuser was made with white polyethylene plastic. Smartphone with the stand and optical diffuser can serve as a soft light source. A convenient sample of 16 faculty member rated 11 slides first under the microscope with its built-in light source and then twice with the new device as a light source on 10-point Likert type scale. Applicability of the device was checked by validity and reliability by Intraclass Correlation Coefficients (ICC) with α = 0.05. Results: The raters were able to examine the slides under the microscope with the new devices as a light source. An overall score (11 slides, 16 observers) for the image quality was 9.36 ± 0.86 (range 6-10). Interrater, intrarater, and test-retest ICC were 0.939 (P < 0.001), 0.853 (P = 0.003), and 0.889 (P < 0.001) respectively which indicate “good” to “excellent” level of reliability. Conclusion: Developed smartphone torch stand with an optical diffuser can serve as an emergency light source in microscopy. This may be a useful tool for settings with a frequent power outage.

How to cite this article:
Mondal H, Mondal S, Das D. Development and applicability of a smartphone torch based emergency light source for microscopy.Indian J Pathol Microbiol 2020;63:258-261

How to cite this URL:
Mondal H, Mondal S, Das D. Development and applicability of a smartphone torch based emergency light source for microscopy. Indian J Pathol Microbiol [serial online] 2020 [cited 2022 Jul 7 ];63:258-261
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Full Text


From its time of invention, light microscope got several addition and modification to reach in its current form.[1] However, the basic principle of using combination of lens and light remain the same. Modern microscopes are now manufactured with built-in illuminator.[2] This facility eliminates the necessity of daylight or artificial light from outside. In addition, for emergency, majority of the microscopes are supplied with an extra mirror system which can be used with alternate source of light. However, when daylight is not adequate, microscopy becomes impossible.

Power outage in India is common problem.[3] In our setting, the physiology laboratory is not well illuminated to get adequate daylight for microscopy. Our smart students started using a smartphone torch as a light source during power failure. They hold the smartphone torch under the condenser to get a satisfactory illumination. This innovative idea could serve as an emergency solution for observation of objects under a microscope in Hematology, Histology, Pathology, Microbiology, or in any allied branches.

However, it is difficult to hold the smartphone while both the hands are engaged on a microscope (e.g., observing cells under oil immersion lens). That was the triggering factor to develop a stand to keep the smartphone torch in the desired place while both hands are kept free for manoeuvring the microscope. We aimed to make the device with commonly available instruments with a negligible investment so that it can be built in any settings. Further, we tested the applicability of this device for common microscopy.

 Materials and Methods

Materials used

For development of the device, the following materials were used:

  1. A scrap carton
  2. A pair of scissors to cut the carton
  3. A blade to cut the carton where scissors cannot be used
  4. A compass to cut a circle for optical diffuser
  5. Dry adhesive to glue the pieces of carton
  6. A roll of PVC tape to reinforce attachment
  7. A piece of white polyethylene plastic for optical diffuser.

Method of development

The height of the stand was made according to the hight of the light source of the microscope. This stand looks like a box without its lower surface and a side [Figure 1]. Then, a portion of the upper surface was cut to accommodate the light of the microscope. For easy navigation of the mechanical stage by the screw-heads, a corner of the stand was cut and discarded. An extra piece of cardboard was attached to elevate the stage slightly above the microscope light and to strengthen the structure for holding a smartphone. For the optical diffuser,[4] first we used two layers of tissue papers. However, due to feathery nature and chances of water damage, we discarded it. Instead, we used a piece of white polyethylene plastic taken from a grocery bag. A piece of a carton was taken and a round-shaped hole was made. On this opening, the plastic was attached with the help of the PVC tape [Figure 1]. The combination of these 2 devices and a smartphone torch can be used as an emergency light source for a microscope.{Figure 1}


When there is no power or it is difficult to get adequate sunlight or light from other sources, this stand can be used as an alternative light source. We need to slide the stand towards the microscope with its open end forward. Then, switch on the smartphone torch and keep the smartphone with the torch upward. After that, place the optical diffuser on the torch [Figure 2].{Figure 2}

Assessment of quality of images

After briefing and obtaining written consent for participation, a convenient sample of 16 faculty member rated the quality of the images. Light binocular microscopes (LYNX, Lawrence and Mayo, India; lamp – S-LED W1) and 11 prepared slides (viz. 3 thin peripheral blood smears, 1 thick peripheral blood smear containing malaria parasite, 1 sputum smear containing acid-fast bacilli (AFB), 1 smear containing gram-positive bacteria, 1 smear containing gram-negative bacteria, 2 liver tissue, 2 skin tissue) were used for quality assessment. First, the raters observed a slide under the microscope with the built-in illumination. Then, they observed the same field twice (i.e., test and retest) under the microscope with the new device as a light source. The scale of rating was ranging from 0 to 10 where 0 indicate “no similarity” and 10 indicate “same quality” in comparison to the image observed with built-in illumination. The numbers in between 0 and 10 is not defined and a higher number indicates better quality.

Validity and reliability

Validity (does it serve the purpose of what it is supposed to do) of the device would be accepted if the raters could identify the object under the microscope with the light of the new device. Reliability (does it provide similar quality of image if observed repetitively) of the device was checked by the consistency in quality of the image as observed by the raters and statistically tested by interrater, intrarater, and test-retest Intraclass Correlation Coefficient (ICC).[5]

Statistical analysis

Scores of the raters were expressed as the mean and standard deviation in Microsoft Excel® 2010 (Microsoft, USA). Intraclass correlation (ICC) for interrater (16 raters, 11 slides, first measurement), intrarater ( first rater, 11 slides, test and retest measurement), and test-retest (16 raters, first slide, test and retest measurement) reliability was calculated in IBM® SPSS® Statistics Version 20 software package (IBM Corporation, USA) with α = 0.05.


The outcome of this study is an emergency smartphone torch stand for microscopes which can be used while common light sources are not available.

[Figure 3] shows the photomicrographs captured by a smartphone camera aided with the simple smartphone adapter for digital photomicrography.[6] [Figure 3]a shows a peripheral blood smear (1000 × magnification, Leishman's stain) where the same microscopic field was captured with the built-in illumination, smartphone torch, and smartphone torch with the diffuser. [Figure 3]b and [Figure 3]c shows liver tissue and skin respectively (400 × magnification, Hematoxylin and eosin stain) with three types of illumination.{Figure 3}

The quality score of different slides is shown in [Table 1]. The lowest score (7.63 ± 0.81) was for peripheral blood smear under oil immersion lens and the highest scores were for gram-negative bacteria (9.75 ± 0.58) and cross-sectional skin (9.75 ± 0.45).{Table 1}

Interrater agreement showed “excellent” (0.939, P < 0.001, CI: 0.869-0.980) ICC. Intrarater and test-retest agreement showed “good” level of ICC (0.853, P = 0.003, CI: 0.453-0.960, and 0.889, P < 0.001, CI: 0.682-0.961, respectively).


This device is a new addition to the literature of microscopy. Making similar devices with household materials do not require any expertise. Additionally, it is ultra-low-cost requiring only a few rupees. Hence, in developing countries, where there is a frequent power outage, this device may help in continuing examination of the object under the microscope. One can use only stand and smartphone torch without the optical diffuser. However, it produces glare around the object which is shown in the images of the middle row in [Figure 3]. Use of the optical diffuser makes the bright incident light to a soft and diffused light.[4] In any situation when the optical diffuser is not available, the smartphone torch covered with 2 layers of white tissue papers also provides a satisfactory soft light.

In our setting, this device was primarily developed for academic purpose in the Department of Physiology. To test its multidisciplinary application, we tested its reliability for different slides obtained from Department of Microbiology, Histology, and Pathology. The result from the raters shows that the quality of the image is almost similar to that obtained with a built-in light source. Hence, not only for academic purpose but this device may also be used in a diagnostic setup. Sputum microscopy and identification of malaria parasite in peripheral blood film are two important microscopy in developing countries.[7],[8] The newly developed device was able to yield a similar quality of image under the microscope both for AFB and malaria parasite [Table 1]. Hence, it may serve the light source in rural settings where a built-in or alternative light source is temporarily unavailable. However, its pitfalls in diagnostic microscopy should be checked in future studies for making an informed choice.

After searching on the internet, we found two devices which can also serve as an emergency light source for microscopy.[9],[10] However, making such devices require the involvement of fund, special tools, and moderate expertise. Additionally, those devices require a power supply. In contrast, our device requires no fund and can be made in any settings and there is no need of additional power supply.

There are certain limitations of the device itself and the rating scale. The device requires continuous usage of the smartphone torch which may hamper the battery life of the smartphone. Any incoming call or message may disturb the microscopy. For making the stand, the size of a smartphone was taken as reference. Smaller feature phones would not fit on this particular stand. For that type of narrow-bodied phone, another stand should be made. For rating quality of the images, a new scale was used. Though the raters were fully explained about the nature of the scale and how to rate it, their first experience of the scale may be a limiting factor.


A smartphone torch stand and optical diffuser can be made in any resource-limited settings with scrap materials for emergency microscopy. This ultra-low-cost device is not only useful in academic purpose; this would also help in the identification of AFB and malaria parasite in any unfavourable situation without common light sources. However, its applicability in diagnostic microscopy is still to be explored in future studies.


We thank the first year medical students (2018-2019 batch) of Fakir Mohan Medical College and Hospital, Balasore, India who started using the smartphone torch as a light source for microscopy in Hematology practical classes during power outage. This may be an example of “necessity is the mother of invention”. We thank Mr. Koushik Saha, Assistant Professor, Department of Anatomy, Fakir Mohan Medical College and Hospital, Balasore for his help and encouragement during the study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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