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Overview of Video Microscopes / Magnifiers |
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Mark C. Hogrebe, Ph.D |
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Video images are everywhere in the workplace, at home, in stores, banks, and restaurants. They are on computers, control displays, flat panels, televisions, cameras, phones, and video games. Video images have become a prominent form of communication and important method for interacting with our environment. A great deal of our information is obtained from observing images on a screen. We are familiar and comfortable with seeing video images and our mindset is accustomed to acquiring information in this manner. It is a natural progression to extend video imaging to the magnification of small objects with video microscopes.
Video microscopes display magnified images on monitors or flat panel displays. Instead of using only light and optics to enlarge an object, video magnifiers use a small image sensing device in combination with optics, light, electronic circuits, and computer software to create magnified images. Various forms of video microscopes have been in use for a number of years in highly technical and specialized fields such as surgery and metrology. With recent advancements in electronics combined with cost reductions, the time has come for video microscopes to be used on a much wider scale in laboratory and industrial settings. Across many occupations and industries, the health of workers can benefit from the significant ergonomic advantages and ease of use inherent with video microscopes. Fewer health issues leads to substantial cost savings through increased productivity, decreased workers’ compensation claims, and reduced absenteeism. |
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| The Need to Inspect Smaller Becomes Larger |
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| There are four factors driving the need for video microscopes in the workplace. The first is the continuing trend to manufacture smaller parts. As instruments and equipment become more compact, the parts that comprise them are smaller and more tightly integrated. The production, assembly, and repair of smaller parts requires magnification because less effort in seeing and decoding visual information results in greater speed, accuracy, and efficiency. Secondly, there is an increased need for quality inspection to reduce defects and to insure error-free procedures in laboratories. Video microscopes enhance many aspects of the quality control process by magnifying defects and documenting with video capture. Third, the increasing age of the workforce demands greater attention to the vision needs of older workers who require significantly more light and magnification than younger employees. Video microscopes offer a user friendly way to provide magnified viewing for the older employees. Finally, greater attention is being given to ergonomic issues in order to protect workers' health and reduce medical costs. As discussed below, video microscopes address many of the ergonomic issues associated with conventional microscope use. |
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Conventional Microscopes: Taxing to Use for Long Periods |
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Looking into the eyepieces of a conventional microscope for the first time is usually not an easy task. Although clarity of image and depth perception are achieved by the experienced user, the beginner may see double images, half moons, and in general have a difficult time coordinating the visual paths. With practice, the visual artifacts disappear and the eyes learn to produce a good stereo image.
Although the eyes may adapt to the complex task of looking through eyepieces, it requires continual effort to align and integrate the visual information. Over time, this sustained effort produces fatigue. Physical fatigue in the neck, shoulders, and back develops from holding the head in an exact position to keep the eyes aligned in the precise path of the microscope optics. Visual fatigue results from the eye muscles performing precise coordination of movements and held in an exact position for long periods. Mental fatigue develops from the brain working constantly to integrate and combine information from two separate visual paths to produce the “stereo” image (Photo 1). |
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The negative impact on the person of prolonged microscope work has been widely discussed, documented, and studied. A quick search of “microscope ergonomics” on the internet shows the extent of the research and dialogue related to health issues associated with the use of conventional microscopes. For example, the Occupational Safety and Health Administration (OSHA) states that, “Microscope work is straining both to the visual system and the musculoskeletal system. Microscope operators are forced into an unusual, exacting position, with little possibility to move the head or the body.” Studies indicate that about 80% of microscope users have experienced job-related musculoskeletal disorder (MSD) pain and that 20% have missed work because of medical problems related to microscope use. The high percentage of health issues has a significant negative impact on employee productivity as well as increasing worker compensation costs. |
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| Photo 1. |
Potential neck, shoulder, and back problems with conventional microscopes.
Video Microscopes Offer a Comfortable Solution |
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The widespread reports of medical problems and health issues associated with prolonged periods of conventional microscope use suggest that alternative methods are needed. Video microscopes project the magnified image on a monitor which frees the person from maintaining the exact body position demanded by the eyepieces of a conventional microscope. Freeing the posture reduces physical fatigue.
With the magnified image on a monitor, the user can observe from various positions and can alter the head, neck, and shoulders to remain comfortable. Many more options for dealing with individual differences become available as well as established ergonomic solutions that are not constrained by a fixed head and shoulder position. For example, chairs, feet, and back supports can be adjusted, users can change postures as often as needed, and prescription glasses can be worn. Handicapped individuals whose disability prevented them from performing work with microscopes may be able to work with magnified images on a monitor.
Viewing magnified images on a video microscope should be as comfortable as other workstation tasks that use a monitor. Visual fatigue is reduced because the eye muscles do not have to hold exact positions for long periods. Mental fatigue is absent since the brain is not working constantly to produce a stereo image from separate visual paths created by the microscope optics. |
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Training is easier with a video microscope because more than one person can view the magnified image (Photo 2). Demonstration of procedures and inspection techniques can be made to groups who view the monitor simultaneously. Everyone sees the same image and observes the live action. Questions can be answered by demonstrating on the spot. Trainees master techniques quicker because the instructor can show and explain as everyone sees exactly what the instructor sees. This basic method of teaching in which the students observe procedures and techniques directly has not always been available for magnified images. |
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| Photo 2. |
Video Microscopes for training with groups. |
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| Video microscopes utilize electronically processed images that can be saved as movies or still images and used for documentation. Images are stored in a variety of file formats depending on the type of signal from the microscope camera and the software for video capture. Saved images are used for a variety of purposes such as documentation in quality control or importing into software that manages patient records. Magnified images can be captured immediately and then emailed anywhere in the world. Images stored on various media such as small “multi-media cards” can be included with forensic evidence or put in a file folder. |
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| Typical Video Microscope Configurations |
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| Typical video microscope configurations consist of a camera connected to a monitor with a cable. The camera is mounted on a “boom” arm/stand (Photo 3) or attached to a conventional microscope (Photo 4). When the camera is on a separate arm, it uses optical lenses mounted in front of the image sensor. Cameras mounted on a conventional microscope use its optics. The monitor displays the magnified images from the camera and can be placed almost anywhere in the workstation. Although there is a lot of flexibility in placing the camera and monitor, their alignment and location may not be user friendly and desirable from an ergonomic standpoint (Photo 4). |
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| Photo 3. |
Camera on boom stand with separate monitor in use. |
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| Photo 4. |
Camera on microscope with separate monitor in use. |
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| It is important to note that increasing the monitor size will make the magnified images look larger, but will not improve the image resolution produced by the optics and camera. A video microscope system that uses a large monitor may report high magnification power based on screen size, but may actually have low resolution and poor clarity. The camera and optics determine the image quality and resolution at higher magnification levels. |
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| The “Ideal” Video Microscope Resolves Ergonomic Issues |
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The design of a video microscope should take into account human needs and capabilities in order to reduce fatigue and discomfort, and to increase productivity and accuracy. While projecting a clear and accurate image, a video microscope must be both user and workspace friendly. It is user friendly when it allows people to work for long periods with minimal effort and stress on the eyes and body. A video microscope is workspace friendly when it can be adjusted easily to accommodate various magnification tasks, takes up the least amount of space, does not interfere with other tasks performed in the workspace, and can be moved out of the way when not in use (Photo 5). |
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| Photo 5. |
Integrated camera and display on adjustable-arm. |
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| User Friendly |
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Integrated for direct line-of-sight. The key to maximizing user comfort and ergonomic benefits in the design of a video microscope is integrating the camera and monitor into a single unit, and then mounting it on an adjustable arm. If the integration of the camera and monitor into a single unit is kept to a compact size through the use of a small TFT flat screen, then a significant ergonomic benefit can be derived from attempting to achieve “direct line-of-sight” viewing. Direct line-of-sight viewing is a concept inherent in many glass magnifiers that are easy to use because they maintain the natural line of sight between the eyes and hands. A compact and integrated video microscope approximates the direct line-of-sight by permitting simultaneous viewing of the original object and magnified image. With very little eye or head movement, the user can see both the object and image (Photo 6). This proximity of object and image in the user’s visual field enhances perspective, comfort, and eye-hand coordination.  The greater the distance and lack of alignment between the object and image, the more difficult it is for the user to coordinate eyes and hands, which leads to increased visual effort and fatigue. For example, a person who must manipulate an object under a camera while trying to view the image on a monitor located on a shelf at the back of a workstation, will have difficulty with eye-hand coordination and become fatigued from constantly alternating views (Photo 4). |
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| Photo 6. |
User can see both image and object. |
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Screen size. The screen on which the image is magnified should not be too small, nor is larger necessarily better. If the screen is too small e.g., 2-inches, the ability to distinguish details is diminished. A large 15 or 17-inch monitor may make the image look bigger without an increase in resolution and at the cost of occupying valuable workstation space (Photo 3). An ideal size is a 6 to 8-inch screen that yields high resolution while displaying a visual field that is comfortable to process at a distance of 12 to 18-inches. This distance from eyes to screen is determined by the user’s arm reach. Moving farther away from the screen will not allow the user to manipulate or work on an object while under the camera lens. With this close eyes-to-screen distance of 12 to 18-inches, users cannot efficiently view at one time more than about 6 to 8-inch sections of a larger screen.
Adjustable arm. A video microscope mounted on an adjustable arm offers significant advantages in ameliorating the ergonomic problems associated with conventional microscopes. The adjustable arm unit can be positioned where it is most comfortable for the individual’s vision requirements, hand/arm positions, and posture. It should be easy to adjust for different job tasks. When more than one person uses the same workstation, the video microscope should be adjustable to meet the unique requirements of each individual. The arm needs to move freely and be positioned with one hand. It is absolutely essential that the adjustable arm protect the video microscope from vibration. The higher the power, the more slight movements will be magnified. A camera mounted on an arm that uses springs is likely to have a significant vibration problem, so it is essential that the arm is built to control vibration.
Working distance. The distance from the bottom of the unit and the work surface needs to be sufficient to perform tasks. Inspection tasks require less working distance than production or repair; however, users generally prefer 8 to 9-inches. With less working distance users feel constrained, especially when working with tools. As the working distance increases above 9-inches, the image on the screen becomes farther removed from direct line-of-sight viewing. This increases the probability of fatigue and posture problems. A video microscope mounted on an adjustable arm easily maintains the proper working distance when accommodating objects of different heights.
Image control. Since video microscopes use a processed image, a great deal of control is exercised over the appearance of the image. Characteristics such as brightness, sharpness, white balance, and negative image can be varied to produce the best image for a particular inspection task. For example, when inspecting objects for defects that are essentially clear such as plastic lenses, adjusting settings to produce a negative image in grayscale mode, together with a backlight, will highlight surface scratches that are otherwise very difficult to see. Video microscopes should have continuous zooming so that images can be made smaller or larger with the touch of a button, instead of having to change lenses. Controls should be located so that users do not have to reach and strain in order to operate them.
Lighting. There are a variety of lighting options for video microscopes. In addition, many use cameras with automatic gain that adjust for different light levels. Together, an automatic white balance and automatic gain provide a great deal of light control. Different levels and colors of ambient light are adjusted to produce a constant image on the screen with correct color and brightness. The light source used by a video microscope should provide even, shadow-free light which is usually accomplished with a “ring light” or circular lamp that surrounds the camera lens. When examining specular or shiny surfaces, the light source should provide sufficient glare control. In order to illuminate depth when inspecting objects with crevices or holes, a unique solution is required in which the light path and camera line-of-sight are identical. |
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| Workspace Friendly |
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| A video microscope should be easily adaptable to a variety of magnification tasks in the workspace with minimal setup time. One mounted on a sturdy, adjustable arm has significant advantages over systems with heavy weighted bases and separate full-size monitors. An adjustable arm clamped to a table edge leaves a very small footprint on the work surface, and uses no surface space at all when mounted to a wall or directly to a workstation vertical track. Other tasks besides magnified viewing can be performed in the same workspace because the video microscope and monitor are not occupying the work surface. In a few seconds, the adjustable-arm video microscope can be pushed out of the way to free up precious space for other tasks at the same workstation. When mounted between two adjacent workstations, the reach of the adjustable arm allows the unit to be used in either location. |
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| Improving Health, Increasing Productivity, and Reducing Costs |
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| The use of video microscopes in the workplace represents a common sense approach to alleviating the fatigue and physical problems associated with conventional microscopes. Since viewing a video microscope is similar to looking at the many displays, screens, and monitors encountered in our daily lives, people acclimate to it quickly. They don’t have to learn to focus their eyes and integrate the separate visual paths of optical scopes. Fewer physical problems develop when viewing for extended periods because there is no need to maintain a fixed posture. This “posture freedom” allows the person to adjust positions as needed in order to alleviate muscle strain in the neck, shoulders, arms, back, and legs. Fewer physical issues for workers means better concentration and productivity, less time off the job, and lower workers’ compensation costs.
Video microscopes allow more workers to be trained quicker through direct observation of the instructor’s actions. No need to have one individual at a time look through conventional eyepieces. Quicker training means employees contribute productively in less time. Easy video capture and documentation allows for fast communication and feedback with suppliers, colleagues, and customers. Early and frequent communication reduces errors that are more costly to fix later in the production cycle. In summary, use of video microscopes and its associated ergonomic benefits result in reduced health problems and increased productivity, that in turn lead to greater cost savings.
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| About the Author |
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| Mark Hogrebe, Ph.D., is president of Dazor Manufacturing Corp. His interests include the ergonomic implications of light and magnification in the workplace, especially as they relate to individual differences in visual acuity, cognitive processing, comfort, and productivity. |
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