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Questar logo from 1990's (27,482 bytes)


Questar QM-100 Long Mount Long Distance Microscope (29,309 bytes) The Questar QM 100 Long Distance Microscope is designed to provide resolutions of as fine as 1 µ (0.00003937007874 inch!) or less thus making it an invaluable instrument for observing materials and biological targets located too distant from the instrument to be observed with conventional microscopes. Common applications have included materials testing (crack propagation, studies of dendrites and other surface features, quality control), studies of bubble formation and flow (fuel dispersion) within a chamber, etc. The QM-100 can be used to focus on a target directly in front of it, or located behind a transparent window (in a furnace, or in a test tube, etc.). Furthermore, the QM-100 can illuminate that target using the coaxial technique, and this is among the many the advantage of these systems: one can observe the target with the Long Distance Microscope while simultaneously lighting the target through the LDM! The system is engineered to accept a diverse selection of optics to increase or decrease magnification and field of view, bandpass filter, color filters for contrast enhancement, polarizing filters, etc.

Right: Questar QM 100 Long Distance Microscope with Quartz optics and with Barlow lenses and lens cover aside at Company Seven (53,911 bytes).
Click on image to see enlarged view (226,260 bytes).

The Questar QM 100 combines the compactness and the ease of use of the Questar QM 1 with the relative aperture and resolution of the larger microscopes. For applications requiring high magnification and resolution, and which will allow the user to work from distances of 15cm (5.91 inches)* to 35cm (13.78 inches), the QM 100 is unrivaled in performance and flexibility.

*With the optional Questar PowerPak 100 then this can be reduced to 10cm (3.9 inches)!

This instrument is a completely different optical formula than the QM 1, it is not merely an adaptation of an existing design. But rather it is an evolutionary development whose concept originated with the QM 1.

Note the different lighting techniques will reveal different features on the target. And use special care when lighting the experiment when working at the closest distances. Since the QM-100 optical tube assembly will be so close to the intended target of observation then conventional lighting might be obscured by the instrument or may be located at such shallow angles to the target that they will not illuminate to the desired depths, and so we recommend coaxial illumination (Fiber Optic Light Guide attached to our optional Brightfield Adapter (P/N 39170) to pump light directly through the QM-100 focused onto the target. Or consider backlighting the object if it is either transparent material or thin enough to have light projected through it. Please contact Company Seven for advice about the applications of our systems and lighting techniques.

Questar QM-100 Long Mount Long Distance Microscope atop Camera Cradle and 3-Axis Translation Stage (93,016 bytes) Specifications:

Optical Characteristics:

  • Design: Maksutov-Cassegrain Catadioptric
  • Standard Corrector Lens: BK7, MgF2 AR Coated; multilayer dielectric coatings optional
  • Optional Corrector Lens: Fused Silica (for enhanced UV spectral response), MgF2 AR Coated
  • Primary Mirror: Pyrex substrate, aluminum coated with SiO overcoat; Zerodur substrate optional
  • Corrector Lens Clear Diameter: 63mm (2.4 inches)
  • Primary Mirror Diameter: 104mm (4.09 inches)
  • Standard Secondary Mirror: aluminum coated with SiO overcoat; silver with ThF4 overcoat optional
  • Secondary Mirror Diameter: 16mm (0.63 inches)
  • Baffling: Helix in central tube, all interior surfaces black anti-reflection coated

Right: Questar QM 100 Long Distance Microscope set for Co-Axial lamination of target (at left).
The QM-100 is shown with optional Camera Cradle supporting a DSLR Camera, atop 3-Axis Translation Stage at Company Seven (93,016 bytes).
Click on image to see enlarged view (284,148 bytes).

Mechanical Characteristics:

  • Barrel Material: Aluminum hollow bar, machined from seamless stock
  • Barrel Length: 25.4cm (10 inches)
  • Control Box: Cast aluminum, 24S-T4, corrosion resistant; selectable axial or 90 degree Port.
  • Internal Beamsplitter: standard, flick knob controlled
  • Tube Assembly Length: 30.8cm (12.11 inches) front cell to focus knob seat
  • Tube Assembly Diameter: 11.4cm (4.48 inches) maximum overall
  • Tube Assembly Height: 20.8cm (8.2 inches) base of mount to top of eyepiece
  • Tube Assembly Weight: 2.27kg (5 pounds)
  • Mount: Full length rail of machined aluminum, 1/4"-20 and 3/8"-16 mounting holes
  • Focus Mechanism: Mirror thimble integral with stainless steel (s.s.) sliding tube.
    Slides on fixed stainless steel light baffle tub (centerless ground). Conical s.s. spring loaded
    Focus rod 303, precision ground, 24 TPI; integrated inside control box
  • Finish: Aluminum components anodized natural, dark blue, or black
  • Carrying Case: ATA, Furnished Standard


  • Focus Range*: 15cm (6 inches) to 35cm (14 inches)
  • * Minimum w/optional PowerPak 100: 10cm (3.9 inches)
  • Optical Resolution: 1.1 microns at 15cm (6 inches)
  • Format: Diffraction Limited Field 12mm diameter
  • Magnifications at image plane may be 3.43X to 8.13X larger
  • Field of View 2/3" format, wider fields possible with larger arrays: 0.375mm (0.0148 inches) to 2.07mm (0.08 inches)
  • Field of View 2/3" format with optional Positive Lens field of view more than 7mm are possible.
  • With Eyepiece, Video Camera, or optional lenses magnifications may span from 48X to 381X or more
  • Standard spectral response: 330nm to 2.3 microns, optional systems with wider spectral response available.
  • Optional extended Ultraviolet and Infrared imaging response: from below 200 nm to 3.5 microns
  • Optional EXFO X-Cite illumination sources and accessories, including the high stability X-Cite exacte system.

Object Distance Numerical Aperture f/No. Depth of Field (Ám)
35.5cm (14 inches) 0.084 20.4 77
33.0cm (13 inches) 0.091 20.1 65
30.5cm (12 inches) 0.098 19.8 56
27.9cm (11 inches) 0.107 19.4 47
25.4cm (10 inches) 0.115 19.5 41
22.9cm (9 inches) 0.117 20.6 39
20.3cm (8 inches) 0.126 21.1 34
17.8cm (7 inches) 0.129 21.9 32
15.2cm (6 inches) 0.139 22.1 28
10.2cm (4 inches) 0.185 22.0 16

Above: Table illustrating Depth of Field, and f-number of the QM-100
  • The forumula used for depth of field calculations is based on the Rayleigh criterion. It is as follows:

    (0.5) (0.546 Ám) / (NA) 2

    For this example the wavelength of light used is at the 0.546 Ám HG spectral line.

  • Perceived depths of field will vary with the user, camera, and wavelength. In general, they will increase when a camera is used.

Field of View (from 2.5 to 0mm top to bottom) along the left side, Working Distance (15 to 35.5cm) left to right. Top to Bottom Dashed Lines are: QM-100 with 172mm 0.9X Positive Lens (from 1.29mm to 2.29mm), at Prime Focus (1.17 to 2.07mm), with 1.5X (0.77 to 1.41mm), with 2.0x (0.59mm to 1.04mm), and with 3.0x Barlow Lens (0.41mm to 0.72mm).

QM 100 Long Distance Microscope Fields of View
Above: Chart illustrating Fields of View of QM-100
with Auxiliary Barlow Lenses, with 172mm Positive Lens, based on 2/3" format camera.
Working Distance QM100 Objective with 0.9x lens OPEN with 1.5x lens with 2.0x lens with 3.0x lens with 2/3" Video*
10.2cm (4 inches) 8.13x 114.3 127.0 190.5 254.0 381.0 262.8
15.2cm (6 inches) 6.15x 86.4 96.0 144.0 192.0 288.0 198.8
17.8cm (7 inches) 5.65x 79.7 88.5 132.8 177.0 265.5 182.7
20.3cm (8 inches) 5.21x 73.4 81.5 122.3 163.0 244.5 168.4
22.9cm (9 inches) 4.81x 67.5 75.0 112.5 150.0 225.0 155.5
25.4cm (10 inches) 4.47x 63.0 70.0 105.0 140.0 210.0 144.5
27.9cm (11 inches) 4.17x 58.5 65.0 97.5 130.0 195.0 134.8
30.5cm (12 inches) 3.90x 54.9 61.0 91.5 122.0 183.0 126.1
33.0cm (13 inches) 3.65x 51.3 57.0 85.5 114.0 171.0 118.0
35.6cm (14 inches) 3.43x 48.2 53.5 80.3 107.0 160.5 110.9

Above: Table illustrating the visual and video magnifications possible
using a 16mm eyepiece open (at "prime focus") and with auxiliary lenses.

    • The magnifications, other than the "OPEN" column are extrapolated data.
    • *Video magnification assumes 2/3" format CCD and 14" Monitor.
    • When comparing video and visual magnifications using the "OPEN" column understand that much of the difference here occurs in the artificial magnification from the CCD to the monitor; this sometimes results in "useless" magnifications.
    • Although eyepiece magnifications appear to be significantly less than CCD magnifications, comparable resolution is achievable due to the resolution limitations of CCD technology and the exceptional physiology of the human eye.


  • Questar QM-100, Model 30003 illustrated two page brochure describing the basic Questar QM-100 Long Distance Microscope. With tables and instrument arrangement drawings. From Company Seven's Library. Download size is 412,734 bytes (in Acrobat Reader ".pdf" format).

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