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Here, we introduce the light and illumination methods that are convenient for observing cylindrical transparent objects made of materials such as resin.

1. Coaxial light alone

When the magnification is very high, the observation will effectively be of a flat surface, allowing for observation with coaxial light alone in some cases.

2. Twin Arm light (from the longitudinal direction)

Illuminate from a low angle along the longitudinal direction of the cylinder.

The brightness is uniform, resulting in an easy-to-observe image.

3. Twin Arm light (from the lateral direction)

Illuminate from a low angle along the lateral direction of the cylinder.

Surface scratches can be clearly observed as well.

The “coaxial light” and “Twin Arm light” used in this case are also available from our company.

High-performance LED lighting for coaxial units (3W) LED-3WLTS

Twin Arm light

Our large-diameter ring light can be mounted at a distance of approximately 30 to 40 cm to illuminate an A4-sized area relatively evenly.

However, this is the practical limit for this level of illumination.

To evenly illuminate areas larger than A4 size, a large lighting system, such as the one shown below, may be necessary.

The following is equipment from LPL (photography equipment manufacturer).

Another method is to attach a surface-emitting light as shown below.

For a simpler solution, you can arrange a desk light-style fluorescent lamp as shown above to achieve broad-area illumination.

(Fluorescent lamps diffuse light more than LEDs, having lower directivity.)

When performing dimension measurement using transmitted light, the appearance can vary depending on the “type of transmitted light” and the “brightness” used.

This article introduces the “recommended light” and “brightness” for dimension measurement using transmitted light, so please be sure to read it through to the end.

・Use “parallel transmitted light”

There are several types of transmitted light devices.

　・Diffused transmitted light (general type of transmitted light)

　・Parallel transmitted light (compact transmitted light suitable for dimension measurement)

　・Telecentric light (high-precision, large-scale light used in projectors and similar devices)

Of course, telecentric light is the most suitable for dimension measurement.

However, it is large in size and comes with a significantly higher cost (it is integrated into high-precision projectors and dimension measuring instruments).

For general use, we recommend parallel transmitted light.

The lighting method becomes particularly important when measuring samples with significant thickness.

(For thin samples, the difference is less noticeable.)

We measured the Mitutoyo block gauge with a width of 9 mm.

＜Diffused transmitted light＞		＜Parallel transmitted light＞

* Each was measured twice consecutively.

For items such as glass scales, either lighting method is suitable.

However, when the specimen has thickness, we recommend parallel transmitted light.

・Adjust the brightness to a “darker” setting

Generally, adjust to a “darker” setting.

Increasing the illuminance causes the white areas (bright spots) to expand.

We measured a glass scale with a radius of 2.5 mm using our non-calibrated microscope.

(When the measured area is white, increasing the brightness causes it to appear larger.)
* To eliminate variation due to the operator, the “Edge Automatic Detection Mode (A)” was set.

＜When adjusted to a brighter setting＞   ＜When adjusted to a darker setting＞   ⇓ Zoom in on the area within the red frame above   ⇓ Zoom in on the area within the red frame above

With our non-calibrated microscope, it is recommended to adjust to a slightly darker setting, within the range where the automatic edge detection mode (A) functions stably.

Dimension measurement (auto-calibration) microscope (medium magnification) CT200HD

Dimension measurement (auto-calibration) microscope (high magnification) CT200HD-H

When performing dimension measurement using transmitted light, the appearance can vary depending on the “type of transmitted light” and the “brightness” used.

This article introduces the “recommended lighting” and “brightness” for dimension measurement using transmitted light, so please read it through to the end.

・Use “parallel transmitted light”

There are several types of transmitted lighting devices.

　・Diffused transmitted light (general type of transmitted light)

　・Parallel transmitted light (compact transmitted light suitable for dimension measurement)

　・Telecentric light (high-precision, large-scale light used in projectors and similar devices)

Of course, telecentric light is the most suitable for dimension measurement.

However, it is large in size and significantly more expensive (it is integrated into high-precision projectors and dimension measuring instruments).

For general use, we recommend parallel transmitted light.

The lighting method is particularly important when measuring samples with significant thickness.

(For thin samples, the difference is less noticeable.)

We measured the Mitutoyo block gauge with a width of 9 mm.

＜Diffused transmitted light＞		＜Parallel transmitted light＞

＊Each was measured twice consecutively.

For items such as glass scales, either lighting method is suitable.

However, when the specimen has thickness, we recommend parallel transmitted light.

・Adjust the brightness to a “darker” setting

Generally, adjust to a “darker” setting.

Increasing the illuminance causes the white areas (bright spots) to expand.

I measured a glass scale with a radius of 2.5 mm using our non-calibrated microscope.

(When the measured area is white, increasing the brightness causes it to appear larger.)
* The “Edge automatic detection mode (A)” was set to eliminate variation due to the operator.

＜When adjusted to a brighter setting＞   ＜When adjusted to a darker setting ＞   ⇓ Zoom in on the area within the red frame above   ⇓ Zoom in on the area within the red frame above

With our non-calibrated microscope, it is recommended to adjust to a slightly darker setting, within the range where the automatic edge detection mode (A) functions stably.

Dimension measurement (auto-calibration) microscope (medium magnification) CT200HD

Dimension measurement (auto-calibration) microscope (high magnification) CT200HD-H

Typically, when magnifying and observing cylindrical shapes with small diameters and high reflectivity (such as wires and filaments), glare may occur, making observation difficult.

This time, various methods of illumination were applied under the following conditions for observation.

(1) Observation with the standard LED ring light

The standard ring light causes reflection (glare) to occur.

(2) Illumination from a low angle along the longitudinal direction of the specimen

(3) Arch light

■ Advanced application

An alternative method is to use the “4-segment LED light” and “V-block” for observation.

＜4 segment LED ring light＞

Illuminate two diagonal points and shine light from the longitudinal direction of the specimen, as shown in (2).

(This alone may be sufficient to achieve the desired effect)

＜V-block＞

Attach a reflector (in this case, white paper) to the V-block to allow the light to wrap around the specimen.

The “LED ring light”, “twin arm light”, and “arch-shaped light” used above are available from our company.

Ring light

Twin arm light

Arch-shaped light LV-AR series arch light

The appearance of concave surfaces can vary depending on the shape and depth.

We observed relatively large concave shapes using various methods for comparison.

The samples are as follows:

1. USB memory connector section

2. Small engine part, φ5mm, with a screw in the 15mm deep section

3. Mechanical pencil lead holder section, φ5mm, with a depth of 6mm

Observation using a standard high-definition microscope TG200HD2 (25 ~ 150x)
1. USB memory 2mm x 10mm, depth 8mm
(30x)	(120x)
Even with a standard microscope, increasing the illumination to its maximum allows for relatively clear observation.
2. Small engine part, φ5mm, with a screw in the 15mm deep section
	Since the depth is 15mm, the light from a standard ring light has difficulty reaching the bottom, making observation challenging.
(80x)
3. Mechanical pencil lead holder section, φ5mm, with a depth of 6mm
(30x)	(120x)
Increasing the magnification causes the image to become slightly darker.
Changing the front ring light of the TG200HD2 to a smaller diameter (LED-16) version   By using a smaller diameter, the illumination angle becomes shallower, allowing the light to reach more easily.
1. USB memory
2. Small engine part
3. Mechanical pencil lead holder section
Changing the lens to a borescope (rod lens)
The borescope (rod lens) is available in sizes of φ4.0mm and φ2.7mm.

IC prints are often made in gray or other colors on the black molded surface, making them difficult to read even when magnified under standard lighting.

■ Standard ring light

■ Dome light (indirect light)

Dome light

■ Polarized observation (inserting polarizing filters at the lens tip and ring light)

Microscope halation removal set GR-HL

For the light-emitting side, we will install the polarizing filter attachment unit that we manufactured.

For the light-incidence side, we will use the MIDOPT polarizing filter, which is installed inside the C-mount.

(It will be mounted inside the camera, as shown below.)

The filter on the light-emitting side is adjustable, allowing for polarization observation with this setup.

Glossy convex surfaces can cause reflections when observed with the ring light, which is standard equipment on our microscopes, making observation difficult.

■ Light

When using a standard ring light, the impact of reflections becomes more significant.	Attaching a polarizing filter to the lens tip and the light side when using ring light can improve the reflections to some extent.
Using twin-arm light can further reduce reflections, as shown in the photo below. (Angle adjustments and other settings are necessary)	Simply adding a polarizing filter to the lens alone can further improve the results, as shown in the photo below.
Observation of a convex lens (object) using the same method (ring light → low-angle twin-arm light).
(Note) For lenses, since the lens itself is transparent, the background color becomes important. In the above example, the background is white, and the lens is not placed directly on the surface but is slightly elevated for observation.

When detecting metal body steps, scratches, dust or foreign particles on transparent surfaces, and dust or foreign particles on mirror-like surfaces using standard light, reflections, and ghosting can occur, making observation difficult.

One method is dark field observation. (For more details, please refer to “What is dark field observation?”)

By setting the background to black and using low-angle LED light, a simple form of dark field observation can be achieved.

If there are steps or scratches on the metal, those areas will appear white under illumination.

Dust and foreign particles on transparent surfaces (lenses) will also appear white under illumination.

Dust on mirror-like surfaces (silicon wafers) will also appear white under illumination.

	Low-angle LED ring light GR56-N
	Low-angle bar LED light (Customized product requested by the customer)

The closer the spherical shape is to a mirror-like surface, the more difficult it becomes to observe. A sphere contains various radii, and the closer it is to a spherical body, the more likely some areas will experience halation, making it impossible to see clearly.

We scratched the mirror-like spherical surface and conducted a comparative observation.

1. When using the halation suppression function (HDR) of a high-definition microscope

We observed the spherical metal using a high-definition microscope.
＜Before halation suppression＞	＜After halation suppression＞

2. When using dome-type light

＜When using a 56-LED ring light＞ Halation occurs with simple reflected light.	＜When using dome-type light＞ By providing uniform illumination to the spherical metal, halation was significantly suppressed.

	Dome light DC-170W
	It is also compatible with our microscopes.

※ When using dome-type lighting in combination with the halation suppression function of a high-definition microscope.

Dome-type light + Without halation suppression function	Dome-type light +With halation suppression function

Using dome-type light and the halation suppression function of the high-definition microscope resulted in a significantly clearer image.

For more details, please get in touch with our technical support.

Coaxial light is designed specifically for “glossy flat surfaces.”

■ Glossy flat surfaces (suitable for coaxial light)

For example, with objects like the ones below, the resulting image would appear as shown on the right.

The caliper also appears as shown on the right.

■ Glossy surfaces with irregularities or curves (not suitable for coaxial light)

Driver

The image will show only the top of the curve (R) illuminated.

Drill bit

The image will show only the edge illuminated.

■ Non-glossy (diffusely reflective) flat surfaces (not suitable for coaxial light)

Paper (printed material)

Using coaxial light results in a dull image. When observing printed material with a “ring light”, the image appears clear, as shown on the right.