1. Applications not suitable for coaxial illumination:

(1) Diffuse reflective objects (paper, resin, painted products, etc.)

Observing with coaxial illumination results in loss of color and creates images with no contrast.

●Business card

(2) Objects with gloss but uneven surfaces

Only the flat portions of the object will shine, while other areas will appear as images without contrast.

●Wire

●Screw

2. Suitable applications for coaxial illumination:

Coaxial illumination is suitable for objects with gloss and flat surfaces.

It is suitable for the following examples:

●Metal plating

●Silicon wafer

●Substrate gold electrodes

Depending on the object, some are suitable for coaxial illumination, while others are more appropriate for ring illumination.

However, ring illumination is more versatile.

Coaxial illumination can only be used for objects that are “glossy” and “flat.”

■Features of Coaxial Illumination

Coaxial illumination is a suitable method for objects with specular reflection (glossy surfaces).

When oblique light, such as from ring illumination, is directed at a specular object, it reflects at the same angle as the incident angle, preventing light from returning to the lens and resulting in a dark image.

However, coaxial illumination is not suitable for glossy objects with uneven surfaces or curvature.

When used on diffusive reflective objects, coaxial illumination causes only the central part to become bright (hotspot), resulting in a foggy image without color contrast.

サンプル1　　　基板の金メッキ部分

The illumination method of a metallurgical microscope (coaxial illumination) is designed for nearly mirror-like, flat objects.

The appearance can significantly differ compared to conventional illumination (ring illumination).

サンプル2　　　1円玉

White and black completely invert.

(The closer the surface is to a mirror finish, the more pronounced this effect becomes.)

サンプル3　　銀メッキのコイン

A silver-plated coin, like the one in the above photo, can be observed with both coaxial and ring illumination.

(Since it is not a perfect specular reflector, both methods are suitable.)

Sample 4: 10-yen coin (diffuse reflector)

A 10-yen coin cannot be observed with coaxial illumination.

Sample 5: Circuit board (observation of diffuse reflector)

Diffuse reflectors cannot be observed with coaxial illumination.

Sample 6: Observation of specular reflectors

Perfect specular reflectors (those close to mirror surfaces) cannot be observed with ring illumination.

Sample 7: Nickel processed product

When using coaxial illumination, please note that diffuse objects cannot be observed.

(Even with metals, black anodizing or paint may be better observed with ring illumination.)

Sample 8: Paper (printed material)

Sample 9: Other objects unsuitable for coaxial illumination

**Ring Illumination**

This provides the most natural appearance, closely resembling the view perceived by the human eye.

For more details on ring illumination, please refer to the following:

**Coaxial Illumination**

When observing reflective objects (such as metals), black and white may reverse depending on the conditions.

For more details on coaxial illumination, please refer to the following:

**Low-Angle Illumination**

Edges appear sharper and more pronounced, resulting in a dark-field-like appearance. (Refer to “Dark-Field Observation” for more information.)

For more details on low-angle illumination, please refer to the following:

The equation is correct: E(θ)=E0(cos⁡θ)4E(\theta) = E_0 (\cos \theta)^4E(θ)=E0​(cosθ)4.

As you move away from the center, the illuminance drops steeply:

• At 30°, it decreases to approximately half (12\frac{1}{2}21​).
• At 45°, it decreases to approximately one-fourth (14\frac{1}{4}41​).

In practical lighting scenarios, the diffusion (or conversely, directionality) of light sources varies, resulting in diverse beam characteristics that may not perfectly align with theoretical values. However, they serve as rough guidelines.

To achieve uniform illumination over a certain area, efforts are made to utilize the central region (the “redder” area) as much as possible and to flatten out its characteristics as much as feasible. This can be achieved by using lenses, diffusers, or other optical elements.

It’s important to note that with point sources (such as small area illuminations), achieving completely uniform illumination across a large area is generally not possible.

●Lumen (lm）     Lumen is a measurement that indicates “how much light is gathered within a certain range from the light source.” It quantifies the luminous flux within a specified angle of emission, regardless of the measuring surface conditions. For example, when indicating the brightness of lighting fixtures like incandescent bulbs or fluorescent lamps, it represents the total luminous flux emitted in all directions. This measurement is commonly found on lighting devices designed to brighten spaces (such as household lighting). With the shift from incandescent bulbs to LEDs, lumens have become the preferred metric over watts. For instance, a 60W incandescent bulb is roughly equivalent to 800 lumens.
● Lux Lux indicates the brightness of a “specific surface” illuminated by light and varies with the measurement distance. It is commonly used for lighting devices where brightness at a certain distance and on a specific surface (lux) is important. In industrial applications, it is used for devices like ring lighting for microscopes and industrial microscopes. In consumer applications, such as desk lamps used for lighting workspaces, lux is often used to express brightness, which aligns better with the intended purpose.
●The measurement method Lux can be easily measured by placing a lux meter on the surface where you want to measure the illuminance. To measure lumens (total luminous flux emitted in all directions), a sophisticated device called an integrating sphere is required.
	＜An integrating sphere＞

Summary: 

**ルーメン (Lumen)**: Indicates “how much light is gathered within a certain range from the light source.” It quantifies the luminous flux within a specified angle of emission, regardless of the measuring surface conditions.

**ルクス (Lux)**: Indicates the brightness of a “specific surface” illuminated by light and varies with the measurement distance. It is commonly used for lighting devices where brightness at a certain distance and on a specific surface (lux) is important.

These metrics help in understanding and quantifying the brightness and efficiency of lighting sources and devices.

(1) When using the XY table,

Place the transmitted illumination (RD-95) underneath a compact stand.
On top of this, install a glass XY table (TK-100N).
This creates a simple transmitted illumination stand.

(2) When using a rotating XY table,

The size of the rotary table matches that of the transmitted illumination (RD-95).
By removing the observation plate from the rotary table and installing the transmitted illumination (RD-95), you create a simple transmitted light stand.

Of course, when using a rotating XY table, similar to (1), you can place the transmitted illumination underneath the stand. You can also use a glass plate on the rotating table to create a transmitted illumination stand.

		Transmitted illumination stand compatible type TK100-N (Stage: Glass)
		Rotating simple XY table T

Coaxial illumination is a lighting method designed for observing specular reflectors.

(It is not suitable for observing diffuse reflectors.)

When observing diffuse reflectors, hotspots (extremely bright areas) occur.

Furthermore, the effect becomes more pronounced at lower magnifications.

(In the case of diffuse reflectors, ring illumination is recommended.)

■Zレンズの最低倍率（X0.7）で上記３点を観察

Even with glossy ceramics, slight hotspots may persist.

Objects ranging from surfaces reflecting surrounding scenery to specular reflectors are within the appropriate observation range.

■ Methods to Reduce Hotspots

If the camera has HDR (High Dynamic Range) capabilities, there is a method to reduce hotspots by sacrificing color vividness.

(However, generally speaking, for diffuse reflectors, it is recommended to use ring illumination rather than coaxial illumination.)

(HDR set to 0 for observing white paper)

（HDR 3　で白紙観察）

Coaxial illumination is a unique lighting method integrated within the optical path of the lens.
(It is effective for observing silicon wafers, plated surfaces, polished metals, etc., and mirror-like objects.)

The differences in the obtained images can be discerned when comparing coaxial illumination with bright-field illumination (such as ring illumination).

	Below is the image captured when photographing a test pattern chrome-deposited on a transparent glass plate (left photo).
(coaxial illumination)	(ring illumination)

Ring illumination provides a more natural appearance, but coaxial illumination offers higher contrast between the glass and pattern areas due to the chrome deposition’s high reflectivity. Depending on the inspection requirements, coaxial illumination can be advantageous. (In the case mentioned, I believe coaxial illumination would be easier for inspecting scratches or defects on the chrome deposition.)

<When coaxial illumination is effective>
It is primarily used when observing flat surfaces with specular reflection (mirror-like objects) or objects close to specular reflection. It enhances strong contrast due to differences in reflectivity.

– Plated metal surface
(coaxial illumination)	(ring illumination)
– Patterns on silicon wafers
(coaxial illumination)	(ring illumination)
– Electrodes on substrate (gold-plated section)
(coaxial illumination)	(ring illumination)

<Instances where coaxial illumination should not be used>
For highly diffuse objects (such as paper, wood, or resin with sandblasting), there is no difference in surface reflectivity (consistent appearance from all angles). Therefore, coaxial illumination would result in images without contrast. Additionally, due to the object’s complete diffuse (Lambertian) nature, hotspots occur in the image (where the center shines brightly).

– White paper (black text printing)
(coaxial illumination)	(ring illumination)

Falling illumination is a lighting method used in microscopes, digital microscopes, and similar devices. It involves illuminating the specimen from above. There are various shapes and types depending on the mounting method and application, such as ring illumination, twin-arm LED illumination, dome-style illumination, arch-shaped illumination, and coaxial illumination.

	Ring illumination GR10-N
	Twin-arm LED illumination SPF-D2

It is effective to use different types of illumination depending on what you want to observe. When attaching to the lens part, ring-shaped illumination is often used.

Ring illumination is attached to the tip of the lens and used for illumination.

I will help you select the appropriate lighting according to your requirements. Please feel free to contact our technical support for assistance.

1. What is Grain Size?

The mechanical properties of metal materials, such as tensile strength and resistance to compressive shear forces, vary depending on the material, necessitating the use of metals appropriate for specific applications. Additionally, heat treatment alters the metallographic structure and, consequently, its mechanical properties. Therefore, the analysis of grain size is a critical inspection for quality assurance of products.

2. Methods for Measuring Grain Size

The commonly used methods to measure the grain size in metals include:

1. Visual comparison using standard charts and a metal microscope (Comparative Method).
2. Incorporating an eyepiece micrometer into the metal microscope for simultaneous observation and comparison (Comparative Method).
3. Incorporating an eyepiece micrometer into the metal microscope for simultaneous observation and calculation (Line-intercept Method).
4. Using a camera and software for grain size measurement (Counting/Planimetric Method, Line-intercept Method).

These methods allow for the analysis of the crystal grain size in metallographic structures.

3. Automatic measurement of metal grain size using software

With method ④ above, the grain size can be measured automatically using software, increasing efficiency.

金属顕微鏡の詳細はこちら

顕微鏡用USB3.0カメラ（500万画素） HDCT-500DN3

粒子解析ソフトウェア G-S Measure（日鉄テクノロジー株式会社製）

4. Additional Convenient Features of Grain Size Measurement Software: Comparative Method

This is a visual inspection method. A sample, such as a metallographic structure, is placed under a microscope. The process involves simultaneous observation of the sample under the microscope and comparison with a “Grain Size Standard Chart (×100) JIS G 0551” or an “eyepiece micrometer (reticle)” printed with the standard chart. The grain size is determined by matching the closest standard chart.

This software facilitates the calculation of grain size by simply selecting the appropriate standard chart while observing the microscope camera’s live video feed. It allows for the superimposition of the standard chart over the live video feed from the microscope camera, providing a highly convenient and efficient feature.

② Counting / Planimetric Method, Line-intercept Method

The Line-intercept Method involves drawing a test line (pattern) on a captured microscopic image. The grain size is calculated by measuring the average line segment length that crosses through each crystal grain when the pattern intersects with the grains. This technique provides an accurate measure of the grain structure’s dimensions by quantifying the interactions between the line and the microstructure.

**Measurement Display Example: ASTM (Line-intercept Method, Line Length Comparison Method)**

After the measurement, areas where the grain boundaries intersect with the test pattern are highlighted in blue.
*Note: The example image measures an area at a microscope magnification of 100 times, within a 1000×1000 dot range.*

5. Conclusion

If the frequency of grain size measurements is high, utilizing the convenient features of this grain size measurement software for automated measurements is key to reducing labor and enhancing efficiency.

・what is welding?

Welding is defined as the process of joining two metal substrates at their junction using heat, pressure, or other methods, or alternatively, joining them by incorporating filler material under heat or pressure.

The primary methods commonly used for heating in welding include electricity, arc discharge, gas, plasma, and laser techniques.

In this process, the weld bead length formed in the weld (weld deposit) significantly affects the strength of the weld joint.

・Evaluation of welding

The portion of the weld where material has been deposited, indicated by the red arrow in the image, is known as the weld bead.

Depending on the welding conditions, the appearance and dimensions (width, length, height) of this weld bead can vary.

The shape of the weld bead allows for the evaluation of whether the welding was performed correctly and if there are any welding defects.

Common welding defects include:

– Insufficient reinforcement
– Overlap
– Undercut
– Porosity
– Cracks

To evaluate this weld bead, it is necessary to measure its three-dimensional shape.

– Inspection in welding involves specifying dimensions in the weld section. This includes the minimum thickness of the weld bead, known as the “throat thickness,” and dimensions such as the “penetration” and “fusion depth,” which measure from the melted metal peak to the surface of the parent metal.

– For more information on measuring weld penetration, click here.

Among the specified dimensions is the “leg length (kyakuchou),” which extends from the weld root section to the end of the weld bead. This leg length serves as one of the criteria for determining the optimal bead width.

Efficiency in measuring the shape and length of weld bead legs.

To ensure welding quality, it is necessary to inspect the weld bead.

Common inspection methods include:

– Visual comparison with a reference sample
– Comparison using a welding gauge and visual inspection

These methods often require high skill from inspectors and can be time-consuming. Moreover, judgments may vary depending on the individual.

Additionally, using welding-specific gauges for measurements requires multiple measurements at various points, which is inefficient.

<Image of welding gauge measurement>

Utilizing the following product can resolve issues related to measuring weld bead lengths:

Recommended product for weld bead length (bead) measurement:

【Weld Bead Length Handy 3D Scanner CSM-HS10WL】

This product is a 3D handheld scanner that allows instant, non-contact and non-destructive measurement of weld bead cross-sections simply by aiming a laser at the weld area to be measured.

*Note: It cannot measure penetration depth inside the weld or internal blowholes.

No need for rulers or welding gauges; it operates using a non-contact optical cutting method triggered by a switch.

You can scan the 3D shape of the laser irradiation line applied to the weld area and measure the cross-sectional view with high accuracy. This allows for instant, non-destructive measurement of weld bead (leg length) without human error or variability.

～ Features of this device include:

Feature 1: Easy-to-use handheld 3D scanner
– Simply connect to a PC or tablet via USB. Once the welding measurement software built into the device is installed on the PC, it can be operated immediately.
– Being handheld makes it easy to handle, allowing measurement of targets that were previously difficult to measure, including large or heavy objects and narrow spaces.

• 。

Feature 2: Measurement by simply aiming and triggering
– When measuring weld beads, conventional methods require the use of a square or welding-specific gauge. With this device, precise measurement with pinpoint accuracy is possible with a single laser shot.
– Simply aim at the weld bead (weld protrusion), pull the trigger switch, and the measurement is done.
– Comes with a detachable guide rod for convenient adjustment of distance and angle during measurements.
– Easily perform 3D measurements of 12 points including “leg length,” “undercut,” “joint angle,” and “excess buildup” using the optical cutting method.

Feature 3: Instant display and saving of leg length measurement results on PC screen
– Measurement results can be saved as files and the data can be utilized in Excel®.
– Numerical results are displayed simultaneously during measurement, ensuring accurate and error-free records.
– Eliminates the need for handwritten records that can be prone to errors and enhances security against tampering.
– Allows for traceability assurance.

～ Additional Convenient Features ~

Feature 1: Equipped with a standard measurement mode convenient for inspecting weld bead (leg length)

・角R(アール)の計測

・Measurement of butt welding

Feature 2: Displaying camera images, laser cross-sectional views, and measurement results on a single screen

• ・Camera Image:
  Displays the captured video of the section through the camera.

  ・Laser Cross-sectional View:
  Clearly displays measurement results with numerical data and cross-sectional diagrams.

  ・Measurement History:
  Displays numerical results of measurements.

Feature 3: Measurement history can be exported to Excel®.

Feature 4: QR Code Reading

Allows easy linkage of measurement results with target items by scanning QR codes or barcodes. This enables the management of measurement results via QR codes.

Additionally, combining QR codes with cloud services enables visualization and digital transformation (DX) of welding operations.

・Summary

If you want to significantly improve and streamline the challenging task of measuring weld bead shapes accurately,

The 【Weld Bead Length Handy 3D Scanner CSM-HS10WL】is incredibly convenient.

・Eliminates variability in measurements by individuals, ensuring quantitative measurement.
・Capable of reading QR codes and linking with product data.
・Enables instant and accurate 3D shape measurement of objects without contact.
・Visualizes anomalies in weld bead areas using color maps.