LED lighting for Machine vision - Optex FA - #16

Points when setting the Lighting

When setting the Lighting it is necessary to consider several factors. Even when using the same Lighting, if the set height is different the captured images are completely different. Also, if the Lighting wavelength (color) is different, the images change. When setting Lighting, please consider the points below:

The Visual Field of Coaxial Lighting

Coaxial Lighting is a type of Lighting in which the surface emitting part of the LED emits light along the same axis as the camera lens, via a half-mirror. The effective visual field of coaxial lighting is dependent upon the distance between the camera and object (OD), the distance between the Lighting and object (LOD), and the size of the light emitting surface. If the OD increases, the visual field grows, but if the LOD increases, the visual field shrinks. The method of calculating the effective visual field is shown below. It is necessary to keep the object within the effective visual field, especially for objects with a high reflectance. This effective visual field is calculated based on the size of the light emitting surface. It is recommended that you set a sufficient visual field, taking into consideration the lower luminance in the surrounding area.

Additive Primary Colors

Subtractive Primary Colors

By combining the light of red, green and blue (additive primary colors) you can create other colors. Green(G) and blue(B) make Cyan(C), B and red(R) make Magenta(M), and R and G make yellow(Y). By combining R, G, and B lights of the same strength, white(W) is created. Combining colors in this way is called additive color mixing.

Colors can also be created by absorbing parts of light. C absorbs R, M absorbs G, and Y absorbs B. C, M, and Y absorb all of the light, and black(K) is created. Combining colors in this way is called subtractive color mixing and CMY are called subtractive primary colors.

The color pattern using CMY is shown below. Also, color images using white, red, green, and blue and the monochrome image are shown. The contrast varies depending on the color of the light. When recognizing the object during image processing, it is important that there is sufficient contrast. During image processing, please select a light color where there is a large contrast between the object color and background color, referring to the color patterns below.

How to Use and Maintain LED Lighting

To get the best performance from LED Lighting:

1. Please avoid using LED lights in a high-temperature environment. Doing so may lower the illuminance and facilitate deteriortion.

If the LED element becomes heated, illuminance is reduced and general performance deteriorates. The half-life of the illuminance of an LED element is said to be about 20,000 hours (Typ.), but if the element is continuously used in a high-temperature environment, its performance may deteriorate quicker.

2. To prevent illuminance reduction and performance deterioration due to the generation of heat:

•Improve the heat dissipation of the LEDs.

• Mount the Lighting on a bracket with good heat conductivity.

• Install a ventilating device.

• Install a fan.

We recommend creating a cool environment which allows easy heat dissipation.

• Turn the Lighting on only when imaging.

The performance of LED Lighting is not affected much by switching the power on and off.

To extend the LED's life, utilize the on/off function controlled by external signals powered by this company, and only turn the LED on when necessary.

• Use lights at low volumes.

If the light is set to a low volume, the current flowing into the LED decreases and the heat generation is suppressed.

To choose Lighting with sufficient brightness, evaluate each Lighting when the camera's aperture is as open as possible.

If using the Lighting continuously, we recommend a volume of 50%. (Even if performance deteriorates and illuminance is reduced, normal use can be restored by increasing the volume.)

3. Use the Lighting as close as possible to the target object.

Since the element itself is small, LEDs can manufactured as small and lightweight lights. The illumninance is inversely proportionate to the square of the distance, and thus using the Lighting at a close distance can increase the light intensity greatly.

X 200mm 300mm 200m_m Y 50mm 50mm 100mm Z_31.8mm 36.2mm 27.5mm

White Lighting

Red Lighting

Green Lighting

Blue Lighting

Color Image

Effective visual I field: z I

Monochrome Image

Notes for use

• Do not look at the source of light directly.

• Do not disassemble or reconstruct the light or power supply.

• Do not touch a product under operation with wet hands.

• Do not use in a high-temperature or high-humidity environment.

• Avoid installing in a dusty place.

• Please use following the recommended guidelines concerning heat generation.

• Please do not use a power supply other than the one provided.

• The AC power supply should have a different power supply from the mo­tive power, electromagnetic valve etc.

• A power supply with an earth terminal should be grounded.

• When installing Lighting, follow all instructions carefully.

^ Please note that the specifications of our products are subject to change without prior notice.

Observing specular transmission light Observing scatter transmission light

(bright field) (dark field)

Lighting Lighting

Differences in observation light due to the relative positions of the Lighting, camera and object.

Depending on the type of object, positional differences of the Lighting, camera and object can affect the image. Each situation is described below:

Observing scatter reflection light

(dark field)

Observing mirror-reflected light (bright field)

I Object J Clouded glass

I Object J Transparent glass

Lighting

Lighting

Camera

Camera

Warranty

• Period of Warranty : The warranty period of this device is one year from delivery.

•The manufacturer will repair or replace the device free of charge.if a malfunction occurs where the manuafacturer is liable, during the warranty period. However, malfunctions caused by the following shall be excluded from the manufacturer's warranty.

1. Damage caused by abuse, misuse, or misapplication 2. Damage where the cause is not the delivered product

3. Damage caused by an unapproved modification or repair. 4. Damage due to natural or other disasters

5. Damage caused by use which exceeds standard product use 6. Damage caused by failure to adhere to guidelines or warnings

The warranty stated herein shall cover only the delivered product.

Damage or injury sustained due to a malfunction to this product is not covered by this warranty.

I Object J White paper

Camera

Camera

The camera and Lighting are on the same side of the mirror, and it is the same as looking directly at the Lighting. Only the direction of the light is different, and the reflected light is captured by the camera. The reflected light and the camera are along the same axis. Evenness rather than brightness is required of the reflected light. Irregularities on the surface and areas of low reflectance are comparatively dark.

The camera captures images of a part of scattered

light reflected off the surface. Light is reflected in every direction so the camera's observation axis is not restricted. Since only a part of the light can be captured, brightness rather than evenness is required. Irregularities on the surface and areas of high reflectance are comparatively bright.

The camera and Lighting are on opposite sides of the glass, and it is the same as looking directly at the Lighting. The camera is aligned with the direction of the light, and the reflected light is captured by the camera. The transmitted light and the camera are along the same axis. Evenness rather than brightness is required of the reflected light. Irregularities on the surface and areas of low reflectance are comparatively dark.

The camera captues images of a part of scattered light transmitted from the surface. Light is reflected in every direction so the camera's observation axis is not restricted. Since only a part of the light can be captured, brightness rather than evenness is required. Irregularities on the surface and areas of high reflectance are comparatively bright.