Optical Sorter
Table of Contents
Wheat Sorting Case

Just like in any industry that will last, there is an ever-changing drive for optical sorting operators to find more innovative and efficient ways with regards to the separation of the different materials they receive at their facilities daily. 

In light of that, new technologies have evolved to improve the processing and sorting of recyclables.

You now have optical sorting systems that can accurately sort recyclables, produce commodities of high quality, increase output, and reduce the time of production.

This ultimately reduces the labor costs that come with alternative methods.

For example, if you took your child to a recycling center, he or she would think that everything at the center is running on magic.

That means you would have to come up with a very concrete explanation to counter that belief. And that is why optical sorting is amazing.

In the last five years, the most significant achievement in optical sorting is the use of light to identify various materials that require sorting.

To be more specific, the optical sorting of this kind is done by examining the properties of light waves.

In this comprehensive guide, you’ll get full information on optical sorting and how to choose the best type of optical sorter for your production process. Let’s dive in. 

Chapter 1:  What is Optical Sorting? 

1.1. What is optical sorting? 

Optical sorting refers to an automated process that involves the use of cameras and lasers to sort solid products.

The process of recognizing the colors, shape, size, structural, and chemical properties depends mostly on the types of sensors used.

The sorting machine obeys the criteria that you dictate in the sorting process.

Additionally, it uses intelligence to identify and sort out products that do not comply with the accept-criteria.

You then remove foreign materials (FM) from the production line and then separate the products into their different grades.

You no longer live in an age where you have to do all the sorting yourself. Manual sorting is subjective, inconsistent, and time-consuming.

But with the use of a sorting machine, the pharmaceutical and nutraceutical industry no longer have to go through the grueling routine of manual sorting.

And the best of all is that you can do waste recycling better and faster.

1.2. What is an optical Sorter? 

An optical sorter is a smart technological device, state of the art equipment that recognizes an object by its shape, color, and size.

This high-performance machine meets extraordinary standards at which it can sort through food products to help your organization serve hygienic foods that are aesthetically pleasing and valuable to customers.

The primary task of optical sorters is to remove all of the negatives and uncertainties that usually comes with sorting manually.

So, it’s either you are looking to streamline the current process you use and improve your ROI significantly.

Optical sorters are useful in many industries. And the best of all is that you can use optical sorters in the food industry, where they sort harvested foods like potatoes, fruits, vegetables, and nuts.

Also, the optical sorter performs a thorough inspection of the full production volumes of the products without causing any damages. 

1.3. Components of Optical Sorters  


If you want to illuminate objects and capture images, a harmonious combination of light and sensors is required.

The images received can then be processed will either be accepted or rejected.

There are different types of sorters, which includes camera and laser sorters. These two features both cameras and lasers. 

The lights and cameras aid with the functioning within visible light wavelengths, infrared (IR) and ultraviolet (UV) spectrum, giving it more diversity.

Camera and Lasers

By expert detection of shades of gray from black, monochromatic cameras have proven effective in sorting items that have high-contrast defects.

Color cameras also help you to detect millions of colors and use this in separating objects from one another, no matter how closely related the colors are.

There are also trichromatic color cameras that can divide light into three colors (namely, red, blue and green) within the visible spectrum, infrared and ultraviolet. This is why they are also called three-channel cameras.

Brilliantly coupled with intelligent software, sorters that come with cameras can detect the color, shape, and size of an object.

There are more intelligent sorters that give you the freedom to define a defective product.

These sorters infrared laser beams to display the beam laser. That said, let’s further talk about lasers and what they do.

What do they do?

Cameras in sorters help to capture the information of a product based on the reflectance of the material.

Additionally, Lasers function at specific wavelengths of lights that are within the visible spectra and beyond. 

A good example is the ability of lasers to detect chlorophyll using stimulating fluorescence at particular wavelengths.

This process is useful in separating foreign materials from green vegetables.

You can make a choice between the different types of cameras based on what your practical sorting demands are.

RGB Camera

This camera makes use of a full color sorter to separate seeds such as rice and to remove defects. Ideally, what the RGB camera does is to capture images that may be difficult for other sorters to identify.

NIR Camera

The Near Infrared camera is best if you have to separate impurities from raw materials such as plastics, stones, glass and other inorganic materials in the recycling field.

The sorting is efficiently done even if the impurities have the same color as the raw materials.

X-Ray Camera

Just as the name suggests, the X-ray camera examines the materials by looking inside to remove any inner defects.

This is possible even in closely related materials such as shells and almonds. With the use of the hyperspectral color spectrum, their inner membranes are examined for contaminants.

Integrity checks are also performed. If any foreign material is detected, it gets removed.

Camera/laser Combination

For maximum efficiency in the production process, you would prefer sorters that have both cameras and lasers.

These kinds of sorters are capable of carrying out material identification of a wide range. The cameras do the sorting by adjusting the color, size, and shape of the material.

And by identifying differences in the structural features, foreign materials are recognized and taken out by the laser sensors.

1.4. Types/Platforms of Optical Sorters

If you want to decide on what the ideal platform for a particular application should be, you should take into cognizance the maturity of a product.

These could be big or small, damp or dry, delicate or sturdy, round, or easily stabilized.

Generally, you can sort products of any size. Products with sizes ranging from 2 metric tons to 35 metric tons on low and high capacity sorting machines respectively can be given out per hour.

Channel Sorters

They are also called chute sorters and are the most simply designed type of color sorters. They are most useful for sorting small and dry products that have consistency in shapes like rice and beans.

color sorter machine

Channel sorters are less expensive and have easy operation mode.

They come with monochromatic or color cameras and are able to identify and remove defects. They can also eliminate foreign objects by detecting color differences.

If you have to sort soft, wet, or even nonhomogeneous products, freefall sorters are best to use. Alternatively, you can also use chute-fed sorters or belt sorters.

Freefall Sorters

From the name, you’d deduce that freefall sorters examine products while they are in the air during the free fall.

Freefall sorters, however, make use of a chute to stabilize products before an in-air check is done.

The advantages of freefall sorters over belt sorters include:

  • These sorters are quite affordable 
  • They have a smaller footprint
  • Freefall and chute-fed sorters low maintenance costs due to the absence of moving parts in their design.

They are most useful for sorting nuts and berries. Seafood, vegetables, and frozen and dried foods can also be sorted. Additionally, they are excellent tools for waste recycling applications.

Belt Sorters

People and industries prefer belt sorting platforms for higher capacity applications such as when you need to sort vegetable and potato products before they are canned, frozen, or dried.

They are also useful in sorting most fresh-cut produce and wet fruits. Also, belt sorters can help with waste recycling.

But how do they work? Belt sorters keep products stabilized on a conveyor belt before the inspection.

There are belt sorters that inspect products only on the belt from the top, and the others carry out an in-air check from the bottom when they launch products off the belt.

It is also critical to note that belt sorters are sometimes made able to carry out the traditional two-way sorting or even the three-way sorting.

This is possible with the two ejector systems and three outfeed streams.

ADR Systems

This is the automated defect removal (ADR) system designed mainly to sort potato strips.

What makes this system peculiar is its ability to not only detect defects in products lined up for production but also cut the defects from the strips.

This is unlike the other types that eject defected products from the production line.

Finally, the ADR comes with a mechanical nubbin grader, which makes use of optical sensors with which it finds and removes flaws or imperfections.

Single-file System

This optical inspection system is useful in the pharmaceutical industry. It does not operate in a bulk mode, unlike the others.

These sorters, however, have not been widely adopted despite their high-grade effectiveness in finding and taking out defective tablets and capsules using variations in size, shape, and color. 

This is because they are costly. They also have minimal throughputs and slow changeover.

People and industries prefer belt sorters to sort capsules, tablets, and soft gels.

Mechanical Graders

These are the most suitable if you want to sort by size.

You should also know that mechanical graders don’t make use of sensors or image processing systems but they remain highly operative.

Do not mix up mechanical graders with optical sorters. They are two different things.

1.5. How do Optical Sorters Work?


The process of sorting is quite straightforward. 

In this section, you will learn how optical sorters work. This will guide you to make informed decisions and avoid unnecessary risks when choosing optical sorters.

First, recyclable material is placed on the accelerator belt to reduce the load on the conveyor.

The conveyor passes the material through luminous light, and while it goes through, some of the light is absorbed.

At this point, a network of camera lenses pointing right at the conveyor belt recognize and take records of light waves as they reflect off the recyclable materials.

Each of the materials in the process generates a peculiar light “signature,” which you can understand by using a spectrometer.

The signatures are also referred to as light fingerprints and are used to differentiate between a large variety of materials.

The lens and the spectrometer both have impressive abilities to identify the material, and the content could either be glass, plastic, wood, paper, and so many other types.

A computer controls the process, and you can program it to work even more specifically in identifying various plastics including polyethylene terephthalate (PET).

Targeting of different types of wood, a glass of different colors, as well as papers, can be done.

Once the spectrometer has stated the material on the conveyor belt as a “target”, the sorter continues the more practical aspect of the process.

The computer that is determining the entire process then finds the location of the target recyclable by calculating it before allowing compressed wind to go into the belt area.

A jet of air goes on to separate the item from others on the control belt. Many times, a quality control step is present to double-check the purity of the commodity you are sorting.

Optical sorting is a faster process, more effective, and significantly less labor-intensive than manual sorting.

Maintenance of the Optical Sorter

Optical sorters are generally easy to maintain, and like every good machine that will last, they too must be checked daily.

Daily inspection is to ensure that all lights are in good condition and also to make sure that the lenses are clean, free of dust and there are no obstructions.

All lights that are burned out must be promptly replaced, and air nuzzle checked to ensure there are no clogs.

You must also regularly review the pressure of your air nozzles to make sure it is at the right level to perform the physical separation.

Also, the controlling computer has to be occasionally recalibrated by an expert to ensure that it does not leave out any desired items on the belt.

Watch this YouTube video

Chapter 2: Why Optical Sorting?

So, why should you trust optical sorting? 

1. GUARANTEED ACCURACY: Color sorting machines are high precision machines. You can efficiently operate them and give up to 99.9% output product purity. The results that they give are outstanding.

2. WIDE ADOPTION IN FOOD INDUSTRIES: Color sorting machines are adopted and used widely in the food industry. Additionally, it is helpful where visual product control is a necessity, such as in the sorting of cereal, legumes, grass seeds, frozen fruits, and berries.

3. WIDE ADOPTION IN NON-FOOD INDUSTRIES: The non-food industries also enjoy the immensely significant benefits of color sorters. In plastic, glass recycling and sorting of wastes, salts, and minerals, color sorters have been widely adopted and found useful.

2.1. Why Optical Sorting Technology is in Demand

Demand is increasing for optical sorters because of the following reasons:

  • The food industry is developing more exponentially and has productivity, financial efficiency, and other issues facing it like never before. That said, the food industry needs equipment to ease its challenges.
  • The fast-rising demand for the world’s food resources has rendered the food supply chain more complicated. While the chain has brought several important benefits, it also presents significant food safety concerns.
  • The more elongated and complex the chain is, the greater the risk of having foods go bad.
  • Effective sorting and quality analysis systems definitely can play an important role in ensuring food safety.

2.2 The General Benefits  

The general benefits of the optical sorter are numerous, and some of them are as follows:

  • Camera-based optical sorters can consistently detect and remove foreign material, unwanted rot, greening defects, blemishes, and damage. This ensures higher yields and a safer, more top-quality final product going to consumers. 
  • Sorting machines can increase processing capacity and lower labor costs, all while producing food of the highest quality and safety standards. 
  • Additionally, the camera-based technologies applied in the different optical platforms allow processors to target their needs in each step of the process specifically. 
  • Camera technology is constantly detecting defects present in materials, making sure of higher resolution, and the technology adopted will not stop rising in quality. 
  • Also, the ability to make use of data management in the use of machines means that real-time monitoring and adjustments of production lines can be done, providing higher level of efficiency.

2.3 Specific Benefits of Optical Sorting  

The usefulness and the importance of sorting machines have grown over time. For example, on the average, there are four sorting machines in a typical plant as of 2019, compared to one about ten years ago. 

As a result of this, the need for data collection has also risen, and optical sorters help to process information about products quicker, optimizing the process.

It also helps that the machines now have interfaces that are user friendly. 

A substitute in the agricultural industry  

The use of optical sorters in the agricultural sector is on the rise because the general skill level of the available labor is reducing, and these machines have to offset the lack of skilled workers.

Additionally, there are fewer people and less knowledge on the market, which forces growers to switch to sorters.  

In other words, you have to switch the machine on and provide sufficient bulk because the optical sorting machine does not get tired or need a coffee break.  

Apart from the shrinking pool of skilled labor, a sharp increase in market demand is also driving the use of these machines.

It is much easier to adjust an optical sorter to meet market demand.

Improved Business Processes  

An optical sorting machine gives you yet another compelling reason to be used because the machines improve your business processes.

Food safety is, after all, one of the essential parts of the story. An accurate sorter makes a crucial contribution to this. 

Additionally, you sort them before they go into the warehouse, before you wash them, once you peel them and then, lastly, when you process them into fresh fries and frozen products, says Alain.  

Increase of industries production line  

An optical sorter aids you in increasing something very crucial to the operations of your factory – the capacity of the factory’s production lines.

Newer models of optical sorters have the technology and capabilities to do this. 

“We are currently working on a free-fall machine. In it, we are installing an optical device consisting of eight lasers and more than 16 receivers,” says Steve Raskin of Optimum Sorting. 

Chapter 3: Optical Sorting Solution and Application by Industry

3.1. Applications of Optical Sorting Solution 

Using optical sorters in the food processing industry will help you minimize the inherent risks of contamination that come as a result of foreign materials or aflatoxins.

Because of this, optical sorters are a smart investment for manufacturers and processors. 

Due to the rapid growth in the food industry, there has also been an increase in the pressures facing it, such as efficiency, productivity, economic, and environmental pressures.

An ever-growing demand for food in the world has resulted in a very dynamic and complex global supply chain, one that generally rises to meet the demand but also has serious safety issues because of the sheer bulk of supplies.

It’s simple; the more complex the global chain of the food supply is, the more risk there is for the food to be contaminated, wasted, or even spoilt. 

For instance, the first three months of 2017 saw a massive recall of nuts and nuts based products in the European food industry.

Closely following were recalls of fruits and fruit-based products, vegetables, fish, and fish-based products.  

The reason for the recalls? Bacterial contamination. Apart from this, there were also recalls due to aflatoxins and unauthorized ingredients.

Bacterial contamination came in at 24% of the recalls; aflatoxins also weighed in with another 20%, and recalls due to unapproved ingredients were about 13%. 

3.2. Agriculture 

3.2.1. Seed sorting 

Seed sorting is a process that aims to get a final product that has a very high level of purity and quality.

To accurately predict or control such processes can be a daunting task, though a possible solution can come from a specially designed systems identification approach.

In this approach, you closely track the seed movements, allowing you to collect data about crucial process parameters easily. 

Generally, optical sorters ensure maximum germination of seeds.

They can do this by detecting seeds and removing unwanted colors, discoloration that might not be noticeable to you, shapes, and sizes that are defective and also foreign materials.  

The laser-like precision of these technologies ensures that your final seed quality is very high, skyrocketing the chances of consistent growth rates.  

Depending on what model you get, you can also successfully sort smaller seed varieties like carrot, onion, and lettuce.  

3.3. Plastic Recycling 

Sorting is very labor-intensive, and it is one of the most critical steps in the recovery of usable materials from the general waste stream.  

Mixed waste is usually too impure for any immediate reclamation, and because of this, you must separate it into the various types of paper, metals, and plastics. 

For some extensive recycling facilities, the sheer volume of potentially recyclable material justifies having expensive and incredibly complicated sorting machines in addition to human sorters.  

However, smaller facilities may have to choose between using human sorters or just technology. And to them, pre-sorting is a big help. 

The most basic sorting equipment is home tubs. If curbside recycling capabilities are available to homeowners, you will most likely empty the bins into larger, separated compartments on a recycling truck.  

In some places, it is an option for consumers to take recyclables to a transfer station, where they are responsible for doing most of the sorting.  

You can label roll-off containers with the products they carry, and loading the containers directly with trucks means there is no further handling of the waste before it gets to the recovery facility. 

3.4. Food Processing 

3.4.1. Identification of defects 

You can easily identify product defects using the sensor technology, and this means that your products have higher resolution and better contrast.

Additionally, the technology improves the quality of food and its safety.  

Also, real-time monitoring and better control of production lines improve efficiency, and this is possible because these machines give you the ability to use data management systems when using them.

3.4.2. Enhancing food safety  

Being able to sort effectively and analyze properly plays a crucial role in enhancing food safety. 

The process of separation for most produce begins in the field, and it is initiated when you sight bigger and more obvious defective material that should not be allowed into the plants used in processing.  

That said, you can easily spot and remove foreign materials such as stones, and in the field.

Chapter 4: Optical Sorting Equipment 

4.1 Factors to Consider When Choosing the Right Optical Sorter Equipment  

Choosing the right equipment – If you are an MRF operator, you should decide what your business goals are when making plans to purchase new sorting equipment.

Also, you must diligently assess whatever equipment you want to buy to see how it would help you achieve the set goals.  

Understand the differences and applications – The latest robotic sorters also have some of the same technology used in optical sorters for years.

Both systems possess high-speed, high-resolution cameras and near-infrared optics that enable them to identify and sort efficiently.

But there is also an area of difference; optical sorters make use of air jets to change the direction of material towards the desired location.

Robotic sorters, however, use an armature that sucks or grapples, and it uses its capabilities to pick up one item and take it to the predetermined location. 

4.2. Choosing the right equipment depending on the applications  

Whether you’re processing solid, industrial, commercial or construction and demolition waste, the equipment you need will depend on the following factors; 

  • The waste stream, 
  • Blend of materials present in the waste, 
  • The scale of operation 
  • Level of contaminants present in the waste.   

If you are working with metal, organics, or plastic, optical sensors can help sort and separate whatever contaminants are present.

Near-infrared spectroscopy has color sensors that can detect materials using color recognition. 

Because of such capabilities, they are ideal for sorting several materials because they detect how various materials reflect light.

As such, you can use them to identify elements that would be otherwise undetectable.

Eddy currents help to sort non-ferrous metals and other materials.

The different physical properties of materials mean that some non-ferrous metals are easier to separate than others. 

Induction sorting can also complement magnetic sorting and eddy current separation by recovering residual materials. Induction sorting detects elements by processing requirements, using sensors to locate materials like stainless steel. 

X-ray technology is another option if you prefer to separate materials by density. It is suitable for glass, metal, stone, and other solid particles.

X-rays are generally able to detect the density of materials and also particle size to separate elements mixed in together.

Examples of such materials are steel, plastic, etc.

Ballistic separators help with the sorting of paper mixed with bottles and cans.

The materials are fed on several paddles to scale the contents down into small fractions.

The fractions are then fed to other machines, for instance, near-infrared sorters, making them an excellent choice for detecting contaminants.  

Bottom Line 

The information you got from this free guide will help you make the right choices in enhancing your production process.

You have everything you need to make your business more productive – from how you can use optical sorters to the various types available. 

Your duty at Key Technology is to ensure you take this step that your business needs and choose a suitable optical sorter.

Refer to this guide to make that critical decision, and we hope you choose wisely.

Edon Zheng

Edon Zheng

Hi, I'm Edon, the co-founder of sgsorter.com, I've been running a factory in China that makes and exports color sorters for 8 years now, and the purpose of this site is to share with you the knowledge related to color sorters from a Chinese supplier's perspective.

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