Chapter 56: The Scanner Technology Evolution |
Brief Summary |
The journey of barcode scanning technology---from the early days of laser-based readers to today's sophisticated image-based systems---has fundamentally reshaped how industries track and manage assets. Modern imagers, equipped with advanced algorithms, can read damaged 2D codes using powerful error correction techniques like Reed-Solomon. However, Code 39, the iconic 'Code 3 of 9,' was designed in an era when laser scanners were the cutting edge, and its reliance on a self-checking mechanism rather than embedded redundancy means that while it remains rugged and reliable under ideal conditions, it lacks the recovery capabilities that make 2D codes resilient in harsh, real-world environments. This chapter explores this technological evolution through practical applications across multiple industries, illustrating how Code 39's design strengths and inherent limitations have shaped its role in the modern barcode ecosystem. |
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1. Introduction: The Barcode That Would Not Die |
In the pantheon of automatic identification technologies, few symbols command as much respect and recognition as Code 39. Known colloquially as 'Code 3 of 9,' this alphanumeric barcode has been a workhorse of industry since its introduction by Intermec Corporation in 1974. It was the first barcode symbology capable of encoding both letters and numbers, a breakthrough that opened the door to a vast array of applications beyond the simple numeric tracking of grocery items . |
For decades, Code 39 was the gold standard. It graced the labels of military equipment for the U.S. Department of Defense, tracked automotive parts moving through complex supply chains, and identified patients in healthcare settings. Its popularity stemmed from a powerful combination of simplicity and robustness. The '3 of 9' in its name refers to its core encoding principle: each character in the barcode is represented by nine elements (five bars and four spaces), of which exactly three are wide and the other six are narrow . This design is what gives Code 39 its famous self-checking property. |
However, the world of barcode scanning has undergone a revolution. The bulky laser scanners of the 1970s and 80s have given way to high-resolution, image-based readers that function like miniature cameras. These modern imagers, powered by sophisticated processing chips, can perform feats that were once the stuff of science fiction. They can capture a 2D code partially obscured by a torn label, smeared with grease, or even scratched directly onto a metal part, and use advanced mathematics to 'fill in the blanks' and recover the encoded data. The key to this modern magic is an error correction algorithm known as Reed-Solomon, a technology that adds redundant data to the code so that the original message can be reconstructed even if a significant portion of the symbol is damaged. |
This is where Code 39's story diverges from that of its modern 2D counterparts. Code 39 was designed for the scanners of its era. Its self-checking property is a form of error *detection*---it prevents a misread character from being misinterpreted as a different, valid character, but it cannot *reconstruct* data that is missing or illegible . While a modern imager can sometimes read a heavily damaged Code 39 symbol thanks to better optics and image processing, the symbology itself contains no mechanism to recover from the kind of severe damage that a 2D code with Reed-Solomon correction can shrug off . |
This chapter will take you on a journey through the evolution of barcode scanners, from the laser to the imager, and examine how this technological shift has impacted the use of Code 39 across various industries. We will see that while Code 39 is often less dense and less forgiving than newer symbologies, its legendary durability and simplicity ensure its survival in specific niches where reliability and ease of printing outweigh the need for ultra-high data density or extreme error correction. |
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2. The Birth of the Scanner: From Movie Sound to the Laser |
To understand the scanner technology that shaped Code 39, we must first look back to its origins. The very first barcode readers were not sleek, handheld devices but were cobbled together from surprising sources. One of the earliest prototypes was derived from an old DeForest movie sound system, where a photosensitive tube that was originally designed to detect variations in light for audio tracks was repurposed to detect light reflected from printed symbols . |
In the early 1960s, the railway industry experimented with a system that used colored strips on railcars to encode a 10-digit number. This early system used an arrangement of colored lights and intensity-detecting sensors to read the codes. Though this specific system failed commercially, it laid the groundwork for future developments. The real breakthrough came with the invention of the laser. The laser provided a highly focused, intense beam of light that could be easily swept across a printed barcode. The reflected light, varying in intensity based on the pattern of black and white bars, was converted into an electrical signal that a decoder could interpret . |
This laser-based approach gave us the 'barcode scanner' as we most commonly remember it. These scanners were primarily designed to read one-dimensional (1D) linear barcodes. For the longest time, the technology available to scan barcodes meant they were limited to those familiar linear arrangements of thick and thin black lines . Code 39, born in this era, was perfectly optimized for this technology. Its encoding scheme, based solely on differentiating between 'wide' and 'narrow' bars, was a perfect match for the binary nature of a laser scan. The scanner's decoder simply needed to measure the relative widths of the bars and spaces to reconstruct the code. This simplicity made Code 39 reliable and easy to implement with the hardware of the day. |
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3. The Anatomy of a Barcode Scanner |
A classic barcode scanner, regardless of its complexity, is built around three essential components: a light source, a sensor, and a decoder . |
The Light Source: This is the element that illuminates the barcode. In the early days, this was typically a laser. The laser's coherent, narrow beam was ideal for precisely sweeping across the alternating dark and light elements of a barcode. |
The Sensor: This component detects the variations in the light reflected from the barcode. When the laser beam hits a white space on the label, a large amount of light is reflected back to the sensor. When it hits a black bar, very little light is reflected. The sensor converts these varying light levels into an electrical signal. |
The Decoder: This is the 'brain' of the scanner. It takes the raw electrical signal from the sensor and translates the width of the bars and spaces into the characters they represent. For a Code 39 symbol, the decoder first identifies the start and stop characters---the asterisk (`*`)---to determine the direction of the scan. It then measures the relative widths of each of the nine elements in a character. Because Code 39 is a 'discrete' symbology with a gap between each character, the decoder can easily parse the data . |
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3.1. Laser Scanners: The Standard for Code 39 |
Laser scanners came in various forms. Early versions were 'fixed raster' scanners, which used a combination of mirrors to create a 2D scanning pattern that could read a 1D barcode from any angle. These became common in grocery store checkouts . For industrial applications, handheld laser scanners---often called 'RF guns' or 'RF scanners'---became ubiquitous . It's important to note that the 'RF' in the name refers to how they communicate with a computer (via a radio frequency signal), not how they scan. |
These handheld devices were a staple in warehouses and factories for decades. Their ability to instantly read a Code 39 label from a short distance made them invaluable for inventory management and tracking. However, as technology continued to advance, the limitations of laser-based reading began to surface. They were, for the most part, limited to reading 1D barcodes. They struggled with codes that were dirty, damaged, or poorly printed. And they couldn't read the new generation of 2D codes like Data Matrix and QR Codes that were starting to enter the market. |
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4. The Shift in Technology: The Rise of the Imager |
The next major leap in scanner technology came with the introduction of Charge-Coupled Device (CCD) scanners in the 1990s. These devices didn't use a laser. Instead, they used a single row of tiny photocells on a chip to function like a 1D camera. When you aimed a CCD scanner at a barcode, it would capture the entire image of the label at once. This was a significant improvement because it meant the scanner no longer relied on a moving laser beam. CCD scanners were cheaper to manufacture than laser scanners and quickly became popular . |
However, the real revolution came when the CCD technology was expanded into two dimensions. By creating a 2D array of photocells, manufacturers could create 'imagers' that functioned like digital cameras. These imagers could capture the full picture of a barcode in a fraction of a second. This opened up a whole new world of possibilities. Suddenly, scanners weren't just reading 1D barcodes; they could read 2D matrix codes like Data Matrix, QR Code, and PDF417, which pack vastly more data into a smaller space . |
The shift from laser scanners to image-based readers is one of the most significant changes in the industry's history. With a laser scanner, the decoding happens in real-time based on the timing of the reflected beam. With an imager, the device captures a full image and then runs sophisticated image-processing algorithms to find and decode the barcode . This software-based approach is far more flexible. An imager can be trained to recognize a barcode even if it's rotated, partially obscured, or printed on a curved surface. |
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4.1. The Hardware: CCD and CMOS |
The two main types of sensor technology used in imagers are CCD and CMOS (Complementary Metal-Oxide-Semiconductor). Both are essentially digital cameras, but they differ in how they capture and process the image. CMOS sensors are generally cheaper, use less power, and are more common in modern devices . The resolution of these imagers continues to improve, allowing them to read smaller and smaller symbols. A wide range of high-resolution CCD and CMOS cameras with sophisticated embedded processors has transformed logistics and supply chain management . |
4.2. The Software: The Key to Modern Decoding |
The real power of an imager lies in its software. When the imager captures an image, it doesn't just look for black and white bars. It applies a whole series of algorithms to clean up the image and decode the data. For example, imagine a barcode on a box that is slightly out of focus. The imager can apply a sharpening filter to make the edges of the bars clearer. If the barcode is printed on a shiny metallic surface, causing glare, the software can use algorithms to remove the glare and recover the underlying pattern. |
These advanced imaging capabilities have fundamentally changed the user experience. A modern imager can instantly read a barcode that would have been a 'no-read' for a laser scanner. As one industry expert noted, 'The $29 USB barcode scanner reads both fine. The beat-up Symbol LS2208 someone dropped off a mezzanine reads both fine. Scanner compatibility hasn't been a meaningful differentiator since 2010' . While this quote highlights the widespread compatibility of modern scanners, it also underscores the point: hardware compatibility is now a given, and the real differentiator is the decoding software's ability to handle challenging codes. |
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5. The Power of Modern 2D Codes: Reed-Solomon Error Correction |
The software in modern imagers doesn't just make it easier to read a clean barcode; it also enables the use of sophisticated error correction that makes barcodes nearly indestructible. The dominant error correction method in 2D barcodes is the Reed-Solomon algorithm, developed in 1960 by Irving Reed and Gustave Solomon . |
The principle behind Reed-Solomon is brilliantly simple and powerful. It works by adding redundant data, called 'error correction codewords,' to the original message. When the scanner reads the symbol, it uses these extra codewords to check the accuracy of the data. If some of the data is missing or damaged---say, a scratch runs through the middle of the QR Code---the decoder can use the redundant information to mathematically reconstruct the missing parts . |
5.1. How Reed-Solomon Works (In Simple Terms) |
Imagine you have a very long word written on a piece of paper, but you're afraid someone might spill coffee on it. To protect it, you write the word twice on the paper, but in a complex pattern. If someone spills coffee on half the paper, you can still reconstruct the whole word by looking at the other half. Reed-Solomon does something similar, but far more mathematically efficient. |
A crucial rule of Reed-Solomon is that for every two error correction symbols added, the system can correct one unknown error (like a scratch) or two known erasures (like a missing piece of the label) . Different 2D symbologies implement this to varying degrees. For example, Data Matrix uses a fixed level of error correction that varies based on the size of the symbol. A very small Data Matrix symbol might be able to recover about 25% of the data, while a larger one can recover up to 28% . PDF417 offers configurable security levels, from 0 to 8, where the number of error correction codewords doubles with each level. At its highest level, a PDF417 code can contain a staggering 512 error correction codewords, allowing it to recover from severe damage . QR Codes and Aztec Codes also use Reed-Solomon, with Aztec offering configurable correction levels from 5% to a massive 95% of the data capacity, which is why it's the standard for resilient applications like airline boarding passes . |
This is a world away from Code 39. While a Code 39 label can be made more reliable by using a Modulo 43 check digit, this only allows the scanner to *detect* that an error has occurred. It cannot *correct* it. If the printer smears one of the bars or a scratch obscures a portion of the code, the scanner may simply fail to read it. In a harsh industrial environment, where labels are subjected to grease, rain, and physical abrasion, this lack of error correction can be a serious vulnerability. |
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6. Code 39: A Symbol of the Old Guard |
Code 39's design was heavily influenced by the technology of the 1970s. Its strengths and weaknesses are a direct reflection of the era in which it was conceived. To understand why it remains in use, we must look at its core technical features. |
6.1. The Self-Checking Property |
The most celebrated feature of Code 39 is its 'self-checking' property. This means that the symbology is designed so that a single printing defect, such as a bar being slightly too wide or too narrow, cannot accidentally transform one valid character into another valid character . |
Each character in Code 39 has a very specific pattern of five bars and four spaces. Because the patterns are distinct, the decoder can often reject a character that has been corrupted. For example, if a wide bar is mistakenly printed as a narrow bar due to poor ink spread, the resulting pattern might not match any valid character in the Code 39 set. The decoder will then flag this as an error, ensuring that the wrong data isn't sent to the computer system . This self-checking nature is why a check digit is technically optional in Code 39, although many applications, such as the U.S. Department of Defense's LOGMARS system, mandate its use for extra security . |
6.2. The Wide-to-Narrow Ratio: Simplicity is Strength |
Code 39's robustness comes from its simplicity. The symbology only requires the scanner to differentiate between two widths: narrow and wide. A common wide-to-narrow ratio is 2.5:1, meaning a wide bar is 2.5 times the width of a narrow bar . This simplicity is a huge advantage in harsh environments. As a developer who has worked extensively with barcodes noted, Code 39's simple two-width scheme means that 'when a label gets smeared with hydraulic fluid or rain-soaked, the scanner can still tell the difference because the ratio only needs to be approximately 2.5:1' . |
This stands in stark contrast to a more dense symbology like Code 128, which uses four different bar widths . A small smudge that turns a width-2 bar into a width-3 bar in Code 128 can produce a completely different character, leading to a misread. Code 39's simple binary choice between 'wide' and 'narrow' makes it remarkably tolerant of variations in printing quality and surface wear. |
6.3. Full ASCII Extension: A Double-Edged Sword |
The base Code 39 symbology can only encode 43 characters: A-Z (uppercase only), 0-9, and seven special characters (`- . $ / + % space`) . In the late 1980s, an extension called 'Extended Code 39' (or 'Full ASCII Code 39') was developed to encode the entire 128-character ASCII set, including lowercase letters and a wider range of punctuation symbols. It does this by encoding each extended character as a pair of regular Code 39 characters. For example, a lowercase 'a' is represented by the combination '+A' . |
While this extension greatly increased Code 39's versatility, it came with a significant drawback: it makes the barcode much longer. Because a single character can take up the space of two, a label encoded with Extended Code 39 can be up to double the length of a standard Code 39 label . This reduced data density can make the label impractical for small items. Furthermore, it can confuse scanners that aren't specifically configured to read the extended format; they might interpret the two-character combination as two separate characters instead of one . In practice, many industrial applications still prefer the simpler, more compact base Code 39 for its reliability. |
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7. Code 39 in the Real World: Industrial Applications |
Despite the rise of 2D codes, Code 39 remains a pervasive presence in many sectors. Its longevity is a testament to its core strengths: it's simple, reliable, and 'good enough' for many uses. |
7.1. The US Military: The LOGMARS Standard |
Perhaps Code 39's most significant and longest-standing endorsement comes from the U.S. Department of Defense. The LOGMARS (Logistics Applications of Automated Marking and Reading Symbols) program mandated the use of Code 39 for all government property marking. This decision, enshrined in standards like MIL-STD-130, has made Code 39 the de facto barcode for military logistics for decades . The military has billions of dollars invested in inventory and logistics systems built around Code 39. Changing to a different symbology would require a massive, costly infrastructure overhaul. As long as the existing systems are adequate, Code 39 will remain in place. For military applications, where data density is less critical than rugged reliability and where a robust, proven standard is paramount, Code 39 continues to serve. |
7.2. The Automotive Industry: The AIAG Standard |
The automotive industry also adopted Code 39 early on, making it a standard for parts labeling throughout the supply chain via the Automotive Industry Action Group (AIAG) standards . In a factory, codes are often printed directly on metal parts or on labels that are subjected to oil, grease, and extreme temperatures. Code 39's tolerance for poor printing and wear makes it ideal for these conditions. A car engine block with a dot-peen (direct part marking) Code 39 can be easily scanned on the assembly line. While newer factories are increasingly adopting Data Matrix for its high density and error correction, the legacy supply chain is deeply entrenched with Code 39, and it remains the expected standard for many suppliers. |
7.3. Healthcare: The HIBC and Beyond |
The healthcare sector, particularly in the United States, has a long history with Code 39. The Health Industry Bar Code (HIBC) standard, used to label medical devices, pharmaceuticals, and patient identification bracelets, is built upon Code 39 . In a hospital setting, the ability to quickly and accurately identify a patient or a medication is a matter of life and death. The human-readable text at the bottom of a Code 39 label provides a critical backup in case the barcode cannot be scanned, a feature not always present with 2D codes. Furthermore, many hospitals use older, but still functional, laser scanners that are perfectly capable of reading Code 39. The investment in these scanners and the systems they interface with is substantial. Code 39's reliability and widespread installed base make it a safe and practical choice for many healthcare applications. |
7.4. General Manufacturing and Tracking |
Beyond these major industries, Code 39 is used in countless internal tracking applications. Libraries use it to track books. Manufacturers use it for work-in-process tracking on the factory floor. Equipment management and document routing systems also rely heavily on it . For any application where the barcode is printed on a label and scanned in a controlled environment, Code 39 is more than sufficient. It is simple to generate, easy to print, and universally readable. As one developer summarized, for any item that stays in the building (internal tracking), Code 39 is a solid choice: 'printed large. It'll survive conditions that would make a Code 128 label illegible' . |
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8. When Code 39 Fails: The Impact of Limited Error Correction |
The most significant vulnerability of Code 39 is its lack of true error correction. While its self-checking property helps prevent misreads, it cannot reconstruct damaged data. This limitation becomes critical in several scenarios, especially as scanner technology has evolved and raised expectations. |
8.1. The Harsh Environment Problem |
Consider a logistics warehouse where packages are exposed to rain, dirt, and physical impact. A Code 39 label that is smeared or torn might be unreadable. The scanner will simply return a 'no-read,' causing a delay in the sorting process. In contrast, a 2D code with Reed-Solomon correction could still be scanned . As the developer noted, Code 39's two-width scheme makes it durable, but it's not invincible: 'Code 39 can be easily damaged and distorted like any linear barcode. It is a width-encoding code 39 symbology which can be quickly become unreadable on a slight ink-spread during printing' . |
8.2. The Direct Part Marking (DPM) Challenge |
One of the most significant trends in modern manufacturing is direct part marking (DPM), where barcodes are etched or stamped directly onto the surface of a metal, plastic, or glass part using laser or dot-peen technology. These marks are permanent and can withstand the rigors of the part's lifecycle. However, DPM marks are often low-contrast and can be difficult to read. The reading of DPM codes is a primary driver for the adoption of image-based barcode readers . These imagers, using advanced lighting and algorithms, are specifically designed to read 2D Data Matrix codes, which are the industry standard for DPM . Data Matrix codes have built-in Reed-Solomon error correction, so even if the dot-peen mark is a bit smudged or has a scratch, the data can still be recovered. |
Code 39 is not well-suited for DPM. It's a linear code, meaning it's longer and requires more space on the part. More importantly, it has no error correction. If a dot-peen mark is poorly executed or becomes worn, the Code 39 symbol becomes unreadable. For critical parts tracking, this lack of redundancy is a deal-breaker. |
8.3. The Density Problem |
Another key limitation is data density. Code 39 is a very wide symbology. Each character takes up a significant amount of horizontal space. For a 10-character code, a Code 39 barcode is roughly 40% wider than an equivalent Code 128 . As one developer put it, 'Code 39's density is the problem. If your label is smaller than 2 inches wide and you need 12+ digits, Code 128 is the only option that fits at scanner-readable resolution' . In many modern applications, where product labels are shrinking and more information needs to be encoded, Code 39's physical size is a major drawback. A lipstick tube or a medical vial simply may not have enough surface area for a large Code 39 label, making a denser Code 128 or a 2D code the only viable choice . |
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9. The Modern Imager: Leveling the Playing Field |
The introduction of the modern image-based scanner has done something remarkable: it has made the hardware differences between symbologies less relevant. A modern imager can read a Code 39 symbol just as easily as a QR Code. It can correct for rotation, poor contrast, and even some damage using software enhancements. This capability has extended the useful life of Code 39 in many applications. A smudged Code 39 label that would have been a 'no-read' for a laser scanner might be perfectly decodable by a modern imager with its advanced image processing algorithms . |
9.1. 'No-Read' Analysis and Process Improvement |
One of the biggest advantages of image-based scanners is their ability to capture and store an image of the barcode for every scan. This feature is invaluable for process improvement. When a scanner fails to read a barcode ('no-read'), the operator can review the image to determine the cause. Was the label tornWas the print head cloggedWas there poor lightingThis ability to analyze failures helps identify and fix problems in the labeling and printing process . This capability is not exclusive to 2D codes; imagers capture images of Code 39 labels as well, making them easier to troubleshoot. |
9.2. Can an Imager 'Correct' a Damaged Code 39 |
This is the central question. Can a modern imager replicate the effect of Reed-Solomon error correction for Code 39The answer is no, but it can come close in many scenarios. The imager's software can use algorithms to improve the contrast, sharpen the edges, and even 'guess' the boundaries of a smeared bar. It can also use pattern recognition to infer a bar's width if it's partially obscured. This means an imager can read a Code 39 label that is in significantly worse condition than a laser scanner could. |
However, if the damage is severe enough that a bar is completely missing or a chunk of the label is torn off, the imager will fail. The decoder has no mathematical basis to reconstruct the missing data. It can't 'invent' a bar that isn't there because there's no redundant information in the code to tell it what it should be. A 2D code with Reed-Solomon, on the other hand, can reconstruct that missing bar. So, while the imager levels the playing field and extends Code 39's life, it cannot overcome its fundamental lack of error correction. |
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10. Industry Cases: Where Code 39 Survives and Thrives |
Despite the advantages of newer symbologies, Code 39 retains a firm foothold in several key areas, often for reasons that have little to do with technology. |
10.1. Case Study: Government and Defense Logistics |
As mentioned, the LOGMARS program is the ultimate example of Code 39's staying power. The U.S. military has an enormous installed base of equipment, documentation, and software systems that rely on Code 39. The cost and logistical nightmare of transitioning to a new symbology would be astronomical. In this context, Code 39 isn't just a barcode; it's a legacy system that is deeply integrated into the fabric of defense logistics. Even if the military wanted to switch to Data Matrix for its error correction, the investment in new printers, new scanners, new software, and re-labeling millions of assets is prohibitive. Code 39 will likely remain a standard for the foreseeable future simply because it's 'good enough' and it's already there. |
10.2. Case Study: Automotive Assembly and Legacy Supply Chains |
Similar dynamics are at play in the automotive industry. Major automakers and their tier-1 suppliers have standardized on Code 39 for parts identification. The AIAG standards are built around it . Suppliers are required to print Code 39 labels on their parts, and the assembly line scanners are configured to read them. While many suppliers are also using Data Matrix for internal tracking, the external-facing label must often be Code 39 to be compatible with the customer's systems. This is a classic case of network effects and supply chain inertia. |
10.3. Case Study: Internal Asset Management and Low-Data Applications |
For a company tracking its own internal assets, like laptops, furniture, or work-in-progress parts, Code 39 remains a highly practical choice. The labels are printed in-house on standard office printers. The codes don't need to be extremely small or hold large amounts of data. The environment is relatively controlled. And the scanners are cheap and ubiquitous. As one practitioner noted, for 'anything that stays in the building,' Code 39 is a reliable workhorse . It's simple to set up, easy to print, and the self-checking property provides a level of security that's adequate for internal use. |
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11. The Future: Coexistence, Not Extinction |
The future of Code 39 is not one of extinction but of coexistence. It is a mature, stable technology that will continue to serve specific niches where its strengths are valued and its weaknesses are not a critical factor. The rise of modern imagers, rather than killing off Code 39, has actually extended its useful life by making it more robust in the face of minor damage. |
11.1. The Role of the Imager in Extending Code 39's Life |
Modern imagers are a testament to the power of software to compensate for hardware limitations. By capturing a high-quality image and applying sophisticated algorithms, they can read Code 39 labels that would have been unreadable even a decade ago. This means that in many environments, the practical reliability of Code 39 has increased, even though the symbology itself hasn't changed. For businesses that have invested heavily in Code 39-based systems, upgrading their scanners to imagers is a cost-effective way to improve system performance without changing their barcodes. |
11.2. The Generational Divide: Old vs. New |
A generational divide is clearly visible in the barcode world. Older engineers and system architects who came of age in the 1980s and 90s are often more comfortable with Code 39 and Code 128. They understand their logic and trust their reliability. Younger engineers, who grew up with smartphones that can read QR Codes, see 2D symbologies as the natural choice. They value the high data density, error correction, and the ability to encode URLs and other complex data. This generational divide is shaping the transition to 2D codes, which is happening slowly but surely. |
11.3. Code 39's Legacy and Continued Relevance |
Code 39's legacy is secure. It was the first alphanumeric barcode and a key enabler of modern logistics. Its simple design and self-checking property made barcoding accessible and reliable. It will continue to be a relevant tool for internal tracking, government applications, and any use case where low cost, simplicity, and ruggedness are more important than data density or extreme error correction. As the technology landscape shifts, Code 39's role will likely become more specialized, but it will not disappear. It will be the 'old reliable' that you can always count on, even if it's not the flashiest option on the shelf. |
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12. Detailed Summary |
The journey of barcode scanning technology is a fascinating story of evolution, from the rudimentary laser-based systems of the 1970s to the sophisticated, image-based readers of today. This evolution has fundamentally reshaped the capabilities and applications of barcodes, creating a stark contrast between the durability of older linear codes like Code 39 and the resilience of modern 2D symbologies. |
The Hardware Revolution: |
The progression from laser scanners to CCD imagers and then to CMOS-based imagers was a pivotal shift. Early laser scanners, while effective for clean, linear barcodes, were limited in their ability to handle damage. They required a clear, undamaged path of alternating bars and spaces. The introduction of imagers, which function as digital cameras, moved the decoding process from the hardware to the software. This allowed for advanced image processing, enabling the reading of codes that were rotated, dirty, or poorly printed. The ability to capture and store images of 'no-reads' also provided invaluable feedback for process improvement, allowing businesses to identify and fix problems in their labeling systems. |
The Software Revolution and 2D Codes: |
The software revolution was most impactful for 2D codes. Symbologies like Data Matrix and QR Code are built upon the Reed-Solomon error correction algorithm. This mathematical technique adds redundant data to the encoded message, allowing the decoder to reconstruct the original data even if a significant portion of the symbol is damaged. This is a fundamental difference from Code 39. Reed-Solomon makes 2D codes virtually indestructible in many real-world scenarios, making them ideal for direct part marking on metal, parts tracking in harsh environments, and any application where label damage is expected. |
Code 39's Technical Identity: |
Code 39 is a product of its era. It was designed to be read by laser scanners and is built on a simple binary logic: wide vs. narrow bars. This simplicity is its greatest strength. The 'self-checking' property ensures that a single printing defect won't cause a misread, as the decoder can easily reject invalid character patterns. Its wide-to-narrow ratio of approximately 2.5:1 means it can tolerate smudges and poor printing that would confuse more dense symbologies like Code 128. However, this simplicity is also its greatest weakness. It lacks the data density for small labels and, most critically, it lacks any error correction. It can only detect errors, not correct them. The Extended Code 39 variant, which supports all 128 ASCII characters, comes at the cost of even lower density and potential scanner compatibility issues. |
Code 39 in Industry: Strengths and Limitations: |
Code 39's industrial applications are a testament to its longevity. Its use in the U.S. military's LOGMARS program and the automotive industry's AIAG standards are the strongest examples of its staying power. In these cases, the cost and complexity of changing a mature, deeply integrated system are immense. Code 39 remains the standard because it is 'good enough' for the task and already ubiquitous. In healthcare, its use in the HIBC standard for medical devices and patient safety is driven by the need for human-readable text as a backup and compatibility with older equipment. Its application in internal asset tracking for libraries, factories, and offices is common, as it is simple, cheap, and easy to generate. |
However, Code 39's limitations are becoming more pronounced. In environments where labels are subject to severe damage, like wet or abrasive conditions, its lack of error correction leads to 'no-reads' that cause delays. For small products like lipstick tubes or medical vials, its large physical footprint makes it impractical. The industry trend toward direct part marking (DPM) with low-contrast, etched symbols is a space where Code 39 is largely unsuitable, as the marks are often low-contrast and lack the redundancy to compensate for printing imperfections. Modern 2D Data Matrix codes, with their built-in error correction, are the standard for DPM. |
The Effect of Modern Imagers on Code 39: |
The advent of the modern imager has not been a death knell for Code 39. Instead, it has been a kind of life support, extending its practical utility. A modern imager can use software to compensate for some of the damage that would have been fatal to a laser scanner. It can improve contrast, sharpen edges, and even infer bar widths in many cases. This means a dirty or smudged Code 39 label is now far more likely to be read than it was in the past. Furthermore, imagers allow for 'no-read' analysis, helping businesses identify process issues. However, there is a hard limit: the imager cannot reconstruct data that is physically missing. If a bar is completely torn off, the imager has no mechanism to guess what it was. |
The Future: A Coexistence of Technologies: |
The future of barcode technology is one of coexistence. Code 39 is not going away. It is an established, reliable standard that will continue to be used in applications where its strengths outweigh its weaknesses. Modern imagers are making it more robust and extend its viability. 2D codes, however, are the future for new applications, especially those requiring high data density, error correction, and direct part marking. The industry is moving toward a multi-symbology future where the choice of barcode is determined not by the scanner's capabilities, but by the specific requirements of the application---a future where Code 39 and Data Matrix can, and will, exist side-by-side. |
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13. Conclusion |
The evolution of scanner technology is a powerful reminder that in the world of engineering, the best solution is not always the newest or the most technically advanced. Sometimes, the simplest solution---the one that is robust, well-understood, and deeply integrated---is the one that endures. Code 39's journey from the standard-bearer of alphanumeric barcoding to a specialized tool in a world of 2D codes is a classic case of this dynamic. It was built for the laser scanners of a bygone era, and its simplicity made it a legend. As technology advanced, its limitations became apparent, but instead of vanishing, it adapted. The modern imager gave it a new lease on life, allowing it to work in a world it was never designed for. And in the end, its sheer ubiquity and reliability ensure that this iconic 'Code 3 of 9' will continue to be part of our technological landscape for decades to come, a living piece of history in the digital age. |
cs@easiersoft.com