Software analysis DRIVES pharmaceutical inspection of capsules and containers
By John Haystead, Contributing Editor
Searle Pharmaceuticals (Cagues, Puerto Rico) is evaluating a new fuzzy-logic-based image-processing system for several high-speed, 300-bottle/minute tablet-packaging assembly lines. The vision-inspection system is capable of simultaneously counting and identifying individual tablets or capsules before they are passed on for final bottling and shipment. In addition to preventing underfilling of bottles, by scanning a less-than-1-mm-wide color-coded band on each tablet, the system can prevent accidental cross-contamination between different product types dispensed by the same assembly machine.
The inspection system is a customized version of the InspectRx in-line automated vision system designed and manufactured by American SensoRx Inc. (Glen Rock, NJ). InspectRx systems are used to inspect pharmaceutical tablets, capsules, packaging containers, and bottles (see Fig. 1). They can check for color consistency, size, broken or inferior tablets, and blister/seal integrity. In addition, the systems can confirm the accuracy of lot number/expiration dates, orientation and integrity of packaging such as bottle caps, and the reading and verifying of arbitrarily oriented text and barcodes.
For Searle, the InspectRx system is being integrated and tested with the Lakso Inc. (Leominster, MA) Reformer slat-filler dispensing machine, which dispenses product at the rate of 96 capsules, six times a second (see Fig. 2). Says Reynaldo Garcia, project engineer for system integrator, Caribbean Instruments Engineering in Puerto Rico, "We were impressed by the fact that the system is largely software-based as opposed to processor and filter hardware intensive. The system is also unique in that it doesn`t require a separate image processor. Because of the resolution of the algorithms, we can actually get more image detail than previously possible using only the system`s Pentium II CPU."
The Lakso dispensing machine is organized into six rotating bars or "slats"; each slat is further divided into two rows of individual cavities approximately 3/4 in. apart that contain the capsules. In total, 96 capsules are dispensed per bar. Capsules are initially loaded into the bars from a vibrating hopper. However, because a few cavities may occasionally not be loaded, the bars must be continuously monitored to prevent underfills.
Originally, this capsule inspection was done manually. Then, a Lakso Microscan laser system was used that passed a laser beam through pin-sized holes in each slat cavity to verify that they were filled. Although reliable, as described by Garcia, the system incorporated 96 light-emitting-diode (LED) sensors. These sensors were difficult to set up and troubleshoot, and, if not kept in perfect alignment, they generated inspection errors. As a result, the system was not able to detect flawed capsules or verify that the correct capsules were dispensed. In contrast, the InspectRx system can count and identify the capsules and can detect foreign material or broken capsules in the product flow.
Mid-air flight
The fact that the capsules cannot be imaged while embedded in their cavities presents a challenge to the vision inspection system. To deal with this, the InspectRx system scans all the capsules in mid-air as they are dropped into sort-and-fill chutes. Rather than rejecting individual capsules, the system continuously tracks the capsules as they are loaded into individual bottles. If filled incorrectly, the entire bottle is rejected from the line.
For the Searle application, synchronous images are acquired by four 720 ¥ 480 ¥ 24-bit JVC (Elmwood Park, NJ) TK1070U CCD video cameras. The InspectRx system divides each pixel into 200 subelements, thereby providing for an actual resolution of 144,000 ¥ 96,000. By using additional magnifying camera lenses, the system is capable of reaching nanometer-level sensitivities. American SensoRx has also enhanced the camera`s color-to-voltage conversion matrix for improved hue-saturation intensity measurements.
The cameras are positioned along the axis of a 42-in. dispensing bar. Says American SensoRx`s founder, chairman, and CEO Sabrie Solomon, "Although the field of view of the cameras is adequate to do the job with only three cameras, four are used to allow for planned future additional inspections of capsule length, width, and depth."
Illumination important
As observed by Solomon, light distribution, a critical aspect of the system`s design, influenced the company to design its own illumination system using a diffuse light source that generates 288,480-cycles/s light. "This extremely high-frequency light source is required to prevent any interference from the ambient (60-Hz) environment light," says Solomon.
A light-hood device controls the illumination environment by reflecting light from the bottom and side of the line conveyer against another semicircular hood to provide indirect or diffuse lighting. The position of the light and its light curtains are adjusted to eliminate specular reflections and to maintain constant brightness levels on the object throughout its range of motion in the image frame.
Image processing
The cameras are linked via RS-232 links to Integral Technologies (Indianapolis, IN) FlashPoint 128 frame-grabber boards for signal digitization at 30 frames/s. American SensoRx has stabilized the boards` operation with its own software to remove drift.
Light-presence/absence sensors are used to synchronize frame capture. According to Solomon, any type of standard triggering sensor can be used, such as laser, infrared (IR), or fiberoptic, with the sensor set to trigger on either the leading or trailing edge of the imaged object. When interrupted, the sensor sends a signal to the frame-grabber board to synchronize data acquisition. To fine-tune the data-acquisition rate, the InspectoRx system also tracks and regulates the speed of the conveyor.
Data are then passed to a National Instruments AT-MIO-16E-10 data-acquisition (DAQ) board, which captures 12-bit data at 1.2 million samples/s. The system can analyze up to 30 frames/s, which, depending on the complexity of the product, typically translates to 15 objects/s. Faster speeds can be achieved with the use of specialized DAQ hardware.
The entire system is controlled by a Pentium II-based 400-MHz computer with 64 Mbytes of DRAM, a 8.9-Gbyte hard drive, and four ISA and four PCI slots. The standard graphics card is replaced by the FlashPoint 128 frame-grabber boards. To protect the system from the harsh manufacturing environment, all system electronics are housed in a National Electronic Manufacturers Association 4-X cabinet.
In the Searle application, two InspectRx systems are used with two cameras in each system. The two system computers are linked via Ethernet cards and Microsoft Corp. (Redmond, WA) NetMeeting software, which allows all the data to be displayed on one monitor (see Fig. 3).
Fuzzy-logic software
The InspectRx Vision for Inspection Systems software includes a Windows 95-based graphical user interface and runs under Windows 95, 98, NT 4.0, or NT 5.0. The fuzzy-logic analysis software compares each image frame against a prestored reference or analysis frames of "ideally good" objects stored on the system`s hard drive in a per-program/per-product arrangement. Analysis frames include pixel comparison, pixel counting, text verification and recognition, barcode verification and reading, and round-shapes verification information. Each analysis frame uses a "key frame" for position and rotation correction. These key frames track the object throughout its range of motion.
In lieu of optical filters on the cameras, the InspectRx system applies electronic color filters to the system`s main "Capture Screen." Up to ten color filters can be applied per frame with a built-in tolerance for pixel jitter. These filters automatically determine the exact shades of color (hue-saturation intensity) within any size field of view or window down to a single pixel, which are then compared against preset tolerance limits.
The production screen displays control charts for real-time monitoring and the maximum deviation from nominal of all the analysis frames. The borders of the frames are displayed in green when the deviation is within production tolerances and in red when the deviation is above production tolerances. A "Custom Screens" menu holds custom-tailored screens developed for specific applications.
If the system software determines that the product is outside the upper or lower control limits, the system generates a 5-V TTL pulse to a solenoid on the rejection mechanism, which shunts the specified bottle to a rejection bin. Operators set the physical parameters and the rejection pulsewidth and delay of the rejection mechanism.
According to Solomon, the system has been successfully tested at American SensoRx and is scheduled for delivery to Searle. According to Searle packaging-improvement specialist, Wilson Lee-Wing, the company is currently evaluating the InspectRx system for a specific color-coded-product manufacturing line. The current two manufacturing lines may soon be expanded to three. It is also considering the system for basic capsule-counting applications on four other lines to prevent the passage of deformed or partial capsules. In addition, Searle may consider the system for use in its blister-seal packaging lines.
FIGURE 1. Prior to a tablet/bottle production run, the InspectRx system is initialized by entering the desired production parameters (top) using a Set-up Screen (bottom). These parameters cover camera, picture, tablet, and dispensing machine characteristics.
FIGURE 2. As the tablet-dispensing machine fills the moving containers, the vision-inspection machine continuously monitors system operation during a bottle-fill production run. Results displayed include the following numbers: inspected slats, good and foreign tablets, ten bottle locations and tablet fill, and accepted and rejected bottles. Tablets are initially loaded into the dispensing machine from a vibrating hopper.
FIGURE 3. For the capsule or tablet vision-inspection application, two InspectRx systems are used with two cameras operating in each system. The two system computers are linked via Ethernet cards and Microsoft Corp. NetMeeting software, which allows all the data to be displayed on one monitor. The Statistics Screen displays a daily, weekly, or monthly status report of each production run. It is also used to save and print the production data results.
