Abstract: A method and apparatus for autodiscriminating and decoding any of a plurality of 1D linear bar code symbols which use different 1D symbologies and of 2D matrix bar code symbols which use different 2D finder patterns and 2D symbologies. A processor stores a plurality of 1D decoding programs, a plurality of 2D decoding programs, and a parameter table that specifies which of said programs are to be enabled. During 1D autodiscrimination, the processor makes no attempt to decode unknown symbols in accordance with 1D decoding programs that are not enabled. During 2D autodiscrimination, the processor makes no attempt to decode unknown 2D symbols in accordance with 2D decoding programs that are not enabled.

Abstract: A method for generating, substantially in real time, a user perceptible indication of the degree to which the distance between a handheld imaging device and a target object approximates the in-focus distance therebetween. A stored image of the target object is sampled, in accordance with a pattern of sampling addresses, to determine the magnitude of the slopes of the transitions of the stored image. The stored image is also sampled to determine the contrast value of the stored image. The highest magnitude slope values and the image contrast value are combined to produce a focus metric signal that is indicative of the degree to which the imaging device approximates an in-focus condition. The focus metric signal is then used to generate a user perceptible signal that can be utilized by an operator to move the imaging device toward its in-focus distance.

Abstract: A method and apparatus for capturing and storing a decodable representation of a 1D or 2D bar code symbol using a hand-held bar code reader having only a 1D image sensor. A succession of 1D digital representations are produced as the reader is moved asynchronously across the symbol to be read. These representations are examined, substantially in real time, and, if the symbol is a 1D symbol, is decoded immediately. If the symbol is not a 1D symbol, these representations are examined for the presence of one of a variety of different types of 2D finder patterns and, when the finder has been identified, decoded with reference to that finder pattern.

Abstract: A portable, hand-held, self-contained two-dimensional bar code reader adapted to the PDF417 symbology, includes a light source, a photodetector, and a decoder. The decoder comprises an 8 bit microcomputer, having an address space of 64K bytes, but actually using an 8K Byte SRAM for data storage, and 32K Byte PEROM for program instructions. Performance is enhanced by a novel program resident in the program memory, and by the use of direct memory access to load signals derived from the photodetector into memory. The unit draws an average of 1.4 watts during a reading operation when the light source is enabled and 0.83 watts during decoding when the light source is disabled. It is capable of reading an 800 character PDF417 symbol at an error correction level of 5 in about 2 seconds.

Abstract: A two dimensional (2D) matrix symbology for use with bar code and other optical readers. A finder structure includes a center square and a plurality of nested squares having centers that approximately coincide with the center square. A symbol descriptor located adjacent to the finder structure encodes data indicating the size of the symbol and the length of the message encoded therein. A reference grid extends throughout the symbol to facilitate the location of individual data elements with respect to the finder structure thereof. The data structure of the symbol is filled with data blocks which are organized into layers which surround the finder structure. Data encoded in the data blocks may be read sequentially within layers and between layers. The symbology is a versatile symbology in that the number of check data blocks is user selectable to provide the desired level of error correction.

Abstract: A linear bar code symbology combines delta distance start and stop patterns, a space efficient, bit oriented data character structure, and Reed-Solomon redundancy for error detection and correction. A method of writing the bar code structures onto a character medium and reading the resulting symbols under adverse conditions is presented.

Abstract: A method of improving throughput in a scanner whose scanning action is capable of being stopped and started instantly, comprising the steps of A) storing results of a first scan of a target containing indicia in a first region of a memory and B) upon determining that the first scan is complete 1) decoding results of the first scan 2) initiating a second scan, 3) storing results of the second scan of the target containing indicia in a second region of a memory, and 4) awaiting completion of the decoding before initiating an additional scan.

Abstract: There is provided a system of detecting mark-sense indicia wherein the images of a light source and the region of sensitivity of a light sensor are substantially coaxial, coplanar, and coextensive throughout the working depth of field. This system is insensitive to the laminate and the diffusion effects. A light source is aimed at a beam splitter that diverts a portion of the light beam through optics that focus the light on a reflective target containing a bar code symbol to be scanned. The reflected beam is returned through the optics and the beam splitter, and a portion of the reflected beam is conducted to a light sensor. In this manner, the light path from the detector to the optical sensor is split twice by the beam splitter. The optics are configured so that the light beams that define the field of illumination and the region of sensitivity and which pass between the optics and the target are congruent, having identical optical axes and angles of divergence.

Abstract: A method is disclosed for the reading graphical indicia that are encoded in accordance with a multidimensional symbology. The indicia are repeatedly scanning a signal representative of a pattern thereof until sufficient information is recognized to assure a valid reading operation. The signal, or a memorized representation thereof is decoded to obtain character information from code words of the indicia. A first value is assigned to each newly recognized character, and a second value is assigned to each character that was recognized in a preceding scan of the indicia. The first and second values are respectively cumulated into first and second sums. A function of the first sum and the second sum is computed, an audible click produced whenever a predetermined value of the function has been attained. The first and second sums are then reset. The rate of clicks informs the user of the progression of the reading operation.

Abstract: A scanner is provided for reading a target containing indicia, such as bar codes, which includes a means for directing the a light source so that it illuminates a target, a photodetector that generates an electrical signal indicative of the intensity of the detected light, a means for decoding the electrical signal to identify the presence of a target containing a region of relatively high reflectivity, and a means for modifying the level of illumination of the light source either from low to high upon recognition of said region of relatively high reflectivity or from high to low when some predetermined condition, such as the end of the indicia scan, or the passage of a time period without reading indicia, is met.

Abstract: A bar code detection circuit accepts as input the discretized analog output of a CCD array, and performs piecewise linear reconstruction to produces a continuous polylinear output signal. In the region of a bar/space transition, the output signal is a close approximation of the reflectance function of a bar code symbol convolved with the system transfer function of the bar code reader. Linear interpolation is performed in order to determine the offset of a given threshold value from an edge of the CCD analog output.

Abstract: A method and apparatus are provided for detecting bar-space and space-bar transitions in a bar code symbol. A sequence of sparsely sampled analog signals from a photodetector in a bar code scanner is representative of the reflectance pattern of a symbol.Following initialization, a threshold, representing the value of the analog signal at a transition point, is derived from observed samples of the bars and spaces in the bar code symbol. Sampled reflectance information is accumulated as the symbol is scanned, and a program driven microprocessor calculates and repeatedly updates this threshold, using observed maxima and minima in the analog samples, and also referencing a binary output to determine whether a bar or space is currently being viewed.When the values of two successive analog samples bracket this threshold, then a bar-space or space-bar transition has occurred. Linear interpolation is performed on the two samples to determine the transition point and an offset from the first of the two samples.

Abstract: An optical bar code reading instrument has a uniport interface circuit which accepts through a common terminal both charging current for the reader's internal rechargeable battery and incoming digital electric information signals. The uniport interface also allows digital electrical signals produced by the instrument to pass through the same terminal.

Abstract: A hand-held instrument for reading a bar code symbol, and analyzing the print quality of the code upon manually scanning the code has a graphic display. The display is driven by a computer which has memory (a block in RAM) in which a multiplicity of data samples representing the reflectance profile of the bar code pattern are entered at a constant rate. The print quality analysis is based upon these samples. The number (count) of these samples represents the duration of the elements (bars and spaces) constituting the code. When the number of samples in successive, adjacent characters (groups of elements, a string of which represents a valid code) differs by 25%, the display is driven to prompt the operator to scan the code again, but more evenly without jerky motion (accelerations or decelerations). When the capacity of the memory block allocated to the scan profile data samples is exceeded, the operator is prompted by the display to scan faster.

Abstract: A portable, hand-held tympanometer that has the capability of performing the tympanometry and of displaying and storing the test results all within the hand-held instrument. A separate unit that is not in any way attached to the tympanometer during the testing is provided to print the test results and to recharge the tympanometer battery. The tympanometer has a body portion and a head portion to which a speculum is attached, the speculum being adapted to engage the canal of the ear being examined in sealed relation thereto. A speaker in the speculum transmits acoustic signals into the ear canal and a microphone in the speculum receives the signals that are reflected back through the canal by the tympanic membrane. A pressure transducer is located in the head portion of the tympanometer, and a miniature pump located in the body portion operates to introduce a range of pressures into the ear canal while the acoustic signals are being transmitted and received.

Abstract: A refreshable dynamic memory is used to drive a video display wherein each row of stored memory is accessed to provide one line of video. The memory row address counter is incremented a number of times during the horizontal retrace period to sequentially refresh a given number of memory rows before another row is displayed. The cycle is repeated until an entire field is displayed. A sufficient number of rows are refreshed during each line whereby the rows are refreshed continually within the storage time of the memory cells.

Abstract: An automatic signal level control for use in a video system using a solid state imager capable of integrating pulsed light images of a target imaged thereon. An automatic gain control is used to adjust the gain of a variable gain amplifier in the output circuit of the image sensor. A strobe lamp is used to illuminate the target during each imaging sequence. The feedback signal to the amplifier is compared to an upper and lower threshold and, in response thereto, the number of pulses generated during each illumination sequence are adjusted to maintain the video signal levels within a desired operating range.

Abstract: Apparatus for synchronizing rotational speed of a color filter wheel to a video field rate using a stepping motor drive. The derivation of the stepping rate is taken directly from the video system's master clock through dividers and a phase locked loop which provide the required fractional rate division. An integrating capacitor in the phase locked loop controls the output of a voltage control oscillator so that at power up the capacitor is charged at a relatively slow rate thus ramping up the stepping rate of the motor until phase locking is achieved. A pair of optical switches monitor the rotation of the filter wheel. If the switches are not made within a predetermined number of steps, the integrating capacitor is discharged and the ramping procedure reinitiated.