Abstract: A method and apparatus for a single densitometer design that is used for all colors within multiple color image processing system. The preferred embodiment employs an LED having a light adjustment mechanism for controlling the amount of light received by a light detector in the densitometer. The coarse light adjustment is provided through a variable aperture. Fine light adjustment is accomplished through controlling the current through the LED, either by a potentiometer or through an automated process. Preferably, each of the LEDs is selected by wavelength to maximize the absorption by the colorant yielding light roughly complimentary to the colorant. The adjustment circuit provides advantage in color printing systems by allowing duplicate versions of the same densitometer circuit to yield similar voltage outputs for different colorants, thereby compensating for different absorption characteristics and light output of different colored LEDs.

Abstract: A method and apparatus for preventing voltage swings within device outputs from reading output node where swings in excess of certain voltages can harm electronics attached to the output node. Specifically, output swings from devices performing logarithmic operations are prevented from reaching the input of an A/D converter, thereby protecting the A/D converter from the large swings possible in logarithmic outputs. A comparator circuit compares the output from the logarithmic amplifier against a threshold and engages the switching mechanism once the threshold is reached. Once the switching mechanism is engaged it applies a predetermined voltage to the output node in place of the true output voltage from the logarithmic amplifier.

Abstract: A method and apparatus for a single densitometer design that is used for all colors within multiple color image processing system. The preferred embodiment employs an LED having a light adjustment mechanism for controlling the amount of light received by a light detector in the densitometer. The coarse light adjustment is provided through a variable aperture. Fine light adjustment is accomplished through controlling the current through the LED, either by a potentiometer or through an automated process. Preferably, each of the LEDs is selected by wavelength to maximize the absorption by the colorant yielding light roughly complimentary to the colorant. The adjustment circuit provides advantage in color printing systems by allowing duplicate versions of the same densitometer circuit to yield similar voltage outputs for different colorants, thereby compensating for different absorption characteristics and light output of different colored LEDs.

Abstract: This invention provides an image-forming machine with a pulse densitometer that avoids the formation of artifacts on electrophotographic films. The image-forming machine may have a charger, an exposure machine, a toning station, a transfer charger, a fusing station, and a densitometer positioned next to a photoconductor. The densitometer may have an emitter, a collector, and a pulse apparatus. The densitometer provides one or more pulses to measure the toner and photoconductor densities. The pulsed emissions are essentially below the exposure threshold of electrophotographic films, especially those sensitive to the infrared spectral region.

Abstract: This invention provides an image-forming machine with a pulse densitometer that avoids the formation of artifacts on electrophotographic films. The image-forming machine may have a charger, an exposure machine, a toning station, a transfer charger, a fusing station, and a densitometer positioned next to a photoconductor. The densitometer may have an emitter, a collector, and a pulse apparatus. The densitometer provides one or more pulses to measure the toner and photoconductor densities. The pulsed emissions are essentially below the exposure threshold of electrophotographic films, especially those sensitive to the infrared spectral region.

Abstract: The invention provides a diagnostic system for a densitometer in an image-forming machine. An image-forming machine with a densitometer diagnostic system may have a photoconductor, one or more chargers, an exposure machine, a toning station, and a densitometer. A densitometer diagnostic system for an image-forming machine may have an emitter, a collector, amplifier circuitry, and diagnostic circuitry. The diagnostic circuitry reduces the drive current to the emitter in the densitometer by a known or calculable value. The output voltage from the amplifier circuitry in the densitometer is reduced in proportion to the reduction in the drive current. To perform diagnostic testing of the densitometer, a first output voltage is obtained from the densitometer without the diagnostic circuitry connected. A second output voltage is obtained from the densitometer with the diagnostic circuitry connected.

Abstract: An auto-ranging densitometer is disclosed for determining the density of a test sample, wherein the densitometer includes a photodetector and an amplifier circuit adapted to produce an output signal proportional to intensity of light on the photodetector. The amplifier circuit has multiple gains that successively increase in an approximately 2:1 ratio increment. An analog to digital converter is adapted to convert the output signal of the amplifier circuit to digital format. A density signal generator circuit is adapted to receive the output of the analog to digital converter, whereby density resolution non-uniformity is minimized due to small gain increments such that the analog to digital converter needs deal with less extreme variations in density resolution.

Abstract: An auto-ranging densitometer includes a photodetector and an amplifier circuit adapted to produce an output signal proportional to intensity of light on the photodetector. The amplifier circuit has multiple gains that successively increase. An analog to digital converter converts the output signal of the amplifier circuit to digital format. A gain select logic outputs a gain code used to select the gain of the amplifier. A density signal generator circuit includes two LUTs, one of the LUTs being adapted to receive the output of the analog to digital converter and produce an output density scaled to include only low order bits; and the other of the LUTs being to receive the gain code and produce an output density scaled to include only high order bits. The outputs of the two LUTs are concantenation added to produce a summation density signal.