Process for dynamically equalizing multichannel optical imaging systems
First Claim
1. A process for equalizing an optical imaging system having a plurality of parallel channels, said method comprising the steps ofrecursively measuring the output intensities of said channels before and after corrective equalization factors are applied to them to provide pre-correction and post-correction intensity measurements;
- said measurements being performed at a resolution of n channels/measurement, where n=1, 2, . . . N/2, and N=the number of channels contained by said imaging system;
averaging said pre-correction intensity measurements to establish a threshold at a preselected percentage of said average;
selecting one of said pre-correction intensity measurements to establish a reference level, said one intensity measurement being equal to or exceeding said threshold by an amount no greater than any of said other pre-correction intensity measurements;
applying separate corrective equalization factors to each set of n channels to equalize said channels on a set-by-set basis;
iteratively adjusting the correction factors for all equalizable sets of channels based on their output intensity relative to said reference level, whereby the output intensities of the respective equalizable sets of channels are brought into balance with said reference level, even in the presence of a significant level of optical crosstalk between neighboring sets of channels.
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Abstract
In accordance with the present invention, correction factors for dynamically equalizing the optical channels of a multichannel optical imaging system, individually or on a group-by-group basis, are recursively computed while the imaging system is idle (i.e., not printing) through the use of an iterative process comprising the steps of: measuring the output intensities of the respective sets of channels, sequentially comparing the measured channel intensities against a system calibrated reference intensity level, and adjusting the correction factor for each set of channels that is found to be operating at an intensity level deviating from the reference intensity level in the direction that is required to reduce the magnitude of the deviation (unless the correction factor value already is at the limit of its dynamic range in that direction). Preferably, the correction factor adjustments are made by incrementing and decrementing their least significant values, thereby maximizing the sensitivity of each iteration of the process to the affect of the immediately preceding iteration on the amount of crosstalk occurring between neighboring sets of channels. For example, the correction factors suitably are multi-bit binary values which are adjusted by incrementing and decrementing their least significant bits (LSB'"'"'s). The reference intensity level typically is calibrated by measuring the uncorrected output intensities of the respective sets of channels and by then selecting the intensity of the set of channels which is determined to be operating at the lowest valid intensity level for use as the reference intensity. Advantageously, this calibration procedure is repeated on a predetermined schedule for recalibrating the reference level from time-to-time to correct for gradual drift in the optical characteristics of the imaging system.
19 Citations
4 Claims
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1. A process for equalizing an optical imaging system having a plurality of parallel channels, said method comprising the steps of
recursively measuring the output intensities of said channels before and after corrective equalization factors are applied to them to provide pre-correction and post-correction intensity measurements; - said measurements being performed at a resolution of n channels/measurement, where n=1, 2, . . . N/2, and N=the number of channels contained by said imaging system;
averaging said pre-correction intensity measurements to establish a threshold at a preselected percentage of said average; selecting one of said pre-correction intensity measurements to establish a reference level, said one intensity measurement being equal to or exceeding said threshold by an amount no greater than any of said other pre-correction intensity measurements; applying separate corrective equalization factors to each set of n channels to equalize said channels on a set-by-set basis; iteratively adjusting the correction factors for all equalizable sets of channels based on their output intensity relative to said reference level, whereby the output intensities of the respective equalizable sets of channels are brought into balance with said reference level, even in the presence of a significant level of optical crosstalk between neighboring sets of channels. - View Dependent Claims (2, 3, 4)
- said measurements being performed at a resolution of n channels/measurement, where n=1, 2, . . . N/2, and N=the number of channels contained by said imaging system;
Specification