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US 4,673,807 AGranted
Automatic range control method for an optical density/dot percentage measuring device
AssigneeDai Nippon Insatso Kabushiki Kaisha
InventorsYuji Kobayashi, Norio Takahashi
Life of this patent
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Abstract
This invention relates to an automatic range control method for a compact and portable optical density/dot percentage measuring device which can use a conventional light table as its light source, and which can digitally display a result of measurement. In the method, information obtained from an A/D converter, which converts a measured analog signal to a digital signal, is positively employed for reducing overall measuring time. An A/D conversion is first made at x1 range by a 10 bit A/D converter. The A/D conversion value is compared with predetermined values to determine a gain to be selected and perform further A/D conversion.
Claims9
An automatic range control method for an optical density/dot percentage measuring device, comprising:
- a photoelectric conversion element for photoelectrically converting a transmitted or reflected light of an object to be measured into a photocurrent;
- an operational amplifier for converting said photocurrent into a voltage signal for amplifying said voltage signal;
- a low-pass filter for cutting off an AC component of said voltage signal from said operational amplifier;
- an A/D converter for converting said voltage signal from said low-pass filter from an analog value into a digital value;
- an operation control unit for outputting, in response to said digital signal, switch control signals for the control of an on/off state of a plurality of analog switches and display data;
- and
- a gain switching circuit having a plurality of feedback resistors and said analog switches connected between the input and output terminals of said operational amplifier for switching a plurality of measurement ranges;
- wherein said operation control unit outputs said switch control signals to said gain switching circuit in such a manner that said operation control unit calculates a value Ii=Vi/Gi based upon a value Vi obtained through said A/D conversion of said voltage signal at a given gain Gi, selects a gain Gi+1 based upon which range of said plurality of mesurement ranges corresponds to said value Ii;
- and if the gain Gi+1 coincides with the current gain Gi, said value Ii is made a fixed value, while if the gain Gi+1 does not coincide with the current gain Gi, then a value Vi+1 is obtained through an A/D conversion of the measured value at the gain Gi+1 to calculate a value Ii+1=(Vi +1)/(Gi +1), and similar procedures are repeated until a coincidence is obtained.
6 more elements
An optical density/dot percentage measuring device, comprising:
- a photoelectric conversion element for photoelectrically converting a transmitted or reflected light of an object to be measured into a photocurrent;
- an operational amplifier for converting said photocurrent into a voltage signal for amplifying said voltage signal;
- a low-pass filter for cutting off an AC component of said voltage signal from said operational amplifier;
- an A/D converter for converting said voltage signal from said low-pass filter from an analog value into a digital value;
- an operation control unit for outputting, in response to said digital signal, switch control signals for the control of an on/off state of a plurality of analog switches and a data signal representative of data to be displayed;
- a display for displaying said data;
- and
- a gain switching circuit having a plurality of feedback resistors connected in parallel between the input and output terminals of said operational amplifier, said analog switches being respectively connected to each of said feedback resistors except the one of said feedback resistors having the largest resistance value.
5 more elements
An optical density/dot percentage measuring device comprising:
- a photoelectric conversion element for photoelectrically converting a transmitted or reflected light of an object to be measured into a photocurrent;
- an operational amplifier for converting said photocurrent into a voltage signal for amplifying said voltage signal;
- a low-pass filter for cutting off an AC component of said voltage signal from said operational amplifier;
- an A/D converter for converting said voltage signal from said low-pass filter from an analog value into a digital value;
- an operation control unit for outputting, in response to said digital signal, switch control signals for the control of an on/off state of a plurality of analog switches and a data signal representative of data to be displayed;
- a display for displaying said data;
- and a gain switching circuit having a plurality of feedback resistors connected in series between the input and output terminals of said operational amplifier, said analog switches being respectively connected between the terminals of said feedback resistors except that connected to the input terminal of said operational amplifier, and the output terminal of said operational amplifier.
4 more elements
Dependencies are inferred from the claim text.