MULTICHANNEL PHOTOMETRIC MEASUREMENT APPARATUS

• US 20120019815A1
• Filed: 07/20/2011
• Published: 01/26/2012
• Est. Priority Date: 07/20/2010
• Status: Active Grant

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Yokogawa Electric Corporation
• Inventors: Ichizawa, Yasushi, Horikoshi, Kumiko, Kakuta, Shigeyuki, Nishida, Kazufumi
• Granted Patent: US 8,547,544 B2
• Time in Patent Office: Days
• US Class Current: 356/217
• CPC Class Codes: G01B 11/0691 of objects while moving G01B11/0616 takes precedence
• CPC Class Codes: G01N 2021/8663 Paper, e.g. gloss, moisture content
• CPC Class Codes: G01N 21/86 Investigating moving sheets G01N21/89 takes precedence

Abstract

A multichannel photometric measurement apparatus according to one embodiment includes: a single signal generator for generating an initial signal, the initial signal containing a harmonic component for collectively generating a plurality of modulation signals; a light emitting device including a plurality of light sources that are respectively drivable by each of the plurality of modulation signals having different frequencies; a light detector for detecting a plurality of kinds of light emitted from the light emitting device; and discriminating means for discriminating a detected signal output from the light detector per frequency domain of each of the different frequencies for each of the modulation signals.

Claims

1. A multichannel photometric measurement apparatus, comprising:

a single signal generator for generating an initial signal, the initial signal containing a harmonic component for collectively generating a plurality of modulation signals;

a light emitting device including a plurality of light sources that are respectively drivable by each of the plurality of modulation signals having different frequencies;

a light detector for detecting a plurality of kinds of light emitted from the light emitting device; and

discriminating means for discriminating a detected signal output from the light detector per frequency domain of each of the different frequencies for each of the modulation signals.

2. The multichannel photometric measurement apparatus according to claim 1,

wherein the signal generator is included in the light emitting device,

wherein the light emitting device further includes a plurality of bandpass filters that extract a predetermined different frequency component from the initial signal generated by the signal generator, and

wherein the plurality of light sources is each drivable by a modulation signal having the frequency component extracted by a corresponding one of the bandpass filters.

3. The multichannel photometric measurement apparatus according to claim 1, wherein the discriminating means includes an A/D converter that matches a width of a time window to load the detected signal with an integral multiple of an inverse of the frequency of the modulation signal to cause a plurality of frequency components contained in the detected signal input to the discriminating means to have an orthogonal relationship with each other.

4. The multichannel photometric measurement apparatus according to claim 1, wherein the signal generator is a rectangular wave generator collectively generating the initial signals as a frequency comb having predetermined frequency intervals.

5. The multichannel photometric measurement apparatus according to claim 2, wherein each of the plurality of bandpass filters has a cutoff characteristic to respectively extract the predetermined different frequency component from the initial signal generated by the signal generator.

6. A multichannel photometric measurement apparatus, comprising:

a single signal generator for generating an initial signal, the initial signal containing a harmonic component for collectively generating modulation signals;

a light emitting device including bandpass filters extracting a plurality of predetermined different frequency components from the initial signal generated by the signal generator, and light sources that are respectively drivable by one of the modulation signals having one of the predetermined different frequency components extracted by the bandpass filters;

a light detector that detects a plurality of kinds of light emitted from the light emitting device and outputs detected signals; and

lock-in amplifiers that receive references signals from the bandpass filters, each of the reference signals having an orthogonal relationship with each other, the lock-in amplifiers discriminating the detected signals for each frequency domain corresponding to each of the predetermined different frequencies components extracted by the bandpass filters.

7. The multichannel photometric measurement apparatus according to claim 6, further comprising an A/D converter that matches a width of a time window to load the detected signals with an integral multiple of an inverse of the frequency of each of the modulation signals to cause a plurality of frequency components contained in the detected signals input to the lock-in amplifiers to have an orthogonal relationship with each other.

8. A multichannel photometric measurement apparatus, comprising:

a single signal generator for generating an initial signal, the initial signal containing a harmonic component for collectively generating a plurality of modulation signals;

a light emitting device including a plurality of light sources that are respectively drivable by each of the plurality of modulation signals having a different frequency;

a light detector for detecting a plurality of kinds of light emitted from the light emitting device; and

a discrete Fourier transform that filters a detected signal output from the light detector per frequency domain of each of the modulation signals.