# US 4,400,089 A · Method of and apparatus for determining optical quality of an article

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- Number: US 4,400,089 A
- Document ID: US4400089A
- Status: Granted
- Kind: A
- Application number: 06/225,541
- Filed: 1981-01-16
- Granted: 1983-08-23
- Earliest claimed: 1979-08-01
- Assignees: PPG Industries, Inc.
- Inventors: Aloysius W. Farabaugh
- Web page: https://patentgrep.com/patent/US4400089A

## CPC

- G01B 7/30: for measuring angles or tapers; for testing the alignment of axes
- B32B 17/10981: {Pre-treatment of the layers}
- G01B 7/087: {for measuring of objects while moving (G01B7/085 takes precedence)}
- G01N 21/896: Optical defects in or on transparent materials, e.g. distortion, surface flaws {in conveyed flat sheet or rod (for other objects G01N21/958)}
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

An interlayer material is scanned prior to laminating same with glass sheets to generate a thickness variation signal, a wedge angle signal and an optical power signal. The signals are then selectively filtered to determine the thickness variation, wedge angle and optical power of the interlayer after lamination.

## Claims

### Claim 1

A method of determining optical property of a transparent plastic sheet defined as a worked sheet exposed to heat or pressure from a transparent plastic sheet defined as an unworked sheet prior to exposure to the heat or pressure, comprising the steps of:
scanning the unworked sheet to generate an optical profile of the unworked sheet; and
altering portions of the optical profile of the unworked sheet to provide an altered optical profile which is the expected optical profile of the worked sheet.

### Claim 2 (depends on 1)

The method as set forth in claim 1 wherein said generating step includes the step of generating a thickness profile of the unworked sheet.

### Claim 3 (depends on 2)

The method as set forth in claim 2 wherein said generating step includes the steps of:
generating a thickness variation frequency signal; and
said altering step includes the step of filtering frequencies above a predetermined value from the thickness variation frequency signal.

### Claim 4 (depends on 1, 2)

The method as set forth in claim 1 or 2 wherein said generating step include the step of generating a wedge angle profile of the unworked sheet.

### Claim 5 (depends on 4)

The method as set forth in claim 4 wherein said generating step includes the steps of:
generating a wedge angle frequency signal; and
said altering step includes the step of filtering frequencies above a predetermined value from the wedge angle frequency signal.

### Claim 6 (depends on 1)

The method as set forth in claim 1 wherein said generating step includes the step of generating an optical power profile of the unworked sheet.

### Claim 7 (depends on 6)

The method as set forth in claim 6 wherein said generating step includes the steps of:
generating an optical power frequency signal; and
said altering step includes the step of filtering frequencies above a predetermined value from the optical power frequency signal.

### Claim 8 (depends on 1)

The method as set forth in claim 1 wherein said step of generating an optical profile includes the steps of:
generating a thickness variation signal of the unworked sheet;
differentiating the thickness variation signal to provide a wedge angle signal;
differentiating the wedge angle signal to provide an optical power signal; and
said altering step includes the step of filtering frequencies above a predetermined value from the optical power signal.

### Claim 9

An electrical system for determining optical property of a transparent plastic sheet defined as a worked sheet exposed to heat or pressure from a transparent plastic sheet defined as an unworked sheet prior to exposure to the heat or pressure, comprising:
means for scanning the unworked sheet to generate optical profile of the unworked sheet; and
means operatively connected to said scanning means for altering portions of the optical profile to provide an altered optical profile which is the expected optical profile of the worked sheet.

### Claim 10 (depends on 9)

The system as set forth in claim 9 wherein said scanning means includes:
means for generating a thickness variation signal of the unworked sheet; and
said altering means includes means for attenuating the thickness variation signal.

### Claim 11 (depends on 9)

The system as set forth in claim 9 wherein said scanning means includes:
means for generating a wedge angle signal of the unworked sheet; and
said altering means includes means for attenuating the wedge angle signal.

### Claim 12 (depends on 9)

The system as set forth in claim 9 wherein said scanning means includes:
means for generating an optical power signal of the unworked sheet; and
said altering means includes means for attenuating the optical power signal.

### Claim 13 (depends on 9)

The system as set forth in claim 9 wherein the sheet is a plastic material used in manufacture of laminates.

### Claim 14 (depends on 13)

The system as set forth in claim 13 wherein said scanning means includes:
means for generating a thickness variation signal; a wedge angle signal; and an optical power signal of the unworked sheet; and
said altering means includes means for attenuating the thickness variation signal; the wedge angle signal; or the optical power signal.