FILL LEVEL MEASURING DEVICE

• US 3,741,656 A
• Filed: 05/27/1971
• Issued: 06/26/1973
• Est. Priority Date: 05/27/1971
• Status: Expired due to Term

• Current Assignee: William A. Shapiro
• Original Assignee: William A. Shapiro
• Inventors: Shapiro, William A.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Evans, F. L.
• Application Number:
  US05/147,554
• Time in Patent Office: 761 Days
• Field of Search: 73/293 250/222R,223R,218 356/201,209,103
• US Class Current: 356/342
• CPC Class Codes: G01F 23/2928 using light reflected on the material surface
• CPC Class Codes: Y10T 117/1004 with means for measuring, testing, or sensing

Abstract

Apparatus employing optical means for measuring the level of a liquid or granular substance in a container under conditions when actual contact or even close proximity of the apparatus and the substance is impractical or undesirable.

Claims

1. Apparatus for measuring the level of a substance in a container, comprising:

means disposed above the container for emitting a light beam which strikes the substance;

part of said light beam being specularly reflected from the surface of the substance, another part being scattered from an incident point on the surface of the substance and yet another part being transmitted through the substance and being scattered from an incident point on the bottom of the container;

said last memtioned light being effective for providing a virtual image of the incident point on the bottom of the container; and

means for determining the relative positions of the incident point on the surface of the substance, the incident point on the bottom of the container and the virtual image of said last mentioned point, said positions being a measure of the level of the substance in the container.

2. Apparatus as described by claim 1, wherein:

the light beam emitting means is laterally disposed relative to the surface of the substance so that the lateral deviation of said incident points varies as the product of the level of the substance and the tangent of the angle that the light beam makes with the normal to the surface of the substance.

3. Apparatus as described by claim 2, including:

an objective lens positioned above the container for intercepting and transmitting the light scattered from the incident point on the surface of the substance and the light scattered from the point on the bottom of the container; and

means positioned above the lens and responsive to the light transmitted thereby for indicating the lateral position of the first mentioned incident point.

4. Apparatus as described by claim 3, wherein:

the objective lens is laterally disposed relative to the surface of the substance to provide an image of the first mentioned point at a predetermined distance from the optical axis of the objective lens.

5. Apparatus as described by claim 4, wherein:

the objective lens is laterally disposed relative to the surface of the substance so that the predetermined distance varies as the product of the focal length of the objective lens and the sine of the angle the light beam makes with the normal to the surface of the substance.

6. Apparatus as described by claim 1, wherein:

the light beam emitting means is laterally disposed relative to the surface of the substance so that the lateral deviation of said incident points varies as twice the product of the level of the substance and the angle the light beam makes with the normal to the surface of the substance.

7. Apparatus as described by claim 3, wherein:

the means positioned above the lens and responsive to the light transmitted thereby for indicating the lateral position of said first mentioned incident point includes light detection means; and

the light from the incident point on the bottom of the container is spread over a large angular interval so as to be within the range of the detection means even when said means is outside the region of specular reflection.

8. Apparatus as described by claim 1, wherein:

the light beam emitting means is laterally disposed relative to the surface of the substance so that the lateral deviation of the incident points is independent of the distance of the relative position determining means from the surface of the substance.