# US 8,786,847 B2 · Light measuring meter apparatus

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,786,847 B2
- Document ID: US8786847B2
- Status: Granted
- Kind: B2
- Application number: 13/004,913
- Filed: 2011-01-12
- Published: 2012-07-12
- Granted: 2014-07-22
- Earliest claimed: 2011-01-12
- Assignees: Underwriters Laboratories Inc.
- Applicants: Ian Lewin; John O'Farrell
- Inventors: Ian Lewin; John O'Farrell
- Web page: https://patentgrep.com/patent/US8786847B2

## CPC

- G01J 1/02: Details
- G01J 1/0219: {Electrical interface; User interface}
- G01J 1/0228: {Control of working procedures; Failure detection; Spectral bandwidth calculation}
- G01J 1/0242: {Control or determination of height or angle information of sensors or receivers; Goniophotometry}
- G01J 1/0266: {Field-of-view determination; Aiming or pointing of a photometer; Adjusting alignment; Encoding angular position; Size of the measurement area; Position tracking; Photodetection involving different fields of view for a single detector}
- G01J 1/04: Optical or mechanical part {supplementary adjustable parts}
- G01J 1/0411: {using focussing or collimating elements, i.e. lenses or mirrors; Aberration correction}
- G01J 1/0437: {using masks, aperture plates, spatial light modulators, spatial filters, e.g. reflective filters}
- G01J 1/0448: {Adjustable, e.g. focussing}
- G01J 1/0466: {with a sighting port}
- G01C 3/085: {with electronic parallax measurement}
- G02B 7/32: using active means, e.g. light emitter {(including both an active and a passive focus detecting device G02B7/285; using ultrasound G02B7/40)}
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

This invention is related to a light measuring apparatus and a method of using the device. It is used to measure various photometric quantities of the light emanating from a distant source of light.

## Claims

### Claim 1

Light measuring apparatus including an enclosure housing supporting a light energy detector, a controller and a distance measuring device for measuring luminous intensity, as measured in candelas, of a source of light of a distant target comprising:
the enclosure housing, having a first end, a lens system including an objective lens and a light energy detector aligned on a single light path extending from the objective lens, the light energy detector having an electronic communication conduit and the light energy detector mounted to receive light energy directed along the single light path from the objective lens;
an infrared detector carried in the enclosure,
a pick off filter located in the enclosure, the pick off filter located such that infrared component of an incoming light beam entering the apparatus through the objective lens is directed to the infrared detector;
a light metering valve located in the enclosure proximate the focal surface location of the objective lens to selectively control light directed along the single light path extending from the objective lens of the enclosure;
the controller including a digital processor in communication with the light energy detector through the electronic communication conduit;
the distance measuring device having electronic communication capability in communication with the controller, the distance measuring apparatus having a receiving energy pulse path located on the single light path extending from the objective lens of the light measuring apparatus;
the distance measuring device comprising a laser diode for projecting a series of pulsed light signals from the first end of the enclosure to the distant target;
a lens at the first end of the enclosure in front of the laser diode and adjacent the objective lens through which the series of pulsed light signal are projected;
the infrared detector receiving reflected pulses of light reflected from the distant target;
an algorithm for comparing the travel time of pulses sent from the light meter to travel time distances over a measured period of time to determine the distance to the target object;
whereby luminous intensity of a distant source of light, measured in candelas, is determined by using the digital processor of the controller to calculate luminous intensity from illuminance and distance measurements.

### Claim 2 (depends on 1)

The invention in accordance with claim 1 wherein the metering valve is an iris diaphragm located at the focal plane of the objective lens.

### Claim 3 (depends on 1)

The invention in accordance with claim 1 wherein the light energy detector is a photo detector.

### Claim 4 (depends on 3)

The invention in accordance with claim 3 wherein the controller comprises a switch for selectively activating the distance measuring device of the light measuring apparatus.

### Claim 5 (depends on 1)

The invention in accordance with claim 1 wherein the light energy detector is a photodiode.

### Claim 6 (depends on 1)

The invention in accordance with claim 1 wherein the digital processor receives data from the light energy detector and from the distance measuring device and outputs data to a display in communication with the digital processor.

### Claim 7 (depends on 1)

The invention in accordance with claim 1 further comprises a screen and light intensity measured by the light-measuring device is displayed on the screen.

### Claim 8 (depends on 1)

The invention in accordance with claim 1 wherein the light meter controller is provided with circuitry to switch the light meter from a setting for measuring light intensity or to a setting for measuring total illuminance, or eye illuminance, or a setting for measuring luminance.