TRICOR's Model 820 Video Photometer

Overview

The Model 820 Video Photometer measures the absolute brightness of any size sample or scene and provides quantitative data in fL or cd/m2. The 820 photometer is used to measure the performance of lamps, LEDs, backlit panels, control switches, etc. It also quantifies reflectance, micro pitting, reflective and transmissive haze, and other appearance characteristics.

The 820 photometer generates a 640 x 480-pixel image digitized to 256 gray levels. This offers a light measurement capability equivalent to 307,000 light meters. The lower cost 820 utilizes an interlaced camera and TRICOR's Eyeppearance® software (a Windows® compatible PC-based software system) to provide analysis tools used to establish photometric levels for an image.

A user-friendly Windows® interface offers many menu options for analyzing the acquired gray scale image; however, the real potential of Eyeppearance® is realized when a calibration transform file is loaded for the image. The calibration transform translates the relative gray levels into absolute radiometric levels. Pixel radiance levels and histogram distributions are given in photopic units.

Menu options, such as the Enhance option, provide a close coupling of the image data and the histogram distribution. The image is highlighted in green for a given section of the histogram. The user can use the mouse to quickly change the highlighted radiance levels in bandwidth and position on the histogram distribution. Also, false coloring can be applied to the image, allowing the user to readily see those areas below, above, and within the user-specified tolerance band. Quantitative values associated with the highlighted area(s) are then displayed on the PC screen.

Another powerful feature of Eyeppearance® is its ability to define up to 254 regions of interest. Each region of interest may be any region as outlined by the user using the mouse. From this region an active subset can be selected, which establishes a new histogram distribution and limits image analysis to this active region only.

Specifications And Features

Type	820: CCD Interlaced video photometer with eight user-selectable shutter speeds
Receptor	Silicon CCD filtered to closely match the CIE relative photopic luminosity response
Calibration	System supplied with one set of calibration curves (one curve for each of the eight shutter speeds at one lens f/stop)
Light Measurement Scales Light meter	Absolute: absolute luminance scale (fL or cd/m2) Digital: 8-bit image scale (256 gray levels) Relative: linear scale based on camera shutter speed
Analysis Capabilities (partial listing)	Pixel interrogation CCF (Color Correction Factor) to correct system response when measuring colored subjects. Real-time false coloring ROI (Region of Interest) selection
Optical System	820: 35-mm, f/1.7 lens standard (other lenses available)
Field of View	820: 13.5° with standard lens
Focusing Distance	820: 15.2 cm (6 inches) to infinity with standard lens
Target Area	Minimum: as small as 1 image pixel 820: [0.051mm (0.002 inch) approx.] Maximum: dependent upon measuring distance and field of view with standard lens
Luminance Units	cd/m2 or fL selectable; calibration values in memory automatically converted for user display
Light Measurement Ranges	820: 0.1 fL to infinity; 0.34 cd/m2 to infinity
Accuracy	±4% of measured value (Measuring conditions: subject: standard illuminant A; ambient temperature: 20° to 30° C (68° to 86° F)
Short-term Repeatability	±0.4% (Measuring subject: standard illuminant A)
Resultant Image	640 x 480 x 8 bits resolution (256 gray levels)
Temperature Ranges	Operating: 0° to 32° C (32° to 90° F); relative humidity less than 85% at 32° C (90° F) Storage: -20° to 55° C (-4° to 131° F) with no condensation

System Components

• 820 Interlaced CCD Camera: With shutter control and 35-mm, f/1.7 lens. 4.6 H x 4.6 W x 15.2 L cm(1.8 H x 1.8 W x 6 L inches) 378 g (13-1/2 oz.)
• Cable: 1.8 m (6 feet) long standard
• Photopic Filter with one set of calibration curves
• Tabletop Tripod
• Image Processing Board
• Eyeppearance® Software
• Reference Manual
• Customer Requirement: Personal Computer: Windows® 98, ME, NT, 2000 with half PCI bus slot available

Options

• Measure luminance to MIL-P-7788E and SAE AS7788

Sample Screenshots

Histogram Classification	Profile Window
Locator Option
Software Specification Window	Typical Image

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