Lighting and illumination have become essential in any sphere of life and they perform an auxiliary function when daylight is not enough or is absent. How much light is necessary? Is artificial light necessary if a natural light, both, inside and outside, is available? When is artificial light a huge help and when is it a complete waste?

In the workplace, the illuminance should be adapted to the visual tasks of the activity. Good lighting is one of the prerequisites for safe and error-free work. Depending on the work task, the minimum illuminance values can vary greatly. For processing or visual inspection of very small details, illuminance levels of 1,000, 1,500 or even 2,000 lux are required. In contrast, in storage areas where only similar large parts are moved but not inspected, it is sufficient to determine an average illuminance of at least 50 lux with the light meter.

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The PCE-172 Light Meter is used for accurate measuring of brightness in the industrial sector, commercial sector, agricultural sector, and for research.

DIN EN 1838 Applied lighting technology – Emergency lighting The national editions of EN 1838 specifically regulate where safety lighting and safety signs must be installed and how they must be checked. Annex A describes the specifications for measuring luminance and illumination and for the lux meters to be used, and Annex B lists the national deviations.

Measuring range: 0.1 … 150,000 lux / 0.01 … 15,000 foot-candleSpectral wavelength range: 360 … 780 nmDisplay: 3.2" colour LCDChromaticity: Ev xy, Ev u'v'

Laserton offers various types of lenses, including plano-convex, plano-concave, double convex, double concave, meniscus, ball, achromatic and cylindrical lenses.

In the USA, the lighting requirements for the workplaces are also divided into general lighting, task-related lighting, and emergency lighting in the event that the general power supply fails. According to the standard 1926.56 of the occupational Safety and Health Administration (OSHA), the following minimum values for the general lighting apply to the workplaces where at least one employee is present:

PCE-LED 20 is a light meter with an external LED light sensor. The cable of the LED light sensor has a length of approximately 1.5 m / 4.9 ft.

Italy For venues such as cinemas or theatres, Italy requires an illuminance of at least five lux in the area of stairways and exits and at least two lux along the rest of the escape routes. The values must be measurable on site. They must be checked with the lux meter at a height of one meter above the floor.

Since large differences in brightness between lighting and background can lead to glare or missing dimly lit signs and obstacles, the following luminous intensities should not be exceeded in accordance with EN 1838:

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The angle of view of the camera is determined by the ratio of the image size on the film and the focal length. Film-based cameras have for a long time mostly used 35-mm film (also called 135 film according to ISO Standard 1007), where the image size on the film is typically 36 mm × 24 mm. (The width of the film spool is 35 mm, somewhat larger than 24 mm, as the picture does not extend to the edges of the spool.) A standard objective then has a focal length of 50 mm. However, modern digital cameras (particularly the more compact ones) often contain image sensors which are smaller than 36 mm × 24 mm, so that an objective lens with a correspondingly smaller focal length (e.g. 32 mm instead of 50 mm) is required for obtaining the same field of view. As many photographers are still used to the previously valid relation between focal length and angle of view, it has become common to specify the effective focal length of an objective of a digital camera as that focal length which would give the same angle of view in combination with ordinary 35-mm film. For example, an objective with a true focal length of 32 mm may then be said to have an effective focal length of 50 mm and thus function as a standard objective, rather than e.g. a macro or tele objective.

- Range: 40 ... 400,000 lux- Accuracy: ± 5% of reading ± 10 digits (10,000 lux)- 3.5-digit LCD display- Incl. ISO Calibration Certificate

Integrated compact fluorescent light (CFL) bulbs are reminiscent of incandescent light bulbs, because both kinds of bulbs feature the same base. Integrated CFLs can be used in many standard incandescent light fixtures. The difference between integrated CFL and incandescent light bulbs is that the service life is much longer (in average 8 – 13 hours) and the energy consumption is ¾ lower for integrated CFL bulbs. Aesthetically, the twisted-tube design of the integrated CFL bulbs looks much different than the egg-shaped design of the incandescent light bulbs. For this reason, some consumers prefer to use incandescent light bulbs in clear glass light fixtures.

The main contents of the BG 131 "Natural and artificial lighting of workplaces" were incorporated into the ASR A3.4 "Lighting" technical guideline for workplaces in 2011. As with other requirements relating to safety and health protection, the PAs also provide targeted support to their member companies in implementing the specifications for lighting.

where <$a$> is the distance from the original focus to the lens. This shows that <$b \approx f$> if <$a \gg f$>, but <$b > f$> otherwise. That relation can be intuitively understood: a focusing power <$1 / a$> would be required to collimate the incident beam (i.e. to remove its beam divergence), so that only a focusing power <$1 / f - 1 / a$> is left for focusing.

Curved laser mirrors usually have a curvature radius somewhere between 10 mm and 5 m. The fabrication of dielectric mirror coatings can be more difficult for very strongly curved mirror substrates, but with refined techniques it is possible to reach focal lengths of only a few millimeters, as required for some miniature lasers.

In a system, an EUV light source makes use of a high power laser to create a plasma. This, in turn, helps emit a short wavelength light inside a vacuum chamber.

What measuring range and accuracy should the light meter have? The measuring range is determined by the application. For many light measurements in recreation rooms, a measuring range of up to 2,000 lux or even 10,000 lux is sufficient. For work areas where a lot of light is required and when outside high illuminance levels from daylight must also be measured correctly, the measuring range should extend at least to 100,000 lux or beyond.

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All values in the OSHA standard are specified in the foot-candle unit of measurement commonly used in America. An illuminance of one foot-candle is equivalent to one lumen over an area of one square foot. The SI unit lux, on the other hand, represents one lumen per square meter of the illuminated area. Many lux meters can display readings in both foot-candle and lux. If the lux meter does not provide the desired unit, the values can be easily converted. The conversion factor between foot-candles and lux is thus equivalent to that between square meters and square feet.

If you have any questions about the light meter products found on this website, please contact the technical sales and support team at PCE Instruments at or +1 (561) 320-9162.

In almost all work areas, LED luminaires have now proven to be an energy-saving alternative to other light sources. Due to the EU Ecodesign Directive with Regulation (EU) 2019/2020, after incandescent lamps, many fluorescent and halogen lamps with comparatively high energy consumption will also be removed from the market. Nevertheless, there are still a large number of light sources with different light spectra. High-quality light meters enable a correction of the measured value adapted to the spectral bandwidth and distribution of the respective light source.

Emergency lighting for workplaces in Australia In Australia, the National Construction Code (NCC) regulates which buildings and areas require emergency lighting. Any building accessible to the public or to employees or customers must be equipped with emergency lighting. The Australian Standard AS/NZS 2293 contains the regulations for the design, installation, operation of emergency lighting and escape route marking. It requires a minimum brightness of one lux for emergency lighting on stairs, an average of at least 0.5 lux on floors, and 0.2 lux as a minimum value. Part two of the standard describes the checks and maintenance that must be carried out and documented every six months, twelve months and every 10 years respectively.

In the current Life Safety Code 101 of the National Fire Protection Association, the Section 7.9 deals with the regulations for the emergency lighting design. The brightness should achieve the average one foot-candle (10.76 lux) and not less than 0.1 foot-candle (1.08 lux) at any point along the escape routes for ninety minutes after the failure of the regular lighting. No SI units are listed in this American standard. If the lux meter is used that cannot display a foot-candle, the lux values obtained must be converted.

Ordinary lenses, working on the basis of refraction, have a focal length which is slightly wavelength-dependent due to the wavelength dependence of the refractive index (–> chromatic dispersion). This effect leads to chromatic aberrations of imaging systems and similar problems in other applications where an optical system is used for a wide range of optical wavelengths. Lens combinations (e.g., objectives for photographic cameras) can be designed such that chromatic aberrations are minimized. Most common is the use of achromatic doublets, i.e., lenses consisting of two different glass materials chosen such that the overall chromatic aberrations are largely canceled.

where it is assumed that the beam radius at the focus is much smaller than the initial beam radius <$w_0$>. (This condition is violated for beams with a too small incident radius; the focus is then larger than according to the given equation.) Also, it is assumed that the beam radius is significantly larger than the wavelength <$\lambda$>, so that the paraxial approximation is valid.

Can the light meter be calibrated and adjusted if necessary? In the areas where too high or too low light intensity has a serious effect, it should be ensured that the measuring device used for testing works correctly. This is done by testing the accuracy of the measurements under specified conditions. Some instrument models can also be adjusted by the user. This means that these models can be readjusted if necessary to output the measurement results as accurately as possible .

The term candela refers to candlelight. Thus, it is easy to remember that a candle flame shines with a luminous intensity of one candela. In contrast, a bright firefly has a luminous intensity of only 0.004 candela, and the daytime running lights on motor vehicles have a luminous intensity of at least 400 candela. The high beam of all headlights on a road vehicle may not shine brighter than 225,000 candela, and beacons used as orientation aids for seafaring may emit 35,000,000 candela, for example. The luminous flux and luminous intensity of luminaires and lighting elements are generally determined in the course of product development and during quality control at the manufacturers' with a special light measuring device.

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Humanity has developed a variety of man-made light sources to illuminate the dark and to light indoor spaces. Recommendations for indoor lighting depend on consumer preference and the location of the light source (e.g., home, office, school, parking lot, street, theater or hospital examination room, operating room, recovery room, etc.).

External sensor with UV correcting filterAuto after 10 minutes of inactivity to conserve battery powerLarge LCDMinimum, Maximum and Data Hold functions0.000 to 1.999 mW/cm2 or 0.000 to 19.9 W/m²1.999 to 19.99 mW/cm2  or 19.99 to 199.9 W/m²

BS ISO 8995 "Lighting of indoor work places" is the British equivalent of ISO 8995/CIE S 008/E and implements its contents into national law. This standard defines the parameters of illuminance, glare and colour rendering for indoor workplaces for variously demanding activities. To ensure good lighting, not only the quantity of light but also its spatial and spectral distribution must be considered. The standard provides the basis for assessing the lighting of workplaces in offices, agricultural buildings, many different craft or industrial buildings, but also for schools, churches, libraries.

For a focusing lens, this means a reduced phase delay for increasing <$r$> coordinate. Note that there are different sign conventions in wave optics, where a phase delay can correspond to a positive or negative change of a phasor (complex amplitude).

Great Britain In Great Britain, the requirements for emergency lighting are regulated in British Standard BS 5266. One of the requirements is that emergency lighting should take effect 5 seconds after the failure of the general lighting system. An extension of this period to 15 seconds is possible in the buildings used mainly by people who know the escape routes.

The following equation allows one to calculate the dioptric power and thus the focal length of lens made of a material with refractive index <$n$> and with curvature radii <$R_1$> and <$R_2$> on the two surfaces:

Jun 27, 2024 — Hyperspectral imaging provides more detailed data than multispectral imaging, allowing more specific analysis and accurate identification of ...

Considerable confusion arises from the fact that in the context of photo cameras the term effective focal length is also used with an entirely different meaning, as explained in the following.

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Unfortunately, the terms are also used differently by other authors. For example, it happens that a focal distance is assumed to be the same as a focal length. Therefore, some product catalogs specify focal lengths, which should actually be called focal distances, and in addition the effective focal length.

In order for the light meter to provide the appropriate values for the application, attention must be paid to the following:

Light Meter PCE-170 A to 40,000 lux, internal sensor, automatic zero adjustment. The light meter has a large measurement range, short response time and a compact housing allowing for quick, effortless one-hand operation.

Directive 89/654/EEC, which defines the minimum safety and health requirements for workplaces, also specifies the requirements for emergency lighting.

The British Standard BS 667 "Illuminance meters. Requirements and test methods" specifies the requirements for lux meters and test methods. It defines two classes of light meters, Class F for field measurements and the more accurate Class L for laboratory measurements. The requirements for the type L lux meter according to this standard are the same as those required for lux the meters by the British-European BS EN 13032-1. However, BS EN 13032-1 requires additional characteristics.

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EN 50172 Safety lighting systems The European standard EN 50172 specifies the minimum requirements for the design, monitoring and maintenance of electrical safety lighting systems in workplaces and in structures where people congregate. It also points out national specifics.

Warning lights on cranes, masts, overhead power lines, towers, chimneys and buildings are also needed, especially at night. They have to be adjusted to the hazard to be expected in their position and height. For example, pilots should be able to detect potential collision points in the vicinity of airfields or hospitals with helipads in good time, even at night or in fog.

The purpose of emergency lighting is to ensure that in the event of power failures due to inadequate lighting, there will be no damage caused by faulty operation or accidents. According to the purpose of the emergency lighting, it can be divided into backup lighting and safety lighting. Backup lighting is used almost only in critical areas where normal lighting cannot continue to operate for a sufficiently long time using an emergency power supply.

For an optical system, which may consist of multiple lenses and other optical elements, the above definition of the focal length cannot be used, as it is not clear a priori for an extended system where to measure the distance to the focus: from the entrance into the optical system, from the exit, the middle, or some other position? In principle, an arbitrary definition of a reference point (e.g. the entrance or the middle) could be used, but that would in general mean that some common rules can not be applied, which e.g. hold for the radius of the beam waist at a focus behind some lens with a given focal length (see below), or the possible magnification of a telescope containing that optical system.

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The safety lighting is often planned and executed with lower illuminance levels than the normal lighting. It is intended to enable orientation in and safe exit out of the building in the event of failure of the normal lighting. In addition to illuminating escape and rescue routes, danger points, signs and warning devices, the safety lighting is also used to prevent panic situations.

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Orienting measurements with a lux meter Orienting measurements of the lighting at the workplace allow an assessment of the actual situation, considering the ambient conditions. The checks can be carried out by competent employees of the company using a suitable lux meter. Prior to the measurement, a measurement grid must be defined which is to be used not only for this series of measurements but also for subsequent regular maintenance.

Low-loss ion-beam-sputtered anti-reflection (AR) coatings with reflectivity less than 0.1% per surface and low-absorption high reflector mirror coatings are available on PPD lenses or can be applied to customer supplied substrates. PPD uses only IBS thin film deposition technology because it is a repeatable process which results in coatings that are durable, stable and easy to clean.

Should the light meter be used continuously at the same position or at different measuring points? Depending on whether the light meter is used for continuous monitoring of lighting conditions at a specific location or for the measurements at different locations, the requirements differ. In the case of the light meter that is to be used stationary in a light-sensitive production process, it makes sense to forward the measured values directly via interfaces to other devices for data evaluation or for controlling the lighting or shading equipment. In the case of devices that are used on as mobile devices at many different measuring points, attention should be paid to the storage options for the measured values. For certain measuring conditions, it is also advantageous if the light meter has an external sensor. The device can then be read-out and operated more easily without the risk of shading the sensor.

Lastly, neon lighting can be found in some indoor environments. Neon lighting is comprised of electrified glass tubes filled with rarefied neon or other gases. The type of gas used in the tube determines the color of the neon light. Neon lights can be used for decorative lighting in bars and nightclubs as well as for small indicator lights in electronic displays.

One may eliminate chromatic aberrations altogether by using optical systems with mirrors only. A curved mirror with radius of curvature <$R$> has a focal length <$f = R / 2$> (for normal incidence), determined only by the geometry and thus independent of the wavelength. On the other hand, for non-normal incidence the focal length in the tangential direction is decreased by the cosine of the angle of incidence, and increased by the inverse cosine of that angle in the sagittal direction. Therefore, such mirrors can introduce astigmatism.

Should the light meter also be used to determine the color temperature of the light? The light meter with additional equipment can also be used to measure light colors. The distribution of the wavelengths or frequencies of the radiation is characteristic for the perceived light color. The color of light not only affects the perception of the illuminated surfaces, it also influences many cell activities in living organisms. The color coordinates of light can be specified as primary colors in three-part additive color models, for example, as red, green, and blue values according to the CIE-RGB color space or as X, Y, and Z values according to the CIE-XYZ color space. Many models that measure the light color not only give the numerical values for the primary colors, but also show the color distribution of the measured light graphically on the colored device display.

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In Australia, the minimum illuminance requirements for occupational health and safety have been specified in Australian Standard AS(/NZS) 1680 "Interior and workplace lighting". Part 3 of this series of standards deals with the measurement, calculation and evaluation of the lighting data, and Part 4 with the maintenance of the electrical lighting.

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In contrast to focal lengths, focal distances are related not to the principal planes but rather to the vertex points of lenses (not caring about a housing, which may be further extended). The front focal distance is thus the distance between front focal point and the entrance surface of the optics, while the back focal distance is the distance between the back surface and the back focal point.

If a divergent (rather than collimated) beam hits a focusing lens, the distance <$b$> from the lens to the focus becomes larger than <$f$> (Figure 2). The lens equation states that

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Based on its accuracy, the light meter can be classified in one of the accuracy classes according to DIN 5032 Part 7. These accuracy classes simplify the selection of device models. An instrument with the accuracy class C should only be used for orienting measurements. Class B and A instrument models can be used for measurements of lighting in businesses and public areas. For particularly precise measurements, on the other hand, the light meter of the highest accuracy class L should be used.

For first-aid stations as well as fire alarm and firefighting equipment, the illuminance of at least five lux must be achieved via the safety lighting. Escape routes in Germany must have an illuminance of at least one lux along the centre line in an emergency, and the centre area of the escape route must have at least 0.5 lux.

Measurement range: 0.00 to 40,000 luxResolution: 0.01 lux in the range 39.99 LuxLarge 5-digit LCD displaySensor: silicon photodiode

Sep 28, 2022 — The colored bands on the outside of the microscope indicate the magnification of the lens. The standard magnification bands are as follows: red ...

PCE Instruments' light meters with data loggers are highly regarded in the industry due to the devices' cosine correction of the angle of incident light. Many light meters include software for detailed analysis and offer different interfaces for transferring measured data to a computer.

PPD manufactures custom, high precision optical components including spherical lenses, lens assemblies and spherical mirror substrates for imaging, machine vision and high energy laser applications from the ultraviolet (UV) through the near-infrared (NIR). Coated and uncoated optics are available from 2 mm to 8” in diameter and in a wide range of materials including fused silica, infrasil, N-BK7, YAG, SF11 and other high index glasses. If your radius of curvature is not yet determined, contact us for information on existing fabrication tooling and test plates, or send us your design specifications for a fully custom lens or mirror quotation.

Since the 2011 edition, ASR A3.4 has been consistent in many areas with the European standard EN 12464. This has significantly simplified the simultaneous application of both standards. In individual cases, however, there are deviations in order to achieve a higher level of protection for workplaces. Depending on the type of activity and ambient conditions, other standards must be considered when planning and maintaining the workplace lighting.

- each employee can perform his tasks without safety and health risks, - every employee can move around the workplace without safety and health risks, and - every employee can leave his workplace safely in dangerous situations.

Measuring range: 40 / 400 / 4000 / 40000 / 400000 lx or fcMeasuring units (selectable): Lux (lx) or footcandle (fc)Accuracy: ± 3% (with a standard incandescent lamp at 2856 K and LED white light), ± 6% for other visible light sources

OPTOMAN's AR-coated lenses are optimized for high laser power applications. These lenses can be used for intracavity, multi-kW CW, and ultrafast pulse applications. Sputtered anti-reflective coatings feature reflectance per surface down to R < 0.01%.

We offer precision optics lenses from 0.5 mm to 500 mm diameter. Surface quality can reach λ/10. All optical materials available.

Whether this rule can also be applied to an extended optical system with focal length <$f$> depends on the applied definition of <$f$>. It is useful to specify an effective focal length which is valid for such relations.

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Germany In the Point 7 of the Technical Regulation for Workplaces ASR A3.4 it goes about the safety lighting for activities, workplaces, work rooms and areas. It states that illuminance needs to be adapted to the hazard situation on site.

The aforementioned incandescent light has been used for decades in numerous indoor lighting applications. Incandescent light bulbs produce a soft and pleasant glow. This is why incandescent lighting still can be found in residential homes, even though incandescent light bulbs consume much more energy. Incandescent lamps get warm over time, and though the extra heat can help keep indoor temperatures warmer during the winter months, careful handling of recently or currently illuminated bulbs is required, because touching the hot light bulbs can burn the skin.

ASR A3.4 states with regard to the lux meter: "If the orienting measurements are carried out during the operation with the purpose of selecting or testing lighting equipment, illuminance meters that comply with at least Class C in accordance with DIN 5035 Part 6, 2006-11 edition, are to be used."

The dioptric power (also called focusing power) of a lens is defined as the inverse of the effective focal length (which is the same is the front and back focal length if the median on both sides of the optics is the same). This means that a strongly focusing lens has a small focal length, but a large dioptric power. For prescription glasses, it is common the specify the dioptric power, whereas the focal length is specified for standard lenses, microscope objectives, and photographic objectives.

The German Social Accident Insurance, with the support of the employers' liability insurance associations, has published a range of information explaining how to implement the requirements for the workplace lighting:

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Another alternative to incandescent lighting is halogen lighting. Sometimes halogen light bulbs are selected for use in table lamps, inside and under cabinets, and in different wall-mounted fixtures. Halogen lights are small in size, contain halogen and inert gas, and offer a higher level of brightness and a longer service life.

How much time can we spend without light? How much can be done, produced or achieved in the darkness? Definitely, not much … Light in the modern world is needed as air, in absolutely all spheres of private and industrial life. Light Meter, represented by a variety of versions with versatile functions, is an auxiliary tool which can be applied easily in the workplace, at home, for monitoring different processes in order to measure the amount of light and other associated parameters and carry out, if necessary, different adjustments for reaching the desirable level of comfort and performance.

- in indoor areas of construction sites and warehouses, in hallways, corridors and along escape routes            5-foot candles,

France In France, only specially certified emergency luminaires may be used. For anti-panic lighting, these emergency luminaires must emit at least five lumens per square meter. Regardless of this, at least two luminaires are required per room. The distance between several emergency luminaires must not be greater than four times their distance from the ground, and not greater than fifteen meters on escape routes.

The PCE-172 Light Meter is used for accurate measuring of brightness in the industrial sector, commercial sector, agricultural sector, and for research.

Measurement range: 0.00 to 40,000 luxResolution: 0.01 lux in the range 39.99 LuxLarge 5-digit LCD displaySensor: silicon photodiodeIncl. ISO Calibration Certificate

A light meter is a device that helps to answer all these and other questions. It is a device which finds its application literally everywhere, from household to work places, streets, recreational and other facilities, illumination of the highspeed and other roads, all possible types of establishments and institutions. A very sensitive electrical device helps to monitor and control the level of illumination of any area. Lux is a standard, well-known unit, in which the measurements are expressed. Another possible term used in some systems may be foot candle (lumens per square foot).

The curvature radii are taken as positive values for convex surfaces and negative for concave surfaces. Positive results are obtained for focusing lenses, negative results for defocusing lenses. The last term is relevant only for thick lenses with substantial curvature on both sides. The formula delivers the focal length within the paraxial approximation, not considering spherical aberrations, for example.

The measurement results are to be evaluated with regard to compliance with the minimum values as well as the achievement of the required uniformity. In the workplaces where the activity requires a high colour rendering index, this should also be checked. Some lux meters allow not only illuminance to be measured but also the colour rendering index. If there is any doubt about the usability of the measurement results, the experts should be consulted. They can carry out specific measurements in accordance with DIN 5035-6 "Lighting with artificial light, Part 6 - Measurement and evaluation" and, in connection with this, provide advice on how to carry out subsequent orienting measurements.

One of the most popular achievements in modern lighting technology is the light emitting diode (LED). LED lights can be found almost anywhere, inside and outside, and are available in different sizes and colors. The LED's greatest advantages are low energy consumption and long service life. These attributes make LEDs very attractive to consumers. LEDs do not emit as much heat as incandescent lights. Even when an LED light is on, there is no risk of burning the skin if the light bulb is touched. In addition, thanks to their epoxy lenses, LEDs are not too fragile. Though LEDs are quite popular nowadays, other types of indoor lighting still are widely used.

The focal distance should also not be confused with the working distance, which is the distance between a specimen and the lens housing. Note that a specimen is not necessarily placed in the focal plane, e.g. when the input light to an objective is not collimated.

Besides, “comfort level” factor, which matters in general for any person, there is also “performance” factor. They now always coincide, due to a huge variety of jobs and tasks, but they should be kept in a certain balance. Educational establishments, hospitals, laboratories, factories etc. – these are the places where the level of light should be sufficient for 100% productivity. For example, if the light required is too bright or it should be too dim, the working process should be organized in such a way, so that the worker had enough breaks, allowing the eyes to relax, and was wearing respective eye protection. At the same time, it should not cause problems for the workers fulfilling other tasks, and whose comfort is totally disturbed by the improper lighting.

Curved mirrors are often used for focusing or defocusing light. For example, within laser resonators curved laser mirrors with dielectric coatings are more commonly used than lenses, mainly because they introduce lower losses.

The formula ignores the constant part of the optical phase change as well as optical aberrations. Note that depending on the function of the lens – for example, focusing collimated input beams or refocusing divergent light –, higher-order terms in the phase profile may be required to avoid optical aberrations.

Selection criteria for the light meter to measure illuminance First, the light meter must be suitable for the purpose of the measurement. This is not only a question of whether the luminous flux, luminous intensity or illuminance is to be determined. It is also important whether the light is to be used primarily for people, for plants or for technical purposes. Most light measurements are intended to measure the illuminance achieved for the particular light use at specific locations. Even if in each case the illuminance is measured in lux, the measured values of different devices at the same position and with the same illumination can differ considerably.

A standard light meter is a useful tool for evaluating indoor lighting conditions, especially those involving incandescent and fluorescent light bulbs. When evaluating LED lighting indoors, an LED-specific light meter is recommended.

Ecoptik produces a wide range of spherical lenses of different types (including meniscus lenses, half ball lenses, custom hyper-hemisphere lenses and achromatic lenses). We are happy to produce custom lenses of many types.

For work areas not covered by those described, the recommendations of the American Standard A11.1-1965, R1970 are the basis for the evaluation.

For a defocusing system, the front focal plane can be located on the output side; it contains a virtual focal point. Again, the focal length is the distance between principal plane and focal plane.

Should the illuminance be measured according to human visual perception or for other purposes? In the standard DIN EN 13032 Part 1, Annex B describes many device-specific parameters that have an influence on the measurement result of the light meter. For the measurements of illuminance in the workplaces, in recreation rooms, playgrounds, sports facilities and traffic routes, it is important that the measurement is made according to the spectral sensitivity of the human eye. The light meter should be able to detect and evaluate the visible spectrum of different light sources according to this spectral sensitivity. In addition, it must also be possible to detect obliquely incident light. For other purposes, the sensitivity to ultraviolet and infrared light, the evaluation of polarized light and of time-varying light, among others, can play a major role.

For some applications, in particular for focusing of imaging systems, it is essential than the focal length of an optical system can be fine adjusted. The following physical principles can be used:

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Workplaces where inadequate lighting poses hazards to workers, the surrounding area or the general public should be equipped with emergency lighting to minimize these hazards. In general, the required emergency lighting should ensure that, in the event of a failure of the normal lighting, the brightness in the affected area is sufficient to identify escape routes, warning, auxiliary and signalling devices and to carry out safety-relevant activities. The specific requirements for planning, installing and testing emergency lighting are defined in directives and standards. There are some country-specific features.

Traditionally, when one thinks of fluorescent lighting, one envisions the long tube-shaped bulbs frequently used in industrial-looking overhead light fixtures. Since these large fluorescent bulbs produce a very bright light, they are often referred to as daylight lamps. Because there is a certain amount of mercury in these kinds of light bulbs, the bulbs should be handled and disposed of carefully.

Similarly, one can define the back focal plane (or second focal plane) and back principal plane (or second principal plane), where horizontal rays occur on the left side, while on the right side one has converging rays for a focusing system and diverging rays for a defocusing system. If the refractive index is the same on the input and output side (e.g. ≈1 for air), the front focal length and back focal length are identical (apart from possible sign differences used by some authors) and can thus simply called the focal length. The two principal planes, however, generally do not coincide for thick lenses, and they can even lie outside a lens.

The explained definition delivers a focal length which can also be used in equations for the size of the focus (see below), for example.

EN 1838 states that the proof can be provided by measurements or binding information from the manufacturer. Since deviations and defects of individual luminaires or lamps, their aging, possible soiling and special local conditions have an influence on the illuminance, on-site measurements with the lux meter should be preferred.

Note that the lens equation applies for rays, assuming that the paraxial approximation is valid, i.e., all angles relative to the beam axis remain small.

When checking the actual lighting situation in the workplaces, a grid of several measuring points in the lighting level must be measured with the light meter. The values determined must be documented. On the one hand, it must be demonstrated that the average illuminance on the work surfaces corresponds at least to the specifications for the activity. On the other hand, the illuminance of the surrounding area must be determined by additional measurements in the vicinity of the work surfaces. The light meters used for the orienting measurements should correspond in their accuracy at least to class C according to DIN 5035 part 6.

Explanations of luminous flux, luminous intensity and illuminance In light measurements, the brightness is specified either for the light source or for the illuminated surfaces. In relation to the light source, a distinction can be made between the total emitted luminous flux in lumens and the luminous intensity in candela, which also takes the beam angle into account. One candela corresponds to one lumen per steradian, i.e. per solid angle unit. In the luminaires and lamps currently available, the luminous flux is almost always specified in lumens. To determine the luminous intensity in candela, the number of lumens must be divided by 4 π for a light source radiating uniformly in all directions, and by 2 π for a light source radiating only in a hemispherical way.

The Model 02-014-1 is an air spaced, computer designed multi-element lens that is diffraction-limited when used with fibers having core diameters as large as 1200 microns. Operational wavelength is 1064 nm. The 02-014 reimages the emitting surface of the fiber with a 0.67× demagnification. Focused spot sizes are significantly smaller than those achievable with single-element lenses used in a similar collimating/focusing configuration. All optical elements are fabricated from high laser-damage resistant glasses and are anti-reflection coated to reduce reflectance per surface to 0.13%. The working distance between the lens and the target is sufficiently large to allow use of a gas nozzle to enhance the cutting or welding process and to prevent debris from depositing on the lens surface.

Light meter is small in size, convenient to operate and since modern devices are equipped with a lighted screen (made of special glass), the reading of the measurements is significantly facilitated. Robust housing of the device protects the photocells from possible damages and excessive exposure to direct light of different origin (it may be natural sunlight, fluorescent light, high-intensity discharge lights, based on different gases).

Note that the locations of the left and right edges of the optical system (e.g. positions of outer lens surfaces, optical windows etc.) or its housing are not relevant for those definitions.

Our spherical lenses are widely used in a variety of industrial and detection cameras, microscopic objectives, spectral imaging, machine vision, infrared night vision and sensing, thermal imaging, environmental protection and biology. Lenses can be equipped with anti-reflective coatings, HR coatings and metallic mirror coatings, dielectric films and spectroscopic films.

Jan 7, 2020 — The Alvium 1500 series is the perfect camera for easy hardware and software integration in embedded applications. All models are equipped with a ...

Too low brightness requires high concentration and leads to higher time requirements and faster fatigue. Excessive differences in brightness in the field of vision and glare caused by excessively bright light or reflections are also disturbing. When planning lighting, it is not only necessary to ensure that the work areas are sufficiently and as uniformly illuminated as possible. In the lighting design it must be also considered what the brightness and the gloss level of the walls and ceilings surrounding the workstation are.

The illuminance for the safety lighting must be selected according to the user group and local conditions. Separate regulations for safety lighting exist, for example, for meeting places, sports facilities, catering establishments, accommodation facilities, sales outlets, schools, hospitals, nursing homes, high-rise buildings and large garages. During regular inspections of safety lighting, the illuminance must be tested under suitable ambient conditions with the suitable lux meter.

The effective and peak luminous intensity of the warning lights can be measured with a lux meter and expressed in candela. The unit candela indicates the luminous flux in relation to the solid angle. The ECE-R65 test guidelines describe two different types of the warning lights that can be approved on the road vehicles. Class 1 includes beacons with a light level independent of the ambient light. Beacons where the light level is lowered at night belong to class 2.

Light plays a major role in most living organisms and in the operation of certain chemical processes. The light radiation occurring at a particular location can be described by the values for brightness determined with a light meter and by the colour of light. However, the term light meter or photometer is used to describe not only the devices for measuring the properties of light, but also the devices that use light sensors to determine quantities that affect the light transmission of the substance under inspection. In the following text, only the devices used to determine the values for light properties of light sources or of illuminated surfaces will be discussed.

- for concrete work, excavations, for refuelling, waste storage areas, loading docks, storage areas, maintenance aisles           3-foot candles,

The light meter consists of a measuring sensor with a handle and a wall bracket with a 1.5 m (4.9 ft) cable, a light transmitter and a digital display. The main area of application of the light meter is in the continuous light measurement and light monitoring of photo laboratories and production rooms (e.g. food or drug production …).Measuring range: 0 … 50000 lux in three areasResolution: 0.1 lx / 1 lxAccuracy: ±5% of reading4 to 20-mA analog output

The backup lighting is intended to guarantee, independently of the normal lighting, that the necessary activities can continue under suitable lighting conditions. For this reason, the illuminance of the backup lighting is usually selected to be as high as that of the normal lighting. This illuminance should be checked at regular intervals with the lux meter for both general and backup lighting.

Arranging proper illumination for the workers performing their tasks outside is even more complicated, since it is difficult to predict and count on permanent stable illumination by natural light sources. That is why auxiliary lighting sources must be provided if the level of the natural light is not sufficient. The same relates to the professionals working in the dark time of the day or having late shifts. The range of workplaces and illumination requirements to them is extremely wide, but all of them have been classified and organized by the official authorities. Health care organizations pay a big attention to this issue, and numerous rules, standards and regulations are continuously discussed and monitored. The requirements to lighting at workplace may be found in the guidelines of International commission on Illumination, ISO 8995, Society of Light and Lighting (SLL) in Britain, European Norms, Illuminating Engineering Society of North America (IES) and similar organizations.

Enter input values with units, where appropriate. After you have modified some values, click a “calc” button to recalculate the field left of it.

If a collimated Gaussian beam with beam radius <$w_0$> hits a focusing lens with focal length <$f$>, the beam radius of the beam waist (focus) after the lens can be calculated with the equation

Different sign conventions for focal lengths are used in the literature. For example, one may have a negative front focal length if the front focal point lies before the front principal plane. Obviously, any equations involving focal lengths should be used with the assumed sign conventions.

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Enter input values with units, where appropriate. After you have modified some values, click a “calc” button to recalculate the field left of it.

Enter input values with units, where appropriate. After you have modified some inputs, click the “calc” button to recalculate the output.

The Directives issued by the Council of the European Communities apply to all member states of the European Communities.

EA Bibikova · 2019 · 5 — We have studied the far-field diffraction of a Gaussian beam by a half-plane edge placed near the beam waist. We have solved numerically the Helmholtz equation ...

Knight Optical has an extensive lens portfolio which are suitable for a variety of applications. Our stock lenses included aspheric, achromatic doublet, ball & half ball, biconvex, cylindrical, condenser, Fresnel, planoconcave/convex, plastic and rod lenses. Knight Optical also offers custom lenses if our stock optics do not meet our customer’s requirements.

A light meter is a very sensitive electronic measuring device used to help monitor the illumination of any given area. Most light meter devices are small in size, simple to operate and equipped with an easy-to-read lighted screen made of special glass. Typically, a heavy-duty housing protects the light sensor inside the light meter from damage. A light meter is used for measuring brightness in lux (lx), foot candle (fc) or candela per square meter (cd/m²)measuring units. Some light meter devices are equipped with an internal memory or data logger to record and save measurements. The measurement of light intensity with a light meter is becoming increasingly important in the workplace due to safety concerns. Light measurement is also necessary to determine the best location and angle when installing and adjusting solar panels.

Light Meter PCE-170 A to 40,000 lux, internal sensor, automatic zero adjustment. The light meter has a large measurement range, short response time and a compact housing allowing for quick, effortless one-hand operation.

The equation shows that what determines the minimum possible beam radius is not the focal length <$f$> alone, but rather the ratio of <$f$> to the radius of the open aperture of the lens, which sets a maximum to the input beam radius <$w_0$>. For a focusing or collimation lens, that ratio is essentially the numerical aperture of the lens.

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A common (but not universally used) approach for the definition of focal lengths of extended systems is based on geometrical optics. For finding the front focal point, one calculates rays which are horizontal on the back side (see Figure 2), using the paraxial approximation. The optical system is considered as a “black box”, where one does not care about the actual ray paths; instead, one works with internal rays which are extrapolated from the outer rays. Based on those extrapolated rays, one can define the front principal plane (or first principal plane). The front focal length is then the distance between the front focal point (in the front focal plane) and the front principal plane (see Figure 2). Some authors define the focal length to be negative in the situation of Figure 2 because the focal point is located before the front principal plane; others take the absolute value.

The lighting situation in the workplaces must be checked on site with a suitable lux meter in accordance with the cycles specified in the planning. The lux meter used must have sufficient accuracy for all light sources to be tested in operation. If the measured values do not correspond to the specifications, the lighting must be adjusted.

A mirror with a curvature radius <$R$> of the surface has a focal length <$f = R / 2$>, if the beam axis is normal to the mirror surface. (We take positive signs for concave curvatures and focusing mirrors.) If there is some non-zero angle <$\theta$> between the beam axis and the normal direction, the focal length is <$f_{\tan} = (R / 2) \cdot \cos \theta$> in the tangential direction (i.e., within the plane of incidence) and <$f_{sag} = (R / 2) / \cos \theta$> in the sagittal direction.

PCE-CRM 40 is a portable handheld LED light meter or spectrophotometer used to accurately measure the correlated color temperature (CCT - in Kelvin), illuminance, chromaticity, excitation purity (Pe), luminous flux (in lumens - lm), RGB and dominant wavelength of light sources such as LED, organic LED (OLED) and other forms of organic electroluminescence (EL).

While luminous flux and luminous intensity can be used to compare the light output of different light sources, illuminance describes how much light is incident on an illuminated surface. Illuminance is specified as an area-related quantity in lux, where one lux is defined as one lumen per square meter. Apart from the sun as a very strong light source, it is easy to see, even without a light meter, that the brightness of the light hitting a surface decreases with increasing distance from the light source. However, it is not only the distance from the light source that affects how much light arrives, but also additional light sources, shading, attenuation, and reflections from surrounding surfaces. The luminous intensity of elements for artificial lighting can also be weakened by aging or soiling. It is therefore advisable to check the illuminance at the relevant points on site not only immediately after installation, but also at regular intervals later with the help of the suitable light meter. In the case of technical systems for the use of sunlight, it is recommended to use the light meter before the installation to check which arrangement is the most favourable. After the installation, it can be checked whether the system achieves the promised performance for the amount of the incident light.

Warning lights are almost always coloured, as additional information can be provided via the colour. Warning lights in plants and on vehicles must be perceived even in bright daylight and concentrated activity or heavy traffic. They must therefore shine with high luminous intensity. As a general rule, warning lights in industrial areas should generally be five times brighter than the ambient lighting. For the warning lights on road vehicles, on the other hand, the light should be ten times brighter than that of the surrounding area.

The majority of people spend a big part of their day at work and it is natural that certain conditions should be created, so that the health and well-being of the workers was not damaged while they are performing their professional tasks. The quality of work and performance directly depends on how comfortable and safe the worker feels at the work place. Depending on the occupation, the amount of required light may differ tremendously. So, excessive light is as bad as scarce and this is quite a challenging task to create perfect working conditions for each particular task.

Therefore, indoor light bulb selection largely depends upon the intended application. However, whether a light bulb is needed for ambient lighting, spotlighting or task-specific use, factors such as service life, energy consumption, aesthetics and price are almost always considered. In addition, special functions like dimming often are added to the equation. Only after analyzing all the required (and desired) lighting parameters can the best (most suitable) indoor lighting solution be identified.

Enter input values with units, where appropriate. After you have modified some inputs, click the “calc” button to recalculate the output.

The United States Occupational Safety and Health Administration (OSHA) requires adequate marking and lighting for each escape route. OSHA's standards, which serve as a basis for assessment, specify the required brightness for signs in escape routes both in the American units such as foot-candles or footlamberts and in the SI units such as lux or candela per square meter. Checks of the required brightness can therefore be performed both with the lux meter designed for American units and with the lux meter that displays SI units.

The minimum illuminance values specified in EN 1838 are not minimum values for the design purposes, but for the maintenance values that must be achieved throughout the service life. Compliance with these values can be checked during regular inspections by taking measurements with a lux meter. Irrespective of these minimum values, the lux meter can be used to prove that the required uniformity of the illumination is maintained with a ratio of the lowest to the highest value of 1 : 40 for escape routes and 1 : 10 for workplaces with special hazards. The colour rendering index of the safety lighting, which should be at least 40, can also be measured with the suitable lux meter.

Various types of optical systems (e.g. microscope objectives and curved laser mirrors) can focus or defocus light, and the focal length is used for quantifying such effects. The simplest case is that of a thin focusing lens (Figure 1a). If a sufficiently large collimated beam of light is incident on the lens, the beam will be focused, and the focal length is the distance from the lens to that focus (assuming that the lens is surrounded by vacuum or air, not by some dense substance with a significant refractive index). For a defocusing lens (Figure 1b), the focal length is the distance from the lens to the virtual focus (indicated by the dashed lines), taken as a negative value. Some authors use different sign conventions, however, in particularly concerning the front and back focal length (see below).

A lens with a given focal length <$f$> (taken as positive in the case of a focusing lens) creates a radially varying phase delay for a laser beam according to the following equation:

Permanently installed or temporarily set up warning lights at construction sites, bridges, scaffolding or other danger points are intended to draw attention to the special situation, especially at night and in poor lighting conditions. To fulfil this purpose, it is important that the warning light shines brightly enough in the directions from which vehicles or pedestrians may approach. This can be checked with the lux meter for the respectively relevant distances.