Luminous Flux
光通量
Luminous Flux (Φv) is energy per unit time (dQ/dt) that is radiated from a source over visible wavelengths. More specifically, it is energy radiated over wavelengths sensitive to the human eye, from about 330 nm to 780 nm. Thus, luminous flux is a weighted average of the Radiant Flux in the visible spectrum. It is a weighted average because the human eye does not respond equally to all visible wavelengths.
光通量（Φ v）是光源在可见波长范围内辐射出的单位时间（dQ/dt）的能，即每秒辐射的能。更具体地说，它是人眼对可见波长敏感的范围内辐射出的能，大约从330 nm到780 nm。因此，光通量是可见光谱中辐射通量的加权平均。它是一个加权平均，因为人眼对所有可见波长的响应并不相同。
The sensitivity of the eye peaks at 555 nm and falls off to approximately 10-4 at 380 and 750 nm. This constitutes the range of daylight sensitivity, or photopic vision. The eye's nighttime sensitivity, called scotopic vision, shifts toward the blue end of the visible, peaking at 507 nm and falling to 10-4 at 340 and 670 nm.
This weighting factor, or luminous efficacy (Vλ), allows for conversion of Radiant Flux to Luminous Flux at any wavelength. In the photopic region, the peak at 555 nm is assigned a conversion value of 683 lumens per Watt. The lumen is the unit of luminous flux, and is defined in terms of the candela, an SI base unit like the meter or second. 1 lumen is defined to be 1/4π candela, the SI base unit of Luminous Intensity.
Since the eye does not see all wavelengths equally well, the efficacy curve is a very important way to determine the Luminous Flux from a source. The Luminous Flux from a monochromatic source producing light at a single wavelength is easiest to determine.
由于人眼对不同波长的光感受能力不同，效能曲线是确定光源光通量的重要方法。来自单色光源的光通量，其值在单一波长下最容易确定。
Φv = Φ *Vλ * (683 lm/W)
Φ v = Φ * V λ * (683 lm/W)
For instance, a 5 mW laser pointer using at a wavelength of 680 nm produces
例如，一个使用波长为680纳米的5毫瓦激光笔会产生
.005 W * .017 * 683 lm/W = .058 lm
While a 5 mW laser pointer at 630 nm produces
尽管一个630纳米的5毫瓦激光笔产生
.005 W * .265 * 683 lm/W = .905 lm, a significantly greater luminous flux.
0.005 W * 0.265 * 683 lm/W = 0.905 lm，这代表显著更大的光通量。
Determining the Luminous Flux from a source radiating over a spectrum is more difficult. It is necessary to determine the Spectral Power Distribution for the particular source. Once that is done, it is necessary to calculate the Luminous Flux at each wavelength, or at regular intervals for continuous spectra. Adding up the flux at each wavelength gives a total flux produced by a source in the visible spectrum.
从辐射谱确定光通量是更具挑战性的。必须确定特定光源的光谱功率分布。一旦完成这一点，就需计算每个波长或在连续谱中定期间隔的波长处的光通量。将每个波长处的光通量相加，即可得到光源在可见光谱中产生的总光通量。
Some sources are easier to do this with than others. A standard incandescent lamp produces a continuous spectrum in the visible, and various intervals must be used to determine the Luminous Flux. For sources like a mercury vapor lamp, however, it is slightly easier. Mercury emits light primarily in a line spectrum. It emits radiant flux at 6 primary wavelengths. This makes it easier to determine the Luminous Flux of this lamp versus the incandescent.
某些光源比其他光源更容易进行这种操作。标准的白炽灯在可见光范围内产生连续谱，必须使用不同区间来确定光通量。然而，对于像汞灯这样的光源，情况稍有不同。汞灯主要以线谱发射光。它在6个主要波长下发射辐射通量。这使得确定该灯的光通量比白炽灯更容易。
Generally, it is not necessary to determine the luminous flux for yourself. It is commonly given for a lamp based on laboratory testing during manufacture. For instance, the Luminous Flux for a 100W incandescent lamp is approximately 1700 lm. We can use this information to extrapolate to similar lamps. Thus the average luminous efficacy for an incandescent lamp is about 17 lm/W. We can now use this as an approximation for similar incandescent sources at various wattages. Often times, the manufacturer will list 'initial lumens' in its data for a lamp. This is the Luminous Flux for that lamp. It is listed in this manner because as a lamp ages, its power distribution shifts slightly and no longer radiates at precisely the wavelengths it did at the time it was new. However, for all intents and purposes, 'initial lumens' may be used for Luminous Flux for any necessary calculation.
通常，自己确定光通量是不必要的。这种光通量通常是在制造过程中通过实验室测试给出的。例如，100瓦的白炽灯的光通量大约为1700流明。我们可以利用这一信息来推断类似灯泡的光通量。因此，白炽灯的平均光效约为17流明/瓦。我们现在可以将这一数值作为近似值，用于各种功率的白炽灯源。通常，制造商会在其数据中列出‘初始流明’。这是该灯泡的光通量。以这种方式列出是因为随着灯泡老化，其功率分布会略有变化，不再精确地在它新时的波长上辐射。然而，对于所有实际用途来说，‘初始流明’可以用于任何必要的计算作为光通量。
人眼的灵敏度在555纳米处达到峰值，而在380和750纳米处下降到约10⁻⁴。这构成了日光灵敏度，或称光觉视觉。人眼的夜间灵敏度，称为视觉（scotopic vision），则向可见光的蓝色端偏移，峰值在507纳米，而在340和670纳米时下降到10⁻⁴。这个权重因子，或发光效率（Vλ），允许将辐射通量转换为光通量。在光觉视觉区域，555纳米处的峰值被赋予683流明每瓦的转换值。流明是光通量的单位，其定义基于坎德拉，这是与米或秒相同的SI基本单位。1流明被定义为1/4π坎德拉，即光通量的SI基本单位。0.005 W * 0.017 * 683 lm/W = 0.058 lm |
