What Makes a Laser Pointer Brighter: 488nm 110mW vs 505nm 70mW

Laser pointers have become a quick and convenient way for presentations, but not all lasers are suitable for this purpose. This article explores the difference in brightness and safety concerns between a 488nm 110mW laser and a 505nm 70mW laser. We will delve into the scientific basis for their apparent brightness and the dangers associated with each, emphasizing the importance of adhering to safety guidelines.

The Safety Concern

First and foremost, it is crucial to acknowledge the potential hazards of these lasers. The advertised power levels can be misleading, as they do not reflect the actual light emitted versus the electrical power consumed. Moreover, laser diode efficiency plays a significant role in determining the actual brightness. It is important to note that both lasers in question are extremely powerful and could cause permanent eye damage if misused. Even lasers with below 1mW power can be dangerous. The IND (hellish) of the laser dictates its safety, and a 1mW visible laser is often considered a 'safe enough' limit to be sold as a laser pointer in some countries. However, even this limit is not without risk, as eye damage can still occur with improper usage.

Retinal Cell Sensitivity

The retinal cells play a critical role in determining the perceived brightness of a laser. The light sensitivity of rods, blue-sensitive, and red-sensitive cones at 505nm is 10 times higher than at 488nm. This means that even though the 505nm laser has a lower power level, it is likely to appear brighter because the human eye is more sensitive to green light. Additionally, the 505nm laser is known to be a green laser, which has a higher photopic efficacy, making it appear more noticeable.

Calculating Apparent Brightness

If you want to calculate the apparent brightness of the light to the human eye, you can look up a "luminous efficacy table" on the web. This table will provide the relative apparent brightness of the same amount of power for a range of wavelengths over the visible light spectrum. The photopic efficacy column is the one you should focus on as it represents the light sensitivity under typical viewing conditions. Use linear interpolation between the table wavelengths and multiply the power (in mW) by the efficacy value for the respective wavelength to get the relative apparent brightness for each laser.

Which Laser Will Appear Brighter?

Based on the calculations, the 488nm 110mW laser should appear about 40% brighter than the 505nm 70mW laser. This is due to the higher power output and the efficacy of the 488nm wavelength. However, it is important to remember that both lasers are extremely powerful, and their use as pointers could be hazardous in environments with reflective surfaces or windows. The beam could accidentally end up in someone's eyes, causing permanent damage before they can blink.

Conclusion

While the 488nm 110mW laser appears to be more powerful, it is not recommended for use as a laser pointer due to its high power output. Similarly, the 505nm 70mW laser, despite being green and more sensitive to the human eye, is still too powerful for safe use as a pointer. The safe use of laser pointers is paramount, and it is essential to adhere to the guidelines regulating laser power levels to prevent potential harm.

Keywords: laser pointer brightness, retinal cell sensitivity, wavelength comparison