Talk about "eye protection table lamp"

The reading of the artificial lighting mode and the visual operation of the video terminal have a certain relationship with the increase of the myopic population. Since the name "eye protection table lamp" subtly caters to the psychological needs of people who have protective vision for reading and desktop visual work, various table lamp products called "eye protection table lamps" are popular in the market.

Because the relationship between "eye protection" and the performance of table lamps has not undergone rigorous scientific argumentation, and the "eye protection" function lacks medical and clinical verification, there is no scientific basis for the term "eye protection table lamp" on the market. A desk lamp that provides illumination for reading or writing is called a reading and writing desk lamp.

1. Quality problems in "eye protection table lamp" products

1) The quality of the lighting on the desktop is not up to standard

The reading and writing table lamp for writing illumination should provide sufficient illumination and illumination uniformity on the illuminated desktop in the normal working position, so that the human eye feels comfortable and is not prone to fatigue.

A table lamp with a nominal eye protection function is usually used to provide reading and writing work illumination, and it is claimed that the product can make the user's eyes feel comfortable, is not prone to fatigue, and can protect eyesight.

2) The disturbance voltage exceeds the limits specified in the standard

The disturbance voltage is a kind of radio disturbance. The disturbance voltage of the desk lamp exceeds the limit, which will affect the normal operation of the surrounding broadcast television reception and instrumentation and automatic control equipment, resulting in failure to properly listen to the viewing and instrument control failure. The main reason is that the filter circuit for suppressing disturbance is not installed in the electronic ballast of the lamp, or the selected component parameters are not appropriate, causing the disturbance voltage to exceed the limit specified by the standard.

3) Unsatisfactory durability test

When working periodically under normal conditions and abnormal conditions, the lamp components should not be damaged prematurely, nor should there be unsafe phenomena such as burnt deformation. If the ballast inside the lamp does not have the protection function under abnormal conditions and burns out, the table lamp cannot work normally for a long time.

2. Working principle of "eye protection table lamp"

The so-called "eye protection table lamp" selling point in the market claims to be "no stroboscopic, with eye protection function". Most "eye protection" desk lamps use electronic ballasts to operate fluorescent lamps at high frequency currents. The frequency is usually above 20 kHz. This frequency is relative to the use of an inductive ballast to operate a fluorescent lamp at a power frequency of 50 Hz. It makes the naked eye less aware of the presence of high frequency flicker. However, even if it is not visible to the naked eye, stroboscopic still exists, but the frequency of fluorescent lamps operating with high frequency electronic ballasts is much higher than that when using power frequency magnetic ballasts. However, the work of high-frequency scintillation visual impact studies has not yet confirmed that retinal neural responses caused by high-frequency light stimulation have an effect on the visual function of the sensory or motor nerves, so it is currently difficult to determine whether it can effectively protect the eyes.

3. High frequency electromagnetic radiation of table lamps

All electronic products have a certain amount of electromagnetic radiation. The reading and writing table lamp with electronic ballast is no exception. There is electromagnetic radiation. Because its operating frequency is generally 20 kHz to 40 kHz, the frequency is relatively low. The human body is best tolerant to electromagnetic radiation at this frequency, and at the same time has a certain distance during normal use, resulting in a very small absorption of the human body. Products that normally meet the requirements of GB 17743-2007 "Limitations and Measurement Methods for Radio Disturbance Characteristics of Electrical Lighting and Similar Equipment" can be used with confidence in normal use.

4. Evaluation of the standard for "eye protection table lamp"

Read and write work desk lamps shall comply with the following safety, electromagnetic compatibility and performance standards. These standards can be referred to when evaluating "eye protection table lamps".

1) Safety standards:

GB 7000.204-2008 "Lamps Part 2-4: Special requirements for portable general-purpose lamps";

GB 7000.1-2007 "Lamps Part 1: General requirements and tests".

2) Electromagnetic compatibility standards:

GB 17743-2007 "Limitations and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment";

GB 17625.1-2003 "Electromagnetic compatibility limit harmonic current emission limit and measurement method (equipment input current per phase ≤ 16A)".

3) Performance standards:

GB/T 9473-2008 "Reading and writing work table lamp performance requirements". The standard also includes the detection of lighting quality.

5. Table lamps and other elements that are conducive to protecting vision

The most important thing in reading and writing work desk lamps is to meet the requirements of comfortable lighting for glare, illumination level and illumination uniformity.

Glare is an important part of evaluating the performance of desk lamps. We all have such life experience. When you meet the sun, you can't see the scene in front. When you cover your eyes with your hands, the scene in front of you is much clearer. This is because the sun's rays shine into the eyes, forming a light curtain, like a curtain in front of the scene, the scene can not be seen. When the reading and writing work table lamp is placed on the table and the height of the lamp body is similar to the height of the eye, if the structure size of the lamp is unreasonable, the light of the lamp overflowing into the eye will cause a light curtain. Therefore, the standard requires the luminaire. When the eye is at a height of 400 mm from the table top and 600 mm from the center of the light source, the inner wall of the light source and the reflector should not be visible.

When the eye moves from a dark environment to a bright place, it will feel glare, and the pupil of the eye will immediately shrink to reduce the incoming light to adapt to the bright environment. This is a natural physiological adaptation phenomenon. Therefore, it is required that the illumination of the table lamp on the table should be relatively uniform, and the illumination area should cover the area of ​​the reading and writing operation. Otherwise, the illumination is uneven in the line of sight of the eye when reading and writing, causing the eye to constantly adjust the pupil at all times. Size, easy to cause visual fatigue. Two levels of illumination are specified for this standard. If you need to work under the desk lamp for a long time, the manufacturer can recommend the user to use a higher level of illumination.

Element 1: On the work surface, there should be luminous flux and corresponding light distribution that meet the illumination requirements.

- There is a certain illumination requirement

For long-term literacy and difficult operations, the illuminance on the work surface should be at least 500 lx (AA grade). For short-term operation, the illumination on the work surface should be at least 250 lx (Grade A). The ratio of the maximum illumination to the minimum illumination of the work surface is not more than 3.

- The power of the light source in the luminaire should not be too low. Compact fluorescent lamps with a power of at least 18 W;

- Illuminate a certain area, the area is a one-third sector of the radius from the center of the circle of 500 mm and 300 mm.

Element 2: There should be a significant amount of overhead light. The environment around the light is illuminated (as shown in Figure 1). So as not to cause bright too bright, dark too dark, should form a smooth transition of light and dark, to facilitate visual comfort, not suitable for visual fatigue.

Element 3: The side of the desk lamp should be transparent. As shown in Figure 1, a smooth transition of light and dark is formed. The brightness of the luminaire surface is between 510 cd/m2 and 170 cd/m2 from any normal use and sitting position. An example of the opaque side of the desk lamp is shown in Figure 2, and an example of light transmission is shown in Figure 3.