我比個數字 香港警察 Hong Kong Police 睇：
//“In the previous [2013] SSM report we analysed 34 cases and only a few of them had confirmed retinal injuries. In this report the number of cases with confirmed retinal injuries have increased [an additional 47 cases are described in the appendix]. If the availability of the handheld lasers continues to increase, along with higher optical power and lower cost, we expect that the number of severe eye injuries will continue to grow. Also, the distance from which the lasers can be used to disrupt various societal functions, such as air traffic (pilots) and policing will also increase.”
“Almost all the reported cases involve young children and teenagers. There is also a huge overrepresentation by males. Often the lasers are sold as toys and purchased by a relative as a gift to a child.”//
傳送門：https://www.laserpointersafety.com/2015-laser-eye-injuries.…
//They found 34 cases from 1999 to 2012. (This does not include the 2013 Saudi Arabian hospital report of 14 young boys injured by high-powered blue lasers, which appeared too late for this study.) Of the 34 cases:
5 were deliberate exposures by the patient (they deliberately stared into the laser for more than a second or two, or numerous times)
5 were deliberate exposures by a doctor, on a patient whose eye was scheduled for removal due to disease//
傳送門：https://www.laserpointersafety.com/2013-laser-eye-injuries.…
用返警察先睇得明的中文來說，就是近代英文文獻內僅有 47 宗因鐳射筆造成的眼睛傷害案例，幾乎全部都係兒童或青少年因為貪玩、多次直視激光造成的，只有極少數是醫療失誤引起。
報告又指，隨住鐳射筆更普及使用，相信案例會增加。我不否認鐳射筆會有危險性（詳情可參考這篇：http://bit.ly/2KA6MtP），節錄如下：
//激光分為不同的類別： Class 1, 1M, 2, 2M, 3R, 3B, 4. 而我們的激光筆上面清楚寫明是屬於 Class IIIb 即是 3B 級別。
據政府機電工程處的網頁所示：
第 3B 類激光產品
直視光束可能會有危險，不過，在某些條件下通過漫反射體來看光束是安全的
連續波輸出功率不超逾 0.5 瓦
例子：用於物理治療的激光器
它說的漫反射 (diffuse reflection) 就是從其他角度看這束激光。而連續輸出功率不超過 0.5W 如果轉做 mW 即等於 500mW 。
根據網頁所講， IIIB 及 IV 是會對眼睛做成影響，隨著激光的強度增加，影響會更大。圖四講解例如 IIIB 的激光如果近距離照射眼睛1/4秒會有中度至高度的損害，而它也說如果距離增加或照射時間減少，損害亦會減少。
而它在網頁中有另外一個大表，舉出了一個數據是 500mW 的激光在 160 米外照射眼睛是安全的。如果是觀測漫反射出來的光線，也是安全的。要令皮膚感到熱力，也只有在長時間近距離照射才會有感覺。//
用份報紙咁近距離照射加熱有煙出，又真的合符實際狀況，且對警方造成巨大傷害嗎？
另外，暫時我們未清楚方同學所購得的鐳射筆功率有多大，在此時刻警方想將之定性為武器實在過早，有影響法官判斷之嫌，促請有關方面不應追風捕影地假設張同學有罪。
圖：Stand News 立場新聞
#科普 #factcheck好重要 #反送中 #黑警
diffuse reflection 在 Diffuse reflection in 5 minutes - YouTube 的必吃
Equivalent to a 50 minute university lecture on diffuse and mixed reflection.0:00 - intro0:10 - paper under a microscope0:45 - diffuse ... ... <看更多>