(written from a Production point of view)
Alexander Singer (born 18 April 1928; age 93), in the 1950s and 1960s also credited as "Alex Singer", was a director who directed a significant number of episodes for Star Trek: The Next Generation, Star Trek: Deep Space Nine, and Star Trek: Voyager.
Hired in 1992, The Next Generation's sixth season episode "Relics", was Singer's directorial debut on the franchise. For Singer, an ardent science fiction and Star Trek: The Original Series fan, this was a particularly satisfying experience, as he had already wanted to work on The Original Series in the 1960s, "I was across the lot for a few years doing Mission: Impossible [like Star Trek, a Desilu production], and I wanted to work with Star Trek. I met Gene Roddenberry and, for one reason or another, it hadn't worked out. So the aspect of the Scotty character and his resurrection had a kind of multiple resonance. Having Jimmy Doohan there, I felt I was in the middle of some kind of mythic experience myself." (Star Trek: The Next Generation 365, p. 273)
Singer has cited the "Relics" bridge scene, due to the fact that only small, cramped part of it was constructed and calling it an "enormous cinematic challenge", as well as Deep space Nine's final episode of season three, "The Adversary", as two of the most challenging Star Trek episodes he directed, in particular the climatic fight scene between Odo and the Changeling for the latter, an visual effects heavy scene he had to do directly on stage, without the benefit of story boards. (Cinefantastique, Vol. 24, issue 3/4, p. 26; Star Trek: Deep Space Nine Companion (p. 251))
According to both Garrett Wang and Robert Picardo, Singer had an unusual method of directing while filming episodes of Star Trek: Voyager. After a take was over, instead of verbally talking to the cast about what they did wrong in a scene, he would make strange facial expressions at them. It was his way of telling them they were being too expressive during a scene. 
In 2012 Singer received an honorary SET Award for his entire Star Trek body of work.
Career outside Star Trek
Alexander Singer, started out his motion picture career as (assistant) cinematographer on 1950s productions such as the 1951 documentary Day of the Fight and the movie Killer's Kiss (1955), both helmed by director Stanley Kubrick, and featuring music by Gerald Fried.
Singer's subsequent directorial career spans more than thirty years, from 1960 to 1998, predominantly working on television productions. His credits included The Fugitive, The Monkees, Mission: Impossible, The Bold Ones: The Lawyers (of which the 1971 episode "The Invasion of Kevin Ireland" won him an Emmy Award the subsequent year), Wonder Woman, Remington Steele, In the Heat of the Night, Walker, Texas Ranger, Jake and the Fatman, many soap operas, and MacGyver. As a science fiction fan, his tenure on Star Trek was something of a dream come true, as he had previously little opportunity to indulge his passion professionally, the 1965 episode "The Derelict" of the television series Lost in Space, and 1976 television movie Time Travelers, his only recorded professional contributions to the genre. Voyager was his last professional work before retirement.
Singer received the following honorary Science, Engineering & Technology Award in the category SET Icon Award
Star Trek credits