I have bought a camera hp , lc100W
I want to use it for lecture record, microphone has not good record, What I must do for the sound? which type of microphone I must buy for it?
The rule of thumb for recording sound is that the closer to the source you get the better the sound. The reason is that the further you are from the source the more you have to increase the recording level, which means you also turn up all the background noise and room ambiance (echo and reverb). Since sound levels diminish proportionally to the square of the distance having the mic twice as far away means one quarter the sound level, or four times more background noise.
Now it doesn't look like there's a microphone input on that camera. If that's the case the only way you can record sound using an external mic is with a separate recorder. You could use a phone if you have one, you can get external mics for phones. Put the mic and recorder close to the source - on the lectern or even on a mic stand. Then you can synch the sound in your editing app. Premiere for example will synch clips automatically from their audio.
It depends on what kind of look you want on your video. You could go with a gooseneck mic, which extends out towards you. It has near presence. If you prefer the microphone not be seen, your best bet is a short shotgun microphone, which you can boom from either above or below the frame line. If using a shotgun mic, laying a blanket down on the ground will reduce slap back from the ceiling to the floor. Shotgun microphones are highly directional, so they can be placed farther from the sound source and reject to a decent extent (depending on your budget) sound that is not within the pickup angle. Microphone distance is not the only thing to consider. Because presence is important for natural sounding audio. A gooseneck mic should be 6"-8" away from your mouth, under the chin. A shotgun microphone's ideal placement would be 12"-24" above or below your head, 6" out from your face towards the camera, and pointed directly at your mouth. If you use say a large diaphram microphone, like a Neumann, you'll want 3-6" typically, but the micrphone will be in front of your face due to it's size.