Ultrasonic ranging module HC - SR04 provides:
2cm - 400cm non-contact measurement function, the ranging accuracy can reach to 3mm
The modules includes ultrasonic transmitters, receiver and control circuit

The basic principle of work:
Using IO trigger for at least 10us high level signal
The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back
IF the signal back, through high level , time of high output IO duration is the time from sending ultrasonic to returning
Test distance = (high level time×velocity of sound (340M/S) / 2

Wire connecting direct as following:
5V Supply
Trigger Pulse Input
Echo Pulse Output
0V Ground

Ultrasonic Ranging Module HC - SR04 documentation

Less influence on the color of reflective objects, reflectivity
Line-up of distance output/distance judgement type
Distance output type (analog voltage) : GP2Y0A21YK
Detecting distance : 10 to 80cm
Distance judgement type : GP2Y0D21YK
Judgement distance : 24cm (Adjustable within the range of 10 to 80cm [Optionally available])
External control circuit is unnecessary4. Low cost

Ultrasonic IR senzor rastojanja - Sharp GP2Y0A21YK documentation
IR senzor rastojanja - Sharp GP2Y0A02YK0F usage example

VCNL4000 is a fully integrated proximity and ambient light digital 16 bit resolution sensor in a miniature lead lesspackage (LLP) for surface mounting. It includes a signal processing IC and supports an easy to use I2C bus communication interface
For more details read documentation.

IR senzor rastojanja i ambijentalnog osvetljenja - VCNL400 documentation

GP2Y0A02YK0F is a distance measuring sensor unit, composed of an integrated combination of PSD (position sensitive detector), IRED (infrared emitting diode) and signal processing circuit. The variety of the reflectivity of the object, theenvironmental temperature and the operating durationare not influenced easily to the distance detection because of adopting the triangulation method. This device outputs the voltage corresponding to thedetection distance. So this sensor can also be used asa proximity sensor.
For more details read documentation.

IR senzor rastojanja - Sharp GP2Y0A02YK0F documentation
IR senzor rastojanja - Sharp GP2Y0A02YK0F usage example