Backlight source and display device

A backlight source, comprising:

• a light source, comprising a plurality of light-emitting units;
• a light-transmitting substrate, located at a light-emitting side of the light source;
• a first lens group, located at a light-exit side of the light-transmitting substrate, and the first lens group comprising a plurality of first lenses;
• a second lens group, located at a light incident side of the light-transmitting substrate, and the second lens group comprising a plurality of second lenses;
• wherein a largest dimension of each first lens in a direction parallel to the light-transmitting substrate is a first dimension, a largest dimension of each second lens in the direction parallel to the light-transmitting substrate is a second dimension, and the first dimension is greater than the second dimension, and an orthographic projection of at least one second lens on the light-transmitting substrate overlaps with an outline of an orthographic projection of at least one first lens on the light-transmitting substrate or is located in an interval between orthographic projections of adjacent first lenses on the light-transmitting substrate;
• a largest dimension of each light-emitting unit in the direction parallel to the light-transmitting substrate is a third dimension, a ratio of the second dimension to the third dimension ranges from 0.2 to 0.5, and a ratio of the second dimension to the first dimension ranges from 0.04 to 0.2.