the loss of the divergent illumination light can be greatly reduced and a brighter image forming apparatus can be arranged note that combinations of the color filters and a white light source may be used in place of the blue and yellow light sources described above after the light components pass through the liquid crystal light valves 1 2 and 3 they are synthesized again through the total reflection mirror 20 the dichroic mirror 9 for transmitting the blue light component and reflecting the green component and the dichroic mirror 11 for transmitting the red light component and reflecting the green and blue light components the synthesized light is projected through the projection lens 6 in this embodiment if the dichroic mirrors 8 and 11 are designed to transmit the red light component and reflect the blue and green light components the dichroic mirrors 8 and 11 can be identical to each other thus resulting in an economical advantage at this time if the dichroic mirrors 8 and 11 are constituted by a single dichroic mirror the number of optical elements and the number of positioning operations can be reduced man 39 s eye is most sensitive to the green light component among the components in the visible range on the other hand when light is obliquely incident on parallel flat plates as in this embodiment an astigmatism occurs judging from these two factors it is found that the number of times of passing of the green light component through a dichroic mirror can be reduced to obtain a high resolving power in this embodiment since the green light component does not pass through a dichroic mirror a display image having a high resolving power can be obtained fig4 is a schematic view showing an arrangement of another embodiment.