JP2021043352A5

JP2021043352A5 -

Info

Publication number: JP2021043352A5
Application number: JP2019165647A
Authority: JP
Filing date: 2019-09-11
Publication date: 2022-09-14
Anticipated expiration: 2039-09-11

Claims

a plurality of laser elements;
a diffractive optical element that diffracts the laser light emitted from each of the laser elements;
a collimating lens that converts each of the laser beams diffracted by the diffractive optical element into parallel light;
each of the laser elements emits laser light having a different wavelength,
The diffractive optical element has a diffractive surface on which a sawtooth-shaped portion having a plurality of parallel linear grooves is formed on the outside ,
each of the laser elements is arranged on one side of the optical axis of the collimating lens in a cross-sectional view including the optical axis of the collimating lens and at positions with different distances from the optical axis;
The laser beams emitted from the laser elements are diffracted by the diffractive optical element in diffraction orders different from each other and synthesized.
Laser light source device.

The direction in which the grooves of the sawtooth-shaped portion extend is perpendicular to the cross section including the optical axis of the collimator lens,
The laser light source device according to claim 1.

The height of the sawtooth-shaped portion of the diffractive optical element is set to a value within a predetermined range so that the laser beams emitted from the respective laser elements are diffracted and combined with a diffraction efficiency of 91% or more. be,
3. The laser light source device according to claim 1.

Let λp be the wavelength of each laser beam emitted from each of the laser elements,
Let np be the refractive index of the diffractive optical element at each of the wavelengths,
Let d be the height of the sawtooth-shaped portion of the diffractive optical element,
When mp is the diffraction order at each of the wavelengths that provides the combination of maximum diffraction efficiencies,
mp is a non-zero integer,
-0.175<d(np-1)/λp-mp<0.175
4. The laser light source device according to any one of claims 1 to 3, satisfying:

-0.1<d(np-1)/λp-mp<0.1
5. The laser light source device according to claim 4, satisfying:

one of the laser elements emits a laser beam having a blue wavelength;
one of the laser elements emits a laser beam having a green wavelength;
one of the laser elements emits laser light having a red wavelength;
The laser light source device according to any one of claims 1 to 5.

In the diffractive optical element, the laser beams of different wavelengths are generated and synthesized into laser beams of at least the fourth order of diffraction or higher.
The laser light source device according to claim 6.

When the wavelengths of the three laser elements having blue, green, and red wavelengths are λ1, λ2, and λ3,
450 nm<λ1<475 nm,
500 nm<λ2<540 nm,
625 nm<λ3<650 nm,
satisfy the
The laser light source device according to claim 6 or 7.

The respective laser elements are arranged at different positions in the optical axis direction of the collimator lens,
The laser light source device according to any one of claims 1 to 8.

The diffractive optical element and the collimating lens are integrated,
The laser light source device according to any one of claims 1 to 9.

A laser light source device according to any one of claims 1 to 10;
a first scanning element that scans laser light having a plurality of wavelengths emitted from the laser light source device in a first direction;
a second scanning element that scans the laser light emitted from the first scanning element in a second direction orthogonal to the first direction;
An image forming apparatus comprising: