how to upload r files (images) with angle 5 and a backend in laravel 5

I am developing a sales system with angular 5 in the forntend and the backend with angular 5, and I need to send to the backend an image that I upload with angular 5 but apparently nothing comes in the code.

This is my productComponet where I receive the product dataComponet.html

export class ProductoNComponent implements OnInit {
titulo: string;
public ima: string = '../../../assets/imagenes/ima.jpg';
public identity;
public token;
producto: Producto;
public  archivo: File = null;
 constructor(
private _route: ActivatedRoute,
private _router: Router,
private CrearProducto: ServicioUser,
private ProductosGuardar: ServicioProducto
) { 
this.titulo = 'Crear Producto'; 
 this.identity = CrearProducto.getIdentity();
 this.token = CrearProducto.getToken();
}

ngOnInit() {
console.log(this.identity);
if (this.identity == null) {
  console.log('si redirecciono');
  this._router.navigate(['login']);
} else {
     this.producto = new Producto(1, '', '', 0, null, null);
     console.log('no redirecciono');
  }
}

This is my service that sends data to larevel

export class ServicioProducto {
ulr: string;
constructor(
  public  _http: HttpClient
) {
    this.ulr = GLOBAL.url;
}
registroProducto(producto, file: File, token): Observable<any> {
            let json = JSON.stringify(producto);
            let params =  new FormData();
        params.append('json', json);
        params.append('file', file);
       params.append('fileName', file.name);
        params.append('Authorization', token);
let json1 = JSON.stringify(producto);
console.log(file.name);
 console.log(json1);
    return this._http.post(this.ulr + 'producto', params);

  }
   prueba(producto) {
     let json = JSON.stringify(producto);
    return json;
    }
  }