Camera preview problem

Ionic Native
1

Hi sir good day.
I have problem in my camera preview.

When I start my camera. my camera preview don’t show what camera.
instead it shows my other modal.

here are some of my snippets in TS.

start(): void {

    this.picture = "";
    this.cameraPreview.startCamera({
        x: 0,
        y: 0,
        width: window.screen.width,
        height: window.screen.height,
        camera: 'rear',
        tapPhoto: true,
        previewDrag: true,
        toBack: true,
        alpha: 1
    }).then(
        (res) => {
            console.log(res)
        },
        (err) => {
            console.log(err)
        });
};