Microdata Open Graph for image of category

<meta property="og:image" content="https://my.site/thumbnail-of-this-category.jpg">

// Microdata Open Graph
$document = JFactory::getDocument();
$document->addCustomTag('<meta property="og:url" content="'.JURI::current().'">');
$document->addCustomTag('<meta property="og:type" content="website">');
$document->addCustomTag('<meta property="og:locale" content="ru_RU">');
$document->addCustomTag('<meta property="og:site_name" content="My Site">');
$document->addCustomTag('<meta property="og:title" content="'. $this->category->name .'">');
$document->addCustomTag('<meta property="og:description" content="'. $this->category->metadesc .'">');

$doc->setMetaData('og:image:secure_url', $ambit->getImg('img_url', $this->images[0]), 'property');

$document->addCustomTag('<meta property="og:image" content="'. $this->_ambit->getImg('img_url', $this->images[0]) .'">');